Wideband linear frequency modulated waveform compensation using system predistortion and phase coefficients extraction method

Abstract

This letter presents an effective method to compensate for the wideband linear frequency modulated waveform errors using system predistortion coefficients. The coefficients can be readily extracted by measuring and analyzing the changing rates of the period of non-constant beat frequencies generated from a non-linear system in the time domain. The amplitude distortion components are examined using the polynomial curve-fitting method. In order to experimentally validate the practical feasibility of the waveform generator and the predistortion coefficients extraction module, the waveform's amplitude ripple, range resolution, and peak sidelobe ratios are measured and analyzed. The measured amplitude ripple at 5.3 GHz is improved from +/- 1.835 to +/- 0.333 dB and from +/- 2.793 to +/- 0.75 dB within 50 and 85 MHz bandwidth, respectively. Finally, the range resolution is improved from 4.102 to 3.103 m for 50 MHz bandwidth and the peak sidelobe ratio is improved from -7.78 to -20.55 dB for 85 MHz bandwidth with the applied predistortion.