Dual Polarized UHF/VHF Honeycomb Stacked-Patch Feed Array for a Large-Aperture Space-borne Radar Antenna

As penetration depth through vegetation and ground becomes more important in active remote sensing applications, there is a shift toward using lower frequencies. To facilitate imaging of ground water, soil moisture and composition, and penetrating through forest canopies, a dual-band synthetic aperture radar (SAR) has been proposed to operate at VHF and UHF frequencies. To accommodate weekly repeat observations from LEO, a swath of roughly 350 Km is needed, requiring a 30-m long antenna aperture from the SAR design point of view. The beams of the UHF and the VHF antennas must coincide in the cross-track direction, resulting in antenna widths of 3m and 11m, respectively. A stacked, linearly dual-polarized patch array feeding a 30 meter diameter parabolic reflector is proposed for this application, which synthesizes near-rectangular effective apertures on the reflector. Using a mesh reflector technology, the mass of such an antenna configuration is about ten times smaller than a corresponding phased-array antenna. A scaled-frequency version of the feed array was initially designed, built, and tested. It was also integrated with a scaled reflector antenna to verify the performance of the overall system. The actual frequency version was then designed, built, and tested. The design of the dual-band stacked array and the power dividers will be discussed, the fabrication process explained, and the approaches used for optimizing the performance characteristics will be presented.