A wideband high-gain high-selectivity filtering antenna with two adjustable radiation nulls

In this paper, a high-gain filtering antenna is proposed without extra filtering circuits. The proposed filtering antenna is composed of a stacked patch, a driven patch with an Omega-shaped slot and a ground etched a theta-shaped slot. There are two radiation nulls located at the lower and upper edges of the passband, respectively, which can be independently tuned by the Omega-shaped slot and stacked patch. In this way, the proposed filtering antenna has a flat gain response within the passband and a high suppression level in the stopband. The Omega-shaped slot can also bring an extra resonant mode to broaden the operating bandwidth. The theta-shaped defected ground structure (DGS) is designed to improve the impedance matching without affecting the filtering performance and the radiation pattern. The proposed filtering antenna is simulated, fabricated, and measured. The simulated and measured results are in good agreement. The measured 10-dB impedance bandwidth is 22.2% from 2 to 2.5 GHz, the maximum realized gain is 9.74 dBi at 2.42 GHz, and the out-of-band suppression is more than 24 dB.