A Circularly Polarized Octagon-Star-Shaped Microstrip Patch Antenna With Conical Radiation Pattern

摘要

A new circularly polarized (CP) microstrip patch antenna with conical radiation pattern is proposed and investigated. The proposed CP antenna has a single feed, a low profile, and a very simple structure. The patch has an octagon-star shape, and can be considered as a superimposition of two square patches. By generating two orthogonal degenerated TM11 modes from the two superimposed square patches, omnidirectional CP radiation is achieved for the proposed antenna. The operation mechanism of the antenna is theoretically explained. A prototype of the proposed antenna is fabricated and measured. Measured results are consistent with the simulated and theoretical results. The antenna can produce a conical CP radiation pattern with a measured average axial ratio (AR) of 1.80 dB in the azimuth plane (theta = 45 degrees) and a measured 3-dB AR bandwidth covering the global positioning system L1 band.