Compact and single-feed circularly polarised microstrip antenna with wide beamwidth and axial-ratio beamwidth

A novel method to realise a single-feed circularly polarised (CP) microstrip antenna with wide beamwidth and axial-ratio (AR) beamwidth is investigated. Two diagonal metal walls are put at the diagonal sides of the microstrip antenna. The diagonal metal walls can excite the orthogonal radiation fields with the same amplitude and 90 degrees phase difference on the radiating patch for CP with wide beamwidth and AR beamwidth. Some parameters which effect on the performances of the antenna are studied. The simulated and measured results of the reflection coefficients, radiation patterns and AR radiation patterns are presented. The 3-dB beamwidths of the right-hand CP (RHCP) radiation patterns in the xoz-plane and the yoz-plane are 105 degrees and 157 degrees, respectively. The 3-dB AR beamwidths of the RHCP radiation patterns in the xoz-plane and yoz-plane are 100 degrees and 155 degrees, respectively. Good CP characteristics of the new structure antenna have been obtained in the whole operating frequency band.