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Lu, Junqi, i Yongxin Guo. "Compact Planar Sparse Array Antenna with Optimum Element Dimensions for SATCOM Ground Terminals". International Journal of Antennas and Propagation 2015 (2015): 1–11. http://dx.doi.org/10.1155/2015/806981.
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A novel antenna array architecture for low-cost and compact SATCOM mobile terminal is presented. Based on equal-amplitude aperiodic phased array with fewer active chain numbers, it possesses advantages including lower weight, less cost, and higher power efficiency compared to conventional periodic phased arrays. It is implemented with printed patch antenna so that it guarantees compactness. The elements position and dimensions are jointly designed, with an effective sparse array synthesis strategy that takes actual patch antenna design constraint into consideration, to obtain a maximum array aperture efficiency. Executable and practical approach for variable dimension patch antenna designing, including defect substrate element and small scale array, is introduced and utilized to implement proposed sparse array. Full-wave simulation results demonstrate the advantages of proposed array antenna as well as the effectiveness of corresponding design approach.
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Shi, Wei, Zuping Qian, Jun Zhou, Xinbo Qu, Yang Xiang i Liu Hong. "A Small Ku-Band Polarization Tracking Active Phased Array for Mobile Satellite Communications". International Journal of Antennas and Propagation 2013 (2013): 1–12. http://dx.doi.org/10.1155/2013/747629.
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A compact polarization tracking active phased array for Ku-band mobile satellite signal reception is presented. In contrast with conventional mechanically tracking antennas, the approach presented here meets the requirements of beam tracking and polarization tracking simultaneously without any servo components. The two-layer stacked square patch fed by two probes is used as antenna element. The impedance bandwidth of 16% for the element covers the operating frequency range from 12.25 GHz to 12.75 GHz. In the presence of mutual coupling, the dimensional parameters for each element of the small 7 × 7 array are optimized during beam scanning and polarization tracking. The compact polarization tracking modules based on the low-temperature cofired ceramic (LTCC) system-in-package (SiP) technology are proposed. A small active phased array prototype with the size of 120 mm (length) × 120 mm (width) × 55 mm (height) is developed. The measured polarization tracking patterns of the prototype are given. The polarization tracking beam can be steered in the elevation up to 50°. The gain of no less than 16.0 dBi and the aperture efficiency of more than 50% are obtained. The measured and simulated polarization tracking patterns agreed well.
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Luo, Xuan, Jun Ouyang, Zhihui Chen, Lei Han i Wei Yan. "A Low-Profile 36-Element K-Band Active Phased Array for Ultra-Small Aperture Application". IEEE Access 8 (2020): 62286–97. http://dx.doi.org/10.1109/access.2020.2983604.
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Knott, Peter, Thomas Bertuch, Helmut Wilden, Olaf Peters, Andreas R. Brenner i Ingo Walterscheid. "SAR Experiments Using a Conformal Antenna Array Radar Demonstrator". International Journal of Antennas and Propagation 2012 (2012): 1–7. http://dx.doi.org/10.1155/2012/142542.
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Conformal antenna arrays have been studied for several years but only few examples of applications in modern radar or communication systems may be found up to date due to technological difficulties. The objective of the “Electronic Radar with Conformal Array Antenna” (ERAKO) demonstrator system which has been developed at the Fraunhofer Institute for High Frequency Physics and Radar Techniques (FHR) is to demonstrate the feasibility of an active electronically scanned antenna for conformal integration into small and medium sized airborne platforms. For practical trials the antenna has been adapted for operation with the Phased Array Multifunctional Imaging Radar (PAMIR) system developed at the institute. The antenna in combination with the PAMIR front-end needed to undergo a special calibration procedure for beam forming and imaging post-processing. The present paper describes the design and development of the conformal antenna array of the demonstrator system, its connection to the PAMIR system and results of recently conducted synthetic aperture radar (SAR) experiments.
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Liu, Rong, Naizhi Wang, Tong Li, Ruoqiao Zhang i Hongchao Wu. "X-Band Active Phased Array Antenna Using Dual-Port Waveguide for High-Power Microwave Applications". Electronics 11, nr 23 (6.12.2022): 4064. http://dx.doi.org/10.3390/electronics11234064.
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An X-band active phased array horn antenna with high power capacity and high peak power is proposed in this paper. At the horn aperture, the baffles are loaded to suppress higher-order modes and eliminate blind spots during beam scanning. Straight walls are added to improve impedance matching. Considering that the peak power that T/R modules can provide is very limited, the proposal of a dual-port waveguide breaks through the bottleneck of the power capacity of a single-port input for the first time. The proposed curved dual-port waveguide is used to connect the horn antenna and the T/R module, which is verified to improve the power capacity of the overall internal structure. Simulated and measured results show that VSWR ≤ 2 in the frequency range of 7.5–8.5 GHz. There is no grating lobe in the ±10° scanning range and the maximum gain drop does not exceed 0.4 dB. The power capacity of the proposed HPM array is 56.34 MW. The phased array antenna has the characteristics of flexible scanning, small size, and high gain, and can be applied in high-power microwave systems.
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Krüger, Frank, Torsten Dahm i Katrin Hannemann. "Mapping of Eastern North Atlantic Ocean seismicity from Po/So observations at a mid-aperture seismological broad-band deep sea array". Geophysical Journal International 221, nr 2 (1.02.2020): 1055–80. http://dx.doi.org/10.1093/gji/ggaa054.
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SUMMARY A mid-aperture broad-band test array (OBS array DOCTAR) was deployed from June 2011 to April 2012 about 100 km north of the Gloria fault in the Eastern North Atlantic in about 5000 m water depth. In addition arrays were installed on Madeira Island and in western Portugal mainland. For the first time in the Eastern North Atlantic, we recorded a large number of high frequency Po and So waves from local and regional small and moderate earthquakes (ML < 4). An incoherent beamforming method was adapted to scan continuous data for such Po and So arrivals applying a sliding window waveform migration and frequency–wavenumber technique. We identify about 320 Po and 1550 So arrivals and compare the phase onsets with the ISC catalogue (ISC 2015) for the same time span. Up to a distance of 6° to the DOCTAR stations all events listed in the ISC catalogue could be associated to Po and So phases. Arrivals from events in more than 10° distance could be identified only in some cases. Only few Po and/or So arrivals were detected for earthquakes from the European and African continental area, the continental shelf regions and for earthquakes within or northwest of the Azores plateau. Unexpectedly, earthquake clusters are detected within the oceanic plates north and south of the Gloria fault and far from plate boundaries, indicating active intraplate structures. We also observe and locate numerous small magnitude earthquakes on the segment of the Gloria fault directly south of DOCTAR, which likely coincides with the rupture of the 25 November 1941 event. Local small magnitude earthquakes located beneath DOCTAR show hypocentres up to 30 km depth and strike-slip focal mechanisms. A comparison with detections at temporary mid-aperture arrays on Madeira and in western Portugal shows that the deep ocean array performs much better than the island and the continental array regarding the detection threshold for events in the oceanic plates. We conclude that sparsely distributed mid-aperture seismic arrays in the deep ocean could decrease the detection and location threshold for seismicity with ML < 4 in the oceanic plate and might constitute a valuable tool to monitor oceanic plate seismicity.
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Kim, Seok, Chan-Mi Song, Seung-Hun Lee, Sung-Chan Song i Hyun-Ung Oh. "Design and Performance of X-Band SAR Payload for 80 kg Class Flat-Panel-Type Microsatellite Based on Active Phased Array Antenna". Aerospace 9, nr 4 (13.04.2022): 213. http://dx.doi.org/10.3390/aerospace9040213.
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The small synthetic aperture radar (SAR) technology experimental project (S-STEP) mission aims to develop an innovative spaceborne SAR microsatellite as a constellation of 32 microsatellites featuring a high-resolution stripmap mode of 1 m. The S-STEP is a spaceborne SAR microsatellite technology demonstration program in which innovative approaches have been proposed and investigated for SAR payload system designs for improving the development speed, affordability, size and weight parameters, and quality of SAR satellite systems. In this study, the major design approach includes a bus–payload integrated flat-panel-type SAR payload based on an active phased-array antenna. This study conducted an SAR image performance analysis considering the mission requirements to validate the feasibility of the innovative SAR payload design of the S-STEP. These performance analysis results are presented to demonstrate the effectiveness of the proposed SAR payload design approach under the new space paradigm.
