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1
Torfs, D., J. De Schutter i J. Swevers. "Extended Bandwidth Zero Phase Error Tracking Control of Nonminimal Phase Systems". Journal of Dynamic Systems, Measurement, and Control 114, nr 3 (1.09.1992): 347–51. http://dx.doi.org/10.1115/1.2897354.
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This paper describes a new feedforward algorithm for accurate tracking control of nonminimal phase systems. Accurate feedforward calculation involves a prefilter design using the inverse system model. Nonminimal phase systems cause problems with this prefilter design, because unstable zeros become unstable poles in the inverse model. The zero phase error tracking control algorithm (ZPETC) consists of a substitution scheme, which removes the unstable zeros. This scheme introduces a small gain error, which increases with frequency, but no phase error. This paper investigates additional properties which give more insight into the ZPETC algorithm, and allow to improve it. The improved algorithm is based on the same substitution scheme as ZPETC, but adds additional feedforward terms to compensate for the gain error. These additional terms increase the frequency range for which the overall transfer function has only limited gain error, without introducing phase errors. The additional feedforward terms repeatedly reduce the tracking error proportional to ε2, ε4, ε6, …, where ε is the ZPETC tracking error. The new feedforward algorithm or new substitution scheme is therefore called “extended bandwidth zero phase error tracking control algorithm” (EBZPETC). Experimental results on a one-link flexible robot compares both methods.
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Huang, Yi Cheng, Shu Ting Li i Kuan Heng Peng. "Precision Motion of Iterative Learning Controller Using Adaptive Filter Bandwidth Tuning by Improved Particle Swarm Optimization Technique". Applied Mechanics and Materials 376 (sierpień 2013): 349–53. http://dx.doi.org/10.4028/www.scientific.net/amm.376.349.
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This paper utilized the Improved Particle Swarm Optimization (IPSO) technique for adjusting the gains of PID and the bandwidth of zero-phase Butterworth Filter of an Iterative Learning Controller (ILC) for precision motion. Simulation results show that IPSO-ILC-PID controller without adaptive bandwidth filter tuning have the chance of producing high frequencies in the error signals when the filter bandwidth is fixed for every repetition. However the learnable and unlearnable error signals should be separated for bettering control process. Thus the adaptive bandwidth of a zero phase filter in ILC-PID controller with IPSO tuning is applied to one single motion axis of a CNC table machine. Simulation results show that the developed controller can cancel the errors efficiently as repetition goes. The frequency response of the error signals is analyzed by the empirical mode decomposition (EMD) and the Hilbert-Huang Transform (HHT) method. Errors are reduced and validated by ILC with adaptive bandwidth filtering design.
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Zhao, Lei, Lei Shi i Congying Zhu. "New Nonlinear Second-Order Phase-Locked Loop with Adaptive Bandwidth Regulation". Electronics 7, nr 12 (23.11.2018): 346. http://dx.doi.org/10.3390/electronics7120346.
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Synchronization of large acquisition bandwidth brings great challenges to the traditional second-order phase-locked loop (PLL). To address the contradiction between acquisition bandwidth and noise suppression capability of the traditional PLL, a new second-order PLL coupled with a nonlinear element is proposed. The proposed nonlinear second-order PLL regulates the loop noise bandwidth adaptively by the nonlinear module. When a large input–output phase error occurs, this PLL reduces the frequency offset quickly by taking advantage of the large bandwidth. When the phase error is reduced by the loop control, the proposed PLL suppresses noises by using the small bandwidth to increase the tracking accuracy. Simulation results demonstrate that the tracking speed of the proposed PLL is increased considerably, and its acquisition bandwidth is increased to 18.8 kHz compared with that of the traditional second-order PLL (4 kHz).
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Passafiume, Marco, Giovanni Collodi, Edoardo Ciervo i Alessandro Cidronali. "A Novel TDoA-Based Method for 3D Combined Localization Techniques Using an Ultra-Wideband Phase Wrapping-Impaired Switched Beam Antenna". Electronics 10, nr 17 (2.09.2021): 2137. http://dx.doi.org/10.3390/electronics10172137.
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This paper presents a novel Time Difference of Arrival-based approach suitable for single-anchor positioning systems, implemented by phase wrapping-impaired array antenna. With the latter being a typical occurrence in large Switched Beam Antenna (SBA) operating in the low microwave range. The proposed method takes advantage from the large bandwidth of radio link, established between the anchor and the positioning target, by generating an unambiguous equivalent phase relationship between antenna array elements. The technique is validated by adopting a relatively large SBA antenna operating in the 4.75–6.25 GHz bandwidth, and capable to position a target in a 3D domain. Experimental data, carried out in the 4–7 GHz frequency bandwidth, show that by dealing properly with the inherent constraint of phase wrapping issues, it is possible to get a significant improvement on the elevation angle with respect to methods not capable to deal with phase reconstruction and thus operating in a phase-less context. Combining range and angle errors, the associated cumulative distribution function error in 90% of cases shows an error of 0.13 m.
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Cruz, Madson Pereira, Rodolfo Novellino Benda, Maria Flávia Soares Pinto Carvalho, Guilherme Menezes Lage, Maria Teresa Cattuzzo i Herbert Ugrinowitsch. "Bandwidth knowledge of results persists on motor skills acquisition". Motricidade 14, nr 2-3 (17.10.2018): 107–14. http://dx.doi.org/10.6063/motricidade.14294.
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The aim of this study was to investigate the short and long-term effects of the bandwidth KR in learning of the absolute and relative dimensions of a motor skill. Twenty-two undergraduate students divided into two groups: G15 who received KR when the relative error exceeded 15%; and G0, with KR after every trial. The study consisted of an acquisition phase, and the volunteers practiced 100 trials with a target time of 850 ms and relative of 22.2%, 44.4% and 33.3% between the first and second, second and third, third and fourth keys, respectively. This phase, KR related to relative time (relative error) was provided according to the group. KR of total target time was available to both groups after all trials. Three retention tests with ten trials were conducted 10 minutes, 24 hours and one week after the acquisition phase. The results showed that G15 had a smaller relative error than G0. This study allows concluding that bandwidth KR in relation relative time error showed its effects in the consistency of relative time. These effects persisted even after seven days after the acquisition phase in a delayed retention test.
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Song, Young-Jin, Thomas Pany i Jong-Hoon Won. "Theoretical Upper and Lower Limits for Normalized Bandwidth of Digital Phase-Locked Loop in GNSS Receivers". Sensors 23, nr 13 (25.06.2023): 5887. http://dx.doi.org/10.3390/s23135887.
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Determining the loop noise bandwidth and the coherent integration time is essential and important for the design of a reliable digital phase-locked loop (DPLL) in global navigation satellite system (GNSS) receivers. In general, designers set such parameters approximately by utilizing the well-known fact that the DPLL is stable if the normalized bandwidth, which is the product of the integration time and the noise bandwidth, is much less than one. However, actual limit points are not fixed at exactly one, and they vary with the loop filter order and implementation method. Furthermore, a lower limit on the normalized bandwidth may exist. This paper presents theoretical upper and lower limits for the normalized bandwidth of DPLL in GNSS receivers. The upper limit was obtained by examining the stability of DPLL with a special emphasis on the digital integration methods. The stability was investigated in terms of z-plane root loci with and without the consideration of the computational delay, which is a delay induced by the calculation of the discriminator and the loop filter. The lower limit was analyzed using the DPLL measurement error composed of the thermal noise, oscillator phase noise, and dynamic stress error. By utilizing the carrier-to-noise density ratio threshold which indicates the crossing point between the measurement error and the corresponding threshold, the lower limit of the normalized bandwidth is obtained.
