A High-Gain Leaky-wave Endfire Antenna Using Multipole Element

This paper presents an all-metal high-gain backward endfire leaky-wave antenna (LWA), which is composed of densely and uniformly arranged dipoles fed by double-sided parallel-strip lines (DSPSL). Different from the conventional LWA, its element is a highly directional endfire multipole which is formed by densely placed dipoles with precise feed phase. The feed phase inversion is achieved through the spiral inversion of DSPSL, meeting the phase requirements of both the element and the array. The dipole unit design includes a parasitic structure to improve the impedance matching between the dipole and DSPSL, and to reduce the mutual coupling between elements, thereby enhancing radiation efficiency and directivity. The proposed antenna achieves a realized gain of 16.7 dBi within an array length of 4.8, a high front-to-back ratio (FTBR) of 28 dB, and a maximum relative sidelobe level of -16 dB at 1 GHz with a 3 dB endfire gain bandwidth of 5.4%.