Low-Profile Circularly-Polarized Single-Probe Broadband Antenna

UCLA researchers from the Department of Electrical Engineering have developed a new technology to enable single-layer single-probe circularly-polarized patch antennas with a compact size and broad axial ratio/impedance matching bandwidth.

Patch antennas are attractive due to their low profile, easy fabrication and polarization versatility; however, the design of a compact, broadband, circularly polarized (CP) patch antenna still remains a significant challenge. Most existing low-profile CP dual-band or wideband antennas require multilayer fabrication, multiple input feeds or complex fabrication processing, raising the overall antenna cost. In addition, typical single-probe CP patch antennas have axial ratio (AR)/impedance (S₁₁)-matching bandwidths less than 1-2%, limiting their efficiency. Although a single-probe CP E-shaped patch antenna had been designed to achieve a 9% AR-S₁₁ bandwidth, the antenna’s large size limits its wide application.

UCLA researchers from the department of electrical engineering have developed a new technology to fabricate CP patch antenna with compact size and decent performance. By fine-tuning the geometry of a half-E shaped patch antenna and utilizing an electrically thick substrate, a substantial size reduction of 50% is achieved compared to the original E-shaped CP patch antenna, while a satisfactory AR-S₁₁ bandwidth of 5.3% can be retained.

A prototype operating over the WLAN band ( 2.4-2.53 GHz) has been developed to demonstrate the design of low-profile circularly-polarized single-probe broadband antenna for radiofrequency communication. The prototype showed a good bandwidth (5.3%, AR ≤ 3 dB and S₁₁ ≤ -10 dB) with a height of roughly λ/10, along with a predominantly unidirectional radiation pattern towards the broadside direction (theta=0).