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Ferrari, Mauro, i Luca Piattella. "0.8–8 GHz 4-bit MMIC phase shifter for T/R modules". International Journal of Microwave and Wireless Technologies 7, nr 3-4 (21.05.2015): 317–26. http://dx.doi.org/10.1017/s1759078715000793.
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This paper presents the design approach and test results of a full passive, decade bandwidth GaAs MMIC, composed by a phase shifter (PS) with a cascaded absorptive single pole double throw switch, suitable for transmitter/receiver modules in active electronically scanned array. The proposed PS – fabricated using a UMS GaAs 0.25 PHEMT process – combines all-pass filters with high-pass filters, in order to provide less than 13 dB insertion loss, less than ±20° phase error and less than ±2.5 dB amplitude error in the 0.8–8 GHz bandwidth.
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Kim, Kyeong-Rok, i Jae-Hyun Kim. "Wideband Waveform Generation Using MDDS and Phase Compensation for X-Band SAR". Remote Sensing 12, nr 9 (1.05.2020): 1431. http://dx.doi.org/10.3390/rs12091431.
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This study investigated wideband waveform generation using a field programmable gate array (FPGA) for X-band high-resolution synthetic aperture radar (SAR). Due to the range resolution determined by the bandwidth, we focused on wide bandwidth generation while preserving spectrum quality. The proposed method can generate wide bandwidth using a relatively low system clock. The new approach was designed in Simulink and implemented by very-high-speed-integrated-circuits hardware description language (VHDL). We also proposed a hardware structure in accordance with the proposed method. Signal connections of FPGA and digital analog converter (DAC) are described in the design of the proposed hardware structure. The developed X-band waveform generator using the proposed method output the desired pulse waveform. For the reduction of phase error and improvement of spectrum quality at the X-band, phase error compensation and pre-distortion were applied to the waveform generator. The results of the simulation and the hardware output demonstrate that the variation and standard deviation of the phase error were improved within the frequency spectrum. Accordingly, the proposed method and the developed waveform generator have the potential to produce a high-resolution image of the area of interest.
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Torfs, Dirk, i Joris De Schutter. "Optimal Feedforward Prefilter With Frequency Domain Specification for Nonminimum Phase Systems". Journal of Dynamic Systems, Measurement, and Control 118, nr 4 (1.12.1996): 791–95. http://dx.doi.org/10.1115/1.2802359.
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The paper shows the influence of the location of unstable zeros on the tracking performance of feedforward prefilters. Unstable zeros are divided into a number of classes. It is shown that existing feedforward prefilters (Zero Phase Error Tracking Control (ZPETC), E-filter, Extended Bandwidth ZPETC, ...) perform well for two classes, but fail for a particular class of unstable zeros. For this class, a characteristic frequency, fc, exists such that the induced gain error attenuates all frequencies of the reference trajectory f ≤ fc and amplifies frequencies f > fc. Hence, it is impossible to freely select the tracking bandwidth. Therefore, an optimal feedforward prefilter for discrete time nonminimum phase systems is presented to deal with this class of unstable zeros. As in the ZPETC method, the prefilter compensates for unstable zeros in the inverse system model, retains the zero phase property, and introduces small gain errors. But in addition, the design minimizes a cost function for which a least square solution is found. A frequency and time domain analysis shows the superior performance of the presented optimal prefilter design even for trajectory with high frequency components.
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Vyomal N, Pandya, P. Rahul Reddy i Abhishek Choubey. "Bandwidth Estimation Algorithm of WestwoodNR for Wireless Network". International Journal of Engineering & Technology 7, nr 2.16 (12.04.2018): 114. http://dx.doi.org/10.14419/ijet.v7i2.16.11521.
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Two widely known parameters of Transmission Control Protocol (TCP) used to control the flow of packets are Congestion Window (cwnd) & Slow Start Threshold (ssthresh). After congestion, slow start phase or fast-retransmit phase come in action wherein TCP has an important role in the reduction of these parameters. This is in response to packet loss identified by TCP. This in turn will cause unnecessary reduction of data flow & degradation of TCP throughput. Researchers have developed some algorithms to come out of this problem, WestwoodNR is one of them. WestwoodNR is using Bandwidth Estimation algorithm to estimate available bandwidth, to make effective use of available network capacity even after the congestion episode. It allows higher values of ssthresh & cwnd when it enters the fast-retransmit phase and slow start phase. In turn this algorithm claims better performance in terms of bandwidth utilization. The focus of this paper is on error recovery mechanisms suitable for WestwoodNR operating over the wireless sub path. These mechanisms have to address the increased bit error probability and temporary disruptions of wireless links. The efficiency of WestwoodNR within wireless scenarios is investigated and possible modifications that lead to higher performance are pointed out.
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Zhang, Xuebo, i Peixuan Yang. "An Improved Imaging Algorithm for Multi-Receiver SAS System with Wide-Bandwidth Signal". Remote Sensing 13, nr 24 (9.12.2021): 5008. http://dx.doi.org/10.3390/rs13245008.
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When the multi-receiver synthetic aperture sonar (SAS) works with a wide-bandwidth signal, the performance of the range-Doppler (R-D) algorithm is seriously affected by two approximation errors, i.e., point target reference spectrum (PTRS) error and residual quadratic coupling error. The former is generated by approximating the PTRS with the second-order term in terms of the instantaneous frequency. The latter is caused by neglecting the cross-track variance of secondary range compression (SRC). In order to improve the imaging performance in the case of wide-bandwidth signals, an improved R-D algorithm is proposed in this paper. With our method, the multi-receiver SAS data is first preprocessed based on the phase center approximation (PCA) method, and the monostatic equivalent data are obtained. Then several sub-blocks are generated in the cross-track dimension. Within each sub-block, the PTRS error and residual quadratic coupling error based on the center range of each sub-block are compensated. After this operation, all sub-blocks are coerced into a new signal, which is free of both approximation errors. Consequently, this new data is used as the input of the traditional R-D algorithm. The processing results of simulated data and real data show that the traditional R-D algorithm is just suitable for an SAS system with a narrow-bandwidth signal. The imaging performance would be seriously distorted when it is applied to an SAS system with a wide-bandwidth signal. Based on the presented method, the SAS data in both cases can be well processed. The imaging performance of the presented method is nearly identical to that of the back-projection (BP) algorithm.
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Chen Peng, 陈鹏, 王荣 Wang Rong, 蒲涛 Pu Tao, 卢麟 Lu Lin, 方涛 Fang Tao i 郑吉林 Zheng Jilin. "Fabrication of Super-Narrow Bandwidth Grating Filter Based on Phase Error Correction". Chinese Journal of Lasers 36, nr 8 (2009): 2076–82. http://dx.doi.org/10.3788/cjl20093608.2076.
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Chen, M. H., K. W. Han, M. H. Yang i X. W. Sun. "Effects of phase-locked loop bandwidth on error vector magnitude in transmitter". Journal of Electromagnetic Waves and Applications 26, nr 10 (lipiec 2012): 1315–22. http://dx.doi.org/10.1080/09205071.2012.699390.
