MIMO-OFDM signal optimization for SAR imaging radar

Abstract

This paper investigates the optimization of the coded orthogonal frequency division multiplexing (OFDM) transmitted signal in a synthetic aperture radar (SAR) context. We propose to design OFDM signals to achieve range ambiguity mitigation. Indeed, range ambiguities are well known to be a limitation for SAR systems which operates with pulsed transmitted signal. The ambiguous reflected signal corresponding to one pulse is then detected when the radar has already transmitted the next pulse. In this paper, we demonstrate that the range ambiguity mitigation is possible by using orthogonal transmitted wave as OFDM pulses. The coded OFDM signal is optimized through genetic optimization procedures based on radar image quality parameters. Moreover, we propose to design a multiple-input multiple-output (MIMO) configuration to enhance the noise robustness of a radar system and this configuration is mainly efficient in the case of using orthogonal waves as OFDM pulses. The results we obtain show that OFDM signals outperform conventional radar chirps for range ambiguity suppression and for robustness enhancement in 2×2 MIMO configuration.

Waveform Design for MIMO Radar and SAR Application

“…The other solution is to use complex symbols instead of 1, that is, the active subchannels are such that a i ¼ e iθ i . The angle θ i can also be introduced as a parameter to optimise in the genetic algorithm but random values lead high PAPR reductions [17].…”

“…(15). (17) With N ¼ 13, the number of couples is 35. This low number allows exhaustive performance comparison to find the best couple.…”