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 ۱۵۴۸ \(mm^۲\) 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 \(\frac{۲\pi}{n}\) 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 ۹۰^{\circ} 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 ۴۸ \(MHz\) and ۶۰ \(MHz\) and high front to back ratio of ۱۶.۱ and ۱۴ at \(f_۱\)=۱.۲۲۷ \(GHz\) and \(f_۲\)=۱.۵۷۵ \(GHz\), respectively. The axial ratio (\(AR\)) beam-width at both frequencies is more than ۶۶^{\circ}.

Keywords:

Axial Ratio , Circular polarization , Dual-band , GNSS , Multiple-Feed