High resolution target range estimation using frequency-stepped CW radar

An optical signal processing algorithm is derived for obtaining high-resolution target range estimates from a small set of narrow-bandwidth frequency-stepped continuous-wave (CW) radar measurements. The derivation is based on minimizing the two-norm of the difference between the sequence of measured reflection coefficients and those produced by a model which assumes that the echoes from the radar channel are impulses in the time domain. The resolution achievable using the proposed optimization algorithm is demonstrated using two sets of measurements taken from an HP-8510 network analyzer, one at the input port of an air-line coaxial standard containing two step discontinuities in characteristic impedance and the other at the input port of a microwave reflectometer test apparatus. Comparison of the results of the optimization approach with those produced by the conventional inverse fast Fourier transform (IFF) technique shows that when the bandwidth is reduced far beyond the point at which the IFFT fails to distinguish two reflections that are known to exist, the optimization approach clearly resolves the reflections, and estimates the range to each source of reflection accurately.<>