Статті в журналах з теми "2.4GHz low-power receivers"

Abstract. This paper presents a receiver signal strength detector based on a discrete Fourier transform implementation. The energy detection algorithm has been designed and measured using a custom multi-standard transceiver ASIC with a low-IF receiver at 0.5, 1 and 2 MHz IF. The proposed implementation directly processes the single bit ΔΣ modulator data and features a clear channel assessment for arbitrary modulation schemes without energy consuming demodulation. Continuous monitoring of the derivative of the RSSI takes advantage of faster coefficient convergence for higher power levels and reduces computation time. A dynamic range of 65 dB has been achieved in FPGA based measurements with a linearity error of less than 1.2 dB. Furthermore, synthesis results for an on-chip implementation for an 130 nm RF CMOS technology show an overall power consumption of 1.5 mW during calculation.

Various GNSS applications require low-cost, small-scale, lightweight and power-saving GNSS devices and require high precision in terms of low noise for carrier phase and code observations. Applications vary from navigation approaches to positioning in geo-monitoring units up to integration in multi-sensor-systems. For highest precision, only GNSS receivers are suitable that provide access to raw data such as carrier phase, code ranges, Doppler and signal strength. A system integration is only possible if the overall noise level is known and quantified at the level of the original observations. A benchmark analysis based on a zero baseline is proposed to quantify the stochastic properties. The performance of the consumer grade GNSS receiver is determined and evaluated against geodetic GNSS receivers to better understand the utilization of consumer grade receivers. Results indicate high similarity to the geodetic receiver, even though technical limitations are present. Various stochastic techniques report normally distributed carrier-phase noise of 2 mm and code-range noise of 0.5–0.8 m. This is confirmed by studying the modified Allan standard deviation and code-minus-carrier combinations. Derived parameters serve as important indicators for the integration of GNSS receivers into multi-sensor-systems.

Noise of a photodetector plays a vital role in determining the minimum detectable signal for lidar and DIAL receivers. A low noise trans-impedance amplifier circuit has been employed to examine the noise of III-V compound infrared detectors. These infrared detectors include InGaAs PIN diodes and newly developed InGaAsSb avalanche photodiodes (APDs) with separate absorption and multiplication (SAM) structure. The noise of these detectors are compared with well-established Si APDs. These measured noises are utilized to compute the figures-of-merit, such as noise-equivalent-power (NEP) and detectivity (D*) of these devices and are presented in this paper.

In order to reduce the power consumption of handset GNSS receivers, we present a novel algorithm that tracks signals at fixed positions of the navigation message in an intermittent mode. The tracking channels only run during the beginning part of the message frame. In the rest they remain in idle state, to reduce power consumption of the channel. The beginning position of each message frame can be estimated accurately, and the beginning messages are constant or can be estimated, thus the coherent integration time can exceed one navigation bit, which can improve the Doppler frequency estimated accuracy. At the fixed position of the frame, the tracking channel only tracks the pseudo-code phase, and does not track the carrier frequency and phase. This algorithm can keep stable tracking for weak signals with 28 dBHz carrier-to-noise ratio (C/N0), while using only 2% of the power required by the computation associated with the traditional tracking.

THE PURPOSE. Consider the issues of electricity quality in power supply systems and the results obtained by the authors of the article when monitoring the electrical energy quality in urban electrical networks with a voltage of 0.4 kV. The results of these measurements indicate that at some facilities there are violations of the electricity quality in almost all indicators. Therefore, to ensure proper quality, it is necessary to develop comprehensive measures to maintain power quality indicators within the established limits.METHODS. When solving the problem, methods of comparison and analysis of experimental data were used. RESULTS. We indicate the main problems which inevitably arise when the quality of electrical energy decreases. Present the causes of the electricity low quality. It is shown that in this case there is a violation of the various electrical receivers operation.CONCLUSION. We indicate that earlier investigations of the electrical energy quality mainly considered power supply systems and power receivers of industrial enterprises. We present the examples of poor electricity quality, including in the event of voltage fluctuations. Therefore, when developing measures to maintain the electricity quality within acceptable limits in urban electrical networks, monitoring of electricity quality indicators should be carried out. Only on the basis of its results it is necessary to develop a set of measures to improve the electricity quality. This approach is also expedient because the electricity consumers can potentially order monitoring of the electric energy quality to specialized organizations and, in case of non-compliance with the requirements of GOST 32144-2013, file lawsuits against power supply organizations about violations of the electricity quality with great chances of satisfying them.

Global navigation satellite system (GNSS)-based attitude determination has been widely applied in a variety of fields due to its high precision, no error accumulation, low power consumption, and low cost. Recently, the emergence of common-clock receivers and construction of GNSS systems have brought new opportunities for high-precision GNSS-based attitude determination. In this contribution, we focus on evaluating the performance of the BeiDou regional navigation satellite system (BDS-2)/BeiDou global navigation satellite system (BDS-3)/Global Positioning System (GPS)/Galileo navigation satellite system (Galileo) attitude determination based on the single-differenced (SD) model with a common-clock receiver. We first investigate the time-varying characteristics of BDS-2/BDS-3/GPS/Galileo line bias (LB) with two different types of common-clock receivers. The results have confirmed that both the phase and code LBs are relatively stable in the time domain once the receivers have started. However, the phase LB is expected to change to an arbitrary value after each restart of the common-clock receivers. For the first time, it is also found that the phase LBs of overlapping frequencies shared by different GNSS systems are identical. Then, we primarily evaluated the performance of BDS-2/BDS-3/GPS/Galileo precise relative positioning and attitude determination based on the SD model with a common-clock receiver, using a static dataset collected at Wuhan. Experimental results demonstrated that, compared with the double-differenced (DD) model, the SD model can deliver a comparable root–mean–square (RMS) error of yaw but a significantly smaller RMS error of pitch, whether for BDS-2, BDS-3, GPS, or Galileo alone or a combination of them. The improvements of pitch accuracy are approximately 20.8–47.5% and 40.7–57.5% with single- and dual-frequency observations, respectively. Additionally, BDS-3 can deliver relatively superior positioning and attitude accuracy with respect to GPS and Galileo, due to its better geometry. The three-dimensional positioning and attitude (including yaw and pitch) accuracy for both the DD and SD models can be remarkably improved by the BDS-2, BDS-3, GPS, and Galileo combination with respect to a single system alone.

Ultra-wideband radio technology (UWB), is a wireless access technology that allows exchanging of data over a radio channel between over short distances at very high speed and low power consumption. UWB signals are short pulses the entire energy of which is distributed over a given wide region of the spectrum. With a sufficiently high total power transmitted over the air and with low power consumption and a pulsed nature of data transmission, a high data transmission rate can be obtained. This work has done interference analysis of ultra-wide bandwidth technologies (UWB) operating in the frequency band 7240-8240 MHz to the Earth monitoring and meteorological satellite systems that operate in this band. Taking into account the rapid development of users’ UWB devices in different frequency bands, the study tries to estimate the long-term impact of aggregate interference from UWB devices located around the satellite Earth stations. The study considers two satellite systems as an example of victim receivers. The UWB density assumptions made in the studies are based on the forecasts of CEPT and UWB Alliance.

This paper introduces an analog notch filtering-based coupling circuit for receivers in ultra-narrowband and narrowband power line communication systems, which are connected to low-voltage electric power grids. It is composed of a twin-T notch analog filter, which is responsible for imposing a significant attenuation on the main frequency (i.e., f0∈{50,60} Hz) in cascade with an elliptic low-pass analog filter, designed with a 3 dB cut-off frequency of fc≫f0. For f0=60 Hz and fc=2 MHz, the prototype of the analog notch filtering-based coupling circuit attains attenuation values of 22 dB and less than 2 dB at the main frequency and in the rest of the frequency bandwidth, respectively, when practical scenarios are considered. Lastly, it shows that the analog notch filtering-based coupling circuit is more effective than a typical capacitive coupling circuit when frequencies lower than 3 kHz are considered for data communication and sensing purposes.

Parabolic trough receivers are a kind of key components of a solar trough power plant, which absorb and transfer the high flux solar energy to the heat transfer fluid flowing in it. A Receiver Impedance Heating (RIH) method is put forward by analyzing the inadequacies of traditional methods. Voltage is imposed on both ends of the receiver and then the receiver is self-heated via a large electrical current flowing through it based on the Joule Effect. Once the receiver reaches a thermal equilibrium the product of voltage imposed on the receiver and electrical current flowing through the receiver is equal to the heat loss of the receiver to ambient environment at corresponding temperature difference of receiver temperature above ambient. The experiment system is simple, low-cost, and easy to operate. Experiment results show that curve of heat loss is smooth and measurement uncertainty is low, which means accuracy of the experiment results is high, while time period to reach a thermal equilibrium at every absorber temperature reduces to 2-3hours which is one fifth of that needed in traditional methods.

