Characterization of Range Resolution as a Function of Bandwidth and Frequency

Wideband radar systems typically express range resolution as a function of bandwidth only. This interpretation of resolution is related to the width of a single peak corresponding to a point scatterer, and is analogous to the Rayleigh criterion in optics. However, if one interprets resolution to mean the ability to resolve two closely spaced scatterers in a downconverted, pulse-compressed radar return, then resolution is a function of frequency as well as bandwidth. This paper shows that, for fixed bandwidth, the quality of peak separation in the processed return of two closely spaced scatterers is a nonlinear, nonmonotonic function of frequency and range separation. Simulation results, using full pulse-compression processing of uncompressed waveform returns, plot peak separation quality as a function of frequency. Analytical results show why this frequency-dependent behavior should be expected and how bandwidth figures in the nonlinearity as well. Frequency-dependent resolution of closely spaced scatterers has implication for applications that need high range resolution and also utilize frequency diversity for operation in a multi-radar environment.