Doppler Aliasing Reduction in Wide-Angle Synthetic Aperture Radar Using a Linear Frequency Modulated Random Stepped-Frequency Waveform.

摘要

This research examines the theory, application, and results of using Random Stepped-Frequency (RSF) waveforms to mitigate Doppler aliasing in a wide- angle Synthetic Aperture Radar (SAR) imaging scenario. Severe Doppler aliasing typically occurs in this scenario since range extent requirements force the pulse repetition frequency to a value violating the lower bound for Doppler aliasing. Building on previous research, this work expands upon RSF waveform analysis using a Linear Frequency Modulated RSF (LFM-RSF) waveform. The RSF waveform suppresses Doppler aliasing by positioning nulls at the aliased scatterer location. Applying LFM with RSF processing theoretically provides greater frequency coverage and aliased scatterer cancellation improvement when compared to fixed frequency values. Results using the LFM-RSF waveform show images with alias mitigation performance consistent with previous non-LFM RSF results. Given a 45 dB image dynamic range and satisfying a time-bandwidth product criterion, the LFM-RSF waveform produces an image with aliased energy reduced by 99.6%. Slightly more energy reduction is possible by violating the time-bandwidth product criterion with an associated frequency overlap between subpulses. This violation leads to additional frequency coverage which enhances aliased energy reduction to 99.9%.