Range-Doppler Imaging with a Laser Radar.

摘要

The design of imaging waveforms for a heterodyne-detection range-Doppler laser radar depends on target dynamics as well as hardware constraints. This article describes the electric fields of the signals, the optimal form of the receiver, and the signal processing issues associated with range-Doppler imaging. The performance of unmodulated pulse trains, linear-frequency-modulated (LFM) chirp pulse trains, and biphase shift-keyed (BPSK) pulse trains as imaging waveforms is addressed. Two methods of coherent imaging are developed: one method is suitable for periodic pulse trains and the other method is a more generalized approach. Relationships between the target spin rate and the waveform parameters for unambiguous range-Doppler imaging are presented: the radar ambiguity function establishes a relative performance comparison of the waveform types. Two receiver block diagrams are presented: one specifically for processing the LFM chirp pulse train waveform and another more generalized processor for a wide variety of pulse train waveforms. Receiver signal processing issues and trade-offs, including range-Doppler coupling and waveform amplitude weighting for reduced range and Doppler sidelobes, are discussed. Firepond indoor test-range images illustrate the beneficial effects of zero padding and incoherent averaging. Finally, we present a scheme that compensates for amplitude errors and phase errors, and results in dramatically improved image quality. Keywords: Range-doppler imaging, Heterodyne-detection range, Reprints, Acoustic detection, Laser radar. (JG)