Frequency Based Design Partitioning to Achieve Higher Throughput in Digital Cross Correlator for Aperture Synthesis Passive MMW Imager

Abstract

Digital cross-correlation is central to many applications including but not limited to Digital Image Processing, Satellite Navigation and Remote Sensing. With recent advancements in digital technology, the computational demands of such applications have increased enormously. In this paper we are presenting a high throughput digital cross correlator, capable of processing 1-bit digitized stream, at the rate of up to 2 GHz, simultaneously on 64 channels i.e., approximately 4 Trillion correlation and accumulation operations per second. In order to achieve higher throughput, we have focused on frequency based partitioning of our design and tried to minimize and localize high frequency operations. This correlator is designed for a Passive Millimeter Wave Imager intended for the detection of contraband items concealed on human body. The goals are to increase the system bandwidth, achieve video rate imaging, improve sensitivity and reduce the size. Design methodology is detailed in subsequent sections, elaborating the techniques enabling high throughput. The design is verified for Xilinx Kintex UltraScale device in simulation and the implementation results are given in terms of device utilization and power consumption estimates. Our results show considerable improvements in throughput as compared to our baseline design, while the correlator successfully meets the functional requirements.

A 1-GHz 64-Channel Cross-Correlation System for Real-Time Interferometric Aperture Synthesis Imaging

“…Considering the higher output bits of an integrator transition at a slower frequency than the lower output bits, we adopted a two-stage architecture for the integrator to minimize the cost of fabric resource. In the first stage, only an accumulator with 15-bit output was implemented using fabric resource for each integrator; in the second stage, we used a DSP slice together with a 512 × 36 dual-port random access memory (DPRAM) in a multiplexed approach to integrate the results from 256 first stage integrators [28]. The DPRAM was used in a ping-pong configuration, with only 256 locations being used at a time, sparing the other 256 for computer read operation, which made it possible to read earlier data while simultaneously performing the next correlation.…”

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

“…The DAC contains 8 channels, and the precision is 16 bits, of which only 13 bits are effective. Also, the external reference voltage of the chip is 1.2 V, and the minimum step voltage is 1200 mV/2 13…”

“…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]. The work presented in this article is a part of further enhancements in this system targeted to improve sensitivity and increase resolution in video rate imaging.…”