Abstract. Iterative channel decoders such as Turbo-Code and LDPC decoders show exceptional performance and therefore they are a part of many wireless communication receivers nowadays. These decoders require a soft input, i.e., the logarithmic likelihood ratio (LLR) of the received bits with a typical quantization of 4 to 6 bits. For computing the LLR values from a received complex symbol, a soft demapper is employed in the receiver. The implementation cost of traditional soft-output demapping methods is relatively large in high order modulation systems, and therefore low complexity demapping algorithms are indispensable in low power receivers. In the presence of multiple wireless communication standards where each standard defines multiple modulation schemes, there is a need to have an efficient demapper architecture covering all the flexibility requirements of these standards. Another challenge associated with hardware implementation of the demapper is to achieve a very high throughput in double iterative systems, for instance, MIMO and Code-Aided Synchronization. In this paper, we present a comprehensive communication and hardware performance evaluation of low complexity soft-output demapping algorithms to select the best algorithm for implementation. The main goal of this work is to design a high throughput, flexible, and area efficient architecture. We describe architectures to execute the investigated algorithms. We implement these architectures on a FPGA device to evaluate their hardware performance. The work has resulted in a hardware architecture based on the figured out best low complexity algorithm delivering a high throughput of 166 Msymbols/second for Gray mapped 16-QAM modulation on Virtex-5. This efficient architecture occupies only 127 slice registers, 248 slice LUTs and 2 DSP48Es.

The Ultra-Wideband Wireless Body Area Network (UWB-WBAN) has been identified to provide an efficient, low-power, and improved wireless communication between sensor nodes worn by the human body to monitor physiological signals. The first part of the UWB receiver is a low noise amplifier (LNA). This article describes an upgrade to a sort of balun LNA that is entirely transistor-based and devoid of inductors for medical worn communication service. The balun LNA uses common gate and a common source configuration which cancels the noise generated by the common gate. This work uses the transistors in place of resistors to minimize the integrated circuit's area, as well as finding the best values for the dimensions of the transistor to minimize energy consumption, achieve a high gain and good linearity. This reduces the noise figure. The designed system utilizes the UWB frequency range of 3-5 GHz and a voltage supply of 1.8V. The designed balun LNA is able to achieve a peak gain of 25.5 dB and noise figure (NF) less than 3.2-3.5 dB using 180µm TSMC CMOS technology. The IIP3 is quite high at 2 dBm, whereas the IIP2 maximum is 21 dBm. The entire power consumption is less than 7.2 mW.

Power line communication (PLC) system is an attractive technology for Smart Grid applications. One key benefit of PLC is its low installation cost because, in PLC technology, we do not need to install any extra cable to extend a network due to the accessibility to low voltage power network. Orthogonal frequency division multiplexing (OFDM) is widely used in PLC networks. Currently, Multiple Input Multiple Output (MIMO) technology is one of the processing techniques appropriate to PLC networks, allowing high data rate. In this work, the MIMO-OFDM system is established to provide better performance over the PLC system by providing communication links with substantial diversity and capacity. However, adapting MIMO to the PLC network involves solving several issues such as MIMO PLC channel modelling and optimisation of the modulation parameters. In this paper, we present measurements results of the transfer function and impulsive noise in the extended frequency range 2-100 MHz. In the simulation part, we evaluate the performance of the proposed receivers in 2×2 MIMO-PLC channels. It is shown that the minimum mean square error (MMSE) receiver can be one of the appropriate candidates for MIMO PLC channels due to its bite error rate (BER) characteristics under impulsive noise.

Radio astronomy in the decameter to centimeter wavelength range is facing new challenges because of man made interferences due to increasing needs in telecommunications. At the Radioastronomy department of Paris Meudon Observatory, we have been working since four years on high dynamic range digital receivers based on Digital Signal Processors (DSP). The first achievement is a digital spectro- polarimeter devoted to spectroscopy of astrophysical radiation in decameter range, now in operation at the Nancay Decameter array. The block diagram of the receiver includes a high dynamic range analogue section followed by a 12 bits analogue to digital converter. The digital part makes use of high power, programmable digital circuits for signal processing, arranged in a dedicated parallel architecture, able to compute in real time the power spectrum and the correlation of the input signals. This receiver was also used, as spectrometer backend, at Nancay decimetric radiotelescope and has performed very well in the presence of very strong interferences. We are presently working on a new digital receiver with broader bandwidth. The objective is 2 × 25 MHz band with at least 60 dB dynamic range. This new receiver will use additional computation power in order to recognise and avoid man made interferences which corrupt the radio astronomical signal. At the Nancay Radioastronomy Observatory, we have started to develop a new digital configurable receiver with 8 times 25 MHz band and ten thousand channels. For low frequency radioastronomy, direct spectrum computation technique is really powerful and offers new capabilities for real time interferences excision. Fig. 1 shows pulsar observations in the presence of interference made with the DSP receiver on the UTR-2 radiotelescope. Fig. 2 shows the effect of satellite interfernce on OH observations made with the Nancay telescope. Fig. 3 shows the block diagram of the DSP system and demonstrates how offline excision of interference in the frequency time-domain enables recovery of the signal. The final spectrum had 960 minutes integration on and off source and took 8045 minutes of procession on a 450 MHz Pentium II.

Abstract. A latitudinal-distributed network of GPS receivers has been operating within Colombia, Peru and Chile with sufficient latitudinal span to measure the absolute total electron content (TEC) at both crests of the equatorial anomaly. The network also provides the latitudinal extension of GPS scintillations and TEC depletions. The GPS-based information has been supplemented with density profiles collected with the Jicamarca digisonde and JULIA power maps to investigate the background conditions of the nighttime ionosphere that prevail during the formation and the persistence of plasma depletions. This paper presents case-study events in which the latitudinal extension of GPS scintillations, the maximum latitude of TEC depletion detections, and the altitude extension of radar plumes are correlated with the location and extension of the equatorial anomaly. Then it shows the combined statistics of GPS scintillations, TEC depletions, TEC latitudinal profiles, and bottomside density profiles collected between September 2001 and June 2002. It is demonstrated that multiple sights of TEC depletions from different stations can be used to estimate the drift of the background plasma, the tilt of the plasma plumes, and in some cases even the approximate time and location of the depletion onset. This study corroborates the fact that TEC depletions and radar plumes coincide with intense levels of GPS scintillations. Bottomside radar traces do not seem to be associated with GPS scintillations. It is demonstrated that scintillations/depletions can occur when the TEC latitude profiles are symmetric, asymmetric or highly asymmetric; this is during the absence of one crest. Comparison of the location of the northern crest of the equatorial anomaly and the maximum latitude of scintillations reveals that for 90% of the days, scintillations are confined within the boundaries of the 50% decay limit of the anomaly crests. The crests of the anomaly are the regions where the most intense GPS scintillations and the deepest TEC depletions are encountered. In accord with early results, we observe that GPS scintillations/TEC depletions mainly occur when the altitude of the magnetic equator F-region is above 500km. Nevertheless, in many instances GPS scintillations and TEC depletions are observed to exist when the F-layer is well below 500km or to persist when the F-layer undergoes its typical nighttime descent. Close inspection of the TEC profiles during scintillations/depletions events that occur when the equatorial F-layer peak is below 500km altitude reveals that on these occasions the ratio of the crest-to-equator TEC is above 2, and the crests are displaced 10° or more from the magnetic equator. When the equatorial F-layer is above 500km, neither of the two requirements is needed, as the flux tube seems to be inherently unstable. We discuss these findings in terms of the Rayleigh-Taylor instability (RTI) mechanism for flux-tube integrated quantities. We advance the idea that the seeming control that the reverse fountain effect exerts on inhibiting or suppressing GPS scintillations may be related to the redistribution of the density and plasma transport from the crests of the anomaly toward the equatorial region and then to much lower altitudes, and the simultaneous decrease of the F-region altitude. These two effects originate a decrease in the crest/trough ratio and a reduction of the crests separation, making the whole flux tube more stable to the RTI. The correspondence between crest separation, altitude of the equatorial F-region, the onset of depletions, and the altitude (latitude) extension of plumes (GPS scintillations) can be used to track the fate of the density structures.

Abstract. Multiple-Input-Multiple Output (MIMO) Synthetic Aperture Radar (SAR) along-track formations can be used to fraction the power resources into compact, lightweight and cost-effective satellites, or to extend the swath coverage beyond the limit provided by a small antenna. In this second case, the Pulse Repetition Frequency (PRF) is kept low by implementing an inversion that solves up to N−1 ambiguities, given N observations. The simultaneous illumination – that allows for the N² gain due to the coherent combination of the N transmitters and the N receivers, is analyzed and shown not to be critical, as the more than N=2 sensors are assumed. Performance is evaluated for the N=2 and N=3 cases and compared with the Single Input Multiple Output formations, where one sensor is transmitting, and all are receiving. Finally, the impact of the across-track deviation from the orbit is modeled and evaluated.

Low-invasive and battery-less implantable medical devices (IMDs) have been increasingly emerging in recent years. The developed solutions in the literature often concentrate on the Bidirectional Data-Link for long-term monitoring devices. Indeed, their ability to collect data and communicate them to the external world, namely Data Up-Link, has revealed a promising solution for bioelectronic medicine. Furthermore, the capacity to control organs such as the brain, nerves, heart-beat and gastrointestinal activities, made up through the manipulation of electrical transducers, could optimise therapeutic protocols and help patients’ pain relief. These kinds of stimulations come from the modulation of a powering signal generated from an externally placed unit coupled to the implanted receivers for power/data exchanging. The established communication is also defined as a Data Down-Link. In this framework, a new solution of the Binary Phase-Shift Keying (BPSK) demodulator is presented in this paper in order to design a robust, low-area, and low-power Down-Link for ultrasound (US)-powered IMDs. The implemented system is fully digital and PLL-free, thus reducing area occupation and making it fully synthesizable. Post-layout simulation results are reported using a 28 nm Bulk CMOS technology provided by TSMC. Using a 2 MHz carrier input signal and an implant depth of 1 cm, the data rate is up to 1.33 Mbit/s with a 50% duty cycle, while the minimum average power consumption is cut-down to 3.3 μW in the typical corner.