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Kojima, Yuki, Kazuo Oki, Kosuke Noborio i Masaru Mizoguchi. "Estimating Soil Moisture Distributions across Small Farm Fields with ALOS/PALSAR". International Scholarly Research Notices 2016 (26.07.2016): 1–8. http://dx.doi.org/10.1155/2016/4203783.
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The ALOS (advanced land observing satellite) has an active microwave sensor, PALSAR (phased array L-band synthetic aperture radar), which has a fine resolution of 6.5 m. Because of the fine resolution, PALSAR provides the possibility of estimating soil moisture distributions in small farmlands. Making such small-scale estimates has not been available with traditional satellite remote sensing techniques. In this study, the relationship between microwave backscattering coefficient (σ) measured with PALSAR and ground-based soil moisture was determined to investigate the performance of PALSAR for estimating soil moisture distribution in a small-scale farmland. On the ground at a cabbage field in Japan in 2008, the soil moisture distribution of multiple soil layers was measured using time domain reflectometry when the ALOS flew over the field. Soil moisture in the 0–20 cm soil layer showed the largest correlation coefficient with σ (r=0.403). The σ values also showed a strong correlation with the ground surface coverage ratio by cabbage plants. Our results suggested that PALSAR could estimate soil moisture distribution of the 0–20 cm soil layer across a bare field and a crop coverage ratio when crops were planted.
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Morabito, Simona, Paola Cusano, Danilo Galluzzo, Guido Gaudiosi, Lucia Nardone, Pierdomenico Del Gaudio, Anna Gervasi i in. "One-Year Seismic Survey of the Tectonic CO2-Rich Site of Mefite d’Ansanto (Southern Italy): Preliminary Insights in the Seismic Noise Wavefield". Sensors 23, nr 3 (2.02.2023): 1630. http://dx.doi.org/10.3390/s23031630.
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A passive seismic experiment is carried out at the non-volcanic highly degassing site of Mefite d’Ansanto located at the northern tip of the Irpinia region (southern Italy), where the 1980 MS 6.9 destructive earthquake occurred. Between 2020 and 2021, background seismic noise was recorded by deploying a broadband seismic station and a seismic array composed of seven 1 Hz three-component sensors. Using two different array configurations, we were allowed to explore in detail the 1–20 Hz frequency band of the seismic noise wavefield as well as Rayleigh wave phase velocities in the 400–800 m/s range. Spectral analyses and array techniques were applied to one year of data showing that the frequency content of the signal is very stable in time. High frequency peaks are likely linked to the emission source, whereas at low frequencies seismic noise is clearly correlated to meteorological parameters. The results of this study show that small aperture seismic arrays probe the subsurface of tectonic CO2-rich emission areas and contribute to the understanding of the link between fluid circulation and seismogenesis in seismically active regions.
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Govorčin, Marin, Boško Pribičević i Shimon Wdowinski. "Surface Deformation Analysis of the Wider Zagreb Area (Croatia) with Focus on the Kašina Fault, Investigated with Small Baseline InSAR Observations". Sensors 19, nr 22 (7.11.2019): 4857. http://dx.doi.org/10.3390/s19224857.
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The wider Zagreb area is considered one of the few seismically active areas in the Republic of Croatia. During the period 1880–1906, moderate to strong seismic activity with three earthquakes magnitude M L ≥ 6 occurred on the NW-SE striking Kašina Fault and since then, the area has not experienced earthquakes exceeding magnitude M L = 5 . In order to estimate the ongoing interseismic strain accumulation along the fault, we analyze Advanced Land Observing Satellite (ALOS) Phased Array L-band SAR (PALSAR) and Environmental Satellite (Envisat)-Advanced Synthetic Aperture Radar (ASAR) datasets acquired over the period 2007–2010 and 2002–2010, respectively. The data were analyzed using small baseline interferometry (SBI) technique and indicate very slow surface deformations in the area, within ±3.5 mm/year, which are in a good agreement with previous geodetic studies. Interseismic strain accumulation analysis was conducted on two 14 km long segments of the Kašina Fault, seismically active in the South and stable in the North. The analysis indicates an ongoing interseismic strain accumulation of 2.3 mm/year on the Southern segment and no detectable strain accumulation on the Northern segment. Taking into consideration the lack of moderate to strong seismic activity in the past 113 years combined with the preliminary geodetic analysis from this study, we can conclude that the Southern segment of the Kašina Fault has the potential to generate earthquake magnitude M w < 6.
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Gu, Chunwang, Hao Liu i Min Yi. "Lightweight Fan-Beam Microstrip Grid Antenna for Airborne Microwave Interferometric Radiometer Applications". Micromachines 14, nr 1 (15.01.2023): 228. http://dx.doi.org/10.3390/mi14010228.
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The microwave interferometric radiometer (MIR) uses aperture synthesis technology to equate multiple small-aperture antennas into a large-aperture antenna to improve spatial resolution. At present, MIR antennas that operate at frequencies above the C-band mostly use horn antennas, waveguide slot antennas, etc., which have the disadvantages of a high profile and large mass. In this paper, a new type of miniaturized, low-profile, and lightweight K-band fan-beam microstrip grid antenna is designed for the airborne campaign of the K-band one-dimensional MIR of a Microwave Imager Combined Active and Passive (MICAP) onboard a Chinese Ocean Salinity Mission (COSM). With a limited size constraint (12.33 mm) on the antenna width, a fan-beam shape antenna pattern was achieved with a 5.34° 3-dB beamwidth in the narrow beam direction and up to a 55° 3-dB beamwidth in the fan-beam direction. A periodic structural unit is proposed in this paper to reduce the design complexity of Taylor weighting, achieving desirable performances on gain (19.1 dB) and sidelobe level (<−20 dB) in the H-plane. Four antenna elements were fabricated and arranged in a non-redundant sparse array. The performance of the four-element sparse array was evaluated with a simulation and real measurement in an anechoic chamber. The coupling between antenna elements was less than −25 dB, and the consistency of phase patterns was better than 3.4°. These results verify the feasibility of the proposed K-band microstrip grid antenna for airborne MIR applications.
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Mizuochi, Hiroki, Masato Hayashi i Takeo Tadono. "Development of an Operational Algorithm for Automated Deforestation Mapping via the Bayesian Integration of Long-Term Optical and Microwave Satellite Data". Remote Sensing 11, nr 17 (29.08.2019): 2038. http://dx.doi.org/10.3390/rs11172038.
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The frequent fine-scale monitoring of deforestation using satellite sensors is important for the sustainable management of forests. Traditional optical satellite sensors suffer from cloud interruption, particularly in tropical regions, and recent active microwave sensors (i.e., synthetic aperture radar) demonstrate the difficulty in data interpretation owing to their inherent sensor noise and complicated backscatter features of forests. Although the sensor integration of optical and microwave sensors is of compelling research interest, particularly in the conduct of deforestation monitoring, this topic has not been widely studied. In this paper, we introduce an operational algorithm for automated deforestation mapping using long-term optical and L-band SAR data, including a simple time-series analysis of Landsat stacks and a multilayered neural network with Advanced Spaceborne Thermal Emission and Reflection Radiometer and Phased Array-type L-band Synthetic Aperture Radar-2, followed by sensor integration based on the Bayesian Updating of Land-Cover. We applied the algorithm over a deciduous tropical forest in Cambodia in 2003–2018 for validation, and the algorithm demonstrated better accuracy than existing approaches, which only depend on optical data or SAR data. Owing to the cloud penetration ability of SAR, observation gaps of optical data under cloudy conditions were filled, resulting in a prompter detection of deforestation even in the tropical rainy season. We also investigated the effect of posterior probability constraints in the Bayesian approach. The land-cover maps (forest/deforestation) created by the well-tuned Bayesian approach achieved 94.0% ± 4.5%, 80.0% ± 10.1%, and 96.4% ± 1.9% for the user’s accuracy, producer’s accuracy, and overall accuracy, respectively. In the future, small-scale commission errors in the resultant maps should be improved by using more sophisticated machine-learning approaches and considering the reforestation effects in the algorithm. The application of the algorithm to other landscapes with other sensor combinations is also desirable.
