A Wideband Circularly Polarized Antenna for Microwave and Millimeter-Wave Applications

A wideband circularly polarized antenna with a single feed is achieved by adjusting the shapes and dimensions of a linearly polarized magneto-electric (ME) dipole antenna. Experimentally, an antenna prototype operating at around 2 GHz exhibits a wide impedance bandwidth of 73.3% for SWR ≤ 2 and 46.6% for SWR ≤ 1.5, a 3-dB axial ratio bandwidth of 47.7% and an antenna gain of 6.8 ± 1.8 dBic. Based on the design operating at lower microwave frequencies, a millimeter-wave antenna is designed on a dielectric substrate. The antenna has a wide impedance bandwidth (SWR ≤ 2) of 56.7% covering 38.5 to 69 GHz and a 3-dB axial ratio bandwidth of 41% covering 45.8 to 69.4 GHz, over which the antenna boresight gain varies from 5 to 9.9 dBic. This validates that the design can be realized on a single-layer printed circuit board.