An all-digital image synthesizer for countering high-resolution imaging radars

Abstract

A digital image synthesizer (DIS), especially useful as a counter-targeting signal repeater, (i.e., for synthesizing the characteristic echo signature of a pre-selected target) is reported. The DIS has a digital radio frequency memory (DRFM) and associated circuitry, including digital tapped delay lines and a modulator in each delay line to impose both amplitude and frequency modulation in each line. A unique property of the digital image synthesizer is its ability to synthesize false targets using wideband chirp signals of any duration. To generate the target, the user can program the target extent (number of taps) and the amplitude and Doppler frequency of each range-Doppler cell within the image. The system-on-a-chip uses a scalable CMOS technology that increases the bandwidth and sensitivity of such a repeater over prior analog based systems. The application specific integrated circuit reduces the noise of the repeated signal, reduces the size and cost of such a system, and permits real time alteration of operating parameters, permitting rapid and adaptive shifting among different types of targets to be synthesized. A scan path test capability is also included to allow intre-schip signal analysis and verification.