SUPPRESSING THE AZIMUTH AMBIGUITIES IN SYNTHETIC-APERTURE RADAR IMAGES

This paper proposes a method for removing the azimuth ambiguities from synthetic aperture radar (SAR) images. The basic idea is to generate a two-dimensional reference function for SAR processing which provides , in addition to the matched filtering for the unaliased part of the r eceived signal, the deconvolution of the azimuth ambiguities. This app roach corresponds to an ideal filter concept, where an ideal impulse r esponse function is obtained even in the presence of severe phase and amplitude errors. Modeling the sampled azimuth signal shows that the a bsolute phase value of the ambiguities cannot easily be determined due to their undersampling. The concept of the ideal filter is then exten ded to accommodate the undefined phase of the ambiguities and also the fading of the azimuth signal. Raw data from the E-SAR system have bee n used to verify the improvement in image quality by using the new met hod. It has a substantial significance in enabling the pulse-repetitio n frequency (PRF) constraints in the SAR system design to be relaxed a nd also for improving SAR image quality and interpretation.