Wideband Low-Profile Circularly Polarized Patch Antenna Using 90° Modified Schiffman Phase Shifter and Meandering Microstrip Feed

• Published in: IEEE transactions on antennas and propagation 2020-07, Vol.68 (7), p.5680-5685
• Main Authors: Qiu, Lei-Lei, Zhu, Lei, Xu, Yanhui
• Format: Article
• Language: English
• Subjects: Bandwidth; Broadband; Circular polarization; Feeds; Impedance; low profile; meandering feed; Microstrip; patch antenna; Patch antennas; Phase shifters; Substrates; wideband axial ratio (AR)
• ISSN: 0018-926X; 1558-2221
• DOI: 10.1109/TAP.2020.2963947

This communication proposes a wideband low-profile circularly polarized patch antenna based on a broadband 90° modified Schiffman phase shifter and a meandering L-shaped microstrip feed. The whole antenna consists of a broadband hybrid feeding network and a circular patch radiator. The hybrid network has two branches that operate in the first and second Schiffman periods, and thus can achieve 113% 10 dB return loss bandwidth and 75% phase shift bandwidth within 90°± 4.6° under a relaxed coupling strength of 1.58. To reduce the profile, the planar microstrip L-shaped feeding probe is properly meandered, which provides not only broadband impedance matching, but also an extra degree of freedom in the reduction of cross polarization, thus achieving a wide axial ratio (AR) bandwidth. Simulated and measured results show that the antenna has indeed achieved a low profile ( 0.05~\lambda _{0} ) with 50.5% impedance bandwidth, 47.8%AR bandwidth, and 34% gain bandwidth (>3 dBi).