Wireless communication nowadays requires a system with reliable performance, efficient use of bandwidth, efficient power, and better coverage because it is in line with human needs for applications that require high and fast data rates. One of the concepts and methods to meet these needs is using an antenna technique with many transmitters and receivers or often called Multiple Input Multiple Output (MIMO), by adding a strategy at the time of delivery, namely the Space-Time Coding (STC) technique. In addition, the application of Orthogonal Frequency Division Multiplexing (OFDM) on MIMO-STC will more efficiently use bandwidth. The Space-Time Trellis Code (STTC) method is one of the diverse techniques in sending data with complex coding so that coding reinforcement is achieved and applied to the OFDM MIMO system. It is hoped that a system with reliable performance can be achieved. The simulation that is carried out presents the STTC and OFDM schemes on multi antennas (2 transmitters x 2 receivers) with a Combiner and Maximum Likelihood Sequence Estimator (MLSE) detection algorithm on the receiver. It is to get the quality of the sending signal in the performance analysis of Bit Error Rate (BER) with Signal to Noise Ratio (SNR). The simulation results are shown by modulation with M-array Phase Shift Keying (MPSK) and the number of symbols sent by giving different input parameter values. The results show that the number of carriers and the size of the Fast Fourier Transform (FFT) is large, and the modulation type with a small constellation produces a low BER and throughput at high SNR.

Nonlinear soft bit detection is essential for the uplink receivers of 5G base stations, especially for users around the cell edge. However, its throughput and computing complexity are always challenges for both research and industry. A low-cost and low-power parallel implementation of a soft-output detector based on sorted QR decomposition (SQRD) and the K-best breadth-first search algorithm is thus proposed to reduce computational complexity and latency. In addition, to save area and reduce latency, two improvement methods are used: (1) reduce the computing cost by saturating and truncating large values during PED computing and (2) reduce the sorting cost by using the binary bit sorting method for a reduced sample set with finite accuracy. Furthermore, a pipelined VLSI architecture is designed using 28-nm digital CMOS technology offered by Semiconductor Manufacturing International Corporation (SMIC). It can achieve a peak throughput of 6400 Mbps while consuming 153 K gates (including all flip-flops) for SMIC’s 28-nm technology and running at 800 MHz, a 32% cost reduction compared with the published reference design.

AbstractWireless sensors have the potential to provide significant insight into in situ physical and biogeochemical processes in sub-ice hydrologic systems. However, the nature of the glacial environment means that sensor deployment and data return is challenging. We describe two bespoke sensor platforms, electronic tracers or ‘ETracers’, and ‘cryoegg’, for untethered, wireless data collection from glacial hydrologic systems, including subglacial channels. Both employ radio frequencies for data transmission, are designed to endure harsh environmental conditions and can withstand low temperatures, high pressure, turbulence and abrasion. We discuss the design, optimization and field testing of the ETracers and cryoegg, culminating in test deployments beneath the Greenland ice sheet. The small, low-cost ETracers were able to travel through subglacial drainage channels, from where they returned water pressure measurements through 100 m of ice, and could measure water depth in crevasses. The larger cryoegg was able to return multi-parameter data from moulins through 500 m of wet ice to receivers up to 2 km away, and from 12 m depth in a proglacial lake to a receiver on the shore. The tests demonstrate that the cryoegg and ETracers are low-power, versatile, robust wireless sensor platforms suitable for glacial environments, which may be used with portable, low-cost receiving equipment.

Abstract We describe the first-season CO Mapping Array Project (COMAP) analysis pipeline that converts raw detector readouts to calibrated sky maps. This pipeline implements four main steps: gain calibration, filtering, data selection, and mapmaking. Absolute gain calibration relies on a combination of instrumental and astrophysical sources, while relative gain calibration exploits real-time total-power variations. High-efficiency filtering is achieved through spectroscopic common-mode rejection within and across receivers, resulting in nearly uncorrelated white noise within single-frequency channels. Consequently, near-optimal but biased maps are produced by binning the filtered time stream into pixelized maps; the corresponding signal bias transfer function is estimated through simulations. Data selection is performed automatically through a series of goodness-of-fit statistics, including χ 2 and multiscale correlation tests. Applying this pipeline to the first-season COMAP data, we produce a data set with very low levels of correlated noise. We find that one of our two scanning strategies (the Lissajous type) is sensitive to residual instrumental systematics. As a result, we no longer use this type of scan and exclude data taken this way from our Season 1 power spectrum estimates. We perform a careful analysis of our data processing and observing efficiencies and take account of planned improvements to estimate our future performance. Power spectrum results derived from the first-season COMAP maps are presented and discussed in companion papers.

Non-orthogonal multiple access schemes with grant free access have been recently highlighted as a prominent solution to meet the stringent requirements of massive machine-type communications (mMTCs). In particular, the multi-user shared access (MUSA) scheme has shown great potential to grant free access to the available resources. For the sake of simplicity, MUSA is generally conducted with the successive interference cancellation (SIC) receiver, which offers a low decoding complexity. However, this family of receivers requires sufficiently diversified received user powers in order to ensure the best performance and avoid the error propagation phenomenon. The power allocation has been considered as a complicated issue especially for a decentralized decision with a minimum signaling overhead. In this paper, we propose a novel algorithm for an autonomous power decision with a minimal overhead based on a tight approximation of the bit error probability (BEP) while considering the error propagation phenomenon. We investigate the efficiency of multi-armed bandit (MAB) approaches for this problem in two different reward scenarios: (i) in Scenario 1, each user reward only informs about whether its own packet was successfully transmitted or not; (ii) in Scenario 2, each user reward may carry information about the other interfering user packets. The performances of the proposed algorithm and the MAB techniques are compared in terms of the successful transmission rate. The simulation results prove that the MAB algorithms show a better performance in the second scenario compared to the first one. However, in both scenarios, the proposed algorithm outperforms the MAB techniques with a lower complexity at user equipment.

Direct conversion receiver (DCR) architecture is a promising candidate in the radio frequency (RF) front end because of its low power consumption, low cost and ease of integration. However, flicker noise and direct current (DC) offset are large issues. Owing to the local oscillator (LO) frequency, which is half of the RF frequency, and the absence of a DC bias current that introduces no flicker noise, the subharmonic passive mixer (SHPM) core topology front end overcomes the shortcoming effectively. When more and more receivers (RX) and transmitters (TX) are integrated into one chip, the linearity of the receiver front end becomes a very important performer that handles the TX and RX feedthrough. Another reason for the requirement of good linearity is the massive electromagnetic interference that exists in the atmosphere. This paper presents a linearity-improved RF front end with a feedforward body bias (FBB) subharmonic mixer core topology that satisfies modern RF front end demands. A novel complementary derivative superposition (DS) method is presented in low noise amplifier (LNA) design to cancel both the third- and second-order nonlinearities. To the best knowledge of the authors, this is the first time FBB technology is used in the SHPM core to improve linearity. A Volterra series is introduced to provide an analytical formula for the FBB of the SHPM core. The design was fabricated in a 0.13 μm complementary metal oxide semiconductor (CMOS) process with a chip area of 750 μm × 1270 μm. At a 2.4 GHz working frequency, the measurement result shows a conversion gain of 36 dB, double side band (DSB) noise figure (NF) of 6.8 dB, third-order intermodulation intercept point (IIP3) of 2 dBm, LO–RF isolation of 90 dB and 0.8 mW DC offset with 14.4 mW power consumption at 1.2 V supply voltage. These results exhibit better LO–RF feedthrough and DC offset, good gain and NF, moderate IIP3 and the highest figure of merit compared to the state-of-the-art publications.

The automatic modulation classification (AMC) is highly important to develop intelligent receivers in different military and civilian applications including signal intelligence, spectrum management, surveillance, signal confirmation, monitoring, interference identification, as well as counter channel jamming. Clearly, without knowing much information related to transmitted data and various indefinite parameters at receiver, like timing information, carrier frequency, signal power, phase offsets, and so on, the modulation’s blind identification has been a hard task in the real world situations with multi-path fading, frequency-selective in addition to the time-varying channels. There are 2 methods could be utilized to decide the classification signal technique: Feature-based (FB) approach and the Maximum likelihood functions (LB) method. With regard to the FB (referred to as pattern-recognition) classification method used in the study. In the presented work, thorough study is provided to find easy method to identify and classify the digital modulation signals at low SNRs. Spectral-based features, high-order statistic features, wavelet-based features, also cyclic features on the basis of cyclostationary typically utilized to determine and discriminate modulation types have been examined. The number of the classifiers which have been utilized in the process of discrimination have been studied thoroughly and compared for helping researchers in determining and finding the drawbacks with pattern-recognition according to past works. The presented study serving as guide with regard to studies of AMC for determining adequate algorithms and features.