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Brokešová, Johana, Jiří Málek, Jiří Vackář, Felix Bernauer, Joachim Wassermann i Heiner Igel. "Rotaphone-CY: The Newest Rotaphone Model Design and Preliminary Results from Performance Tests with Active Seismic Sources". Sensors 21, nr 2 (14.01.2021): 562. http://dx.doi.org/10.3390/s21020562.
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Rotaphone-CY is a six-component short-period seismograph that is capable of the co-located recording of three translational (ground velocity) components along three orthogonal axes and three rotational (rotation rate) components around the three axes in one device. It is a mechanical sensor system utilizing records from elemental sensors (geophones) arranged in parallel pairs to derive differential motions in the pairs. The pairs are attached to a rigid frame that is anchored to the ground. The model design, the latest one among various Rotaphone designs based on the same principle and presented elsewhere, is briefly introduced. The upgrades of the new model are a 32-bit A/D converter, a more precise placing of the geophones to parallel pairs and a better housing, which protects the instrument from external electromagnetic noise. The instrument is still in a developmental stage. It was tested in a field experiment that took place at the Geophysical Observatory in Fürstenfeldbruck (Germany) in November 2019. Four Rotaphones-CY underwent the huddle-testing phase of the experiment as well as the field-deployment phase, in which the instruments were installed in a small-aperture seismic array of a triangular shape. The preliminary results from this active-source experiment are shown. Rotaphone-CY data are verified, in part, by various approaches: mutual comparison of records from four independent Rotaphone-CY instruments, waveform matching according to rotation-to-translation relations, and comparison to array-derived rotations when applicable. The preliminary results are very promising and they suggest the good functionality of the Rotaphone-CY design. It has been proved that the present Rotaphone-CY model is a reliable instrument for measuring short-period seismic rotations of the amplitudes as small as 10−7 rad/s.
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Birring, Anmol. "Optimizing Probe Active Aperture for Phased Array Weld Inspections". Materials Evaluation 79, nr 8 (1.08.2021): 797–804. http://dx.doi.org/10.32548/2021.me-04220.
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Phased array ultrasonic testing (PAUT) has become a popular nondestructive technique for weld inspections in piping, pressure vessels, and other components such as turbines. This technique can be used both in manual and automated modes. PAUT is more attractive than conventional angle-beam ultrasonic testing (UT), as it sweeps the beam through a range of angles and presents a cross-sectional image of the area of interest. Other displays are also available depending on the software. Unlike traditional A-scan instruments, which require the reconstruction of B- and C-scan images from raster scanning, a phased array image is much simpler to produce from line scans and easier to interpret. Engineering codes have incorporated phased array technology and provide steps for standardization, scanning, and alternate acceptance criteria based on fracture mechanics. The basis of fracture mechanics is accurate defect sizing. There is, however, no guidance in codes and standards on the selection and setup of phased array probes for accurate sizing. Just like conventional probes, phased array probes have a beam spread that depends on the probe’s active aperture and frequency. Smaller phased array probes, when used for thicker sections, result in poor focusing, large beam spread, and poor discontinuity definition. This means low resolution and oversizing. Accurate sizing for fracture mechanics acceptance criteria requires probes with high resolution. In this paper, guidance is provided for the selection of phased array probes and setup parameters to improve resolution, definition, and sizing of discontinuities.
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Demmer, David, Francesco Foglia Manzillo, Samara Gharbieh, Maciej Śmierzchalski, Raffaele D’Errico, Jean-Baptiste Doré i Antonio Clemente. "Hybrid Precoding Applied to Multi-Beam Transmitting Reconfigurable Intelligent Surfaces (T-RIS)". Electronics 12, nr 5 (27.02.2023): 1162. http://dx.doi.org/10.3390/electronics12051162.
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In this work, we study hybrid precoding techniques applied to multi-user Transmitting Reconfigurable Intelligent Surface (T-RIS) systems. The T-RIS considered here is a large array of electronically reconfigurable antenna elements illuminated by a small set of active sources. When it comes to digital signal-processing techniques applied to T-RIS systems, it is necessary to consider realistic models to bridge the gap with theoretical results. For this reason, we propose a multi-beam T-RIS propagation model with strong phase quantization constraints and limited beam codebooks. First, the proposed model is validated by characterizing a Ka-band T-RIS. Then, we optimize the quad-beam T-RIS structure by tuning the focal distance between the lens and the focal sources according to two metrics: (i) the per-user antenna gain (analog-only approach), and (ii) the per-user average rate (hybrid digital/analog approach). For both indicators, the system performance is evaluated in a multi-user scenario by assuming imperfect channel state information. We show that considering only the analog precoder is sufficient to optimize the T-RIS. However, the fully hybrid precoding scheme is required to deal with inter-user interference. We propose a codebook-aware optimization that improves the aperture efficiency of the T-RIS system.
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Aminev, A. M., A. V. Gilev, D. Yu Grishin, V. E. Zaytsev i V. N. Sergeev. "Automated active phased array control stand software". Journal of «Almaz – Antey» Air and Space Defence Corporation, nr 4 (30.12.2019): 93–102. http://dx.doi.org/10.38013/2542-0542-2019-4-93-102.
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The study suggests using a software platform for multidimensional data cubes in automated active phased array control stands. The application of the platform greatly facilitates and accelerates the display and analysis of very large volumes of data coming from large-aperture active phased arrays during the measurement process, so that the end user can make spontaneous data requests. The study shows the prospects of using this platform for radar systems as a whole.
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Shishov, Yu A., D. V. Gubanov i M. G. Vakhlov. "Calibration of receiving-transmitting channels of large-aperture active phased antenna array". Issues of radio electronics, nr 11 (18.01.2021): 30–36. http://dx.doi.org/10.21778/2218-5453-2020-11-30-36.
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NagaPavani, G., Ch Lakshmi Prasanna i Dr N.N. Sastry. "An ultra-wide band printed small aperture tapered slot phased array antenna covering 6-18GHZ". International Journal of Engineering & Technology 7, nr 4 (24.09.2018): 2628. http://dx.doi.org/10.14419/ijet.v7i2.18.12763.
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For phased array applications covering ultra wide bandwidth, it is necessary to restrict the size of the aperture to less than λ/2 at highest frequency of operation. For 6-18 GHz coverage, an aperture size of less than 9.76mm is required for scanning to ±450 without appearance of grating lobes and occurrence of element pattern nulls over the band. Meeting this requirement a printed tapered slot antenna has been designed with the above aperture size. Detailed parametric studies have been carried out over 6-18 GHz and dimensions have been opti-mized for return loss. The design has been carried out with HFSS software. A return loss of less than -7.5dB across 5.6 - 20 GHz has been obtained for a single antenna. Also satisfactory radiation patterns have been obtained.
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Gribanov, A. N., S. E. Gavrilova, O. V. Pavlovich, G. F. Moseychuk i A. N. Titov. "Method of forming and scaling phased array expanded beams". Journal of «Almaz – Antey» Air and Space Defence Corporation, nr 3 (30.09.2019): 19–29. http://dx.doi.org/10.38013/2542-0542-2019-3-19-29.
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The paper focuses on the phase synthesis of one-dimensionally expanded phased array beams. In the study we used the fan partial diagram method. By this method and applying the known amplitude distribution in the aperture and the desired beam shape, we were able to unambiguously determine the desired phase distribution by means of simple calculations. The method is applicable for a phased antenna array and an active phased antenna array with linear and flat apertures. The study is the first to discuss the scaling properties of expanded beams, which allow one to obtain many synthesis options from only one option by multiplying the phase distribution by the scaling factor. Four important properties of scaling are formulated and proved, which must be taken into account when scaling. The paper gives the results of mathematical simulation and experimental measurements, proving the efficiency of the method
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Won, Young-Jin, Kyun Ho Lee i Jae-Hyun Lee. "Performance Improvement of Spaceborne SAR Using Antenna Pattern Synthesis Based on Quantum-Behaved Particle Swarm Optimization". International Journal of Antennas and Propagation 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/6928970.
