A Compact High-Gain Periodic Leaky-Wave Endfire Antenna Based on Dual-Degree-of-Freedom Design Method

In this letter, a compact high-gain periodic leaky-wave endfire antenna is proposed. It has the advantages of compact structure, high gain, and high gain-to-length ratio by satisfying the Hansen–Woodyard (H–W) condition. To meet the H–W condition, a dual-degree-of-freedom design method (DDFM) is proposed, which enhances flexibility by designing the feedline and elements independently. By this means, a π phase loading structure can be easily designed to meet the phase demand of the H–W condition. Furthermore, based on the DDFM, the elements can couple energy from two paths simultaneously, achieving a uniform radiation aperture within a compact structure, which realizes the aperture distribution demand of the H–W condition. Finally, to validate the proposed methods, the antenna is fabricated and measured, achieving a high gain of 14.1 dBi, and a high gain-to-length ratio of 5.4 with a compact size of 5.10$\lambda_{0}\times 0.30\lambda_{0}\times 0.02\lambda_{0}$.