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Bredfeldt, Jeremy S., Xin Miao, Evangelia Kaza, Manuel Schneider, Martin Requardt, Thorsten Feiweier, Ayal Aizer i in. "Patient specific distortion detection and mitigation in MR images used for stereotactic radiosurgery". Physics in Medicine & Biology 67, nr 6 (11.03.2022): 065009. http://dx.doi.org/10.1088/1361-6560/ac508e.
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Abstract Objective. In MRI-based radiation therapy planning, mitigating patient-specific distortion with standard high bandwidth scans can result in unnecessary sacrifices of signal to noise ratio. This study investigates a technique for distortion detection and mitigation on a patient specific basis. Approach. Fast B0 mapping was performed using a previously developed technique for high-resolution, large dynamic range field mapping without the need for phase unwrapping algorithms. A phantom study was performed to validate the method. Distortion mitigation was validated by reducing geometric distortion with increased acquisition bandwidth and confirmed by both the B0 mapping technique and manual measurements. Images and contours from 25 brain stereotactic radiosurgery patients and 95 targets were analyzed to estimate the range of geometric distortions expected in the brain and to estimate bandwidth required to keep all treatment targets within the ±0.5 mm iso-distortion contour. Main Results. The phantom study showed, at 3 T, the technique can measure distortions with a mean absolute error of 0.12 mm (0.18 ppm), and a maximum error of 0.37 mm (0.6 ppm). For image acquisition at 3 T and 1.0 mm resolution, mean absolute distortion under 0.5 mm in patients required bandwidths from 109 to 200 Hz px−1 for patients with the least and most distortion, respectively. Maximum absolute distortion under 0.5 mm required bandwidths from 120 to 390 Hz px−1. Significance. The method for B0 mapping was shown to be valid and may be applied to assess distortion clinically. Future work will adapt the readout bandwidth to prospectively mitigate distortion with the goal to improve radiosurgery treatment outcomes by reducing healthy tissue exposure.
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Kottas, James A. "Training Periodic Sequences Using Fourier Series Error Criterion". Neural Computation 5, nr 1 (styczeń 1993): 115–31. http://dx.doi.org/10.1162/neco.1993.5.1.115.
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Training a network to learn a set of periodic input/output sequences effectively makes the network learn a mapping between amplitudes and phases in Fourier space. The spectral backpropagation (SBP) training algorithm is a different way of doing this task. It measures the Fourier series components of the output error sequences and minimizes the total spectral energy as an adaptation criterion. This approach can train not only the weights but also time delays associated with the interconnects. Furthermore, the cells can have finite bandwidth via a first-order low-pass filter. Having adaptable time delays gives the SBP algorithm a powerful way to control the phase characteristics of the network.
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Schempf, H., i D. R. Yoerger. "Study of Dominant Performance Characteristics in Robot Transmissions". Journal of Mechanical Design 115, nr 3 (1.09.1993): 472–82. http://dx.doi.org/10.1115/1.2919214.
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Six different transmission types suitable for robotic manipulators were compared in an experimental and theoretical study. Single-degree-of-freedom mechanisms based on the different transmissions were evaluated in terms of force control performance, achievable bandwidth, and stability properties in hard contact tasks. Transmission types considered were (1) cable reducer, (2) harmonic drive, (3) cycloidal disk reducer, (4) cycloidal cam reducer, (5) ball reducer, and (6) planetary/cycloidal gear head. Open loop torque following error, attenuation and phase lag, and closed loop bandwidth and stability margin were found to be severely dominated by levels of inertia, stiffness distribution and variability, stiction, coulomb and viscous friction, and ripple torque. These aspects were quantified and shown to vary widely among all transmissions tested. The degree of nonlinearity inherent in each transmission affected its open and closed loop behavior directly, and limited the effectiveness of controller compensation schemes. Simple transmission models based on carefully measured transmission characteristics are shown to predict stability margins and achievable force-control bandwidths in hard contact to within a 5 to 15 percent error margin.
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Li, Qunsheng, i Yan Zhao. "An Innovative High-Precision Scheme for a GPS/MEMS-SINS Ultra-Tight Integrated System". Sensors 19, nr 10 (17.05.2019): 2291. http://dx.doi.org/10.3390/s19102291.
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The Doppler-assisted error provided by a low-precision microelectromechanical system (MEMS) strapdown inertial navigation system (SINS) increases rapidly. Therefore, the bandwidth of the tracking loop for a global positioning system (GPS)/MEMS-SINS ultra-tight integration system is too narrow to track Doppler shift. GPS measurement error is correlated with the MEMS-SINS velocity error when the Doppler-assisted error exists, leading to tracking loop lock loss. The estimated precision of the integrated Kalman filter (IKF) also decreases. Even the integrated system becomes unstable. To solve this problem, an innovative GPS/MEMS-SINS ultra-tight integration scheme based on using high-precision carrier phase measurements as the IKF measurements is proposed in this study. By assisting the tracking loop with time-differenced carrier phase (TDCP) velocity, the carrier loop noise bandwidth and code correlator spacing are reduced. The tracking accuracies of the carrier and code are increased. The navigation accuracy of GPS/MEMS-SINS ultra-tight integration is further improved.
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Zhai, Yu, Xiaoxing Fang, Kejia Ding i Fei He. "Miniaturization Design for 8 × 8 Butler Matrix Based on Back-to-Back Bilayer Microstrip". International Journal of Antennas and Propagation 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/583903.
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A low-cost, compact 8 × 8 Butler matrix based on a novel bilayer microstrip configuration is presented and implemented for 4.3 GHz telecommunication application. A back-to-back placed bilayer microstrip structure has been proposed to avoid using crossover. To expand operational bandwidth of the Butler matrix, a three-branch line directional coupler has been employed as 3 dB/90° bridge, and a kind of improved two-order Schiffman phase shifter has been adopted as fixed phase shifter. For application of indoor wireless communication, a compact broadband 8 × 8 Butler matrix has been designed and fabricated. The measured results show that the return loss of the matrix is lower than −10 dB, the isolation is better than 17 dB, the power distribution error is less than ±2.0 dB, the phase error is less than ±15°, and the relative bandwidth is more than 23%.
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Chen, Chwan-Hsen, Hendrik Van Brussel i Jan Swevers. "Extended Pole Placement Method With Noncausal Reference Model for Digital Servo-Control". Journal of Dynamic Systems, Measurement, and Control 117, nr 4 (1.12.1995): 641–44. http://dx.doi.org/10.1115/1.2801127.
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The extended pole placement (EPP) method extends the well-known pole placement method to digital servo-control with known control inputs. A servo-control system designed using the EPP method achieves an accurate command response through the use of a noncausal reference model and an accurate approximation of nonminimum-phase zeros. The phase error of the command response between the desired output and the actual output may be made arbitrarily small, while its gain extends uniformly to a selectable bandwidth. A selectable feedforward bandwidth is important in controlling flexible structures where unmodeled resonances might be excited by rough feedforward inputs. Experimental results on a machine tool slide show that a controller designed by the EPP method yields better servo performance for cornering and contour tracking tasks than an E-filter-enhanced zero phase error tracking controller.
