Range autofocusing for FMCW radars using time warping and a spectral concentration measure

This paper proposes a novel range autofocusing algorithm for linear frequency modulated continuous wave radars based on time warping and a spectral concentration measure. The algorithm deals with the estimation and correction of nonlinearities caused by the voltage controlled oscillator´s nonlinear tuning curve and assumes that this curve is described by an a priori known model and depends only on a few unknown parameters. The procedure is based on time warping the beat signal in turn with every function resulted from different model parameters combinations and evaluating the concentration of the warped signal´s spectrum. The estimated nonlinearity parameters of the model are the ones which provide the best spectral concentration. The algorithm is tested with simulations and real data provided by an X-band radar.