High-efficiency wideband and compact circularly polarized microstrip antenna with wide beamwidth

A novel compact circularly polarized (CP) microstrip antenna is presented. The antenna introduces a square radiation patch with a crossed slot to improve the impedance matching and reduce the antenna sizes. In addition, the proposed radiation structure makes the antenna a good CP property in the normal direction and also in the horizontal direction, so a super wide beamwidth of the axial ratio (AR) is obtained. Low-loss substrate and no-resistor feeding network are utilized to maximize the antenna radiation efficiency. Based on the above design, The profile and the length of the antenna are 0.073λ0 and 0.275λ0 respectively (λ0 is the wavelength in free space). The impedance bandwidth for VSWR≤2 is 21.9%, and the AR bandwidth for AR≤3dB is 9.1%. In the overlap band, the radiation efficiency can reaches more than 97%, and the gains are over 5.1dBic. Especially, the beamwidth for AR≤3dB can cover more than 190°.