Many Beidou navigation satellite system (BDS) receivers or boards provide dual-frequency measurements to conduct precise positioning and navigation for low-power consumption. Cycle-slip processing is a primary work to guarantee consistent, precise positioning with the phase data. However, the cycle-slip processing of BDS dual-frequency phases still follows with those of existing GPS methods. For single-satellite data, cycle-slip detection (CSD) with the geometry-free phase (GF) is disturbed by severe ionospheric delay variations, while CSD or cycle-slip repair (CSR) with the Melbourne–Wubbena combination (MW) must face the risk of the tremendous disturbance from large pseudorange errors. To overcome the above limitations, a new cycle-slip repair method for BDS dual-frequency phases (BDCSR) is proposed: (1) An optimal model to minimize the variance of the cycle-slip calculation was established to the dual-frequency BDS, after correcting the ionospheric variation with a reasonable and feasible way. (2) Under the BDS dual-frequency condition, a discrimination function was built to exclude the adverse disturbance from the pseudorange errors on the CSR, according to the rankings of the absolute epoch-difference GFs calculated by the searched cycle-slip candidates after correcting the ionospheric variation. Subsequently, many compared CSR tests were implemented in conditions of low and medium elevations during strong geomagnetic storms. Comparisons from the results of different methods show that: (1) The variations of ionospheric delays are intolerable in the cycle-slip calculation during the geomagnetic storm, and the tremendous influence from the ionospheric variation should be corrected before calculating the cycle-slip combination with the BDS dual-frequency data. (2) Under the condition of real dual-frequency BDS data during the geomagnetic storm, the actual success rate of the conventional dual-frequency CSR (CDCSR) by employing the optimized combinations, but absenting from the discrimination function, is lower than that of BDCSR by about 2%; The actual success rate of the CSD with MW (MWCSD), is lower than that of BDCSR by about 2%. (3) After adding gross errors of 0.7 m to all real epoch-difference pseudoranges epoch-by-epoch, results of CDCSR and MWCSD showed many errors. However, BDCSR achieved a higher actual success rate than those of CDCSR and MWCSD, about 43% and 16%, respectively, and better performance of refraining the disturbance of large pseudorange error on the cycle-slip determination was achieved in the BDCSR methodology.

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 207385, “Ultradeep LWD Electromagnetic Directional Resistivity for Waterflood Mapping: A Game Changer,” by Parmanand Thakur, SPE, Maniesh Singh, SPE, and Saif Al Arfi, ADNOC, et al. The paper has not been peer reviewed. _ Abu Dhabi’s thick Lower Cretaceous carbonate reservoirs experience injection water overriding oil. The water is held above the oil by negative capillary pressure until a horizontal borehole placed at the reservoir base creates a small pressure drawdown. This causes the water above to slump unpredictably toward the horizontal producer, increasing water cut and eventually killing the well under natural lift after a moderate amount of oil production. Water slumping is difficult to forecast using the reservoir model. This paper showcases the successful deployment of an ultradeep electromagnetic (EM) directional resistivity instrument to map injection-water movement. Ultradeep Electromagnetic Technology Two of the most-significant drivers of the depth to which an EM field will penetrate the formation are the spacing between transmitter and receiver antennas and the transmission frequencies. These can be modified at the tool-design stage and with ultradeep EM tools by placing the transmitter and receiver antenna on different drill collars. Modifying the bottomhole assembly (BHA) allows the spacing between the antennas to be optimized for reservoirs of differing thickness (Fig. 1). Increasing the transmitter-receiver spacing, coupled with decreasing the transmission frequency, generates an EM field that penetrates further into the formation and allows a greater depth of investigation. The transmitter is placed closest to the bit, with two receivers placed farther back in the BHA. To map reservoir units close to the wellbore in greater detail, the first receiver can be connected directly to the transmitter. To increase depth of investigation in thicker reservoirs, the spacing can be increased. The farther the receivers are placed from the transmitter, the greater the depth of detection. Lower frequencies are used by these tools in the range of 2–64 kHz. In low- to mid-range resistivities, the lower frequencies provide a greater depth of investigation but with lower spatial resolution. At higher resistivities, greater depths of detection can be achieved with the higher-frequency options. In one field example, using the lowest frequencies and a transmitter-to-receiver spacing of 133 ft, it was possible to identify resistivity boundaries up to 225 ft away from the well. Measurements from ultradeep azimuthal EM tools are pulsed to the surface as components of the EM field from multiple spacings for multiple frequencies. Inversion algorithms are used to convert this to a model representing the subsurface, depicting resistivity boundaries. The position of these boundaries can be tracked many feet from the wellbore and used to place the well in the optimal position during drilling. This technology can be used to map units that the well may never penetrate, such as the water zone in this case, which was anticipated to be approximately 80 ft above the well.

Abstract. Continuous and spatially distributed data of snow mass (water equivalent of snow cover, SWE) from automatic ground-based measurements are increasingly required for climate change studies and for hydrological applications (snow hydrological-model improvement and data assimilation). We present and compare four new-generation sensors, now commercialized, that are non-invasive and based on different radiations that interact with snow for SWE monitoring: cosmic-ray neutron probe (CRNP), gamma ray monitoring (GMON) scintillator, frequency-modulated continuous-wave radar (FMCW radar) at 24 GHz and global navigation satellite system (GNSS) receivers (GNSSr). All four techniques have relatively low power requirements, provide continuous and autonomous SWE measurements, and can be easily installed in remote areas. A performance assessment of their advantages, drawbacks and uncertainties is discussed from experimental comparisons and a literature review. Relative uncertainties are estimated to range between 9 % and 15 % when compared to manual in situ snow surveys that are also discussed. Results show the following. (1) CRNP can be operated in two modes of functioning: beneath the snow, it is the only system able to measure very deep snowpacks (> 2000 mm w.e.) with reasonable uncertainty across a wide range of measurements; CRNP placed above the snow allows for SWE measurements over a large footprint (∼ 20 ha) above a shallow snowpack. In both cases, CRNP needs ancillary atmospheric measurements for SWE retrieval. (2) GMON is the most mature instrument for snowpacks that are typically up to 800 mm w.e. Both CRNP (above snow) and GMON are sensitive to surface soil moisture. (3) FMCW radar needs auxiliary snow-depth measurements for SWE retrieval and is not recommended for automatic SWE monitoring (limited to dry snow). FMCW radar is very sensitive to wet snow, making it a very useful sensor for melt detection (e.g., wet avalanche forecasts). (4) GNSSr allows three key snowpack parameters to be estimated simultaneously: SWE (range: 0–1000 mm w.e.), snow depth and liquid water content, according to the retrieval algorithm that is used. Its low cost, compactness and low mass suggest a strong potential for GNSSr application in remote areas.

Numerous field acquisition examples and case studies have demonstrated the importance of recording, processing, and interpreting broadband land data. In most seismic acquisition surveys, three main objectives should be considered: (1) dense spatial source and receiver locations to achieve optimum subsurface illumination and wavefield sampling; (2) coverage of the full frequency spectrum, i.e., broadband acquisition; and (3) cost efficiency. Consequently, an effort has been made to improve the manufacturing of seismic vibratory sources by providing the ability to emit both lower (approximately 1.5 Hz) and higher frequencies (approximately 120 Hz) and of receivers by utilizing single, denser, and lighter digital sensors. All these developments achieve both operational (i.e., weight, optimized power consumption) and geophysical benefits (i.e., amplitude and phase response, vector fidelity, tilt detection). As part of the effort to reduce the acquisition cycle time, increase productivity, and improve seismic imaging and resolution while optimizing costs, a novel seismic acquisition survey was conducted employing 24 vibrators generating two different types of sweeps in a 3D unconstrained decentralized and dispersed source array field configuration. During this novel blended acquisition design, the crew reached a maximum of 65,000 vibrator points during 24 hours of continuous recording, which represents significantly higher productivity than a conventional seismic crew operating in the same area using a nonblended centralized source mode. Applying novel and newly developed deblending algorithms, high-resolution images were obtained. In addition, two data sets (i.e., low-frequency and medium-high-frequency sources) were merged to obtain full-bandwidth broadband seismic images. Data comparisons between the distributed blended and nonblended conventional surveys, acquired by the same crew during the same time over the same area, showed that the two data sets are very similar in the poststack and prestack domains.

The paper evaluates the possibilities of connecting and using publicly available Arduino GPS Gy-GPSV3 modules based on the Ublox NEO-M8N chip and GPS/GLONAS ATGM336H with the NMEA 0183 Protocol. Both modules are equipped with active antennas, are configured for GPS (USA), GLONASS (Russia) and Beidou (China) satellites and are close in terms of their declared technical characteristics. They perform their functions of tracking coordinates and calculating the primary parameters of the carrier’s movement quite satisfactorily, both in conditions of a favorable landscape, and in conditions of mountainous terrain and urban development. Relatively low power consumption (25-30 mA) and dimensions, easy connection allow them to be used in Autonomous monitoring systems. However, a stable accuracy of more than 10 m is achieved only if there is simultaneous communication with 10 satellites or more, and signal reception inside premises and other shielded objects is not provided. A real cold start lasts more than a minute. Setting the operating modes of the modules provides mainly only filtering of measurement errors in a given range of heights and speeds. Of these modules, GPS/GLONAS ATGM336H is in clear priority, since it is significantly ahead in accuracy, availability of command control, and cost (at the moment it is 3 times cheaper) at standard settings when using the same type of antenna, power supply, and dimensions. No significant impact of visible environment phenomena on the operation of GPS receivers used (communication with satellites) was recorded. At the same time, closely located or relatively powerful household radio frequency transmitters affect accuracy, reducing it by 2-3 times. Signal communication can be improved by using or adding a more powerful overall antenna, which in certain conditions will also allow you to capture satellites that are closer to the horizon. As a result, with such characteristics and capabilities, the considered GPS modules can be successfully used only for navigation purposes and for receiving accurate time signals (synchronization of measurements). Using them for the purpose of measuring physical quantities (for example, parameters of surface waves, level, flow velocity, etc.) with modern requirements for accuracy makes sense only for large-scale processes.