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Zhao, Li Ru, Xiao Zhang Zhang, Kai Zhang i Tong Zhang. "Research on Control Precision of the Neutron Bandwidth Chopper". Applied Mechanics and Materials 220-223 (listopad 2012): 1077–83. http://dx.doi.org/10.4028/www.scientific.net/amm.220-223.1077.
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Operation of neutron bandwidth limiting chopper requires high controlling precision. Phase difference between the chopper rotor and the synchronous pulse signal should be maintained to be fixed. Rotating frequency of the rotor needs to be very stable. To achieve the above technical requirements, control scheme, dynamic balance, and other means are made. Thus influences to control accuracy are effectively reduced, which are from rotor asymmetry and neutron absorbing materials. In the case described in this paper, phase tracking error was controlled under ±0.10752°with 90% confidence for the designed chopper.
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Sugak, Mikhail, Svyatoslav Ballandovich, Grigory Kostikov, Lubov Liubina i Yury Antonov. "Increasing bandwidth of full-metal slot reflectarray antennas". ITM Web of Conferences 30 (2019): 05023. http://dx.doi.org/10.1051/itmconf/20193005023.
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Results of theoretical and experimental investigations of full-metal slot reflectarray antennas with increased bandwidth are presented. Bandwidth increasing is achieved by means of certain sizes choice for each reflective element so that the phase-error minimum in a required frequency range would be created . Two prototypes - single-layer and two-layer - of K-band slot reflectarray antennas have been manufactured and tested. Effectiveness of the described designing routine is proved by experimental data: achieved bandwidth for the single-layer and two-layer structure is 25% and 32% respectively.
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PU, XIAO, KRISHNASWAMY NAGARAJ, JACOB ABRAHAM i AXEL THOMSEN. "A NOVEL FRACTIONAL-N PLL BASED ON A SIMPLE REFERENCE MULTIPLIER". Journal of Circuits, Systems and Computers 21, nr 06 (październik 2012): 1240010. http://dx.doi.org/10.1142/s0218126612400105.
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A wide loop bandwidth in fractional-N PLL is desirable for good jitter performance. However, a wider bandwidth reduces the effective oversampling ratio between update rate and loop bandwidth, making quantization error a much bigger noise contributor. A successful implementation of a wideband frequency synthesizer is in managing jitter and spurious performance. In this paper we present a new PLL architecture for bandwidth extension. By using clock squaring buffers with built-in offsets, multiple clock edges are extracted from a single reference cycle and utilized for phase update, thereby effectively forming a reference multiplier. This enables a higher oversampling ratio for better quantization noise shaping and makes a wideband fractional-N PLL possible.
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Torres Nova, Juan Mario, i Hernán Paz Penagos. "Studying and comparing spectrum efficiency and error probability in GMSK and DBPSK modulation schemes". Ingeniería e Investigación 28, nr 3 (1.09.2008): 75–80. http://dx.doi.org/10.15446/ing.investig.v28n3.15123.
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Gaussian minimum shift keying (GMSK) and differential binary phase shift keying (DBPSK) are two digital modulation schemes which are -frequently used in radio communication systems; however, there is interdependence in the use of its benefits (spectral efficiency, low bit error rate, low inter symbol interference, etc). Optimising one parameter creates problems for another; for example, the GMSK scheme succeeds in reducing bandwidth when introducing a Gaussian filter into an MSK (minimum shift ke-ying) modulator in exchange for increasing inter-symbol interference in the system. The DBPSK scheme leads to lower error pro-bability, occupying more bandwidth; it likewise facilitates synchronous data transmission due to the receiver’s bit delay when re-covering a signal.
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Chen, Xiao Gang, Chao Jiang, Zhao Xu Liu i De Xiu Huang. "Spectral Efficiency of Phase Encoding OCDMA Systems". Advanced Materials Research 760-762 (wrzesień 2013): 133–36. http://dx.doi.org/10.4028/www.scientific.net/amr.760-762.133.
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The spectral efficiency and bit-error-rate (BER) of phase encoding optical code division multiple access (OCDMA) systems is evaluated, coherent time-spreading (TS) and spectral phase encoding (SPE) OCDMA systems are considered. The results indicate that SPE-OCDMA has better tolerance to performance degradation due to receivers bandwidth limitation than TS-OCDMA system, while for the practical en/decoders with implementable longest code length, TS-OCDMA can yield a spectral efficiency advantage over SPE-OCDMA systems.
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Zhang, Geng, Mingche Lai i Fangxu Lyu. "A Multichannel, High-Bandwidth Wirelane Receiver for D2D Interconnects". Electronics 11, nr 18 (10.09.2022): 2864. http://dx.doi.org/10.3390/electronics11182864.
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This paper proposes a multichannel and high-bandwidth (BW) receiver for standard packaging die-to-die (D2D) interconnects. The receiver adopts forward clock (FCK) architecture of the high-density transmission standard, which consists of 16 high-speed data paths and a pair of low-speed differential clocks for 512 Gbps BW. To reduce the chip area and power consumption, a common minimal phase-locked loop (MINI-PLL) and data adjustment (CDA) circuit to replaces the clock data recovery circuit (CDR) in the traditional receiver. A delay-matching circuit is adopted to combat PVT variation and lane skew. In addition, a high linearity phase interpolator (PI) circuit design is used in the minimum phase-locked loop (MINI-PLL) to adjust the clock phase and improve the clock jitter performance. Using 28 nm CMOS technology, the overall link power consumption is 1.56 pJ/b. Bit error rate (BER) is less than 10−15 under the real S-parameters with a channel loss of 10db@16GHz.
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Lee, Haemin, Chang-Sik Jung i Ki-Wan Kim. "Feature Preserving Autofocus Algorithm for Phase Error Correction of SAR Images". Sensors 21, nr 7 (29.03.2021): 2370. http://dx.doi.org/10.3390/s21072370.
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Autofocus is an essential technique for airborne synthetic aperture radar (SAR) imaging to correct phase errors mainly due to unexpected motion error. There are several well-known conventional autofocus methods such as phase gradient autofocus (PGA) and minimum entropy (ME). Although these methods are still widely used for various SAR applications, each method has drawbacks such as limited bandwidth of estimation, low convergence rate, huge computation burden, etc. In this paper, feature preserving autofocus (FPA) algorithm is newly proposed. The algorithm is based on the minimization of the cost function containing a regularization term. The algorithm is designed for postprocessing purpose, which is different from the existing regularization-based algorithms such as sparsity-driven autofocus (SDA). This difference makes the proposed method far more straightforward and efficient than those existing algorithms. The experimental results show that the proposed algorithm achieves better performance, convergence, and robustness than the existing postprocessing autofocus algorithms.
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Tung, E. D., M. Tomizuka i Y. Urushisaki. "High-Speed End Milling Using a Feedforward Control Architecture". Journal of Manufacturing Science and Engineering 118, nr 2 (1.05.1996): 178–87. http://dx.doi.org/10.1115/1.2831010.
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Experiments are performed for end milling aluminum at 15,000 RPM spindle speed (1,508 m/min cutting speed) and up to 3 m/min table feedrate using an experimental machine tool control system. A digital feedforward controller for feed drive control incorporates the Zero Phase Error Tracking Controller (ZPETC) and feedforward friction compensation. The controller achieves near-perfect (±3 μm) tracking over a 26 mm trajectory with a maximum speed of 2 m/min. The maximum contouring error for a 26 mm diameter circle at this speed is less than 4 μm. Tracking and contouring experiments are conducted for table feedrates as high as 10 m/min. Frequency domain analysis demonstrates that the feedforward controller achieves a bandwidth of 10 Hz without phase distortion. In a direct comparison of accuracy, the machining errors in specimens produced by the experimental controller were up to 20 times smaller than the errors in specimens machined by an industrial CNC.
