A Compact Omnidirectional Patch Antenna with Loaded Inductors and Capacitors

This paper proposes a compact monopolar patch antenna with loaded inductors and capacitors. The inductors and capacitors are introduced on two concentric slots on the patch layer. With these components, an extra phase shift can be added to the wave path from the center to the outer edge. Thus, the resonant frequency is shifted downward. To verify the idea, a prototype operating at 1.9 GHz is designed. Compared with the reference monopolar patch antenna of the same size, the resonant frequency of the proposed design is reduced by 23.3%. This design provides a 10-dB impedance bandwidth of 10.1% (1.79-1.98 GHz).