Metallic-Waveguide-Fed and Low-Sidelobe mmW Endfire Antenna Based on SSPP

This letter addresses the antenna challenges faced in corridor-like environments in the Internet-of-Things (IoT) world. High-gain and large-bandwidth antenna with fixed beam is required and the spoof surface plasmon polariton (SSPP)-based millimeter-wave (mmW) endfire antenna fits the requirement perfectly. Few SSPP mmW antennas have been reported, and most of the existing SSPP antennas are fed by SubMiniature version A (SMA) and fabricated by printed circuit board (PCB). Considering that metallic waveguide is the most important feeding interface and dielectric loss severely degrades antenna efficiency at mmW band, this letter proposes a metallic-waveguide-fed SSPP-based endfire antenna at 60 GHz. A sword-shaped grooved copper rod is inserted into a metallic waveguide to form the proposed antenna. The tapered handle penetrates into the trapezoidal matching air cavity for wideband matching. The grooves are tapered to achieve high endfire gain and low sidelobes (SLLs). The computer numerical control (CNC)-machined prototype verified the design strategy. The measured results show that the −10 dB impedance bandwidth is basically 45.6∼>67 GHz and within 55 GHz to 65 GHz, the endfire gains are 12.1 dBi to 15.6 dBi and the SLLs are better than −17.1 dB and −21.1 dB in E- and H-planes, respectively. This letter also proposes a new concept for designing mmW antennas by simply inserting a customized radiator into an open waveguide.