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Song, Young-Jin, i Jong-Hoon Won. "Table-Based Adaptive Digital Phase-Locked Loop for GNSS Receivers Operating in Moon Exploration Missions". Sensors 22, nr 24 (19.12.2022): 10001. http://dx.doi.org/10.3390/s222410001.
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An adaptive digital phase-locked loop (DPLL) continually adjusts the noise bandwidth of the loop filter in global navigation satellite system (GNSS) receivers to track signals by measuring the signal-to-noise ratio and/or dynamic stress. Such DPLLs have a relatively large amount of computational complexity compared with the conventional DPLL. A table-based adaptive DPLL is proposed that adjusts the noise bandwidth value by extracting it from the pre-generated table without additional calculations. The values of the noise bandwidth table are computed in an optimal manner in consideration of the thermal noise, oscillator phase noise, and dynamic stress error. The calculation method of the proper integration time to maintain the stability of the loop filter is presented. Additionally, the simulation is configured using the trajectory analysis results from the Moon exploration mission and shows that the proposed algorithm operates stably in harsh environments, while a conventional fixed bandwidth loop cannot. The proposed algorithm has a similar phase jitter performance to the existing adaptive DPLL algorithms and has an execution time that is approximately 2.4–5.4 times faster. It is verified that the proposed algorithm is computationally efficient while maintaining jitter performance.
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Wang, Rui, i Zhong Wu. "Suppressing Quadrature Error and Harmonics in Resolver Signals via Disturbance-Compensated PLL". Machines 10, nr 8 (18.08.2022): 709. http://dx.doi.org/10.3390/machines10080709.
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The aim of this study was to obtain accurate angular positions and velocities from resolver signals; resolver-to-digital conversion (RDC) often adopts a phase-locked loop (PLL) as a demodulation algorithm. However, resolver signals often come with quadrature errors and harmonics, which lead to a severe reduction in PLL accuracy. The conventional PLL does not consider the impact of the quadrature error, and the bandwidth of the PLL is much larger than the fundamental frequency of resolver signals for pursuing a low dynamic error. These reasons render the retention of resolver harmonics in the demodulation results. In this paper, a disturbance-compensated PLL (DC-PLL) is proposed, which consists of a phase detector for suppressing quadrature error and harmonics (SQEH-PD) and a second-order observer. Firstly, since the quadrature error does not change with the angle velocity, the pre-estimated quadrature error is used in the SQEH-PD to compensate for the quadrature error in resolver signals. Secondly, although the frequency of the harmonics changes with the velocity, the amplitudes of the harmonics do not change. Therefore, the pre-estimated amplitudes of harmonics and estimated angular position are used in the SQEH-PD to compensate for the harmonics in resolver signals. Thirdly, a second-order observer is designed to estimate the angular position and velocity by regulating the phase detector error. Compared with the conventional PLL, the proposed DC-PLL has a stronger anti-disturbance ability against the quadrature error and harmonics by configurating the phase detector error and the estimated position error, which have a linear relation. Simulation and experimental results prove the effectiveness of the proposed method.
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Chen, Xing, Tianzhu Yi, Feng He, Zhihua He i Zhen Dong. "An Improved Generalized Chirp Scaling Algorithm Based on Lagrange Inversion Theorem for High-Resolution Low Frequency Synthetic Aperture Radar Imaging". Remote Sensing 11, nr 16 (10.08.2019): 1874. http://dx.doi.org/10.3390/rs11161874.
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The high-resolution low frequency synthetic aperture radar (SAR) has serious range-azimuth phase coupling due to the large bandwidth and long integration time. High-resolution SAR processing methods are necessary for focusing the raw data of such radar. The generalized chirp scaling algorithm (GCSA) is generally accepted as an attractive solution to focus SAR systems with low frequency, large bandwidth and wide beam bandwidth. However, as the bandwidth and/or beamwidth increase, the serious phase coupling limits the performance of the current GCSA and degrades the imaging quality. The degradation is mainly caused by two reasons: the residual high-order coupling phase and the non-negligible error introduced by the linear approximation of stationary phase point using the principle of stationary phase (POSP). According to the characteristics of a high-resolution low frequency SAR signal, this paper firstly presents a principle to determine the required order of range frequency. After compensating for the range-independent coupling phase above 3rd order, an improved GCSA based on Lagrange inversion theorem is analytically derived. The Lagrange inversion enables the high-order range-dependent coupling phase to be accurately compensated. Imaging results of P- and L-band SAR data demonstrate the excellent performance of the proposed algorithm compared to the existing GCSA. The image quality and focusing depth in range dimension are greatly improved. The improved method provides the possibility to efficiently process high-resolution low frequency SAR data with wide swath.
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Asoodeh, Alireza, i Mojtaba Atarodi. "A Full 360$^{\circ}$ Vector-Sum Phase Shifter With Very Low RMS Phase Error Over a Wide Bandwidth". IEEE Transactions on Microwave Theory and Techniques 60, nr 6 (czerwiec 2012): 1626–34. http://dx.doi.org/10.1109/tmtt.2012.2189227.
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Chen, Zhen, Zhimin Zhang, Yashi Zhou, Pei Wang i Jinsong Qiu. "A Novel Motion Compensation Scheme for Airborne Very High Resolution SAR". Remote Sensing 13, nr 14 (12.07.2021): 2729. http://dx.doi.org/10.3390/rs13142729.
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Due to the atmospheric turbulence, the motion trajectory of airborne very high resolution (VHR) synthetic aperture radars (SARs) is inevitably affected, which introduces range-variant range cell migration (RCM) and aperture-dependent azimuth phase error (APE). Both types of errors consequently result in defocused images, as residual range- and aperture-dependent motion errors are significant in VHR-SAR images. Nevertheless, little work has been devoted to the range-variant RCM auto-correction and aperture-dependent APE auto-correction. In this paper, a precise motion compensation (MoCo) scheme for airborne VHR-SAR is studied. In the proposed scheme, the motion error is obtained from inertial measurement unit and SAR data, and compensated for with respect to both range and aperture. The proposed MoCo scheme compensates for the motion error without space-invariant approximation. Simulations and experimental data from an airborne 3.6 GHz bandwidth SAR are employed to demonstrate the validity and effectiveness of the proposed MoCo scheme.
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Qin, Haoye, i Zhong Wu. "Angle Tracking Observer with Improved Accuracy for Resolver-to-Digital Conversion". Symmetry 11, nr 11 (1.11.2019): 1347. http://dx.doi.org/10.3390/sym11111347.