Terahertz electronics has been a topic of research and development for many years, motivated largely by the technological needs of the radio astronomy and remote sensing scientific communities. Over the past decade, however, this field has experienced dramatic growth and intense, renewed interest from academic researchers and federal agencies, as well as from industry. This interest has arisen, in part, from recent funding initiatives from the federal government (such as DARPA's Terahertz Electronics Program), but is also largely due to the establishment of a commercial infrastructure that has made test and measurement instrumentation available to the engineers and scientists working at these frequencies. Moreover, the emergence of CMOS as a potential submillimeter-wave device technology has greatly expanded access to this spectral region by providing circuit designers with a platform for realizing terahertz circuits without need for specialized fabrication facilities or processes. The recent and rapid progress in terahertz electronics has created a demand for improved approaches to packaging and integration, as well as a need for new measurement instrumentation for characterizing emerging terahertz devices. This paper focuses on two recent research developments aimed at addressing these needs and broadening the technology base for both terahertz system implementation and terahertz metrology. These developments include (1) the development of a direct-contact probe technology that permits on-wafer scattering-parameter characterization and measurement of planar integrated devices at frequencies to 1 THz and beyond, and (2) the establishment of processing technologies that permit fabrication of highly-integrated submillimeter-wave diode-based circuits, such as heterodyne receivers and frequency multipliers, that are based on heterogeneous integration of III-V semiconductor devices with thin silicon membranes as a support and integration substrate. The technical foundation for each of these efforts is micromachining of silicon that allow the formation of mechanically-robust and low-loss membrane carriers to support terahertz devices and circuitry. Two examples of heterogeneous integration with silicon as an approach to packaging terahertz components are detailed in this paper. These include development of micromachined probes for on-wafer measurements of devices and circuits in the WR-1.0 waveguide band (0.75 – 1.1 THz). The probe design concept will be presented and methods for characterizing the probe described. Measurements demonstrate that the probes exhibit an insertion loss of less than 7 dB and return loss of greater than 15 dB over 750—1100 GHz band, yielding the first demonstration of on-wafer probe operating above 1 THz. In addition, an example of heterogeneous integration/packaging of a submillimeter-wave frequency quadrupler operating at 160 GHz with efficiency of 30% and corresponding output power of 70 mW will be discussed. The quadrupler design includes two frequency doubler stages in cascade and is based on a balanced circuit architecture that addresses degradation issues often arising from impedance mismatches between multiplier stages. A unique quasi-vertical diode fabrication process consisting of transfer of GaAs epitaxy to the thin silicon support substrate is used to implement the quadrupler, resulting in an integrated drop-in chip module that incorporates 18 varactors, matching networks and beamleads for mounting.

PurposeA recent innovative technology used in wireless communication is recognized as multiple input multiple output (MIMO) communication system and became popular for quicker data transmission speed. This technology is being examined and implemented for the latest broadband wireless connectivity networks. Though high-capacity wireless channel is identified, there is still requirement of better techniques to get increased data transmission speed with acceptable reliability. There are two types of systems comprising of multi-antennas placed at transmitting and receiving sides, of which first is diversity technique and another is spatial multiplexing method. By making use of these diversity techniques, the reliability of transmitting signal can be improved. The fundamental method of the diversity is to transform wireless channel such as Rayleigh fading into steady additive white Gaussian noise (AWGN) channel which is devoid of any disastrous fading of the signal. The maximum transmission speed that can be achieved by spatial multiplexing methods is nearly equal to channel capacity of MIMO. Conversely, for diversity methods, the maximum speed of broadcasting is much lower than channel capacity of MIMO. With the advent of space–time block coding (STBC) antenna diversity technique, higher-speed data transmission is achievable for spatially multiplexed multiple input multiple output (SM-MIMO) system. At the receiving end, detection of the signal is a complex task for system which exhibits SM-MIMO. Additionally, a link modification method is implemented to decide appropriate coding and modulation scheme such as space diversity technique STBC to use two-way radio resources efficiently. The proposed work attempts to improve detection of signal at receiving end by employing STBC diversity technique for linear detection methods such as zero forcing (ZF), minimum mean square error (MMSE), ordered successive interference cancellation (OSIC) and maximum likelihood detection (MLD). The performance of MLD has been found to be better than other detection techniques.Design/methodology/approachAlamouti's STBC uses two transmit antennas regardless of the number of receiver antennas. The encoding and decoding operation of STBC is shown in the earlier cited diagram. In the following matrix, the rows of each coding scheme represent a different time instant, while the columns represent the transmitted symbols through each different antenna. In this case, the first and second rows represent the transmission at the first and second time instant, respectively. At a time t, the symbol s1 and symbol s2 are transmitted from antenna 1 and antenna 2, respectively. Assuming that each symbol has duration T, then at time t + T, the symbols –s2* and s1*, where (.)* denotes the complex conjugate, are transmitted from antenna 1 and antenna 2, respectively. Case of one receiver antenna: The reception and decoding of the signal depend on the number of receiver antennas available. For the case of one receiver antenna, the received signals are received at antenna 1 , hij is the channel transfer function from the jth transmit antenna and the ith receiver antenna, n1 is a complex random variable representing noise at antenna 1 and x (k) denotes x at time instant k ( at time t + (k – 1)T.FindingsThe results obtained for maximal ratio combining (MRC) with 1 × 4 scheme show that the BER curve drops to 10–4 for signal-to-noise (SNR) ratio of 10 dB, whereas for MRC 1 × 2 scheme, the BER drops down to 10–5 for SNR of 20 dB. Results obtained in Table 1 show that when STBC is employed for MRC with 1 × 2 scheme (one antenna at transmitter node and two antennas at receiver node), BER curve comes down to 0.0076 for Eb/N0 of 12. Similarly, when MRC with 1 × 4 antenna scheme is implemented, BER drops down to 0 for Eb/N0 of 12. Thus, it can be concluded from the obtained graph that the performance of MRC with STBC gives improved results. When STBC technique is used with 3 × 4 scheme, at SNR of 10 dB, BER comes nearer to 10–6 (figure 7.3). It can be concluded from the analytics observed between AWGN and Rayleigh fading channel that for AWGN channel, BER is found to be equal to 0 for SNR value of 13.5 dB, whereas for Rayleigh fading channel, BER is observed nearer to 10–3 for Eb/N0 = 15. Simulation results (in figure 7.2) from the analytics show BER drops to 0 for SNR value of 12 dB.Research limitations/implicationsOptimal design and successful deployment of high-performance wireless networks present a number of technical challenges. These include regulatory limits on useable radio-frequency spectrum and a complex time-varying propagation environment affected by fading and multipath. The effect of multipath fading in wireless systems can be reduced by using antenna diversity. Previous studies show the performance of transmit diversity with narrowband signals using linear equalization, decision feedback equalization, maximum likelihood sequence estimation (MLSE) and spread spectrum signals using a RAKE receiver. The available IC techniques compatible with STBC schemes at transmission require multiple antennas at the receiver. However, if this not a strong constraint at the base station level, it remains a challenge at the handset level due to cost and size limitation. For this reason, SAIC technique, alternative to complex ML multiuser demodulation technique, is still of interest for 4G wireless networks using the MIMO technology and STBC in particular. In a system with characteristics similar to the North American Digital mobile radio standard IS-54 (24.3 K symbols per sec. with an 81 Hz fading rate), adaptive retransmission with time deviation is not practical.Practical implicationsThe evaluation of performance in terms of bit error rate and convergence time which estimates that MLD technique outperforms in terms of received SNR and low decoding complexity. MLD technique performs well but when higher number of antennas are used, it requires more computational time and thereby resulting in increased hardware complexity. When MRC scheme is implemented for singe input single output (SISO) system, BER drops down to 10–2 for SNR of 20 dB. Therefore, when MIMO systems are employed for MRC scheme, improved results based on BER versus SNR are obtained and are used for detecting the signal; comparative study based on different techniques is done. Initially ZF detection method is utilized which was then modified to ZF with successive interference cancellation (ZFSIC). When successive interference cancellation scheme is employed for ZFSIC, better performance is observed as compared to the estimation of ML and MMSE. For 2 × 2 scheme with QPSK modulation method, ZFSIC requires more computational time as compared to ZF, MMSE and ML technique. From the obtained results, the conclusion is that ZFSIC gives the improved results as compared to ZF in terms of BER ratio. ZF-based decision statistics can be produced by the detection algorithm for a desired sub-stream from the received vector whichs consist of an interference which occurred from previous transmitted sub-streams. Consequently, a decision on the secondary stream is made and contribution of the noise is regenerated and subtracted from the vector received. With no involvement of interference cancellation, system performance gets reduced but computational cost is saved. While using cancellation, as H is deflated, coefficients of MMSE are recalculated at each iteration. When cancellation is not involved, the computation of MMSE coefficients is done only once, because of H remaining unchanged. For MMSE 4 × 4 BPSK scheme, bit error rate of 10–2 at 30 dB is observed. In general, the most thorough procedure of the detection algorithm is the computation of the MMSE coefficients. Complexity arises in the calculation of the MMSE coefficients, when the antennas at the transmitting side are increased. However, while implementing adaptive MMSE receivers on slow channel fading, it is probable to recover the signal with the complications being linear in the antennas of transmitter node. The performance of MMSE and successive interference cancellation of MMSE are observed for 2 × 2 and 4 × 4 BPSK and QPSK modulation schemes. The drawback of MMSE SIC scheme is that the first detected signal observes the noise interference from (NT-1) signals, while signals processed from every antenna later observe less noisy interference as the process of cancellation progresses. This difficulty could be overcome by using OSIC detection method which uses successive ordering of the processed layers in the decreasing power of the signal or by power allocation to the signal transmitted depending on the order of the processing. By using successive scheme, a computation of NT delay stages is desired to bring out the abandoned process. The work also includes comparison of BER with various modulation schemes and number of antennas involved while evaluating the performance. MLD determines the Euclidean distance among the vector signal received and result of all probable transmitted vector signals with the specified channel H and finds the one with the minimum distance. Estimated results show that higher order of the diversity is observed by employing more antennas at both the receiving and transmitting ends. MLD with 8 × 8 binary phase shift keying (BPSK) scheme offers bit error rate near to 10–4 for SNR (16 dB). By using Altamonti space ti.Social implicationsIt should come as no surprise that companies everywhere are pushing to get products to market faster. Missing a market window or a design cycle can be a major setback in a competitive environment. It should be equally clear that this pressure is coming at the same time that companies are pushing towards “leaner” organizations that can do more with less. The trends mentioned earlier are not well supported by current test and measurement equipment, given this increasingly high-pressure design environment: in order to measure signals across multiple domains, multiple pieces of measurement equipment are needed, increasing capital or rental expenses. The methods available for making cross-domain, time-correlated measurements are inefficient, reducing engineering efficiency. When only used on occasion, the learning curve to understand how to use equipment for logic analysis, time domain and RF spectrum measurements often requires an operator to re-learn each piece of separate equipment. The equipment needed to measure wide bandwidth, time-varying spectral signals is expensive, again increasing capital or rental expenses. What is needed is a measurement instrument with a common user interface that integrates multiple measurement capabilities into a single cost-effective tool that can efficiently measure signals in the current wide-bandwidth, time-correlated, cross-domain environments. The market of wireless communication using STBCs has large scope of expansion in India. Therefore, the proposed work has techno-commercial potential and the product can be patented. This project shall in turn be helpful for remote areas of the nearby region particularly in Gadchiroli district and Melghat Tiger reserve project of Amravati district, Nagjira and so on where electricity is not available and there is an all the time problem of coverage in getting the network. In some regions where electricity is available, the shortage is such that they cannot use it for peak hours. In such cases, stand-alone space diversity technique, STBC shall help them to meet their requirements in making connection during coverage problem, thereby giving higher data transmission rates with better QOS (quality of service) with least dropped connections. This trend towards wireless everywhere is causing a profound change in the responsibilities of embedded designers as they struggle to incorporate unfamiliar RF technology into their designs. Embedded designers frequently find themselves needing to solve problems without the proper equipment needed to perform the tasks.Originality/valueWork is original.

