Compact Octagonal Patch Antenna Array with Enhanced Isolation and Cross Polarization

Microstrip patch antennas are often used in array configurations where specific requirements such as antenna gain, beamwidth, polarization and low profile are of primary importance. In this paper, an octagonal patch antenna is designed, simulated and tested to investigate its effects on the well-known drawbacks of a microsrtip patch antenna, i.e. the fringing effects and the undesired mutual and isolation coupling existent between array elements. It is found that patch corrugations technique in specific patch edges strongly affect the resonant frequency, so that, if properly chosen and controlled, they might also compensate the existing fringing effect and greatly reduce the undesired coupling between antenna elements and the cross-polarization levels as well, while keeping the antenna overall size very compact. The investigation focuses on the H-plane feeding configuration as its cross-polarization is unacceptably high for some applications. These multiple improvements however, are on the cost of a slight reduction of the peak gain. Full-wave analysis simulations with HFSS (finite element) is used in the investigations. A sample 2-element octagonal patch antenna is fabricated and measured to validate the simulation results. Excellent agreement is observed between the measured and simulated responses of the antenna.