Resolution issues in radar signal analysis
Classical work in the field of high-resolution radar often assumes that an echo signal is made of a number of components that can be decomposed via Fourier analysis. Adjacent components are said to be resolved in the frequency domain if the intensity between them drops at least 3 decibels. This working definition is an extension of Lord Rayleigh's criterion for optical resolution. The problem with this approach is that whereas Rayleigh's criterion assumes signal incoherence, a high-resolution radar signal is often the coherent sum of sinusoids. The purpose of this thesis is to discuss the consequences of using Rayleigh's criterion in the analysis of radar signals. Specifically, computer simulations using a complex signal is analyzed via the periodogram as the relative phase between the two components of the signal is allowed to change. The net effect introduced by this phase variation is to reduce or increase the spacing and intensity between two adjacent spectral peaks. These changes are due to constructive or destructive interference of spectral cross terms that cannot be ignored when attempting to resolve frequency components from one another. Thus, the use of Rayleigh's criterion to define the resolution of a high-resolution radar system is inappropriate since phase difference information determines the relative range and relative doppler of a multi-component target.
Ochoa Gutierrez, Hector A, "Resolution issues in radar signal analysis" (2003). ETD Collection for University of Texas, El Paso. AAIEP10359.