Few studies have focused on how power influences an idea receiver's endorsement of creative ideas. By integrating associative evaluation theory with insights from the power literature, we identify power as an important receivers’ factor that accentuates the relation between an idea's creativity level and receivers’ endorsement. We contend that the idea generator's status is a boundary condition and, together with creativity level, the idea generator's status jointly influences the degree to which idea receivers’ power affects idea endorsement. We conducted four studies to test our hypotheses. Study 1 was a laboratory experiment. It found a two-way interaction of receiver power and creativity level, showing that compared to low-power receivers, high-power receivers expressed stronger endorsement of ideas with high levels of creativity. Study 2 was a field study in a manufacturing company. It replicated Study 1's findings and further found a three-way interaction showing that the moderating effect of receiver power was strengthened when the generator had higher rather than lower status. Studies 3 and 4 respectively replicated the two-way and three-way interactions using experiments and demonstrated positive associations as the theorized mediator, providing empirical support for the positive association account. We discuss implications of these studies and call for future research to deepen our understanding of how creative ideas are endorsed in the workplace.

AbstractWe present a miniaturized quantum key distribution system, designed to augment the more mature quantum key distribution systems currently commercially available. Our device is designed for the consumer market, and so size, weight and power are more important than raw performance. To achieve our form factor, the transmitter is handheld and the receiver is a larger fixed terminal. We envisage users would bring their transmitters to centrally located receivers and exchange keys which they could use at a later point. Transmitting qubits at 80 MHz, the peak key rate is in excess of 20 kbps. The transmitter device fits within an envelope of <150 ml, weighs 65 g and consumes 3.15 W of power.

Nowadays, indoor localization systems using IEEE 802.11 have been actively explored for location-based services, since GPS cannot identify floors or rooms in buildings. However, the user-side device is usually large and consumes high energy. In this paper, the authors propose a fingerprint-based indoor localization system using IEEE 802.15.4 that allows the use of a small device with a long-life battery, named FILS15.4. A user carries a small transmitter whose signal is received by multiple receivers simultaneously. The received signal strengths are compared with the fingerprints to find the current location. To address signal fluctuations caused by the low-power narrow-band signal, FILS15.4 limits one room as the localization unit, prepares plural fingerprints for each room, and allocates a sufficient number of receivers in the field. For evaluations, extensive experiments were conducted at #2 Engineering Building in Okayama University and confirmed high detection accuracy with sufficient numbers of receivers and fingerprints.

Concentrated solar power (CSP) plants have the potential to reduce the consumption of nonrenewable resources and greenhouse gas emissions in electricity production. In CSP systems, a field of heliostats focuses solar radiation on a central receiver, and energy is then transferred to a thermal power plant at high temperature. However, maximum receiver surface fluxes are low (30–100 W cm−2) with high thermal losses, which has contributed to the limited market penetration of CSP systems. Recently, small (∼4 cm2), laminated micro pin-fin devices have shown potential to achieve concentrated surface fluxes over 100 W cm−2 using supercritical CO2 as the working fluid. The present study explores the feasibility of using these microscale unit cells as building blocks for a megawatt-scale (250 MW thermal) open solar receiver through a numbering-up approach, where multiple microscale unit cell devices are connected in parallel. A multiscale model of the full-scale central receiver is developed. The model consists of interconnected unit cell and module level (i.e., multiple unit cells in parallel) submodels which predict local performance of the central receiver. Each full-scale receiver consists of 3000 micro pin-fin unit cells divided into 250 modules. The performance of three different full-scale receivers is simulated under representative operating conditions. The results show that the microscale unit cells have the potential to be numbered up to megawatt applications while providing high heat flux and thermal efficiency. At the design incident flux and surface emissivity, a global receiver efficiency of approximately 90% when heating sCO2 from 550 °C to 650 °C at an average incident flux of 110 W cm−2 can be achieved.

AbstractA spectrogram of Power Line Harmonic Radiation (PLHR) consists of a set of lines with frequency spacing corresponding exactly to 50 or 60 Hz. It is distinct from a spectrogram of Magnetospheric Line Radiation (MLR) where the lines are not equidistant and drift in frequency. PLHR and MLR propagate in the ionosphere and the magnetosphere and are recorded by ground experiments and satellites. If the source of PLHR is evident, the origin of the MLR is still under debate and the purpose of this paper is to understand how MLR lines are formed. The ELF waves triggered by High-frequency Active Auroral Research Program (HAARP) in the ionosphere are used to simulate lines (pulses of different lengths and different frequencies). Several receivers are utilized to survey the propagation of these pulses. The resulting waves are simultaneously recorded by ground-based experiments close to HAARP in Alaska, and by the low-altitude satellite DEMETER either above HAARP or its magnetically conjugate point. Six cases are presented which show that 2-hop echoes (pulses going back and forth in the magnetosphere) are very often observed. The pulses emitted by HAARP return in the Northern hemisphere with a time delay. A detailed spectral analysis shows that sidebands can be triggered and create elements with superposed frequency lines which drift in frequency during the propagation. These elements acting like quasi-periodic emissions are subjected to equatorial amplification and can trigger hooks and falling tones. At the end all these known physical processes lead to the formation of the observed MLR by HAARP pulses. It is shown that there is a tendency for the MLR frequencies of occurrence to be around 2 kHz although the exciting waves have been emitted at lower and higher frequencies. Graphical Abstract