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This study improves the performance of a spaceborne synthetic aperture radar (SAR) system using an antenna mask design method and antenna pattern synthesis algorithms for an active phased array SAR system. The SAR antenna is an important component that affects the SAR system performance because it is closely related to the antenna pattern. This study proposes a method for antenna mask design that is based on several previous studies as well as the antenna pattern synthesis algorithm, which is based on quantum-behaved particle swarm optimization (QPSO) for an active phased array SAR system. The performance of the designed antenna masks and synthesized patterns demonstrate that the proposed mask design method and antenna pattern synthesis algorithm based on QPSO can be used to improve the SAR system performance for spaceborne applications.
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Kuznetsov, Grigory, Vladimir Temchenko, Maxim Miloserdov i Dmitry Voskresenskiy. "Modifications of active phased antenna arrays near-field diagnosis method based on compressive sensing". International Journal of Microwave and Wireless Technologies 11, nr 7 (18.07.2019): 568–76. http://dx.doi.org/10.1017/s1759078719000989.
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AbstractThis paper presents two modifications of compressive sensing (CS)-based approach applied to the near-field diagnosis of active phased arrays. CS-based antenna array diagnosis allows a significant reduction of measurement time, which is crucial for the characterization of electrically large active antenna arrays, e.g. used in synthetic aperture radar. However, practical implementation of this method is limited by two factors: first, it is sensitive to thermal instabilities of the array under test, and second, excitation reconstruction accuracy strongly depends on the accuracy of the elements of the measurement matrix. First proposed modification allows taking into account of thermal instability of the array by using an iterative ℓ1-minimization procedure. The second modification increases the accuracy of reconstruction using several simple additional measurements.
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O'Donnell, M., i S. W. Flax. "Phase Aberration Measurements in Medical Ultrasound: Human Studies". Ultrasonic Imaging 10, nr 1 (styczeń 1988): 1–11. http://dx.doi.org/10.1177/016173468801000101.
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Using a modified real-time phased array sector scanner, phase aberrations and amplitude fluctuations across the imaging aperture have been measured in a number of human subjects. Data from these subjects were classified into two categories based on the quality of conventional longitudinal images of the liver. Measured phase aberrations were very small in all subjects exhibiting high quality images. In contrast, large phase aberrations were measured in subjects producing low quality images. However, there were no significant amplitude variations across the array for all subjects studied. These results suggest that the absence of significant phase aberrations is a necessary condition for high quality phased array imaging. If so, improvements in clinical image quality in Such Subjects may be possible.
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Fatemi, Reza, Behrooz Abiri, Aroutin Khachaturian i Ali Hajimiri. "High sensitivity active flat optics optical phased array receiver with a two-dimensional aperture". Optics Express 26, nr 23 (31.10.2018): 29983. http://dx.doi.org/10.1364/oe.26.029983.
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Xiang, Meng, Yu Xiao, Bin Xi, Yue Zhang i Shiyou Xu. "Design of an S-Band Phased Array with Modified Dipoles". International Journal of Antennas and Propagation 2021 (29.11.2021): 1–8. http://dx.doi.org/10.1155/2021/3306011.
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A wideband, low cross-polarization, high-gain, and wide-angle scanning antenna array is presented in this paper. The antenna array contains 8 subarrays in the horizontal dimension, and each subarray contains 4 unit cells. A two-side printed dipole with an amendatory equivalent circuit model is adopted, and the metal vias are introduced in the element design to ameliorate the cross-polarization level. A radome, acting as the wide-angle impedance matching layer, is introduced to achieve wide-angle scanning. A prototype of a 4 × 8 array is fabricated and measured. The results show that the operating bandwidth of aperture efficiency (BWAE) above 60% is about 26.7% from 2.6 GHz to 3.4 GHz. The measured scanning loss in the H-plane is 2.7 dB when scanning up to 60° with active voltage standing wave ratio (VSWR) <3, and the gain can achieve 21 dB at 3 GHz with a cross-polarization level below −30 dB at all angles.
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Lay, Vera, Franziska Baensch, Sergej Johann, Patrick Sturm, Frank Mielentz, Prathik Prabhakara, Detlef Hofmann, Ernst Niederleithinger i Hans-Carsten Kühne. "SealWasteSafe: materials technology, monitoring techniques, and quality assurance for safe sealing structures in underground repositories". Safety of Nuclear Waste Disposal 1 (10.11.2021): 127–28. http://dx.doi.org/10.5194/sand-1-127-2021.
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Abstract. Within the project SealWasteSafe, we advance construction materials and monitoring concepts of sealing structures applied for underground disposal of nuclear or toxic waste. As these engineered barriers have high demands concerning integrity, an innovative alkali-activated material (AAM) is improved and tested on various laboratory scales. This AAM has low reaction kinetics related to a preferential slow release of the heat of reaction in comparison to alternative salt concretes based on Portland cement or magnesium oxychloride cements. Hence, crack formation due to thermally induced strain is reduced. After successful laboratory scale analysis (Sturm et al., 2021), the AAM is characterised on a larger scale by manufacturing test specimens (100–300 L). Conventional salt concrete (DBE, 2004) and the newly developed AAM are compared using two specimen geometries, i.e. cylindrical and cuboid. A comprehensive multisensor monitoring scheme is developed to compare the setting process of AAM and salt concrete for these manufactured specimens. The analysed parameters include temperature and humidity of the material, acoustic emissions, and strain variations. Passive sensor systems based on radiofrequency identification technology (RFID) embedded in the concrete, enable wireless access to temperature and humidity measurements and are compared to conventional cabled systems. Additionally, fibre-optic sensors (FOS) are embedded to record strain, but also have potential to record temperature and moisture conditions. Part of this project aims at demonstrating the high reliability of sensors and also their resistance to highly alkaline environments and to water intrusion along cables or at sensor locations. Further technical improvements were implemented so that first results clearly show the scalability of the setting process from previous small-scale AAM experiments and particularly the high potential of the newly developed approaches. Furthermore, ultrasonic methods are used for quality assurance to detect obstacles, potential cracks and delamination. On the one hand, both active and passive ultrasonic measurements complement the results obtained from the multisensor monitoring scheme for the produced specimens. On the other hand, the unique large aperture ultrasonic system (LAUS) provides great depth penetration (up to nearly 10 m) and can thus be applied at in situ sealing structures built as a test site in Morsleben by the Federal Company for Radioactive Waste Disposal (Bundesgesellschaft für Endlagerung, BGE) as shown by Effner et al. (2021). An optimised field lay-out identified from forward modelling studies and advanced imaging techniques applied to the measured data will further improve the obtained results. To characterise the inside of the test engineered barrier and achieve a proof-of-concept, an ultrasonic borehole probe is developed to enable phased arrays that can further improve the detection of potential cracks. Modelling results and first analysis of semispherical specimens confirmed the reliability of the directional response caused by the phased arrays of the newly constructed ultrasonic borehole probe. Overall, the project SealWasteSafe improves the construction material, multisensor monitoring concepts and ultrasonics for quality assurance. This will help to develop safe sealing structures for nuclear waste disposal. The outcomes are particularly valuable for salt as a host rock but partly also transferrable to alternative conditions.
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Oppermann, Martin, Joerg Schroth i Felix Thurow. "Transmit/Receive (T/R) Modules – Key Elements for Phased Array Antennas". Additional Conferences (Device Packaging, HiTEC, HiTEN, and CICMT) 2013, CICMT (1.09.2013): 000054–58. http://dx.doi.org/10.4071/cicmt-2013-tp24.
