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[ACM Press the 2018 International Conference - Tianjin, China (2018.09.19-2018.09.21)] Proceedings of the 2018 International Conference on Electronics and Electrical Engineering Technology - EEET '18 - An Exploratory Analysis of Speckle Noise Removal Methods for Satellite Images
摘要： image processing procedure, Satellite images captured in a variety of modalities serve as the primary source for many applications. Satellite image processing extracts the image /spectral information represented in the form of pixels, classifies those pixels based on the similarity measures and further analyzes the inherent data, as per the requirements. The foremost objective of satellite processing is to automatically categorize the pixels in an image into the respective land cover class labels or themes. These pixels are classified by its spectral information and it is determined by the relative reflectance in various bands of wavelength. The accuracy and outcomes of any satellite the application domain, directly depends on its quality. Satellite images are invariably degraded by speckle noise. Hence, preprocessing the images for speckle noise suppression and/or cloud removal is deemed an inevitable component in satellite image processing. Researchers have proposed a spectrum of methods for speckle noise/cloud removal. A detailed review on the significant research publications on speckle noise removal are summarized in this article. The consolidation of methodology merits and demerits of the select research articles are presented in this paper. This review article on speckle noise removal is designed as a ready-reference for those researchers working in satellite image processing. irrespective of
关键词： RADAR,SAR,Review,Speckle Noise,Satellite images,Noise filters,Literature Survey
更新于2025-09-23 15:23:52
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Fast modeling of electromagnetic scattering from 2D electrically large PEC objects using the complex line source type Green's function
摘要： This study introduces an alternative approach to the numerical solution of two-dimensional (2D) electromagnetic scattering problems by a numerical method of moments (MoM). The real source position vector is replaced by a complex quantity, then Green’s function generates a complex source point beam, therefore the interactions between the far zone elements in the impedance matrix are neglected, except the basis functions near to the edges, strongly localizing the impedance matrix. The memory storage increases with the number of edges, but for a fixed number of the edges, it is linearly proportional with N, i.e. O(N). Consequently, the overall running time can be drastically reduced and the far zone scattering pattern and the near field can be found. The proposed procedure is first explained for the single perfectly electrically conducting (PEC) strip geometry, then extended to the scattering by 2D PEC objects with closed polygonal cross-sections. Numerical results are presented for a strip and a square cylinder in both polarizations. The relative errors are also compared with the standard MoM.
关键词： computational electromagnetics,radar cross section,Electromagnetic scattering
更新于2025-09-23 15:23:52
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Compact polarimetry for automotive applications
摘要： Though compact polarimetric approaches have been developed and applied in space and geo researching systems they have not been taken into consideration in automotive applications, yet. A sensor system has been designed to conduct polarimetric measurements in the 77 GHz frequency band, which is permitted for automotive usage. This system is able to transceive linearly as well as circularly polarized electromagnetic continuous waves. Depending on the case of application, the frequency output can be set statically or modulated over time within adjustable parameters. Hence, a variety of compact polarimetric modes can be performed and compared with full polarimetric approaches. Two compact polarimetric modes, dual-circular polarimetric mode, and circular-transmit-linear-receive, will be introduced and applied in this contribution. Their operability in this frequency range will be investigated after the microstrip antennas as well as the beam focusing dielectrical lense are characterized. Finally, results of a realistical measurement set-up will confirm the practicability of compact polarimetric approaches for double bounce recognition.
关键词： modelling and measurements,Antenna design,radar
更新于2025-09-23 15:23:52
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Time reversal imaging based on joint space–frequency and frequency–frequency data
摘要： A new time reversal (TR) method for target imaging is proposed in this paper. Through single measurement by the antenna array, the received signals are utilized to form the space–frequency–frequency multistatic data matrix (MDM). Singular value decomposition is applied to the matrix to obtain the left singular vectors which span the signal subspace. The obtained vectors are divided into multiple subvectors by two different schemes and used to provide target signatures in the form of coarse frequency dependence and relative phase shifts that can be exploited to construct the imaging function. The performance of the proposed method is investigated through numerical simulations for both single and multiple targets, and the results are compared with the traditional TR method using the frequency–frequency MDM. It turned out that the proposed method is able to achieve high resolution with limited array aperture and shows satisfactory robustness in noise environment. Furthermore, experimental results are provided to show the availability of the method in practical applications.
