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 5.10λ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub>×0.30λ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub>×0.02λ<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub>.