Absolute phase determination techniques in SAR interferometry

Soren N. Madsen

doi:10.1117/12.210860

5 June 1995 Absolute phase determination techniques in SAR interferometry

Soren N. Madsen

Proceedings Volume 2487, Algorithms for Synthetic Aperture Radar Imagery II; (1995) https://doi.org/10.1117/12.210860
Event: SPIE's 1995 Symposium on OE/Aerospace Sensing and Dual Use Photonics, 1995, Orlando, FL, United States

Abstract

Cross-track interferometric SAR can provide 3D radar images. The technique relies on determining the target elevation from the difference in slant range observed by two antennas having a cross-track separation. The range difference is estimated very precisely using the phase difference observed in an interferogram obtained from the two complex images. A key problem is that the range difference can only be determined to within a multiple of the wavelength, as the phase difference is measured modulo 2(pi) . This paper discusses two different methods to determine the unknown multiple of 2(pi) : 1) the split-spectrum algorithm, and 2) the residual delay estimation algorithm. The split-spectrum algorithm utilizes the carrier frequency dependence of the interferometric phase, as subdividing the available range bandwidth into two bands provides two slightly different interferograms. The phase difference of the interferograms corresponds to an interferogram obtained with a system having a carrier frequency which is the difference between the two band centers. THe residual delay estimation method is based on the full bandwidth, one-look images used to form the interferogram and involves precision interpolation and coregistration steps. Principles are presented, along with possible implementations of the algorithms. Principle error sourses, as well as advantages and disadvantages from a processor design and implementation point of view are also discussed.

Citation Download Citation

Soren N. Madsen "Absolute phase determination techniques in SAR interferometry", Proc. SPIE 2487, Algorithms for Synthetic Aperture Radar Imagery II, (5 June 1995); https://doi.org/10.1117/12.210860

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