An evaluation of near-field spatial feeds for phased array antennas

Microwave distribution systems for phased array antennas are always being optimized for compactness and higher performance. Hard wired corporate feeds are usually the implementation of choice because design information is well understood. However, compromises in system size, weight and performance are usually made as a trade for ease of design. Spatial near-field feed networks on the other hand have the potential of higher compactness and performance but are much harder to implement because their design information is not as well understood. This paper presents an example near-field spatial feed using a horn antenna feeding a three horn array. The demonstration is used to validate a near-field antenna array sampling technique developed for the purpose of designing near-field spatial feeds. The work includes the full 3D electromagnetic modeling of the feed, the optimization of the feed and finally the experimental testing of the feed. The modeled versus measured data presented will show that compact high performance spatial near-field feeds can be accurately modeled and implemented for specific feed requirements.