High Resolution Imaging of Chaotic Bistatic Radar

Abstract

High resolution imaging using chaos-based frequency modulation (CBFM) in a bistatic radar system is evaluated in terms of the cross-ambiguity function. A 3-D Lorenz system is used to generate and transmit a wideband CBFM waveform. The bistatic radar's receiver is synchronized with its transmitter utilizing a direct synchronization scheme. The cross-correlation between the reconstructed and transmitted waveforms is of high quality and, consequently, down-range resolution is achievable. However, cross-range resolution is more elusive as the shape of the cross-ambiguityg function between the reconstructed waveform and scattered echo depends on the geometric configuration of the bistatic radar. For the cosite region and nonnegative look angles of the receiver-centered region, the ambiguity function has a near thumbtack shape. For negative look angles of the receiver-centered region, cross-range resolution is gradually lost. To assess high-resolution capability, the signature analysis of a complex point target is modeled. Results demonstrate that the synchronized chaotic FM bistatic radar provides a high range and cross range resolution with negligible sidelobes. Using an entropy analysis, it is determined that when only the echo is corrupted with additive noise, high resolution imaging is feasible for low SNR. In contrast, if both the target echo and the waveform received from the transmitter are corrupted with noise, imaging is adversely affected for relatively high noise levels.