Performance Evaluation of a Passive Millimeter-Wave Imager
ABSTRACT A cross-correlating 186-GHz passive millimeter-wave imager has been built. The key components in the signal processing hardware are two 186-GHz receivers and a broadband complex correlator. To evaluate the performance of this imager, its point-spread function, beam pattern, baseline vector, and their variations with the scanning direction have been experimentally measured and derived. Some of these results are needed for optimizing the imager's parameter settings. Others are required for implementing the modulated-beam and modulated-scene algorithms proposed in a previous paper dealing with the imager's fringe in its point-spread function. These results will also reveal any problems in the construction process of the imager. The theoretical bases for these measurements are analyzed. Novel algorithms for deriving each antenna's point-spread function and beam pattern, as well as the imager's baseline vector from the measurement results of the imager's point-spread function and beam pattern are proposed and successfully applied in the measurements. Experimental results are presented and discussed.
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ABSTRACT: We describe the design and application of a system for measuring the magnitude and phase of antenna radiation patterns in the 182-194 GHz frequency range. A heterodyne receiver comparing antenna and reference signals is designed from readily available components and incorporated into a 12-m anechoic chamber. The chamber is used with or without a compact-range reflector for compact-range or far-field measurement of antennas up to 0.6 m in diameter. The measured phase variation of the system, when idle, averages 0.3° over 227 s and 4.5° over 30 min. The amplitude stability is better than ±0.15 dB over a 63-h period. Verification of the system is obtained through comparison with other measurements and calculated results on horn and pillbox antennas. The applications of the system are illustrated through its use in characterizing the magnitude and phase radiation patterns of a new beam-scanning pillbox antenna for a 186-GHz imaging system.IEEE Transactions on Antennas and Propagation 01/2012; 60(4):1744-1757. · 2.33 Impact Factor
Conference Paper: Wireless tomography, Part I: A novel approach to remote sensing[Show abstract] [Hide abstract]
ABSTRACT: Wireless tomography, a novel approach to remote sensing, is proposed in Part I of this series. The methodology, literature review, related work, and system engineering are presented. Concrete algorithms and hardware platforms are implemented to demonstrate this concept. Self-cohering tomography is studied in depth. More research will be reported, following this initiative.Waveform Diversity and Design Conference (WDD), 2010 International; 09/2010
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ABSTRACT: We propose a novel blind image deconvolution (BID) regularization framework for compressive sensing (CS) based imaging systems capturing blurred images. The proposed framework relies on a constrained optimization technique, which is solved by a sequence of unconstrained sub-problems, and allows the incorporation of existing CS reconstruction algorithms in compressive BID problems. As an example, a non-convex lp quasi-norm with 0 < p < 1 is employed as a regularization term for the image, while a simultaneous auto-regressive (SAR) regularization term is selected for the blur. Nevertheless, the proposed approach is very general and it can be easily adapted to other state-of-the-art BID schemes that utilize different, application specific, image/blur regularization terms. Experimental results, obtained with simulations using blurred synthetic images and real passive millimeter-wave images, show the feasibility of the proposed method and its advantages over existing approaches.IEEE Transactions on Image Processing 06/2013; · 3.20 Impact Factor