Improved radar range and velocity resolution using the fast orthogonal search

Abstract

AbstractThe authors show improved radar range and velocity resolution is achieved using fast orthogonal search in place of the standard fast Fourier transform. The method reliably detects targets that are close either in range or in velocity, which is relevant today given recent advances in target swarms. The method presented also allows radars to detect slower targets closer to the zero‐Doppler region, like uncrewed aerial systems (drones) moving slowly to escape detection. The authors also show a novel method for estimating the velocity spectrum of a pulse‐Doppler radar using the in‐phase and quadrature samples directly by presenting unique terms to the fast orthogonal search. This eliminates the need to convert into complex samples for processing. The authors compared the performance of the new fast orthogonal search method against the fast Fourier transform using both simulated pulse‐Doppler radar data and real frequency‐modulated continuous wave radar data taken in an anechoic chamber. The simulated pulse‐Doppler scenarios included targets closely spaced in velocity and targets near the zero‐Doppler null, all at a variety of signal‐to‐interference ratios. In all cases, the fast orthogonal search method was shown capable of detecting both the closely‐spaced and near‐zero‐Doppler targets a greater percentage of time compared to the fast Fourier transform. Furthermore, when the methods were compared using real frequency‐modulated continuous wave radar data, the stationary targets were resolved at 0.4 m using the fast orthogonal search as compared to 0.6 m for the fast Fourier transform. Thus, this new method is capable of greater radar range and velocity resolution than the fast Fourier transform.