Compact Filtering Monopole Antennas Based on the Miniaturised Coupled Filter

In this paper, two co-designed linear and circular polarized compact filtering monopole antennas based on the recently developed miniaturized coupled filter, namely the two-stage split ring resonator (SRR)-inspired high-frequency-selective filter, are proposed and demonstrated. The used filter is consisting of two groups of twist-modified SRRS and is inserted in the feeding line of the conventional wide band planar monopole antennas to filter out the unwanted out-of-band antenna gain. The measured results show that such filtering antennas have sharp dropped out-of-band radiation gain feature. These filtering antennas is suitable for the Internet of Things devices application.