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Modern Active Electronically Steered Antennas (AESA) are operating in different platforms and systems. Inside EADS/CASSIDIAN the focus on X-Band antennas today is in airborne and fighter nose radars, in satellite based SAR antennas (Synthetic Aperture Radar) for earth observation and ground surveillance and security radars. Active antennas are assembled with hundreds or even thousands of T/R modules. This paper will describe an example of a so called standardized module solution based on LTCC package technology. State-of-the-art modules are assembled with active components like MMICs realized in GaAs technology, e.g. Low Noise Amplifier (LNA) and High Power Amplifier (HPA), Silicon based devices and passives. Assembly technologies are optimized for high yield series production inside CASSIDIAN MicroWave Factory. New semiconductor technologies, like GaN (Gallium Nitride) are enablers for a new T/R module generation. GaN/SiC based MMICs with higher power density compared with GaAs based devices are technological challenges for innovative thermal management solutions and assembly alternatives. GaN power devices are soldered on modern heatsink materials with high thermal conductivity and matched CTE (between MMIC and heatsink). Results of thermal simulations comparing different heatsink materials in combination with soldering techniques will be discussed and an optimized solution will be shown. Another type of T/R Module technology based on RF-PCB and packaged MMICs will be discussed. Future applications of ground-based security radars, active antenna products with a one-dimensional array and needs for cost-effective solutions seem to be SMD-based products. Different packages, e.g. QFN (Quad Flat Pack no Lead) and ceramic based (HTCC), mainly for power devices will be shown and compared.
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Oppermann, Martin, Joerg Schroth i Felix Thurow. "Transmit/Receive (T/R) Modules—Key Elements for Phased Array Antennas". Journal of Microelectronics and Electronic Packaging 10, nr 3 (1.07.2013): 116–19. http://dx.doi.org/10.4071/imaps.381.
Pełny tekst źródłaStreszczenie:
Modern active electronically steered antennas (AESA) operate in different platforms and systems. Inside EADS/CASSIDIAN, the focus on X-band antennas today is on airborne and fighter nose radars, in satellite based SAR antennas (synthetic aperture radar) for earth observation, and ground surveillance and security radars. Active antennas are assembled with hundreds or even thousands of transmit/receive modules. This paper will describe an example of a so-called standardized module solution based on LTCC package technology. State-of-the-art modules are assembled with active components such as MMICs realized in GaAs technology, for example, the low noise amplifier (LNA) and the high power amplifier (HPA), silicon based devices, and passives. Assembly technologies are optimized for high yield series production inside CASSIDIAN MicroWave Factory. New semiconductor technologies, such as GaN (gallium nitride) are enablers for a new transmit/receive module generation. GaN/SiC based MMICs with higher power density compared with GaAs-based devices are technological challenges for innovative thermal management solutions and assembly alternatives. GaN power devices are soldered on modern heat sink materials with high thermal conductivity and matched CTE (between the MMIC and the heat sink). The results of thermal simulations comparing different heat sink materials in combination with soldering techniques will be discussed and an optimized solution will be shown. Another type of transmit/receive module technology based on RF-PCB and packaged MMICs will be discussed. Future applications of ground-based security radars, active antenna products with a one-dimensional array, and the need for cost-effective solutions seem to be a good fit for SMD-based products. Different packages, for example, QFN (quad flat pack no lead) and ceramic based (HTCC), mainly for power devices will be shown and compared.
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Makhoul, Eduardo, Antoni Broquetas, Francisco Lopez-Dekker, Josep Closa i Paula Saameno. "Evaluation of the Internal Calibration Methodologies for Spaceborne Synthetic Aperture Radars with Active Phased Array Antennas". IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 5, nr 3 (czerwiec 2012): 909–18. http://dx.doi.org/10.1109/jstars.2012.2199087.
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Yanchun, Zheng, Miao Cunjian, Hong Lixiang i Guo Weican. "An Experimental Study on Phased Array Ultrasonic Testing for Internal Inspection of Gas Storage Wells". Materials Evaluation 80, nr 8 (1.08.2022): 40–45. http://dx.doi.org/10.32548/2022.me-04278.
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A reduction in wall thickness, caused by corrosion, of the inner and outer surfaces of underground compressed natural gas storage wells is one of the main causes of failure. Therefore, taking wall thickness measurements is an important task during periodic inspection. This study proposes a corrosion detection technique based on the well’s shape using cylindrical convex ultrasonic phased array and develops a cylindrical convex phased array probe with 512 elements. Using an example well of ∅177 × 10.36 mm, the influences of process parameters such as active aperture, focal length, gain, and gate threshold are studied. In addition, an experiment is conducted on a sample well with artificial defects for parameters optimization. Next, experimental tests are carried out on the well at the test platform according to the optimized parameters. The results show that the proposed technique is of high sensitivity and efficiency for the detection of corrosion defects and is able to detect pitting corrosion of more than ∅2 mm and line corrosion of 1 mm width.
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Xu, Zheng, Chengxiang Hao, Kuiwen Xu i Shichang Chen. "A Compact Ku-Band Active Electronically Steerable Antenna with Low-Cost 3D T/R Module". Wireless Communications and Mobile Computing 2019 (22.04.2019): 1–8. http://dx.doi.org/10.1155/2019/5287679.
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This paper presents a novel compact Ku-band active electronically steerable antenna array design with a low-cost and integrated T/R 3D module employed for airborne synthetic aperture radar (SAR) systems. The entire system adopts 3D multilayer technology with vertical interconnection to construct the hermetically packaging RF modules. By assembling different multifunctional modules into a whole multilayer board, the 3D T/R technique greatly improves the system integration and reduces implementation cost and size. Besides, a wideband circular polarized antenna array was designed in LTCC and connected to the proposed T/R modules to form a complete AESA. The whole proposed antenna system has been fabricated and experimentally investigated. Measurement results showed very good phased array performances in terms of gain, axial ratio, and radiating patterns. The low-cost, lightweight, and low-power features exhibited by the proposed design validate its applicability for weight and power constrained platforms with great electronic steering ability.
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Bachmann, Markus, Marco Schwerdt i Benjamin Bräutigam. "Accurate Antenna Pattern Modeling for Phased Array Antennas in SAR Applications—Demonstration on TerraSAR-X". International Journal of Antennas and Propagation 2009 (2009): 1–9. http://dx.doi.org/10.1155/2009/492505.
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The high flexibility and tight accuracy requirements of today's spaceborne synthetic aperture radar (SAR) systems require innovative technologies to calibrate and process the SAR images. To perform accurate pattern correction during SAR processing, an Antenna Model is used to derive the multitude of different antenna beams generated by active antenna steering. The application of such an Antenna Model could be successfully demonstrated for the TerraSAR-X mission, launched in 2007. The methodology and the results of the inorbit verification with an achieved accuracy of better than dB is reviewed in this paper in detail showing its outstanding accuracy.
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Parshina, E. S. "Technique for spatial interference reduction and its application in monopulse radar with active phased array antenna". Issues of radio electronics, nr 12 (3.02.2021): 17–22. http://dx.doi.org/10.21778/2218-5453-2020-12-17-22.
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The paper describes monopulse radar with sidelobe-blanking system. The antenna of the sidelobe-blanking system is one subarray of the radar’s active phased array antenna. The elements of the subarray is also used for sum and difference pattern generation. It is shown that if aperture distribution required to produce low-sidelobe sum pattern is used, the pattern of one subarray will satisfy the requrements for antenna of the sidelobe-blanking system. An example of designing the monopulse radar with sidelobe-blanking system is presented. Sum pattern of the radar anettena is produced with different low-sidelobe pattern synthesis procedures. The analysis of monopulse radar parameters and sidelobe-blanking system performance is done.
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Renkwitz, Toralf, Carsten Schult i Ralph Latteck. "VHF antenna pattern characterization by the observation of meteor head echoes". Atmospheric Measurement Techniques 10, nr 2 (14.02.2017): 527–35. http://dx.doi.org/10.5194/amt-10-527-2017.
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Abstract. The Middle Atmosphere Alomar Radar System (MAARSY) with its active phased array antenna is designed and used for studies of phenomena in the mesosphere and lower atmosphere. The flexible beam forming and steering combined with a large aperture array allows for observations with a high temporal and angular resolution. For both the analysis of the radar data and the configuration of experiments, the actual radiation pattern needs to be known. For that purpose, various simulations as well as passive and active experiments have been conducted. Here, results of meteor head echo observations are presented, which allow us to derive detailed information of the actual radiation pattern for different beam-pointing positions and the current health status of the entire radar. For MAARSY, the described method offers robust beam pointing and width estimations for a minimum of a few days of observations.
