Electrically small, planar, wideband filtering antenna with dual ring patches

Abstract

A simple, planar, electrically small antenna with both wide bandwidth and good out-of-band filtering selectivity is presented. The proposed filtering antenna is mainly composed of a small driven patch and a slotted ground plane. Two slots are etched in the ground plane to form two square ring patches that can generate a new resonant mode and two radiation zeros, and a T-shaped stub is loaded not only to enhance the impedance bandwidth but also to increase the out-of-band rejection level. A prototype is fabricated and measured. The measured -10 dB fractional impedance bandwidth is 23.05% (2.61-3.29 GHz) centred at 2.95 GHz with the realised gain values 2.95 ± 0.34 dBi in the operational band, with two radiation zeros located at 2.27 and 3.62 GHz, respectively, even with electrically small size ka = 0.98. The experimental results are in good agreement with the simulated values.