A Broadband and High-Gain Endfire Antenna Array Fed by Air-Substrate Parallel Strip Line

A broadband and high-gain endfire antenna array fed by an air-substrate parallel strip line is proposed in this communication. It has a simple and planar structure consisting of multiple dipole radiating elements and one parallel strip line. By utilizing the center-fed dipole working between the first and third resonances as the radiating element, the antenna array could obtain stable radiating capability over a broad bandwidth. Fed by an air-substrate parallel strip line working on the TEM mode, the antenna array achieves a moderate phase constant, which is helpful for realizing stable endfire radiation. The radiating element separation is optimized to eliminate the high-order spatial harmonics, ensuring single beam radiation. Fabricated by thin copper plates, the merits of the antenna array include lightweight, low cost, and easy fabrication. According to the measured results, the antenna array has a good match and a stable endfire radiation pattern over the operating band from 4 to 10.5 GHz with the measured gain varying from 10.1 to 13.5 dBi.