A Wideband Via Fed Circularly Polarized Microstrip Antenna on a Multi-layer Substrate

A wideband circularly polarized, via fed microstrip antenna on a multi-layer dielectric was investigated for applications in Retrodirective Arrays (RDA) mounted on Unmanned Aerial Vehicles (UAVs), both in a single element and an array. The fabricated element achieved an effective bandwidth of 1 GHz, or 33%, at a design frequency of 3 GHz across both the measured S-11 and axial ratio bandwidths. It achieves this wideband performance without the use of an air gap, or electrically large feed networks seen in other wideband microstrip antennas, reducing the cost and size of the antenna. The coupling was then measured between antennas in a 2 by 5 element array, with this information used in the design of the phase conjugate network of an RDA.