Every act of art is able to reveal, balance and revive the relations between a territory and its inhabitants (François Davin, Southern Forest Sculpture Walk Catalogue)Introducing the Understory Art in Nature TrailIn February 2015, a colossal wildfire destroyed 98,300 hectares of farm and bushland surrounding the town of Northcliffe, located 365 km south of Perth, Western Australia (WA). As the largest fire in the recorded history of the southwest region (Southern Forest Arts, After the Burn 8), the disaster attracted national attention however the extraordinary contribution of local knowledge in saving a town considered by authorities to be “undefendable” (Kennedy) is yet to be widely appreciated. In accounting for a creative scene that survived the conflagration, this case study sees culture mobilised as a socioeconomic resource for conservation and the healing of community spirit.Northcliffe (population 850) sits on a coastal plain that hosts majestic old-growth forest and lush bushland. In 2006, Southern Forest Arts (SFA) dedicated a Southern Forest Sculpture Walk for creative professionals to develop artworks along a 1.2 km walk trail through pristine native forest. It was re-branded “Understory—Art in Nature” in 2009; then “Understory Art in Nature Trail” in 2015, the understory vegetation layer beneath the canopy being symbolic of Northcliffe’s deeply layered caché of memories, including “the awe, love, fear, and even the hatred that these trees have provoked among the settlers” (Davin in SFA Catalogue). In the words of the SFA Trailguide, “Every place (no matter how small) has ‘understories’—secrets, songs, dreams—that help us connect with the spirit of place.”In the view of forest arts ecologist Kumi Kato, “It is a sense of place that underlies the commitment to a place’s conservation by its community, broadly embracing those who identify with the place for various reasons, both geographical and conceptual” (149). In bioregional terms such communities form a terrain of consciousness (Berg and Dasmann 218), extending responsibility for conservation across cultures, time and space (Kato 150). A sustainable thematic of place must also include livelihood as the third party between culture and nature that establishes the relationship between them (Giblett 240). With these concepts in mind I gauge creative impact on forest as place, and, in turn, (altered) forest’s impact on people. My abstraction of physical place is inclusive of humankind moving in dialogic engagement with forest. A mapping of Understory’s creative activities sheds light on how artists express physical environments in situated creative practices, clusters, and networks. These, it is argued, constitute unique types of community operating within (and beyond) a foundational scene of inspiration and mystification that is metaphorically “rising from the ashes.” In transcending disconnectedness between humankind and landscape, Understory may be understood to both culturalise nature (as an aesthetic system), and naturalise culture (as an ecologically modelled system), to build on a trope introduced by Feld (199). Arguably when the bush is cultured in this way it attracts consumers who may otherwise disconnect from nature.The trail (henceforth Understory) broaches the histories of human relations with Northcliffe’s natural systems of place. Sub-groups of the Noongar nation have inhabited the southwest for an estimated 50,000 years and their association with the Northcliffe region extends back at least 6,000 years (SFA Catalogue; see also Crawford and Crawford). An indigenous sense of the spirit of forest is manifest in Understory sculpture, literature, and—for the purpose of this article—the compilation CD Canopy: Songs for the Southern Forests (henceforth Canopy, Figure 1).As a cultural and environmental construction of place, Canopy sustains the land with acts of seeing, listening to, and interpreting nature; of remembering indigenous people in the forest; and of recalling the hardships of the early settlers. I acknowledge SFA coordinator and Understory custodian Fiona Sinclair for authorising this investigation; Peter Hill for conservation conversations; Robyn Johnston for her Canopy CD sleeve notes; Della Rae Morrison for permissions; and David Pye for discussions. Figure 1. Canopy: Songs for the Southern Forests (CD, 2006). Cover image by Raku Pitt, 2002. Courtesy Southern Forest Arts, Northcliffe, WA.Forest Ecology, Emotion, and ActionEstablished in 1924, Northcliffe’s ill-founded Group Settlement Scheme resulted in frontier hardship and heartbreak, and deforestation of the southwest region for little economic return. An historic forest controversy (1992-2001) attracted media to Northcliffe when protesters attempting to disrupt logging chained themselves to tree trunks and suspended themselves from branches. The signing of the Western Australian Regional Forest Agreement in 1999 was followed, in 2001, by deregulation of the dairy industry and a sharp decline in area population.Moved by the gravity of this situation, Fiona Sinclair won her pitch to the Manjimup Council for a sound alternative industry for Northcliffe with projections of jobs: a forest where artists could work collectively and sustainably to reveal the beauty of natural dimensions. A 12-acre pocket of allocated Crown Land adjacent to the town was leased as an A-Class Reserve vested for Education and Recreation, for which SFA secured unified community ownership and grants. Conservation protocols stipulated that no biomass could be removed from the forest and that predominantly raw, natural materials were to be used (F. Sinclair and P. Hill, personal interview, 26 Sep. 2014). With forest as prescribed image (wider than the bounded chunk of earth), Sinclair invited the artists to consider the themes of spirituality, creativity, history, dichotomy, and sensory as a basis for work that was to be “fresh, intimate, and grounded in place.” Her brief encouraged artists to work with humanity and imagination to counteract residual community divisiveness and resentment. Sinclair describes this form of implicit environmentalism as an “around the back” approach that avoids lapsing into political commentary or judgement: “The trail is a love letter from those of us who live here to our visitors, to connect with grace” (F. Sinclair, telephone interview, 6 Apr. 2014). Renewing community connections to local place is essential if our lives and societies are to become more sustainable (Pedelty 128). To define Northcliffe’s new community phase, artists respected differing associations between people and forest. A structure on a karri tree by Indigenous artist Norma MacDonald presents an Aboriginal man standing tall and proud on a rock to become one with the tree and the forest: as it was for thousands of years before European settlement (MacDonald in SFA Catalogue). As Feld observes, “It is the stabilizing persistence of place as a container of experiences that contributes so powerfully to its intrinsic memorability” (201).Adhering to the philosophy that nature should not be used or abused for the sake of art, the works resonate with the biorhythms of the forest, e.g. functional seats and shelters and a cascading retainer that directs rainwater back to the resident fauna. Some sculptures function as receivers for picking up wavelengths of ancient forest. Forest Folk lurk around the understory, while mysterious stone art represents a life-shaping force of planet history. To represent the reality of bushfire, Natalie Williamson’s sculpture wraps itself around a burnt-out stump. The work plays with scale as small native sundew flowers are enlarged and a subtle beauty, easily overlooked, becomes apparent (Figure 2). The sculptor hopes that “spiders will spin their webs about it, incorporating it into the landscape” (SFA Catalogue).Figure 2. Sundew. Sculpture by Natalie Williamson, 2006. Understory Art in Nature Trail, Northcliffe, WA. Image by the author, 2014.Memory is naturally place-oriented or at least place-supported (Feld 201). Topaesthesia (sense of place) denotes movement that connects our biography with our route. This is resonant for the experience of regional character, including the tactile, olfactory, gustatory, visual, and auditory qualities of a place (Ryan 307). By walking, we are in a dialogue with the environment; both literally and figuratively, we re-situate ourselves into our story (Schine 100). For example, during a summer exploration of the trail (5 Jan. 2014), I intuited a personal attachment based on my grandfather’s small bush home being razed by fire, and his struggle to support seven children.Understory’s survival depends on vigilant controlled (cool) burns around its perimeter (Figure 3), organised by volunteer Peter Hill. These burns also hone the forest. On 27 Sept. 2014, the charred vegetation spoke a spring language of opportunity for nature to reassert itself as seedpods burst and continue the cycle; while an autumn walk (17 Mar. 2016) yielded a fresh view of forest colour, patterning, light, shade, and sound.Figure 3. Understory Art in Nature Trail. Map Created by Fiona Sinclair for Southern Forest Sculpture Walk Catalogue (2006). Courtesy Southern Forest Arts, Northcliffe, WA.Understory and the Melody of CanopyForest resilience is celebrated in five MP3 audio tours produced for visitors to dialogue with the trail in sensory contexts of music, poetry, sculptures and stories that name or interpret the setting. The trail starts in heathland and includes three creek crossings. A zone of acacias gives way to stands of the southwest signature trees karri (Eucalyptus diversicolor), jarrah (Eucalyptus marginata), and marri (Corymbia calophylla). Following a sheoak grove, a riverine environment re-enters heathland. Birds, insects, mammals, and reptiles reside around and between the sculptures, rendering the earth-embedded art a fusion of human and natural orders (concept after Relph 141). On Audio Tour 3, Songs for the Southern Forests, the musician-composers reflect on their regionally focused items, each having been birthed according to a personal musical concept (the manner in which an individual artist holds the totality of a composition in cultural context). Arguably the music in question, its composers, performers, audiences, and settings, all have a role to play in defining the processes and effects of forest arts ecology. Local musician Ann Rice billeted a cluster of musicians (mostly from Perth) at her Windy Harbour shack. The energy of the production experience was palpable as all participated in on-site forest workshops, and supported each other’s items as a musical collective (A. Rice, telephone interview, 2 Oct. 2014). Collaborating under producer Lee Buddle’s direction, they orchestrated rich timbres (tone colours) to evoke different musical atmospheres (Table 1). Composer/Performer Title of TrackInstrumentation1. Ann RiceMy Placevocals/guitars/accordion 2. David PyeCicadan Rhythmsangklung/violin/cello/woodblocks/temple blocks/clarinet/tapes 3. Mel RobinsonSheltervocal/cello/double bass 4. DjivaNgank Boodjakvocals/acoustic, electric and slide guitars/drums/percussion 5. Cathie TraversLamentaccordion/vocals/guitar/piano/violin/drums/programming 6. Brendon Humphries and Kevin SmithWhen the Wind First Blewvocals/guitars/dobro/drums/piano/percussion 7. Libby HammerThe Gladevocal/guitar/soprano sax/cello/double bass/drums 8. Pete and Dave JeavonsSanctuaryguitars/percussion/talking drum/cowbell/soprano sax 9. Tomás FordWhite Hazevocal/programming/guitar 10. David HyamsAwakening /Shaking the Tree /When the Light Comes guitar/mandolin/dobro/bodhran/rainstick/cello/accordion/flute 11. Bernard CarneyThe Destiny Waltzvocal/guitar/accordion/drums/recording of The Destiny Waltz 12. Joel BarkerSomething for Everyonevocal/guitars/percussion Table 1. Music Composed for Canopy: Songs for the Southern Forests.Source: CD sleeve and http://www.understory.com.au/art.php. Composing out of their own strengths, the musicians transformed the geographic region into a living myth. As Pedelty has observed of similar musicians, “their sounds resonate because they so profoundly reflect our living sense of place” (83-84). The remainder of this essay evidences the capacity of indigenous song, art music, electronica, folk, and jazz-blues to celebrate, historicise, or re-imagine place. Firstly, two items represent the phenomenological approach of site-specific sensitivity to acoustic, biological, and cultural presence/loss, including the materiality of forest as a living process.