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°.