A Simple Electromagnetically Fed Circularly-Polarized Circular Microstrip Antenna

Existing literature on circularly polarized antennas fed with a microstrip transmission line does not include a systematic methodology to control and tune the reflection coefficient (S11) and axial ratio (AR). To enable systematic tuning of those performance metrics, this study proposes a new, circularly polarized, circular microstrip patch antenna with truncated square slot. A combination of an edge-truncated square-slot and noncontacted electromagnetic coupling methods implemented in combination with circular patch results in a directional, left-handed circularly polarized (LHCP) pattern. This article discusses the analysis of several slot shapes that contribute to a good circularly polarized antenna. It also shows that the square slot with truncated edges is more effective in producing circular polarization than the conventional circular and usual square slot. Simulated and experimental results are in good agreement and indicate a -10-dB S11 and a 3-dB AR bandwidth of about 90 MHz and 25 MHz, respectively.