Synthetic aperture radar imaging algorithm for antenna coupling

EM coupling between antennas on a complex platform is an important issue in antenna design. We set out to develop an imaging algorithm to pinpoint these locations on the platform that give rise to antenna interactions based on the coupling data between antennas. Our approach to this problem is based on inverse synthetic aperture radar (ISAR). ISAR imaging is a standard technique to map the locations of dominant scattering off a target based on the multi-frequency, multi-aspect backscattered data. We have already extended this concept to the far-field antenna radiation problem by introducing the antenna SAR (ASAR) imaging concept. By collecting multi-frequency, multi-aspect radiation data from an antenna in the presence of the platform, we showed that it is possible to image the locations of the dominant secondary radiation off the platform. In this paper, we further extend this concept to the near-field antenna coupling problem by constructing the antenna coupling SAR (ACSAR) image of the platform. We show that a platform image can be generated by processing multi-frequency, multi-spatial radiation data about a receiver location from a transmitting antenna. Examples of the ACSAR image are presented by using the computed data from the shooting and bouncing ray (SAR) code Apatch. In addition, we present a fast algorithm for ACSAR image formation that is specifically tailored to the SAR technique. By taking advantage of the ray tracing information within the SAR engine, we show that the ACSAR image can be formed with little additional computation time than simple ray tracing.