Two-dimensional zero intermediate frequency vector filtering method for SAR interferograms

This paper presents a new filtering algorithm for SAR interferograms. The proposed algorithm assimilates the idea of zero intermediate frequency (ZIF) in radio technique. It transforms the raw interferogram to the zero intermediate frequency (ZIF) one and then filters it by vector filter. So, it is called as zero intermediate frequency vector (ZIFV) filtering. Firstly, the raw intergerogram is mapped to a vector interferogram, which includes the sine signal and the cosine one. Secondly, the vector interferogram is transformed to spectrum by using two-dimensional fast Fourier transform (FFT). Thirdly, the zero intermediate frequency is calculated and then a new reference interferogram is derived from it. And then, the ZIFV interferogram is calculated from the reference interferogram and the raw interferogram. Finally, the ZIFV interferogram is filtered by vector filtering method and the filtering result of the raw interferogram is obtained. Experiments show that the new ZIFV filtering algorithm can resolve the difficulty in dealing with dense fringe in SAR interferograms. The filtering effect is excellent for interferograms, especially for dense fringes.