Antenna distortions in multiple phase centre interferometric systems

Radars that employ interferometry, such as along track interferometric SAR and displaced phase centre antenna (DPCA) systems, require a minimum of two receiving, spatially displaced, phase centres with which to compare signals. With advanced phased array technology, beam forming may be used to generate multiple effective phase centres on one antenna. When such an antenna undergoes symmetric distortions, the sub-apertures that form the phase centres experience asymmetric distortions. In this paper the two deterministic mechanical distortions of bowing and twisting are considered. A first order analysis obtains expressions for the patterns of the deformed apertures in terms of the patterns of the non-deformed arrays. For the principal aperture that undergoes symmetric distortion, it is shown that the deformations introduce phase variations and blurring across the pattern. For the sub-apertures, additional phase steering terms arise producing a skewing of the beams. However, the effective position of the phase centres remains unchanged