Homodyne FMCW radar range resolution effects with sinusoidal nonlinearities in the frequency sweep

Abstract

This paper presents analysis and simulation results describing the effects on the range resolution of linear frequency modulated continuous wave (FMCW) homodyne radar due to sinusoidal nonlinearities in the frequency sweep. Short range applications such as collision avoidance and missile seekers use homodyne FMCW radar. Good range resolution is important to target-to-clutter contrast and to support target discrimination. In FMCW radar systems, range resolution depends on the transmitted bandwidth, the processed overlap between the transmitted and received frequency sweeps, the receiver frequency resolution, and the frequency sweep linearity. Frequency sweep nonlinearity is often the limiting factor in FMCW radar range resolution. This paper specifically addresses the effect of both the amplitude and the frequency of the sinusoidal frequency sweep nonlinearity on the target return spectrum and consequently the range resolution. These results are applicable to the design of modem closed-loop linearizers such as those used for varactor tuned Gunn diode oscillators in millimeter wave (MMW) FMCW radars, because after piecewise linear compensation the residual errors are approximately sinusoidal.