Chirp diversity waveform design and detection by stretch processing

Abstract

Pulse trains are among the most commonly used waveforms in radar. Examples are pulse-Doppler radar, stepped-frequency, up-down chirps, stepped-chirps and frequency-coded waveforms, among others. In this work, we propose a pulse train modeled after chirplet chains where the basic elements of the waveform are contiguous linear chirps of arbitrary chirp rates and offset frequencies without using frequency coding. The receiver structure employs a bank of stretch processors each tuned to different chirps. The beat frequencies are separated from the cross term spectra by tuning the slopes and offsets of the individual chirps. The waveform can also be tuned to remove the range-Doppler coupling common to linear chirps. The detector can handle delays in the fraction of the pulse width, Doppler, as well as clutter suppression by isolating secondary target returns.