Analysis of the Multimode Feedhorn Concept for Multichannel SAR-GMTI

Abstract:
The paper describes the experimental performance evaluation of a novel and innovative concept to add a multichannel Ground Moving Target Indication (GMTI) capability to a SAR reflector antenna with a standard single feed. This approach exploits the capability to achieve a phase center displacement combining signals obtained from different electromagnetic excitation modes of the feedhorn. While in the past this so-called multimode concept has been mainly analyzed in theory and by various antenna lab measurements, several flight experiments have been recently conducted to verify and demonstrate the GMTI performance. The theoretical and experimental analysis provides insight into the effectiveness of multimode SAR-GMTI applications, such as ATI based on the SAR image, as well as post-Doppler GMTI approaches based on STAP. It introduces practical lessons learned along with an example of the detection and parameter estimation for a large vessel using ATI. The paper finishes with an examination of the expected performance improvement when switching the transmitter between modes. This could be a potential upgrade to a three channel system.