关键词： time reversal imaging,EM field theory,Radar
更新于2025-09-23 15:23:52
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[IEEE 2018 17th International Conference on Ground Penetrating Radar (GPR) - Rapperswil, Switzerland (2018.6.18-2018.6.21)] 2018 17th International Conference on Ground Penetrating Radar (GPR) - Full Waveform Inversion of Cross-hole Radar Data Using Envelope Objective Function
摘要： The full waveform inversion (FWI) has been used as a high resolution imaging method for cross-hole radar inversion implementation, however, when FWI is used to process field data, it encounters a variety of problems and causes the inversion to fall into a local minimum. One problem is that the GPR data lacks low frequency information. An effective way is to provide an accurate initial model for FWI. The fact is that the underground media is unknown which results in difficult to obtain ideal result in FWI. By means of the derivation of the objective function, the gradient formula of the envelope waveform inversion (EWI) is derived by taking the derivation of the EWI misfit function with respect to the model parameter. By comparing the inversion results of the EWI with that of the traditional FWI without low-frequency information in the observed GPR data, we found that the EWI can effectively restore missing low-frequency information and has better inversion ability for low-frequency missing data.
关键词： cross-hole radar,envelope,full waveform inversion,low frequency component,initial model
更新于2025-09-23 15:23:52
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[IEEE 2018 25th IEEE International Conference on Image Processing (ICIP) - Athens, Greece (2018.10.7-2018.10.10)] 2018 25th IEEE International Conference on Image Processing (ICIP) - Recovery of UWB Radar Signals in Spectrally Restricted Environments
摘要： This paper presents a novel technique to recover the missing spectral information due to RF spectral restriction in ultra-wideband (UWB) synthetic aperture radar (SAR) imaging. We address a critical problem in UWB radar imaging: radar transmission is prohibited in reserved frequency bands specified by local frequency management agencies. We model the problem in a compressed sensing setup where a time-sparse received radar signal at each aperture is collected in the incoherent frequency domain using a stepped-frequency implementation. Using electromagnetic (EM) finite-difference, time-domain (FDTD) data of various targets and clutter objects computed at all viewing aspect angles, we show that the proposed technique can successfully recover the relevant information on targets of interest even from a large percentage of missing frequency bands.
关键词： step-frequency,sparse recovery,synthetic aperture radar,spectral restriction,Ultra-wideband
更新于2025-09-23 15:23:52
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Finite-Difference Time-Domain Modeling for Electromagnetic Wave Analysis of Human Voxel Model at Millimeter-Wave Frequencies
摘要： The finite-difference time-domain (FDTD) modeling of a human voxel model at millimeter-wave (mmWave) frequencies is presented. It is very important to develop the proper geometrical and electrical modeling of a human voxel model suitable for accurate electromagnetic (EM) analysis. Although there are many human phantom models available, their voxel resolution is too poor to use for the FDTD study of EM wave interaction with human tissues. In this paper, we develop a proper human voxel model suitable for mmWave FDTD analysis using the voxel resolution enhancement technique and the image smoothing technique. The former can improve the resolution of the human voxel model and the latter can alleviate staircasing boundaries of the human voxel model. Quadratic complex rational function is employed for the electrical modeling of human tissues in the frequency range of 6–100 GHz. Massage passing interface-based parallel processing is also applied to dramatically speed up FDTD calculations. Numerical examples are used to illustrate the validity of the mmWave FDTD simulator developed here for bio electromagnetics studies.
