Omega-K algorithm — A generalization for highly squinted spotlight SAR imaging with dechirp-on-receive

Advanced synthetic aperture radar (SAR) systems achieve high spatial resolution by using wide range bandwidth combined with long azimuth illumination time. In order to deal with such sensor parameters, high quality SAR focusing methods and often preprocessing of the raw data are necessary. Omega-K processing is commonly accepted as the ideal solution to the SAR focusing problem. Dechirp-on-receive can be used to reduce the analog bandwidth of SAR raw data. In this paper, a ready for implementation formulation of the Omega-K algorithm for squinted spotlight SAR with dechirp-on-receive is presented. The dechirp-on-receive procedure is analyzed showing that a phase error is induced. A method is presented which compensates this phase error by using a combination of a frequency dependent time shift filter and a constant time shift filter. Therewith, the theoretical achievable resolutions of the focused image reconstructed from both dechirped and chirped input data can be obtained.