Design of a Broadband High-Gain End-Fed Coaxial Collinear Antenna

Omnidirectional antennas are widely used for mobile communications in the base transceiver station. This letter introduces a high-gain coaxial collinear (CoCo) antenna with a stable radiation pattern. To design a wideband end-fed CoCo antenna, we modify the classic center-fed CoCo antenna structure with an appending wire-mesh structure. The proposed CoCo antenna's $-$10 dB impedance bandwidth and gain bandwidth (1 dB variation of maximum gain versus frequency) at a center frequency of 900 MHz is three times higher than the classical center-fed CoCo's equivalent bandwidth, thus retaining 9 dB gain. The unique feeding configuration is designed to create the broadband end-fed antenna and minimize the feeding cable effect on the omnidirectional radiation pattern. We prototype an antenna to evaluate the design performance and confirm the simulation results. The measured results show 8.5 dBi directivity and 125.5 MHz bandwidth at 900 MHz center frequency.