Compact filtering antenna using CRLH resonator and defected ground structure

A compact filtering antenna with high band-edge gain selectivity using a composite right-/left-handed (CRLH) resonator and a defected ground structure is presented. The CRLH resonator resonates at the zeroth-order mode and acts as the first stage of the corresponding filter; an octagonal patch acts as a radiator as well as the last stage of the filter. The design procedure follows the circuit approach - synthesis of bandpass filters. The filtering antenna has two poles in the passband and two radiation nulls (zeros) at the band edges. Compared to the conventional patch antenna, the proposed filtering antenna, with little extra circuit area, has flat gain response within the passband, good selectivity at the passband edge and wider bandwidth. Measurement results show that the filtering antenna can operate at 5.29 GHz, has a 430 MHz bandwidth and a 2.5 dBi antenna gain in the broadside (+Z) direction within the passband.