“Singing Up the Land”In Aboriginal Australia “there is no place that has not been imaginatively grasped through song, dance and design, no place where traditional owners cannot see the imprint of sacred creation” (Rose 18). Canopy’s part-Noongar language song thus repositions the ancient Murrum-Noongar people within their life-sustaining natural habitat and spiritual landscape.Noongar Yorga woman Della Rae Morrison of the Bibbulmun and Wilman nations co-founded The Western Australian Nuclear Free Alliance to campaign against the uranium mining industry threatening Ngank Boodjak (her country, “Mother Earth”) (D.R. Morrison, e-mail, 15 July 2014). In 2004, Morrison formed the duo Djiva (meaning seed power or life force) with Jessie Lloyd, a Murri woman of the Guugu Yimidhirr Nation from North Queensland. After discerning the fundamental qualities of the Understory site, Djiva created the song Ngank Boodjak: “This was inspired by walking the trail […] feeling the energy of the land and the beautiful trees and hearing the birds. When I find a spot that I love, I try to feel out the lay-lines, which feel like vortexes of energy coming out of the ground; it’s pretty amazing” (Morrison in SFA Canopy sleeve) Stanza 1 points to the possibilities of being more fully “in country”:Ssh!Ni dabarkarn kooliny, ngank boodja kookoorninyListen, walk slowly, beautiful Mother EarthThe inclusion of indigenous language powerfully implements an indigenous interpretation of forest: “My elders believe that when we leave this life from our physical bodies that our spirit is earthbound and is living in the rocks or the trees and if you listen carefully you might hear their voices and maybe you will get some answers to your questions” (Morrison in SFA Catalogue).Cicadan Rhythms, by composer David Pye, echoes forest as a lively “more-than-human” world. Pye took his cue from the ambient pulsing of male cicadas communicating in plenum (full assembly) by means of airborne sound. The species were sounding together in tempo with individual rhythm patterns that interlocked to create one fantastic rhythm (Australian Broadcasting Corporation, Composer David Pye). The cicada chorus (the loudest known lovesong in the insect world) is the unique summer soundmark (term coined by Truax Handbook, Website) of the southern forests. Pye chased various cicadas through Understory until he was able to notate the rhythms of some individuals in a patch of low-lying scrub.To simulate cicada clicking, the composer set pointillist patterns for Indonesian anklung (joint bamboo tubes suspended within a frame to produce notes when the frame is shaken or tapped). Using instruments made of wood to enhance the rich forest imagery, Pye created all parts using sampled instrumental sounds placed against layers of pre-recorded ambient sounds (D. Pye, telephone interview, 3 Sept. 2014). He takes the listener through a “geographical linear representation” of the trail: “I walked around it with a stopwatch and noted how long it took to get through each section of the forest, and that became the musical timing of the various parts of the work” (Pye in SFA Canopy sleeve). That Understory is a place where reciprocity between nature and culture thrives is, likewise, evident in the remaining tracks.Musicalising Forest History and EnvironmentThree tracks distinguish Canopy as an integrative site for memory. Bernard Carney’s waltz honours the Group Settlers who battled insurmountable terrain without any idea of their destiny, men who, having migrated with a promise of owning their own dairy farms, had to clear trees bare-handedly and build furniture from kerosene tins and gelignite cases. Carney illuminates the culture of Saturday night dancing in the schoolroom to popular tunes like The Destiny Waltz (performed on the Titanic in 1912). His original song fades to strains of the Victor Military Band (1914), to “pay tribute to the era where the inspiration of the song came from” (Carney in SFA Canopy sleeve). Likewise Cathie Travers’s Lament is an evocation of remote settler history that creates a “feeling of being in another location, other timezone, almost like an endless loop” (Travers in SFA Canopy sleeve).An instrumental medley by David Hyams opens with Awakening: the morning sun streaming through tall trees, and the nostalgic sound of an accordion waltz. Shaking the Tree, an Irish jig, recalls humankind’s struggle with forest and the forces of nature. A final title, When the Light Comes, defers to the saying by conservationist John Muir that “The wrongs done to trees, wrongs of every sort, are done in the darkness of ignorance and unbelief, for when the light comes the heart of the people is always right” (quoted by Hyams in SFA Canopy sleeve). Local musician Joel Barker wrote Something for Everyone to personify the old-growth karri as a king with a crown, with “wisdom in his bones.”Kevin Smith’s father was born in Northcliffe in 1924. He and Brendon Humphries fantasise the untouchability of a maiden (pre-human) moment in a forest in their song, When the Wind First Blew. In Libby Hammer’s The Glade (a lover’s lament), instrumental timbres project their own affective languages. The jazz singer intended the accompanying double bass to speak resonantly of old-growth forest; the cello to express suppleness and renewal; a soprano saxophone to impersonate a bird; and the drums to imitate the insect community’s polyrhythmic undercurrent (after Hammer in SFA Canopy sleeve).A hybrid aural environment of synthetic and natural forest sounds contrasts collision with harmony in Sanctuary. The Jeavons Brothers sampled rustling wind on nearby Mt Chudalup to absorb into the track’s opening, and crafted a snare groove for the quirky eco-jazz/trip-hop by banging logs together, and banging rocks against logs. This imaginative use of percussive found objects enhanced their portrayal of forest as “a living, breathing entity.”In dealing with recent history in My Place, Ann Rice cameos a happy childhood growing up on a southwest farm, “damming creeks, climbing trees, breaking bones and skinning knees.” The rich string harmonies of Mel Robinson’s Shelter sculpt the shifting environment of a brewing storm, while White Haze by Tomás Ford describes a smoky controlled burn as “a kind of metaphor for the beautiful mystical healing nature of Northcliffe”: Someone’s burning off the scrubSomeone’s making sure it’s safeSomeone’s whiting out the fearSomeone’s letting me breathe clearAs Sinclair illuminates in a post-fire interview with Sharon Kennedy (Website):When your map, your personal map of life involves a place, and then you think that that place might be gone…” Fiona doesn't finish the sentence. “We all had to face the fact that our little place might disappear." Ultimately, only one house was lost. Pasture and fences, sheds and forest are gone. Yet, says Fiona, “We still have our town. As part of SFA’s ongoing commission, forest rhythm workshops explore different sound properties of potential materials for installing sound sculptures mimicking the surrounding flora and fauna. In 2015, SFA mounted After the Burn (a touring photographic exhibition) and Out of the Ashes (paintings and woodwork featuring ash, charcoal, and resin) (SFA, After the Burn 116). The forthcoming community project Rising From the Ashes will commemorate the fire and allow residents to connect and create as they heal and move forward—ten years on from the foundation of Understory.ConclusionThe Understory Art in Nature Trail stimulates curiosity. It clearly illustrates links between place-based social, economic and material conditions and creative practices and products within a forest that has both given shelter and “done people in.” The trail is an experimental field, a transformative locus in which dedicated physical space frees artists to culturalise forest through varied aesthetic modalities. Conversely, forest possesses agency for naturalising art as a symbol of place. Djiva’s song Ngank Boodjak “sings up the land” to revitalise the timelessness of prior occupation, while David Pye’s Cicadan Rhythms foregrounds the seasonal cycle of entomological music.In drawing out the richness and significance of place, the ecologically inspired album Canopy suggests that the community identity of a forested place may be informed by cultural, economic, geographical, and historical factors as well as endemic flora and fauna. Finally, the musical representation of place is not contingent upon blatant forms of environmentalism. The portrayals of Northcliffe respectfully associate Western Australian people and forests, yet as a place, the town has become an enduring icon for the plight of the Universal Old-growth Forest in all its natural glory, diverse human uses, and (real or perceived) abuses.ReferencesAustralian Broadcasting Commission. “Canopy: Songs for the Southern Forests.” Into the Music. Prod. Robyn Johnston. Radio National, 5 May 2007. 12 Aug. 2014 <http://www.abc.net.au/radionational/programs/intothemusic/canopy-songs-for-the-southern-forests/3396338>.———. “Composer David Pye.” Interview with Andrew Ford. The Music Show, Radio National, 12 Sep. 2009. 30 Jan. 2015 <http://canadapodcasts.ca/podcasts/MusicShowThe/1225021>.Berg, Peter, and Raymond Dasmann. “Reinhabiting California.” Reinhabiting a Separate Country: A Bioregional Anthology of Northern California. Ed. Peter Berg. San Francisco: Planet Drum, 1978. 217-20.Crawford, Patricia, and Ian Crawford. 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