基于77 GHz逆合成孔径雷达的二维成像系统

Two-Dimensional Imaging System Based on 77 GHz Inverse Synthetic Aperture Radar

摘要: 针对逆合成孔径雷达(ISAR)成像分辨率和成像速度要求较高的问题，设计了一个77 GHz ISAR二维成像系统。采用距离–多普勒(RD)算法进行成像，中控采集系统采用以FPGA为核心的ADC采集板卡，信号源采用19 GHz宽屏带射频源，收发模块采用倍频放大结构。上位机发送指令控制信号，中控采集板卡控制转台旋转以及射频源产生扫频信号，经发射天线倍频至77 GHz，然后接收天线将回波信号下变频至中频信号进入采集板卡，最后将采样数据传输至上位机中通过算法成像。测试结果表明，该系统实现了77 GHz雷达信号发生、系统时钟同步精度为78 ps、最大采样率为250 MSPS、最大传输速率为5 Gb/s，且单通道ADC采集的中频数字信号可以使二维成像满足理论分辨率，即6.9 cm × 4.0 cm；在实际工程中其信号带宽大、采样速率快、成像速度快和成像分辨率高等特性，满足了对物体进行二维成像的需求。

Abstract: A 77 GHz ISAR two-dimensional imaging system was designed to address the problems of high imaging resolution and speed requirements in inverse synthetic aperture radar (ISAR). The imaging was performed using the range-doppler (RD) algorithm, while an ADC acquisition board with an FPGA core was employed in the central control acquisition system. A wideband RF source with a frequency of 19GHz and a transmit/receive module adopting a multiplier amplification structure were used. The central control acquisition board controlled the rotation of the turntable and generated a sweep signal via the RF source, in response to the instruction signal sent from a host computer. After being doubled to 77 GHz by a transmitting antenna, the echo signal was received by another antenna and down-converted into an intermediate frequency signal that entered the acquisition board. The sampled data was eventually transmitted to the host computer for reconstruction through algorithms. The testing results indicate that this system achieved 77 GHz radar signal generation, a clock synchronization accuracy of 78 ps, the highest sampling rate of 250 MSPS, the maximum transmission rate of 5 Gb/s, and that the intermediate frequency digital signals collected by a single channel ADC could satisfy the theoretical resolution, i.e. 6.9 cm × 4.0 cm, for two-dimensional imaging. This system had high signal bandwidth, fast sampling rate, high imaging speed, and resolution, which met the demand for two-dimensional object imaging in practical engineering.