Synthetic aperture radar (SAR) system limitations due to phase errors

The performance of high and very high resolution radar systems with synthetic apertures (SAR) is primarily limited by low and high frequency phase errors along the synthetic aperture. Causes of phase errors and the effects they exert on the behavior of the system are reviewed. Given the dominant importance of the quadratic phase error components as factors that limit the attainable resolution, all subsequent considerations are concentrated on this part of the phase errors. An attempt was made to obtain a direct estimate of the loss of resolution due to acceleration and velocity errors rather than an exact calculation of the pulse response in azimuth. Both aircraft and satellites are assumed as carrier platforms for this purpose. The numerical evaluation of the deduced relationships shows that aircraft-mounted SAR systems of high resolution and great range are very clearly limited by quadratic phase errors. Satellite-mounted SAR systems of the planned type, however, are in no way limited by phase errors because the proposed resolutions remain far below the existing limiting values. But this problem will become of increasing importance in the course of future development with its trend towards satellite-borne systems with ever higher resolutions.