关键词： human tissue,electromagnetic wave,Doppler radar,dispersion model,bioelectromagnetics,Finite-difference time-domain (FDTD) method,parallel processing
更新于2025-09-23 15:23:52
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Retrieval of Ionospheric Faraday Rotation Angle in Low-frequency Polarimetric SAR Data
摘要： A low-frequency spaceborne synthetic aperture radar (SAR) working system, e.g., operating at the L-band or P-band, has great advantages of military target detection and biomass monitoring. Nevertheless, it is more susceptible to ionospheric effects compared with the higher frequency system. A trans-ionospheric wave propagation model is established in this paper to incorporate ionospheric effects on SAR signals. As one of the signi?cant distortion sources for the polarimetric SAR (PolSAR), Faraday rotation (FR) is mainly imposed by background ionosphere, and its spatial variation is discussed. FR estimators have been devised in succession to estimate FR angle (FRA), and various potential novel estimators can still be derived. But, from a viewpoint of theoretical expressions, the earliest estimator is bound to be the optimal one. Based on PolSAR real data, this mathematical conclusion is further validated via comprehensive performance analysis as to estimation bias and standard deviation rather than the existent root-mean-square principle. Finally, a step-by-step procedure of the FRA map is proposed and operated with an application of the airborne P-band PolSAR data. In particular, the ambiguity error of FRA estimates within a SAR observation is simulated and resolved. By processing the ALOS-2 real data, the spatial distribution of FRAs is retrieved and used to operate ionospheric total electron content soundings.
关键词： FR angle (FRA) map,ionospheric TEC soundings,Faraday rotation (FR) estimators,Spaceborne synthetic aperture radar (SAR)
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP) - Auckland (2018.8.5-2018.8.8)] 2018 IEEE Asia-Pacific Conference on Antennas and Propagation (APCAP) - Moving Target Detection for THz SAR Systems Based on Multilook Processing
摘要： Compared with conventional X-band synthetic aperture radar (SAR) systems, THz SAR is more sensitive to Doppler vibration and has better detection performance for moving targets. In this paper, a moving target detection scheme is designed for terahertz SAR systems based on multilook processing. The Doppler spectrum is divided into several sub-looks and focused separately to generate corresponding sub-images. Moving targets are indicated through sharpness detection of the sub-images. The effectiveness of the proposed algorithm is veri?ed by simulated data.
关键词： terahertz,multilook processing,moving target detection,Synthetic aperture radar
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE Asian Solid-State Circuits Conference (A-SSCC) - Tainan, Taiwan (2018.11.5-2018.11.7)] 2018 IEEE Asian Solid-State Circuits Conference (A-SSCC) - A CMOS 76-81 GHz 2TX 3RX FMCW Radar Transceiver Based on Mixed-Mode PLL Chirp Generator
摘要： A fully integrated 76-81 GHz frequency-modulated continuous-wave (FMCW) radar transceiver (TRX) in 65nm CMOS is presented. Two transmitters (TXs) and three receivers (RXs) are integrated for MIMO processing. A 38.5 GHz mixed-mode PLL with reconfigurable loop bandwidth and frequency doubling scheme are employed to generate the reconfigurable FMCW chirp waveforms. Passive voltage-mode down-conversion is utilized to improve the RX linearity against TX leakage. A bottom-switching PA is proposed to realize the Bi-Phase modulation, and the magnetically-coupled resonator technique is used to effectively expand the link bandwidth. Measurement results show that the FMCW TRX could generate reconfigurable chirps with the bandwidth from 250 MHz to 4 GHz and the period from 600 us to 10 ms. The root-mean-square (RMS) frequency error is less than 251 kHz. The TX maximum output power is 13.4 dBm and is adjustable within 3 dB by reconfiguring its LDO output voltage. The RX achieves 15.3 dB noise figure and -8.5 dBm RF input-referred PldB. Real-time experiments are carried out using the proposed TRX chip, in which the measured average distance error is 10 cm. The overall power consumption is 921mW with 2-TXs and 3-RXs powered on.
关键词： transceiver,PLL,CMOS,mm-wave,Radar,frequency-modulated continuous-wave (FMCW)
更新于2025-09-23 15:23:52