Compact 2.4-GHz filtering monopole antenna based on modified SRR-inspired high-frequency-selective filter

In this paper, a co-designed compact filtering monopole antenna based on the recently developed two-stage split ring resonator (SRR)-inspired high-frequency-selective filter is proposed and demonstrated. The used filter is consisting of two groups of twist-modified SRRs and is inserted in the feeding line of a conventional wide band planar monopole antenna to filter out the unwanted out-of-band antenna gain. The impedance matching and radiation gain of the co-designed filtering antenna are numerically and experimentally demonstrated and a good agreement between them is obtained. The measured results show that such filtering antenna has a 3-dB gain bandwidth of 16.7% centered at 2.4 GHz with peak gain of 2.4 dBi and sharp dropped out-of-band radiation gain feature.