Minimizing ISL in DFT-Spread OFDM Radar Using Complementary Overlaying and Greedy-MSA Optimization

This paper proposes a new scheme of discrete Fourier transform (DFT)-spread orthogonal frequency division multiplexing (OFDM) radar waveform design for system unwanted signal levels decreasing at the receiver. The proposed method mitigates limitations like grating lobe formation and reduced range resolution in interleaved frequency division multiplexing (IFDM). It also addresses high-range side lobes and signal amplitude fluctuations common in conventional OFDM radars. The proposed approach is divided into two sections: First, design a sequence of bi-phase elements as primal part of transmitted waveform and minimize its’ auto-correlation integrated side lobe level (ISL) through a modified simulated annealing algorithm based on a greedy search (greedy-MSA). Refinements have been made to various aspects of the SA algorithm: the initial temperature to adjust acceptance probability, the perturbation function to increase the diversity of generated solutions, and the local probing strategy with sequential search to improve solution effectiveness—Secondly, we employ a frequency multiplexing approach based on interleaved DFT-spreading to positioning it as a viable candidate solution for joint radar communication (JRC) applications due to OFDM drawbacks. The main contribution of this section is the elimination of auto-correlation grating lobes in the IFDM waveform. This is achieved through time-domain modifications of the waveform by overlaying a phase sequence onto the outer frame while preserving the auto-correlation characteristics of the primal phase sequence. Simulation results demonstrate that our methodology significantly surpasses existing techniques in decreasing unwanted signal levels.