A Millimeter-Wave Gain Filtering Transmitarray AntennaDesign Usinga Hybrid-Lens

This letter proposes a millimeter-wave gain-filtering transmitarray (TA) antenna using a hybrid lens. The hybrid lens is incorporated by a substrate integrated waveguide (SIW) cavity bandpass filter and a dielectric lens. The dielectric lens serving as a phase shifter is seamlessly coated on the SIW bandpass filter to achieve a codesigned architecture. The proposed hybrid lens unit cell (UC) is required not only to fulfill the desired phase shifts but also maintain a stable bandpass response, simultaneously. Therefore, the specific shape of the dielectric-lens UC must be optimized to minimize its impacts on the bandpass response of the original SIW bandpass filter as much as possible to ensure the filtering performance of the proposed hybrid-lens UC. After some optimizations, the dielectric-lens UC based on the air-perforated dielectric square post (APDSP) is determined finally. The simulated results show that the bandpass responses of the hybrid-lens UC are still maintained when the profile of the APDSP-based dielectric-lens UC is varied to satisfy a full phase-cycle (2π). The proposed hybrid-lens UCs are arranged reasonably to construct a TA antenna to fulfill the high gain and gain-filtering performance. The simulated and measured results are consistent, revealing the proposed TA antenna has a gain of 25.5 dBi at 35 GHz and a bandpass gain-filtering response over 30-40 GHz.