Singly-Fed Circularly Polarized Circular Aperture Antenna With Conical Beam

A singly-fed circular aperture antenna radiating left-hand circularly polarized conical beam is proposed. The circularly polarized characteristic is realized by exciting TM
₀₁
and TE
₀₁
modes in a circular waveguide simultaneously. Through optimized design, the antenna provides an impedance bandwidth (|S
₁₁
| <; -10-dB) of 5%, from 12.15 to 12.8 GHz, and an axial ratio bandwidth (AR <; dB) of 4.8%, from 12.2 to 12.8 GHz. At the central frequency 12.5 GHz, a flare angle of 28
^°
of the radiation pattern and a measured gain of 7.5 dBic have been achieved. Good agreement has been observed between simulated results and measured ones.