A compact single-layer wideband filtering antenna with capacitively loaded short-circuited parasitic patches

A compact single-layer wideband filtering antenna with a simple structure is presented in this letter. It consists of a rectangular driven patch, a pair of short-circuited parasitic patches, and two pairs of rectangular slots. A short-circuited parasitic patch is employed to capacitively load at each radiating edge of the driven patch to enhance the impedance bandwidth and facilitate filtering response. Based on this arrangement, a radiation null at the upper stopband is generated due to the effect of multipath coupling so as to improve the upper stopband frequency selectivity. Moreover, two pairs of slots are etched into the driven patch to produce an in-band resonance and a radiation null at the lower-band edge to further broaden the impedance bandwidth and enhance the lower stopband frequency selectivity. A prototype of the developed filtering antenna with a center frequency of 4.96 GHz is fabricated and tested for validation. The measured values are consistent with the simulated ones, indicating a wide impedance bandwidth of 16.5% (4.55-5.37 GHz), and a maximum realized gain of 6.3 dBi. Compared with the previously reported filtering antenna, the developed filtering antenna can achieve a wideband filtering response even with a low profile of 0.026 lambda(0) and a small antenna size of 0.19 lambda(2)(0).