Joint range-azimuth resolution limit for radar coincidence imaging based on spatial information theory

Abstract

Resolution is a fundamental performance metric in radar imaging. In radar coincidence imaging (RCI), resolution is determined by the correlation between the reference radiation field and the target echo signal, leading to a coupling between range and azimuth resolutions. Additionally, noise significantly impacts the resolution. This paper develops a joint range-azimuth resolution limit (JRL) for RCI based on spatial information theory, providing a comprehensive resolution analysis under noisy conditions. Based on the imaging model of RCI, we derive the scattering information (SI) of two adjacent scatterers and decompose it into in-phase and quadrature components through Singular Value Decomposition (SVD). The JRL is defined as a critical state at which the quadrature component of SI reaches 1 bit. We derived the closed-form expression of the JRL using a second-order Taylor series expansion. Furthermore, the range resolution limit (RRL) and azimuth resolution limit (ARL) are derived from the closed-form JRL, which quantifies the relationship between the JRL and key factors, including the transmitting signal bandwidth, array aperture, number of transceiver antennas, and signal-to-noise ratio (SNR). Monte Carlo simulations validate the proposed JRL by comparing it with the resolution limits of conventional imaging methods in RCI.