A New Design Approach to Improve the Circular Polarization Characteristics of a Microstrip Antenna

Designing a circularly polarized (CP) microstrip patch on a thick substrate is a bit tricky. It is a challenge to achieve the overlap of the required impedance matching as well as axial ratio (AR) lower than 3 dB over a common band of frequencies. In this work, a new design approach has been presented. Some strategic engineering in the form of a pair of metallic stubs for a circular patch has been adopted. This provides a flexibility of varying the frequency corresponding to the best AR slightly without affecting the impedance matching bandwidth. Using this approach effective CP bandwidth of a conventional design is improved to 5%.