A Filtering Antenna With Improved Frequency Selectivity and Wideband Harmonic Suppression

In this communication, a compact filtering antenna with high frequency selectivity and intensive harmonic suppression over a wide frequency range (3 f0) is proposed. The antenna mainly consists of a planar inverted-F structure (PIFS), a square patch, two parasitic halfwavelength strips, and a layer of metasurface under the patch. The PIFS, parasitic strips, and patch are cross-coupled and tuned at their fundamental mode to produce the 3rd-order filtering response with enhanced bandwidth and sharp roll-off at band-edges. To suppress the higher-order harmonics, a split ring resonator (SRR) is firstly inset into the PIFS to reject the main input power. Then, a layer of metasurface is introduced under the patch to further absorb extra power. As a result, the radiation efficiency at the 2nd-order harmonic can be reduced from 40% to 4%. The principles of the proposed antenna are investigated in detail. The filtering antenna is prototyped and verified, exhibiting a passband from 2.5 to 3.0 GHz and a gain suppression of 24 dB from 3.1- 6.0 GHz and 18 dB from 6.0 to 9.0 GHz.