Design of a multi‐fed combined circularly polarized inverted‐F antenna with stable phase center

Abstract

In this article, a circularly polarized (CP) multi-fed combined inverted-F antenna (IFA) with highly stable phase center is presented. Based on the analysis of the traditional IFA unit, a four-ports fed CP combined IFA is designed. Consisting of four combined IFAs, the antenna radiator has a shape of British Union Jack. In addition, four parasitic strips are introduced to improve the phase enter performance. A four-way Wilkinson power divider is designed to feed the four IFA antennas with equal amplitudes and incremental phase difference of 90, which can maintain stable phase center. To validate the design, a prototype of the antenna working at global positioning system L1 band has been simulated, fabricated, and measured. The measured 3-dB axial ratio bandwidth is from 1.4 to 1.8 GHz. The maximum gain of 8.02 dBic is obtained at 1.58 GHz. Due to the symmetric structure, the simulated deviation of the phase center is smaller than 5.8 at the center operating frequency.