Single-layer Millimeter Wave Filtenna with Quasi- Elliptic Gain Response Under Dual-mode Resonance

A novel single-layer low-cost filtering antenna (filtenna) with a low profile is proposed firstly for millimeter wave (mmWave) applications. The filtenna consists of a circular substrate integrated waveguide (SIW) cavity, a metal post for power feeding, a metal post for improving sideband suppression, and a slot for radiating power. In the passband, two high-order modes in the circular SIW cavity are excited to the slot, which are TM210 mode and TM020 mode. An additional post is used to suppress the contaminating modes. It is shown that the filtenna can achieve simulated and measured -10 dB impedance fabricated bandwidth (FBW) of 8.9% (26.13 - 28.54 GHz) and 8.2% (26.58 - 28.86 GHz), respectively. The filtenna features stable radiation patterns with an average gain of 4.7 dBi. The lower and upper sideband rejection level exceeds 25 dB and 14 dB, respectively. The filtenna exhibits a single-layer structure, high selectivity, and lowcost advantages, which can be a good candidate for 5G mmWave applications.