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A resolver is an absolute shaft sensor which outputs pair signals with ortho-symmetric amplitudes. Ideally, they are sinusoidal and cosinusoidal functions of the shaft angle. In order to demodulate angular position and velocity from resolver signals, resolver-to-digital conversion (RDC) is necessary. In software-based RDC, most algorithms mainly employ a phase-locked loop (PLL)-based angle tracking observer (ATO) to form a type-II system. PLL can track the detected angle by regulating the phase error from the phase detector which depends on the feature of orthogonal symmetry in the resolver outputs. However, a type-II system will result in either steady-state errors or cumulative errors in the estimation of angular position with constant accelerations. Although type-III ATOs can suppress these errors, they are still vulnerable to high-order acceleration signals. In this paper, an improved PLL-based ATO with a compensation model is proposed. By using dynamic compensation, the proposed ATO becomes a type-IV system and can reduce position estimation errors for high-order acceleration signals. In addition, the parameters of ATO can be tuned according to the bandwidth, noise level and capability of error suppression. Simulation and experimental results demonstrate the effectiveness of the proposed method.
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Matricciani, Emilio, i Carlo Riva. "Transfer Functions and Linear Distortions in Ultra-Wideband Channels Faded by Rain in GeoSurf Satellite Constellations". Future Internet 15, nr 1 (3.01.2023): 27. http://dx.doi.org/10.3390/fi15010027.
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Because of rain attenuation, the equivalent baseband transfer function of large bandwidth radio-links will not be ideal. We report the results concerning radio links to/from satellites orbiting in GeoSurf satellite constellations located at Spino d’Adda, Prague, Madrid, and Tampa, which are all sites in different climatic regions. By calculating rain attenuation and phase delay with the Synthetic Storm Technique, we have found that in a 10-GHz bandwidth centered at 80 GHz (W-Band)—to which we refer to as “ultra-wideband-, both direct and orthogonal channels will introduce significant amplitude and phase distortions, which increase with rain attenuation. Only “narrow-band” channels (100~200 MHz) will not be affected. The ratio between the probability of bit error with rain attenuation and the probability of bit error with no rain attenuation increases with rain attenuation. The estimated loss in the signal-to-noise ratio can reach 3~4 dB. All results depend on the site, Tampa being the worst. To confirm these findings, future work will need a full Monte Carlo digital simulation.
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Magauer, Andreas, i Soumitro Banerjee. "Transmission of Binary Information with a Chaos Coded Communication System using QDPSK-Modulation". Zeitschrift für Naturforschung A 53, nr 12 (1.12.1998): 1022–28. http://dx.doi.org/10.1515/zna-1998-1215.
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Abstract Synchronisation of chaotic oscillators offers a way of practical application of the theory of Chaos in obtaining secure communication. In this work we introduce a nonautonomous chaotic system with sinusoidal external force for communication of binary signals. The information is applied to the phase position of the sinusoidal forcing signal of the chaotic oscillator using a quadrature difference phase shift keying (QDPSK) modulation. An inverse synchronisation system approach with direct modulation is applied. We describe the system in detail and discuss the requirements of a secure communication system. Issues related to bit error rate, transfer rate, signal to noise ratio, channel bandwidth, bandwidth efficiency and channel capacity are discussed, and the properties of the realized communication system are placed in relation to the requirements of a secure communication system.
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Turovsky, O. L., i L. A. Kirpach. "EFFECT OF PHASE INSTABILITY OF GENERATORS ON THE OPERATING PARAMETERS OF A CARRIER FREQUENCY SYNCHRONIZATION SYSTEM AGAINST A BACKGROUND OF ADDITIVE GAUSSIAN NOISE AND A DOPPLER FREQUENCY SHIFT". Collection of scientific works of the Military Institute of Kyiv National Taras Shevchenko University, nr 67 (2020): 62–71. http://dx.doi.org/10.17721/2519-481x/2020/67-07.
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The article deals with the systems of phase synchronization of radio engineering devices of communication technology. The purpose of the article is theoretical research in the direction of development, analysis and improvement of known and synthesis of new phase synchronization circuits, characterized by high noise immunity, accuracy and speed with simplicity of design. The problem is solved to investigate the possibilities of closed and combined synchronization systems for operation under conditions of phase instability of generators in a communication channel against the background of external additive Gaussian noise and Doppler frequency shift. The following results were obtained. The analysis of closed-type synchronization systems during operation under the conditions of phase instability of generators is carried out and its inconsistency is shown in order to minimize the phase error variance and increase the dynamics during carrier frequency monitoring. The process of synthesis of open communication in the combined synchronization system is refined and analytical dependences are offered, which allow to refine the technique of synthesis of open communication for the combined synchronization system with regard to the phase instability of the generators against the background of the influence of the adducts. Conclusions. Increasing the noise bandwidth of the proportional-integrating filter of the closed-loop phase-in-phase synchronization system to the parameters of the ideal filter impairs the dynamics of the specified system. For the combined synchronization system, in the conditions of phase instability of the generators, an increase in the noise bandwidth of the input signal can be achieved by applying a closed-loop proportional-integrating filter and by making appropriate selection of parameters of the transfer function of the link of the open channel. In the conditions of phase instability of the generators in the combined system of synchronization by selecting the parameters of the proportional-integrating filter, it is possible to provide the necessary dynamics of the system and to achieve the optimal value of the dispersion of the phase error in it. Taking into account Doppler noise under conditions of phase instability of generators for a closed-type synchronization system and a combined synchronization system requires a reduction of the optimal value of the noise bandwidth.
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Jabir, M. V., N. Fajar R. Annafianto, I. A. Burenkov, M. Dagenais, A. Battou i S. V. Polyakov. "Versatile quantum-enabled telecom receiver". AVS Quantum Science 5, nr 1 (marzec 2023): 015001. http://dx.doi.org/10.1116/5.0123880.
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We experimentally demonstrate a quantum-measurement-based receiver for a range of modulation schemes and alphabet lengths in a telecom C-band. We attain symbol error rates below the shot noise limit for all the studied modulation schemes and the alphabet lengths [Formula: see text]. In doing so, we achieve the record energy sensitivity for telecom receivers. We investigate the trade-off between energy and bandwidth use and its dependence on the alphabet length. We identify the combined (energy and bandwidth) resource efficiency as a figure of merit and experimentally confirm that the quantum-inspired hybrid frequency/phase encoding has the highest combined resource efficiency.
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Ershadi, S. E., A. Keshtkar, A. Bayat, A. H. Abdelrahman i H. Xin. "Rotman lens design and optimization for 5G applications". International Journal of Microwave and Wireless Technologies 10, nr 9 (26.06.2018): 1048–57. http://dx.doi.org/10.1017/s1759078718000934.
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AbstractThe next generation of wireless networks (5G) employs directional transmission at millimeter wave (mmW) frequencies to provide higher bandwidth and faster data rates. This is achieved by applying antenna arrays with proper beam steering capabilities. Rotman lens has long been used as a lens-based beamformer in electronically scanned arrays and its efficient design is important in the overall performance of the array. Minimizing the phase error on the aperture of the antenna array is an important design criterion in the lens. In this paper, a 7 × 8 wideband Rotman lens is designed. Particle swarm optimization is applied to minimize the path length error and thereby the phase error. The optimized lens operates from 25 to 31 GHz, which covers the frequency bands proposed by the Federal Communications Commission for 5G communications. The proposed optimized lens shows a maximum phase error of <0.1°. The proposed Rotman lens is a good candidate to be integrated with wideband microstrip patch antenna arrays that are suitable for 5G mmW applications.
