Analysis and design of a compact circularly polarized microstrip antenna with cross-shape shorting strips

In this paper, a detailed research on the shorting probe loaded patch antenna with the help of transmission line model loaded by an equivalent circuit model of shorting probe is done and a compact circularly polarized microstrip antenna (CPMA) with an extraordinarily small electrical size of 0.16λ(length) × 0.16λ(width) × 0.08λ(height) at 1.268GHz (λ is the wavelength in free space) is designed. Instructed by the research on the shorting probe, the bandwidth enhancement of the proposed antenna is achieved. In order to obtain the best circularly polarized(CP) radiation performance, several types of perturbations on the shorting probe are studied and a novel perturbation structure, unequal length cross-shape shorting strips, is proposed. The simulated and measured results show that the 3dB axial ratio(AR) bandwidth of 1.6%(20MHz) is realized, which means that the proposed antenna can be used for the applications of BD3 band(1.268GHz ± 10MHz) of Beidou (COMPASS) Navigation System.