A Single-Layer Dual-Band Shorted-Patch Antenna with Same Circularly Polarization Based on Multi-Resonant Modes

A shorted-patch antenna (SPA) towards dual-band and circularly-polarization (CP) is proposed. Initially, several modes are selected to require the orthogonal electric-field components for CP generation. Next, the short pins are inserted below the rectangular patch to turn up TM 0,1/2 mode closely to TM 1,1/2 mode. Besides, a narrow rectangular slot is properly etched on the top-layer of the SPA to move down TM3,3/2 mode in proximity to TM 0,3/2 mode. In addition, an annular slot is properly etched around the feeding port for good impedance matching. Finally, the results illustrate that its effective bandwidth $(\vert S_{11}\vert and $\text{AR} ) is held around 1.19% (2.684-2.716 GHz) in low frequency band and 1.05% (5.683-5.743 GHz) in high frequency band. Additionally, the proposed SPA achieves CP radiation performances in dual bands, while keeping low-profile, single feeding and single-element properties.