<title>Nonlinear stepped chirp waveforms with subpulse processing for range side lobe suppression</title>

Abstract

The linear step frequency pulse compression waveform suffers from a) range ambiguities due to periodicities in the discrete Fourier transform (DFT) and b) signal-to-noise ratio (SNR) losses due to amplitude weighting used to suppress nominal range sidelobes. Mark Waibridge of DERA Malvern, U.K., has proposed a nonlinear step frequency waveform which is derived from sampling a Doiph Chebyshev weighting function. The waveform does not exhibit range ambiguities and achieves low near-in sidelobes without incurring the SNR loss associated with conventional sidelobe suppression techniques. This paper assesses an implementation of the non-linear step frequency waveform by quantifying range sidelobes, range resolution, and range-Doppler coupling. The waveform has application in ultra-high range resolution profile generation.

Adaptive gradient search for optimal sidelobe design of hopped‐frequency waveform

“…Lo and Lee [16] and Lo [17] studied the statistic properties of an antenna array when its elements are placed randomly over an aperture by using the Monte Carlo method, based on which it is pointed out that space‐tapered, or density‐tapered arrays have larger chance to yield a low sidelobe level than non‐tapered ones. The features of density‐tapered (space‐tapered or frequency‐tapered) can also be found in [9–11, 13–15]. According to these results, the use of frequency‐tapered initialisations can improve the chance that the final results obtain close to the global optimum.…”

“…Based on the fact that the autocorrelation function (ACF) of signal is Fourier transform of its power spectrum, [9] proposed a nonlinear stepped‐frequency waveform whose frequencies density would approximate a particular window function. With a similar idea, [10] obtained the frequency combination by uniformly sampling the frequency modulation against time function of non‐linear frequency modulation (NLFM). Although both methods above are easy for implementation, their performances are far from optimality in terms of pulse compression given limited pulse number.…”

Study on non-linear stepped chirp radar system

“…Coherent receivers are used to sort and mix the returns. Then the sub-pulse compression is accomplished in each pulse repetition period [5]. Phase variation under the -4dB PRT1-l t range of main lobe of sub-pulse compression output can be ignored, which keeps the coherent phase information required to complement the 10FT.…”

Low-rate sampling technique for range-windowed radar/sonar using nonlinear frequency modulation

“…Such NLFM waveforms have been investigated in the open literature (e.g. [3,6,8,12,13,16,17]) for the case of conventional matched filtering.…”