Cavity-Backed Self-Phased Circularly Polarized Multidipole Antenna With Wide Axial-Ratio Beamwidth

A cavity-backed, self-phased, circularly polarized (CP) antenna with a wide beamwidth based on multidipole is proposed for global positioning system applications. The radiator of this antenna consists of a pair of longer dipoles and a pair of shorter dipoles, which contribute to the CP radiation. A cavitybacked reflector is employed to achieve a unidirectional pattern with a wide axial-ratio (AR) beamwidth, high gain, and high front-to-back ratio (FBR). Measurements show that the proposed antenna achieves a wide impedance bandwidth of 52.4% from 1.24 to 2.12 GHz with a return loss of more than 15 dB and a 3-dB AR bandwidth of 7.55% from 1.53 to 1.65 GHz. Furthermore, a high FBR of more than 27.3 dB and a high gain of 7.7 ± 0.3 dBi are achieved within the 3-dB AR bandwidth. In particular, the antenna also shows a right-hand circular polarization radiation with extremely wide 3-dB AR beamwidth of 254° and 245° in the xoz- and yoz-planes at the center frequency of 1.58 GHz, respectively.