Optimizing the OFDM Radar Waveform for Low-Angle Target Tracking Using WAF Criteria

Abstract

A novel algorithm is proposed to enhance the wideband ambiguity function (WAF) of radar by designing an orthogonal frequency division multiplexing (OFDM) waveform. This design improves signal resolution, leading to more accurate tracking of low-angle targets. The goal is to optimize the volume of the OFDM signal's WAF to approximate the desired ambiguity function volume in the delay-Doppler plane. This optimized waveform improves the delay (range) resolution of the radar system by enhancing the auto-correlation function (ACF). Additionally, using a multicarrier OFDM signal improves delay resolution by the number of subcarriers. The phase and amplitude coding technique further improves delay and Doppler. It is important to note that the waveform design considers various factors that affect low-angle target tracking, such as atmospheric attenuation, surface reflection, diffraction, and refraction. Theoretical expressions for each area, along with tabular and graphical results applicable to common radar frequencies and radar-target paths, are provided. When modeling specular multipath signals, the effects of the earth's curvature and the linear refractivity gradient of the horizontally stratified atmosphere are also taken into account. The methodology used is the LSE method utilized in designing the waveform. The main results obtained demonstrate enhancements not only in the Doppler and delay ambiguity function, but also in angle measurement and RMSE. Finally, our work demonstrates improved performance when compared with the articles.