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Levy, Benzion, Ely Levine i Yosef Pinhasi. "Super Directional Antenna—3D Phased Array Antenna Based on Directional Elements". Electronics 11, nr 14 (17.07.2022): 2233. http://dx.doi.org/10.3390/electronics11142233.
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This paper describes an antenna design approach for achieving super directivity in an AESA (Active Electronic Scanned Array) radar using an unconventional 3D phased array (PA) antenna concept based on directional Yagi–Uda elements. The proposed scheme is shown to have a wider scanning feature, with higher directivity in comparison to the same geometry dipole array without increasing the element number. The antenna’s microwave design includes an antipodal Yagi–Uda antenna element that is implemented efficiently on a microstrip PCB using a balun (balance–unbalance)-fed network. This type of antenna is valuable in restricted aperture scans for achieving a narrow antenna beam that increases the angular resolution and measurement precision of tracked targets and also enlarges the detection range or, alternatively, achieves the same performance with a lower number of elements—meeting the goal of low-cost production. The notable result of the high antenna directivity was obtained by both the element and the array architecture, which allowed for improvements in the Array Factor (AF) directivity by increasing the element’s spacing and broadening the scan sector, achieved via the suppression of the element’s Grating Lobe (GL). Another important benefit of this antenna design is the superior coupling reduction caused by its enlarged element distances, which are very significant in electronic scans. An outstanding opportunity to exploit this low coupling can be found in separated MIMO radar architecture. Other benefits of this design’s architecture are the support of a combined module and antenna on a unified board thanks to the End-Fire radiation pattern, its low frequency sensitivity, and its low-cost manufacturing.
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Tong, San-Qiang, Bing-Zhong Wang i Ren Wang. "A tightly coupled dipole array used for radiation power improvement on finite radiation aperture". Acta Physica Sinica 70, nr 20 (2021): 204101. http://dx.doi.org/10.7498/aps.70.20210309.
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Radiation power of an electromagnetic wave plays a decisive role in its transmission distance. Traditionally, the radiation power can be improved by expanding the radiation aperture size of the antenna array or increasing input power of the unit cell. However, the radiation aperture size is always restricted by assembly space. The input power improvement of the unit cell is always limited by the signal source. It is difficult to improve radiation power on a finite radiation aperture. However, the radiation power on a finite radiation aperture is related closely to the number of antenna elements and the radiation efficiency of the antenna array. It is useful to arrange more elements and improve radiation efficiency of the antenna array to improve the radiation power on a finite radiation aperture. Wideband wide-angle scanning phased array is able to make full use of a finite radiation aperture. The wide-angle scanning properties make it possible for the radiated power to cover a wide area. In this paper, a compact wideband wide-angle scanning tightly coupled dipole array (TCDA) is proposed. A high permittivity substrate and compact wideband balun are used for miniaturizing the antenna array. The period of the unit cell is only 0.144<i>λ</i><sub>high</sub> × 0.144<i>λ</i><sub>high</sub> (<i>λ</i><sub>high</sub> is the wavelength at the highest operation frequency in free space). Parameters of the balun are optimized to improve impedance matching between the balun and the antenna array. Two bilateral frequency selective surfaces (FSSs) are used to replace traditional dielectric superstrate to improve the impedance matching between the antenna array and free space. A low-loss dielectric substrate is used to reduce dielectric loss of the antenna array. In these ways, the radiation efficiency is greatly improved. The simulation results show that the proposed antenna array operates at 1.7–5.4 GHz (3.2:1) while scanning up to 65° in the E plane, 45° in the H plane and 60° in the D plane with following a rigorous impedance matching criterion (active VSWR < 2). A 16 × 16 prototype array is fabricated and measured. Good agreement is achieved between the simulation results and the measurement results. Compared with the designs in the literature, the proposed antenna array has an excellent performance in radiation power on a finite radiation aperture.
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Lee, Jae-Duk. "Study on Active Return Loss of Phase Encoding Code Using Extended Coupling Matrix for Active Phased Array Synthetic Aperture Radar Application". Journal of Korean Institute of Information Technology 17, nr 5 (31.05.2019): 57–64. http://dx.doi.org/10.14801/jkiit.2019.17.5.57.
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Ye, Yuan, Shaozhi Wang, Boyuan Liu, Qingping Wang, Yang Zhou, Jingjian Huang, Xi Chen, Quan Xue i Naichang Yuan. "Novel Planar Ultra-Wideband Modular Antenna Array with Low Profile". Electronics 11, nr 24 (14.12.2022): 4173. http://dx.doi.org/10.3390/electronics11244173.
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A planar ultra-wideband modular antenna array with an ultra-low profile based on a tight coupling effect is proposed. The antenna array is composed of multi-layer printed circuit boards. Since its frequency operation can extend up to the grading lobe frequency, the number of T/R components for the antenna aperture is reduced to the greatest extent. Specifically, a horizontal “fin” structure is added on the parallel feeding lines, which assists in improving the impedance matching of the array. In order to break the bandwidth limitation of the low-frequency loop mode, a capacitive short-circuit probe is introduced to push the common-mode resonance point into the low-frequency band. Finally, subject to Active VSWR < 3, the array can realize E-plane, H-plane, and D-plane ± 45° beam scan coverage across the 6:1 frequency band (3.48–20.97 GHz). A 128-element prototype was processed and tested to validate the design. This array not only has the advantages of low profile, modularity, easy assembly, and maintenance but also minimizes the number of T/R components and reduces the cost of phased array antennas.
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Lemaitre, Gerard Rene, Pascal Vola, Patrick Lanzoni, Silvio Mazzanti, Frederic J. Dérie i Frederic Y. Gonté. "Active Optics—Advances of Cycloid-like Variable Curvature Mirrors for the VLTI Array". Photonics 9, nr 2 (26.01.2022): 66. http://dx.doi.org/10.3390/photonics9020066.
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Elasticity theory and active optics led us to the discovery of three geometrical configurations of variable curvature mirrors (VCMs) that are either cycloid-like or tulip-like thickness distributions. Cycloid-like VCMs are generated by a uniform load—air pressure—applied over the mirror rear surface, and reacts without any bending moment along its circular contour. This particular VCM configuration is of practical interest because it smoothly generates accurate optical curvatures, varying from plane at rest to spherical curvatures up to f/2.9 over 16-mm aperture under 6.5-bar air pressure. Starting from the thin plate theory of elasticity and modeling with NASTRAN finite element analysis, one shows that 3-D optimizations—using a non-linear static flexural option—provide an accurate cycloid-like thickness distribution. VCM elasticity modeling in quenched stainless steel–chromium substrates allows the obtaining of diffraction-limited optical surfaces: Rayleigh’s criterion is achieved over a zoom range from flat to f/3.6 over 13-mm clear aperture up to 6-bar loading. These VCMs were originally developed and built at the Marseille Observatory in 1975 and implemented as a cat’s-eye mirror of IR Fourier-transform interferometers for laboratory recording of fast events in gas molecular spectroscopy. Later, for high-angular resolution astronomy with the ESO VLTI array—an interferometer made of 8 m Unit Telescopes (UTs) and 1.8 m Auxiliary Telescopes (ATs)—such VCMs were inevitable components to provide in a 3″ co-phased field-of-view since 1998. They were implemented (1) as cat’s eye mirrors of the height delay-lines beam recombination lab and (2) as ATs mirror-pair for output pupil conjugation of the movable x–y baseline. From the ESO-AMU approved convention of making 10 VCM spares up to 2024, the present modeling should provide a diffraction-limited extended field-of-view. It is pure coincidence that present results from modeling with an outer collarette are identical to results from analytic theory without collarette.
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Ambrozinski, Lukasz, Tadeusz Stepinski, Tadeusz Uhl, Janusz Ochonski i Andrzej Klepka. "Development of Lamb Waves-Based SHM Systems". Key Engineering Materials 518 (lipiec 2012): 87–94. http://dx.doi.org/10.4028/www.scientific.net/kem.518.87.
