Compact and High-Gain Endfire Leaky-Wave Antenna Based on the Improved EH₀-Mode

An endfire leaky-wave antenna (LWA) with high gain and compact size is proposed based on the improved fundamental mode (EH₀-mode). The EH₀-mode of a microstrip line can radiate energy by loading metal pins on the line. However, due to the fringe effects of a finite ground plane, it cannot achieve exact endfire radiation. In this work, by changing the ground width of the EH₀-mode antenna to be the same as the strip width, a virtually infinite ground plane is effectively equivalent at the center of the substrate. Additionally, by loading asymmetrically biased patches, overlapped radiation fields are introduced to realize exact endfire radiation. The functional relationship between antenna gain and propagation constant is investigated to generate a gain contour plot, which can provide the optimal phase constant and leakage constant for maximum antenna gain. To validate these analyses, an antenna prototype is designed and fabricated, achieving a gain of 16.3 dBi in a compact size. The measured results are in good agreement with the simulated results, verifying the proposed design method for an LWA with a high gain and endfire radiation.