A Back-Fire to Forward Wide-Angle Beam Steering Leaky-Wave Antenna Based on SSPPs

We demonstrate an efficient back-fire to forward wide-angle beam steering leaky-wave antenna (LWA) based on a large dispersion gradient planar spoof surface plasmon polariton (SSPP) transmission line (TL) with split-ring units. To convert the highly confined SSPP waveguiding mode to a radiation mode, two arrays of metallic patches are periodically arranged on both sides of the SSPP TL. The patches are designed as two combined half-elliptical shapes to mitigate the open stopband effect and enhance the radiation performance. We propose a theoretical method to interpret the mechanism and predict the directional pattern of the LWA. To verify the proposed method, the SSPP TL and LWA prototypes are fabricated and measured. The calculation, simulation, and experimental results match well and show that the main beam of the LWA can steer a wide range of 112 degrees from back-fire (-90 degrees) to the forward quadrant of 22 degrees passing through the broadside in 6.3-11 GHz, demonstrating a large scanning rate of 2.07 degrees/%. Furthermore, the LWA also possesses the advantages of low profile, high average gain (12 dBi), high average efficiency (95%), and low sidelobe level (<-13 dB). This work provides an alternative route to achieving wide-angle LWAs for promising microwave radar and wireless communication applications.