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Guided waves (GW) based methods are a promising tool for structural health monitoring (SHM) of plate-like metallic and composite structures in which high safety standards are required. In this paper we present research with the aim to design and manufacture a prototype of Lamb waves (LW) SHM system. Two approaches can be applied for SHM of plate-like structures. One of them can be based on a sparse array and damage imaging involving incoherent summation of signals envelope. The second approach involves phased arrays with transducers spaced at a distance lower than half wavelength of the excited Lamb-mode. The influence of an arrays parameters on beamforming of Lamb waves is discussed in the case of linear array. It appears that an unequivocal localization of damage on a plate requires a 2D arrays topology; therefore a star-shaped active array was designed and manufactured for the developed SHM system. Two signal processing approaches were applied for that array, the standard one, based on the delay and sum (DAS) synthetic aperture focusing scheme, and the second one, using a self-focusing technique to obtain the separate images for each scatterer existing in the plate.
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Li, Lei, Kuan Yang, Xiaoyu Bian, Qinghui Liu, Yizhuo Yang i Fengying Ma. "A Gas Leakage Localization Method Based on a Virtual Ultrasonic Sensor Array". Sensors 19, nr 14 (17.07.2019): 3152. http://dx.doi.org/10.3390/s19143152.
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In traditional sensory array-based acoustic emission methods that are used for gas leakage localization, the localization resolution depends on the spatial aperture of the array, that is, the number of sensors. Most of the existing methods use small arrays that can only achieve low-resolution localization results because of limitations such as the amplitude and phase consistency, the complexity and cost of the system. This paper reports the first application of a virtual phased array for gas leakage detection to obtain high-resolution localization results. This method uses a virtual linear ultrasonic sensor array composed of only two sensors to acquire leakage signals. Then, we use the virtual beamforming algorithm based on the cross-power spectrum to estimate the location of the leakage source. Several experiments were conducted to evaluate the effectiveness and operability of the proposed method. The impacts of various factors on the performance of the localization technique are compared and discussed, including factors such as the number of sensors and the distance between the leak hole and virtual array. The results demonstrate that the proposed method accurately and reliably localizes gas leakages.
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Pankov, V. V., i D. S. Pomerantsev. "ULTRASOUND TESTING WITH USING OF THE PHASED ARRAY PROBES. BASIC PRINCIPLES. PART 1". Kontrol'. Diagnostika, nr 261 (marzec 2020): 38–43. http://dx.doi.org/10.14489/td.2020.03.pp.038-043.
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This article discusses the current state of standardization in the Russian Federation in the field of application of ultrasonic testing using a phased array. Attention is drawn to the problem of the lack of national standards (especially terminological), which clearly hinders the active development and implementation of the PA UT method in practice. The basic principles of the classical technology of phased arrays are analyzed. Electronic linear scanning, electronic scanning and combined scanning. Combined scanning has several advantages: a high probability of detecting defects, high scanning speed, quick setup and calibration, quick data analysis and small file size in comparison with conventional sector scanning. Some difficulties were noted when trying to work with classical DGS-curves using the synthetic focusing methods SAFT or FMC / TFM with beam focusing at each image reconstruction point.
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Sung, Jin-Bong, Se-Young Kim, Jong-Hwan Lee i Byeong-Tae Jeon. "Development and Performance Compensation of the Extremely Stable Transceiver System for High Resolution Wideband Active Phased Array Synthetic Aperture Radar". Journal of Korean Institute of Electromagnetic Engineering and Science 21, nr 6 (30.06.2010): 573–82. http://dx.doi.org/10.5515/kjkiees.2010.21.6.573.
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Zhang, Haiyan, Yaqun Liu, Guopeng Fan, Hui Zhang, Wenfa Zhu i Qi Zhu. "Sparse-TFM Imaging of Lamb Waves for the Near-Distance Defects in Plate-Like Structures". Metals 9, nr 5 (29.04.2019): 503. http://dx.doi.org/10.3390/met9050503.
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The ultrasonic phased array total focusing method (TFM) has the advantages of high imaging resolution and high sensitivity to small defects. However, it has a long imaging time and cannot realize near-distance defect imaging, which limits its application for industrial detection. A sparse-TFM algorithm is adopted in this work to solve the problem regarding rapid imaging of near- distance defects in thin plates. Green’s function is reconstructed through the cross-correlation of the diffuse full matrix captured by the ultrasonic phased array. The reconstructed full matrix recovers near-distance scattering information submerged by noise. A sparse array is applied to TFM for rapid imaging. In order to improve the imaging resolution, the location of active array elements in the sparse array can be optimized using the genetic algorithm (GA). Experiments are conducted on three aluminium plates with near-distance defects. The experimental results confirm that the sparse-TFM algorithm of Lamb waves can be used for near-distance defects imaging, which increases the computational efficiency by keeping the imaging accuracy. This paper provides a theoretical guidance for Lamb wave non-destructive testing of the near-distance defects in plate-like structures.
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Останков, А. В., А. С. Нечаев i С. Ю. Дашян. "SYNTHESIS OF PHASED ARRAY ANTENNA WITH FLAT-TOPPED DIRECTIONAL PATTERN". ВЕСТНИК ВОРОНЕЖСКОГО ГОСУДАРСТВЕННОГО ТЕХНИЧЕСКОГО УНИВЕРСИТЕТА, nr 3 (2.07.2021): 78–84. http://dx.doi.org/10.36622/vstu.2021.17.3.011.
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При синтезе фазированной антенной решетки с секторной диаграммой направленности методами, основанными на разложении диаграммы в обобщенный ряд Фурье, затруднительно обеспечить заданные показатели качества направленности. Причинами ухудшения показателей секторной диаграммы являются конечное число используемых при синтезе базисных функций и ограниченность в пространстве амплитудно-фазового распределения на апертуре решетки. Цель работы - показать на примере линейной эквидистантной антенной решетки, что применение при синтезе оптимизированного шаблона оригинальной формы позволяет достичь улучшенных показателей секторной диаграммы направленности. Для обеспечения предыскажений диаграммы направленности предложен шаблон, один параметр которого определяет ширину, а второй - степень сглаженности вершины диаграммы. Малое число параметров шаблона дает возможность при его оптимизации отказаться от методов эволюционного поиска и упростить процедуру синтеза. На конкретных примерах показано, что применение оптимизированного шаблона позволяет достичь улучшенных показателей секторной диаграммы направленности. Так, удается существенно снизить амплитуду переколебаний вершины диаграммы направленности при максимально возможной крутизне её скатов, а также добиться точного соответствия ширины диаграммы исходно заданному сектору. Применение представленной методики синтеза позволяет проектировать линейные фазированные антенные решетки для формирования секторных диаграмм направленности с улучшенными показателями качества It is difficult to provide the specified indicators of the directivity quality of the flat-topped radiation pattern when synthesizing a phased array antenna using methods based on the expansion of the diagram into a generalized Fourier series. The reasons for the deterioration of the flat-topped radiation pattern indicators are the finite number of basic functions used in the synthesis and the space limitation of the amplitude-phase distribution at the array aperture. The purpose of the work is to show, using the example of a linear equidistant array antenna, that the use of an optimized template of the original form in the synthesis makes it possible to achieve improved indicators of the flat-topped radiation pattern. To ensure the predistortion of the radiation pattern, we proposed a template, one parameter of which determines the width, and the second, the degree of smoothness of the pattern vertex. A small number of template parameters make it possible, when optimizing it, to abandon the methods of evolutionary search and to simplify the synthesis procedure. Using specific examples, we show that the use of an optimized template allows you to achieve improved indicators of a flat-topped radiation pattern. As a result, it is possible to significantly reduce the amplitude of oscillations of the top of the radiation pattern at the maximum possible steepness of its fronts, as well as to achieve an exact match of the width of the pattern to the initially specified sector. The application of the presented synthesis technique allows designing linear phased arrays antenna for the formation of flat-topped radiation patterns with improved quality indicators
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Rusov, Yu S., i S. S. Krapivina. "Research of the Possibilities of Matching the Multi-element Receiving-Transmitting Irradiator Aperture". Radio Engineering, nr 1 (30.05.2021): 1–13. http://dx.doi.org/10.36027/rdeng.0121.0000168.
