Microstrip-fed broadband circularly polarised monopole antenna

A microstrip-fed broadband circularly polarised (CP) monopole antenna was studied. A broad impedance bandwidth and wide axial ratio bandwidth (AR-BW) could be achieved simultaneously. This antenna used a conventional monopole architecture, except for its deforming ground plane and asymmetric-feed approach. The asymmetric-feed was used to provide an orthogonal component distinct from its original linear polarisation. In addition, by embedding a slit and a stub on the ground plane, this antenna could generate CP wave radiation and achieve a broad impedance bandwidth. According to the measurement results, the impedance bandwidth was 6.56 GHz for a 10 dB return loss, which covered a range of 2.32–8.88 GHz. The AR-BW was 1.2 GHz for a 3 dB AR, which covered a range of 3.2–4.4 GHz.