Dual mode circularly polarised patch antenna exited by dual mode defected ground square ring resonator

In this paper, an novel dual mode circularly polarized(CP) patch antenna is designed and analyzed. The antenna is composed of a square radiating patch, a metallic ground plane and a microstrip feedline. A defected ground square ring resonator (DGSRR) loaded with defected perturbation is etched on the metallic ground plane. The degenerate modes of the DGSRR are produced by loading the defected perturbation to make a dual mode resonator. Then two sets of degenerate orthogonal TM 01 and TM 10 modes of the square patch antenna are excited simultaneously by the dual mode resonator, which realize the CP radiation pattern and two orthogonal radiation modes. And also the two radiation modes can improve the impedance bandwidth. The simulated results show that two resonance frequencies are at 3.43 and 3.57 GHz respectively, the −10 dB impedance bandwidth is about 410 MHz (11.7% at the center frequency of 3.5 GHz) and the 3-dB axial ratio bandwidth is about 100 MHz. This single feed patch antenna is valuable in 5G communication systems for its compact structure, considerable bandwidth, CP radiation pattern and easy fabrication.