3-D-Printed Dielectric Lens with Cone-Shaped Cavity for Axial Ratio Beamwidth Enhancement of Circularly Polarized Patch Antenna

Abstract

A 3-D-printed dielectric lens is proposed in this paper to widen the 3-dB axial-ratio beamwidth (ARBW) of conventional circularly polarized (CP) patch antenna. The proposed lens is constructed by a solid dielectric cylinder with a cone-shaped air cavity. To illustrate the working principle, the geometric optics method is introduced, then refractions of the CP wave caused by the lens are theoretically analyzed and the related equations of axial ratio (AR) are derived. Besides, the key parameters that affect the ARBW of the CP antenna are adequately investigated, and the general rules are summarized to design it conveniently. To provide two orthogonal modes at center frequency, a dual-feed network is used to drive the patch antenna. To demonstrate, prototypes with and without lens are designed, fabricated, and measured. The experimental results show a good agreement with the simulated ones in terms of returned loss, radiation pattern, gain, and AR. The measured 15-dB impedance bandwidth is 20.4%, the 3-dB AR bandwidth is 17.5%, and the peak gain at main radiated direction is 5.5 dBic. Furthermore, the compared results in measurements show that by using the proposed lens, the 3-dB ARBW of CP antenna can be extended effectively from 82° to 162°, which is highly demanded in global navigation satellite system for reducing multipath interference. Finally, the applicability of the proposed lens is discussed including the available frequency bandwidth, the size of ground plane, and the feasibility for other types of CP patch antennas.