High Range Resolution Synthesized by Non-linear Stepped-Frequency Chirp Pulse Train

Traditional stepped frequency chirp pulse train methods suffer from high sidelobes and ambiguous peaks, known as grating lobes and difficulty in compensating Doppler effect caused by target motion. This paper investigates a class of non-linear stepped frequency chirp pulse train with low sidelobes and capability to cancel clutter and to compensate motion. We present analytic expression for its autocorrelation function (ACF) and propose an improved method to produce the non-linear stepped frequency chirp pulse train with small grating lobes and small overlap ratio for sub-pulse of large time bandwidth product. A method for estimation a target’s radial velocity is developed, which avoids multiple bursts required by other methods. The high signal-to-noise (SNR) ratio as a result of sub-pulse compression assures the accuracy of estimation. The Cramer-Rao bound for lower limit on the velocity estimation of the pulse train is derived to demonstrate its performance. Key-Words: Non-linear stepped-frequency chirp pulse train, Autocorrelation function, Grating lobes suppression, Motion compensation, Cramer-Rao bound, One-dimensional range profile