Small size base station antenna using phase difference feed for narrowband ubiquitous communication

Recently, system studies and hardware investigations on wide area ubiquitous network systems have been conducted. In this paper, we propose a compact sector antenna structure based on a co-linear array antenna that employs phase-difference feeding for a suitable base station in a wide area ubiquitous network system. In order to reduce the element interval with the goal of miniaturizing the sector antenna, we clarify the antenna feeding conditions while considering the mutual coupling between elements. Moreover, to achieve the proposed antenna structure, we employ a vertically arranged offset configuration that suppresses the influence on the radiation characteristics to 0.5lambda_o. To verify the antenna design, we developed a prototype antenna for the VHF band. We confirm that the measured results are in good agreement with the calculated results.