Design of a novel four-feed dual-band microstrip antenna with pure circular polarization and analysis of circular polarization parameters

In this study, a novel dual-band multiple-feed microstrip antenna is introduced for GNSS applications. The proposed antenna has a compact size of 1548 mm² and counts as a low-cost, low-profile antenna. The mathematical equations of multiple-feed configuration are driven to analyze circular polarization (CP) generation and find the effective parameters on CP value. It is shown that for an n-feed symmetric antenna, the phase shift of 2π/n between ports leads to pure CP, regardless of the electrical field pattern. However, if the first feed electric field has equal value in the x and y direction and also 90° phase shift, the CP value is increased. A symmetric four-feed configuration is employed on the antenna to generate CP. Also, fractal circular rings and perturbing sectors are applied to miniaturize the antenna and improve the CP value. Numerical simulation shows that all feeding network requirements are met and the phase shift is satisfied at both frequencies by using the coupler technique. Furthermore, results show desirable band width of 48 MHz and 60 MHz and high front to back ratio of 16.1 and 14 at f1=1.227 GHz and f2=1.575 GHz, respectively. The axial ratio (AR) beam-width at both frequencies is more than 66°.