Comparison of the Performance between a Parasitically Coupled and a Direct Coupled Feed for a Microstrip Antenna Array

This communication presents an alternate methodology - parasitically coupled feed - for exciting a four element microstrip array radiating primarily in the broadside direction. Typically, a four element microstrip array is fed directly through a corporate feed network using T-junctions and quarter wave transformers. The proposed parasitically coupled feeding of the array simplifies the geometry and results in a smaller size for the array. In this study, the matching of the microstrip array and the radiation characteristics of the two different feeding mechanisms are simulated using an electromagnetic analysis code and then implemented in hardware for comparison of the performance of each mechanism. The microstrip line based array feed and the parasitically coupled feed both have similar bandwidth characteristics and radiate in the broadside direction with similar gains. The simulated efficiency of the proposed parasitically fed broadside array antenna is around 85% to 90% over majority of the bandwidth and compares well with the conventional direct feed structure.