Adaptive LFM waveform diversity

Abstract

Previous work has addressed adaptive radar waveforms that may be designed to be spectrally orthogonal to a received, in-band, time-varying, interference environment. This paper introduces a different adaptive waveform technique whereby a standard LFM waveform is modified to minimize its adjacent-band interference to other spectral users. In addition, results are shown for in-band and/or adjacent-band spectral suppression for improving radar performance and minimizing interference to other spectral users while maintaining good ambiguity function performance. Ambiguity functions are plotted for each case showing good approximation to the ideal LFM ambiguity function.

Adaptive Noise Waveform Design for Radar

“…The initial phase vector waveform is set to the ideal (unmodified) LFM waveform for the minimization's starting condition. By setting the minimization options to run as "Large Scale" and inputting the function evaluation (4), its gradient (5), and its Hessian (6), then the algorithm first modifies the waveform phases that provide the greatest benefit towards minimizing (4). The algorithm concludes once the phases change only less than a specified threshold for each iteration.…”

“…Traditionally, radar waveforms are fixed, and do not adapt to perform better in the presence of clutter and/or interference, nor do they traditionally adapt their waveforms to minimize interference to adjacent-band users. However, recent related research exists in adaptive radar waveform design, including noise waveforms [1][2][3][4][5][6][7].…”

Adaptive waveform design for interference mitigation in SAR

“…Within the past 10 years, waveform design efforts have become increasingly spectrum-conscious; either from the perspective of spectral coexistence with surrounding transmitters or from a performance perspective to exploit optimal occupation of the RF spectrum to yield enhanced performance metrics. The spectral waveform design literature generally demonstrates one the following: 1) addition of small modifications to the standard linear frequency modulated (LFM) waveform to place nulls in the spectrum to remove RFI or to maintain co-existence with surrounding RF users [14,15,16,17], 2) waveform design with forbidden bands where the spectrum cannot place energy or where it is optimal for avoiding transmitters [18,19,20,21], 3) waveform optimization with forbidden regions while also attempting to optimize for another performance metric or feasibility constraint [22,23,24], 4) or more recently, by exploiting multiple-input-multiple output (MIMO)-radar to harness both frequency and spatial diversity to achieve spectral co-existence with other RF users [25,26,27,28,29].…”

Development and Analysis of New NLFM Waveform for Achieving Sidelobe Reduction and Narrowing of Main lobe Width

“…Digital radars can perform pulse compression using various techniques. Among the pulse compression techniques, LFM is the most popular technique because of its ease of generation and doppler tolerance [1]. The main drawback of LFM, however, is yielding high sidelobe levels.…”