Initial Results of a Passive Millimeter-Wave Imager Used for Concealed Weapon Detection Bhu-2d-U

Abstract

A passive millimeter-wave imager BHU-2D-U has been developed by Beihang University. This imager is designed for detecting concealed weapons on human body. It is a subsequent model of BHU-2D, which is also developed by the same group. In this paper, the improvements of BHU-2D-U over BHU-2D are introduced. Firstly, BHU-2D-U is used for whole body scan, which is different from BHU-2D. Thus, the field of view (FOV) of the new imager is enlarged and a new antenna array type is adopted. Secondly, the enlarged FOV requires smaller antenna spacing and compact receiver arrays. In order to reduce the volume of the receivers, I/Q demodulators operating in double side band mode are adopted because it does not need the image-reject filter, which is usually a bulky one. Thirdly, the quantity of the correlators increases because the number of receiving elements is doubled. To cope with the increase of the correlator quantity, a multiplexing technique is used in the FPGA internal layout of the correlator array unit. After a brief introduction, the system design and configuration is illustrated in detail. Finally, imaging experiments on a person with concealed weapon are conducted, by which the design and image reconstruction algorithms are verified. To conclude, initial results of BHU-2D-U have proved that the improvements are effective.

Custom versus Cell-Based ASIC Design for Many-Channel Correlators

“…Cross-correlation is extensively used for signal processing in aperture-synthesis-based radio astronomy and is currently being considered also for remote sensing applications [4], [5] as well as security scanning applications [6], [7]. In these applications, the main driver for processing power is imaging resolution.…”

Near Field Image Reconstruction Algorithm for Passive Millimeter-Wave Imager Bhu-2d-U

“…For BHU-2D-U, the background cancelation technique has been used to reduce the influences of aliasing error and system offset [5,6]. Thus the visibility function samples need to be pre-processed before image reconstruction…”

“…A two-dimensional SAIR imager BHU-2D-U has been developed at Beihang University with an imaging distance about 3 m [6], which is operated under the near-field condition of the utilized antenna array. Thus, the Fourier imaging theory generally employed in the interferometry and radio astronomy applications does not apply any longer.…”

High-Precision Phase Shifting and Real-Time Calibration of Phased Arrays for Passive Millimeter-Wave Imaging Applications

“…In order to improve the imaging resolution, aperture synthesis using interferometric technique has been successfully used for synthesizing very large apertures for radio telescopes like Very Large Array (VLA), Atacama Large Millimeter/sub-millimeter Array (ALMA), and Allen Telescope Array (ATA) [10]. Two versions of synthetic aperture passive millimeter wave imagers for security screening application, i.e., BHU-2D [11] and BHU-2D-U [12], have already been developed and tested by Beihang University. BHU-2D has 24 receiving elements with 160 MHz bandwidth, and BHU-2D-U has 48 receiving elements with 200 MHz bandwidth [13].…”