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Ma, Chunjiang, Xiaomei Tang, Zhicheng Lv, Zhibin Xiao i Guangfu Sun. "High-Precision Pseudo-Noise Ranging Based on BOC Signal: Zero-Bias Mitigation Methods". Applied Sciences 9, nr 15 (3.08.2019): 3162. http://dx.doi.org/10.3390/app9153162.
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In high precision applications based on binary subcarrier offset (BOC) signals, zero-bias of the digital discriminator is an error of importance. Unlike the thermal noise error, zero-bias is a fixed deviation that is challenging to eliminate by filtering in the time domain. In this paper, a statistical error analysis model for the zero-bias of BOC signal’s digital phase discriminator is established. The evaluation of the zero-bias is inseparable from the spreading code sequence and the initial phase of the signal through defining the concept of statistics maximum and statistics standard deviation. Based on the zero-bias statistical error analysis model, two receiver parameter design methods, namely, the baseband signal sampling frequency and the early-late correlation interval, are proposed. The performance of the algorithm is simulated on account of the limited bandwidth, Doppler frequency offset and thermal noise. The simulation results prove that the proposed algorithm can suppress the standard deviation of zero-bias within one phase resolution, which contributes substantially to the improvement of the measurement accuracy of pseudo-noise ranging.
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Soyjaudah, K. M. S., i M. A. Hosany. "Combined Huffman Code and Generalized Array Codes Employing Phase/Frequency Modulation". Journal of Circuits, Systems and Computers 12, nr 01 (luty 2003): 93–109. http://dx.doi.org/10.1142/s0218126603000866.
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The authors present a simple technique to combine source coding, channel coding and modulation. This technique employs the Huffman code for source coding, Generalized Array Codes (GAC) for channel coding and Phase/Frequency (BFSK/MPSK) for modulation. The combined scheme has the advantage of reducing the redundancy, providing error protection and simultaneously optimizing on channel bandwidth. It is shown the combined system gives the same performance as its separate counterparts but has lower complexity. The algorithm used to construct the combined trellis decoder employing phase/frequency for a given source text file is designed and implemented in software. The error performances for the combined schemes using BFSK/MPSK modulation are compared with those employing coded as well as Uncoded MPSK modulation. Such a Block Coded Modulation (BCM) scheme is suitable for both information storage and digital transmission systems.
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Zhang, Zhe, MaoLiu Lin, QingHua Xu i JiuBin Tan. "Accurate and robust estimation of phase error and its uncertainty of 50 GHz bandwidth sampling circuit". Science in China Series F: Information Sciences 50, nr 6 (grudzień 2007): 905–14. http://dx.doi.org/10.1007/s11432-007-0062-1.
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Chen, Zhe, Debin Hou, Ji-Xin Chen, Pinpin Yan, Lei Bao, Zheying Hong i Yuanye Zheng. "A K-Band FMCW Frequency Synthesizer Using Q-Boosted Switched Inductor VCO in SiGe BiCMOS for 77 GHz Radar Applications". Electronics 9, nr 11 (17.11.2020): 1933. http://dx.doi.org/10.3390/electronics9111933.
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In this article, a fractional-N phase-locked loop (PLL) with integrated chirp generation circuit block for a 76~81 GHz frequency-modulated continuous-wave (FMCW) radar system is presented. Thanks to the switched inductor voltage-controlled oscillator (VCO) topology, the linearity, phase noise, chirp bandwidth, and chirp rate of the FMCW synthesizer can be optimized for the short-range radar (SRR) and long-range radar (LRR) applications, with switch at ON/OFF states, respectively, according to different requirements and concerns. In this way, the proposed FMCW synthesizer shows improved phase noise for switch OFF-state, good for LRR applications, compared to the conventional single-varactor VCOs or cap-bank VCOs. The switch loss at ON-state is further decreased with the Q-boosting technique, which helps the FMCW synthesizer to simultaneously obtain a wide chirp bandwidth, steep modulation rates and good phase noise for SRR applications. The FMCW synthesizer is fabricated in 0.13 µm SiGe BiCMOS technology, occupies an area of 1.7 × 1.9 mm2, and consumes 330 mW from a 3.3 V voltage supply. Measured results show that the FMCW synthesizer can cover 25.3~27 GHz (with a frequency tripler to fully cover 76~81 GHz band), showing optimized phase noise, chirp bandwidth, linearity, and modulation rates performance. The measured K-band phase noise is −110.5 dBc/Hz for switch OFF-state, and −106 dBc/Hz for switch ON-state at 1 MHz offset. The normalized root mean square (RMS) frequency error is 518 kHz for chirp rate of ±14.6 MHz/μs and 1.44 MHz for chirp rate of ±39 MHz/μs for the 77 GHz band. Moreover, the integrated waveform generator offers fully programmability in chirp rate, duration and bandwidth, which supports multi-slope chirp generations. With a frequency tripler, the chip is well suited for the 76~81 GHz FMCW radar system.
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Lee, Kyeong Ha, Seung Guk Baek, Hyouk Ryeol Choi, Hyungpil Moon, Sang-Hoon Ji i Ja Choon Koo. "Feedforward model-inverse position control of three-stage servo-valve using zero magnitude error tracking control". Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 233, nr 7 (5.07.2018): 2340–48. http://dx.doi.org/10.1177/0954406218786533.
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Three-stage servo-valves are popularly used in hydraulic systems that require large flow rate and high pressure. For a proper control of flow direction and flow rate fed into a hydraulic actuator, securing a proper position control bandwidth is a critical task for the servo-valve. In this paper, a set of popular control methods are systematically studied and a control method is selected. It is proven that the feedforward model-inverse control is the most effective method in terms of the control bandwidth. In the present work, the feedforward closed-loop architecture is adopted and the closed-loop system is estimated in a linear discrete-time transfer function by recursive least squares method. On recognizing a nonminimum phase zero problem, this work implements the zero magnitude error tracking control, an approximate model-inverse technique, in order to overcome the problem. As a result, the effectiveness of the proposed feedforward model-inverse position control strategy is verified.
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WOO, YOUNGSHIN, YOUNG MIN JANG i MAN YOUNG SUNG. "A NOVEL METHOD FOR HIGH-PERFORMANCE PHASE-LOCKED LOOP". Journal of Circuits, Systems and Computers 13, nr 01 (luty 2004): 53–63. http://dx.doi.org/10.1142/s0218126604001271.
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In this paper, we propose a phase-locked loop (PLL) with dual PFDs and a modified loop filter in which advantages of both PFDs can be combined and the trade-off between acquisition behavior and locked behavior can be achieved. By operating the appropriate PFD connected to the well-adjusted charge pump and regulating the loop bandwidth to input frequency ratio with an input divider and a modified loop filter, an unlimited error detection range, a high frequency operation, a reduced dead zone and a higher speed lock-up time can be achieved. The proposed PLL structure is designed using 1.5 μm CMOS technology with 5 V supply voltage.
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Hargreaves, Neil D. "Air‐gun signatures and the minimum‐phase assumption". GEOPHYSICS 57, nr 2 (luty 1992): 263–71. http://dx.doi.org/10.1190/1.1443239.
