ENHANCED AZIMUTH RESOLUTION FOR SPACEBORNE INTERRUPTED FMCW SAR THROUGH SPECTRAL ANALYSIS

Frequency Modulated Continuous Wave (FMCW) is an alternative to pulsed mode operation of Synthetic Aperture Radar (SAR). It has advantages of less power requirements, low mass, low cost, and therefore simpler system; but the disadvantage is requirement of separate antennas for transmission and reception. Interrupted FMCW can use a single antenna by interleaving transmission and reception, but the disadvantage is discontinuity of data in azimuth which, after processing leads to the appearance of unwanted spikes paired with the compressed pulse. This paper presents a solution for the one-dimensional azimuth processing of interrupted data. An allpole model is fitted on each individual segment of deramped azimuth data, and spectrum is estimated which reveals the target locations corresponding to that segment. Finally, the spectrum of all the segments is added to obtain a complete target profile in azimuth. Three different methods have been used for calculating model coefficients, and the results have been compared. It is shown that covariance method and Burg's method give sharp peaks for target locations.