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Currently, aperture antennas with spatial excitation, such as reflector antennas and phased array antennas, are widely used in radar. The composition of such an antenna includes an irradiator, which can be made in the form of a small-element array of radiators to form a set of necessary radiation patterns. Monopulse irradiators are often used, which form both total and difference directional patterns. When performing an irradiator based on waveguide parts, radiators in the form of horns or open ends of waveguides are installed in its aperture. Waveguide irradiators with four and twelve horns are widely used. One of the main electrical characteristics of such an irradiator when used as part of a receiving-transmitting antenna is the isolation of the transmitting and receiving paths. Matching the aperture of the transmitting and receiving irradiator has a significant effect on the isolation of its waveguide channels. With small transverse dimensions of the radiators in the form of open ends of waveguides, it is not possible to obtain high isolation of waveguide channels without the use of additional matching elements. The task of research the effect of matching the aperture of a waveguide multi-element irradiator on the isolation of its transmitting and receiving channels, as well as the ways of matching its radiators, is set.The article considers a four-horn irradiator, the aperture of which contains radiators in the form of open ends of a square waveguide. Each radiator has the radius rounding required for the manufacture of the product using the available technological processes. To match the emitter, a dielectric plate is installed inside it. During the research the thickness of the plate and its location relative to the aperture plane changed. The characteristics of matching the radiators with a plate made of teflon, polyethylene and ST-4 material based on polymers filled with titanium dioxide are presented.The proposed method of matching the opening of a multi-element irradiator with a transverse emitter size of 0,68λ (λ is the wavelength in free space corresponding to the average frequency of the operating band) makes it possible to improve the isolation of the receiving and transmitting waveguide channels by at least 4 dB in the frequency band of up to 3%.
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Wang, Yan, Xiaoyue Zhang, Xing Yang, Zhiji Wang, Yuefei Yan, Biao Du, Jiliang Zhang i Congsi Wang. "A Novel Swept-Back Fishnet-Embedded Microchannel Topology". Micromachines 14, nr 9 (31.08.2023): 1705. http://dx.doi.org/10.3390/mi14091705.
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High in reliability, multi in function, and strong in tracking and detecting, active phased array antennas have been widely applied in radar systems. Heat dissipation is a major technological barrier preventing the realization of next-generation high-performance phased array antennas. As a result of the advancement of miniaturization and the integration of microelectronics technology, the study and development of embedded direct cooling or heat dissipation has significantly enhanced the heat dissipation effect. In this paper, a novel swept-back fishnet-embedded microchannel topology (SBFEMCT) is designed, and various microchannel models with different fishnet runner mesh density ratios and different fishnet runner layers are established to characterize the chip Tmax, runner Pmax, and Vmax and analyze the thermal effect of SBFEMCT under these two operating conditions. The Pmax is reduced to 72.37% and 57.12% of the original at mesh density ratios of 0.5, 0.25, and 0.125, respectively. The maximum temperature reduction figures are average with little change in maximum velocity and a small increase in maximum pressure drop across the number of fishnet runner layers from 0 to 4. This paper provides a study of the latest embedded thermal dissipation from the dimension of a single chip to provide a certain degree of new ideas and references for solving the thermal technology bottleneck of next-generation high-performance phased array antennas.
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Lan, Tian, Qiu-Cui Li, Yu-Shen Dou i Xun-Ya Jiang. "A Study of a Wide-Angle Scanning Phased Array Based on a High-Impedance Surface Ground Plane". International Journal of Antennas and Propagation 2019 (20.01.2019): 1–10. http://dx.doi.org/10.1155/2019/8143104.
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This paper presents a two-dimensional infinite dipole array system with a mushroom-like high-impedance surface (HIS) ground plane with wide-angle scanning capability in the E-plane. The unit cell of the proposed antenna array consists of a dipole antenna and a four-by-four HIS ground. The simulation results show that the proposed antenna array can achieve a wide scanning angle of up to 65° in the E-plane with an excellent impedance match and a small S11. Floquet mode analysis is utilized to analyze the active impedance and the reflection coefficient. Good agreement is obtained between the theoretical results and the simulations. Using numerical and theoretical analyses, we reveal the mechanism of such excellent wide scanning properties. For the range of small scanning angles, these excellent properties result mainly from the special reflection phase of the HIS ground, which can cause the mutual coupling between the elements of the real array to be compensated by the mutual coupling effect between the real array and the mirror array. For the range of large scanning angles, since the surface wave (SW) mode could be resonantly excited by a high-order Floquet mode TM−1,0 from the array and since the SW mode could be converted into a leaky wave (LW) mode by the scattering of the array, the radiation field from the LW mode is nearly in phase with the direct radiating field from the array. Therefore, with help from the special reflection phase of the HIS and the designed LW mode of the HIS ground, the antenna array with an HIS ground can achieve a wide-angle scanning performance.
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Li, Bing, Zemin Wang, Jiachun An, Baojun Zhang, Hong Geng, Yuanyuan Ma, Mingci Li i Yide Qian. "Ionospheric Phase Compensation for InSAR Measurements Based on the Faraday Rotation Inversion Method". Sensors 20, nr 23 (1.12.2020): 6877. http://dx.doi.org/10.3390/s20236877.
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The ionospheric error can significantly affect the synthetic aperture radar (SAR) signals, particularly in the case of L band and lower frequency SAR systems. The ionospheric distortions are mixed with terrain and ground deformation signals, lowering the precision of the interferometric measurements. Moreover, it is often difficult to detect the small-scale ionospheric structure due to its rapid changes and may have more influence on ionospheric phase compensation for InSAR measurements. In this paper, we present a Faraday rotation (FR) inversion method and corresponding procedure to compensate the ionospheric error for SAR interferograms and to detect the variations of small-scale ionospheric disturbances. This method retrieves the absolute total electron content (TEC) based on the FR estimation and corrects the ionospheric error for synthetic aperture radar interferometry (InSAR) measurements by transforming the differential TEC into the ionospheric phase. In two selected study cases, located in high latitude and equatorial regions where ionospheric disturbances occur frequently, we test the method using the Phased Array L-band Synthetic Aperture Radar (PALSAR) full-polarimetric SAR images. Our results show that the proposed procedure can effectively compensate the ionospheric phase. In order to validate the results, we present the results of ionospheric phase compensation based on the split-spectrum method as a comparison to the proposed method. To analyze the ability of our proposed method in detecting small-scale ionospheric disturbances, TEC derived from FR estimation are also compared with those derived from the global ionosphere maps (GIM). Our research provides a robust choice for the correction of ionospheric error in SAR interferograms. It also provides a powerful tool to measure small-scale ionospheric structure.
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Moroz, A. V., V. V. Davydov, K. Yu Malanin, A. A. Krasnov i V. Yu Rud’. "Features of the construction of the noise compensation circuit of a small-sized active phased antenna array". Journal of Physics: Conference Series 1400 (listopad 2019): 044009. http://dx.doi.org/10.1088/1742-6596/1400/4/044009.
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Efimov, A. G., S. A. Korneev, V. S. Matveev i V. V. Chistyukhin. "Designing Multi Beam Receiving and Transmitting Aperture LEO Space Communication Systems". Proceedings of Universities. Electronics 26, nr 1 (luty 2021): 64–73. http://dx.doi.org/10.24151/1561-5405-2021-26-1-64-73.
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In designing the receiving-transmitting active phased antenna array (APAA) an important problem is an achievement of the level of maximum outcome between the receiving and transmitting channels. In the work, the concept of building multi-beam receiving-transmitting antenna systems based on APAA has been considered. The criteria for selecting the type of emitter for an S-band antenna with the specified parameters have been presented. It has been shown that the use of a turnstile emitter based on the printing technology can reduce the complexity of manufacturing without compromising the technical parameters. In accordance with the requirements for volume of the tasks of APAA being designed the optimal geometric and electric characteristics of the turnstile radiator have been calculated. In designing the radiating apertures of the multi-element APAA the specifics of the dependence of their electric characteristics on the inter-element distance has been taken into consideration. To increase the circular polarization coefficient of the apertures being designed, the method of tearing apart of the radiator with further compensation of the obtained phase using the phase rotators APAA has been implemented. The estimates of the energy characteristics of the multi-element antennas with a given scanning sector for various inter-element distances have been given. To ensure the separation of the receiving and transmitting antennas the recommendations have been presented.