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The air‐gun array signature is close to minimum‐phase as a function of continuous time, in the sense that for processing purposes its phase spectrum can be derived from the Hilbert transform of the logarithm of its amplitude spectrum. This phase spectrum is different, however, from the minimum‐phase spectrum that is estimated by spiking deconvolution for a sampled and time‐windowed version of the signature. As a consequence, there can be large phase errors when spiking deconvolution is applied to an air‐gun signature or to a recording instrument response. The errors can be shown to consist primarily of a time shift and, at least visually over a limited bandwidth, a phase rotation of the output wavelet. The time shift is introduced by time sampling, while the phase rotation is caused by the spectral smoothing generated by time windowing. If the seismic wavelet as a whole, and not just the air‐gun signature, is minimum‐phase, then the total residual phase error after spiking deconvolution, including also the error due to data noise, can also be shown to be close to a time shift and a phase rotation. This may be physical justification for the phase rotation schemes that are often successful in matching seismic data and well‐log synthetics. The minimum‐phase assumption can be used for statistical air‐gun array signature deconvolution, providing that a limited amount of deterministic information (the instrument slopes and the source and receiver depths in the approach used here) is available to guide the process in those areas of the spectrum that are critical to the phase computation. Date examples show that, with care, almost identical results can then be obtained from either purely statistical deconvolution or deterministic deconvolution plus statistical deconvolution of multiples and ghosting.
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Musch, T., i B. Schiek. "A Fractional Ramp Generator with Improved Linearity and Phase-Noise Performance for the Use in Heterodyne Measurement Systems". Advances in Radio Science 3 (12.05.2005): 75–81. http://dx.doi.org/10.5194/ars-3-75-2005.
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Abstract. Concepts for the generation and the measurement of highly linear frequency ramps are presented. The fractional ramp synthesiser concept shown here is able to generate frequency ramps with a very low phase noise level, a very good frequency linearity and reproducibility. Related to the bandwidth of the generated frequency ramps of 4.5 GHz a relative linearity error below 4·10–10 is demonstrated in a prototype system. This linearity error is close to the limit set by the phase noise floor of the ramp generators and marks a significant improvement over existing aproaches (Musch and Schiek, 2000). The basic measurement sensitivity due to the phase noise is 1.8·10–10 without averaging. As the phase noise is important for the linearity of the frequency ramp the set-up has to be optimised for a good phase noise behaviour, too. In order to achieve this good phase noise a special phase-frequency detector is introduced that is especially designed for the use in a fractional phase locked loop.
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Liu, Feng, i Dong Po Ren. "An Improved TCP Congestion Control Algorithm in High Speed Satellite Links". Applied Mechanics and Materials 667 (październik 2014): 129–32. http://dx.doi.org/10.4028/www.scientific.net/amm.667.129.
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The throughput of traditional TCP degrades drastically in high speed satellite links, where the characteristics of long round trip time (RTT) and high bit error rate (BER) happen together. Two typical improved algorithms, Hybla and Westwood, are designed to solve the problems of long RTT and high BER respectively. TCP-HW which combines the advantages of Hybla and Westwood is proposed in this paper, on the basis of consideration of both long RTT and high BER. At slow start and congestion avoidance phase, TCP-HW adopts a radical congestion window (cwnd) growth policy to eliminate the low data transmission rate bring by long RTT as Hybla does. At fast retransmit and fast recover phase, TCP-HW updates the cwnd according to the estimated available bandwidth in Westwood to avoid the frequently unnecessary reduction of cwnd due to high BER. There, the cwnd can be kept large enough to achieve high throughput. Simulation results in NS2 indicate that the change of RTT and packet error rate (PER) has little impact on TCP-HW and the bandwidth utilization of TCP-HW can reach more than fifty percent in the 1Gbps GEO satellite link with 500ms RTT and 0.001 PER. In addition, TCP-HW still have good fairness.
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Cheng, Xiang, Shun Xu, Yan Liu, Yingchao Cao, Huikai Xie i Jinhui Ye. "Development of an Optoelectronic Integrated Sensor for a MEMS Mirror-Based Active Structured Light System". Micromachines 14, nr 3 (27.02.2023): 561. http://dx.doi.org/10.3390/mi14030561.
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Micro-electro-mechanical system (MEMS) scanning micromirrors are playing an increasingly important role in active structured light systems. However, the initial phase error of the structured light generated by a scanning micromirror seriously affects the accuracy of the corresponding system. This paper reports an optoelectronic integrated sensor with high irradiance responsivity and high linearity that can be used to correct the phase error of the micromirror. The optoelectronic integrated sensor consists of a large-area photodetector (PD) and a receiving circuit, including a post amplifier, an operational amplifier, a bandgap reference, and a reference current circuit. The optoelectronic sensor chip is fabricated in a 180 nm CMOS process. Experimental results show that with a 5 V power supply, the optoelectronic sensor has an irradiance responsivity of 100 mV/(μW/cm2) and a −3 dB bandwidth of 2 kHz. The minimal detectable light power is about 19.4 nW, which satisfies the requirements of many active structured light systems. Through testing, the application of the chip effectively reduces the phase error of the micromirror to 2.5%.
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Boiko, Juliy, i Oleksander Eromenko. "Signal Processing in Telecommunications with Forward Correction of Errors". Indonesian Journal of Electrical Engineering and Computer Science 11, nr 3 (1.09.2018): 868. http://dx.doi.org/10.11591/ijeecs.v11.i3.pp868-877.
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<span lang="IN">The development of mechanisms of increase efficiency of frequency-shift keying signals processing in telecommunications using algorithms of noise immunity channel coding in obstacle effect conditions is held in the article. The synthesis of the frequency-shift keying signal processing unit accounting intersymbol communication which is inherent for such signals with continuous phase is held. The conditions of the compromise implementation in the telecommunication information transmission channel with frequency shift keying and error correction coding for setting the optimal encoding rate in the range of the bandwidth of the information transmission system are explored. Linear cyclic codes Bose-Chaudhuri-Hocquenghem (BCH) are used for studying. By means of Matlab the article focuses on the definition of energetic benefit compared to uncoded system in case of equality of the bandwidth of the information transmission system with coding and without coding.</span>
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Liu, Wei, Hongqiang Wang, Qi Yang, Bin Deng, Lei Fan i Jun Yi. "High Precision Motion Compensation THz-ISAR Imaging Algorithm Based on KT and ME-MN". Remote Sensing 15, nr 18 (5.09.2023): 4371. http://dx.doi.org/10.3390/rs15184371.
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In recent years, terahertz (THz) radar has been widely researched for its high-resolution imaging. However, the traditional inverse synthetic aperture radar (ISAR) imaging algorithms in the microwave band perform unsatisfactorily in the THz band. Firstly, due to THz radar’s large bandwidth and short wavelength, the rotation of the target will result in serious space-varying(SV) range migration and space-varying phase error. Furthermore, it is challenging to accurately estimate the rotational velocity and compensate for phase errors in the presence of severe range migration effects. Therefore, in this paper, a high-precision THz-ISAR imaging algorithm is proposed. The algorithm includes the following step: First, the SV first-order range migration(FRM) is corrected using keystone transform (KT); then, the minimum entropy based on modified newton (ME-MN) is used to estimate the rotational velocity roughly, and the remaining SV second-order range migration(SRM) is corrected to obtain the range profile with the envelope alignment. Finally, the echo after the envelope alignment is processed for the second time based on ME-MN. The target rotation velocity is accurately estimated, and the phase error is compensated to obtain a well-focused imaging result. The validity of the proposed method is verified by numerical simulation and electromagnetic calculation data.