Ka-Band Circularly-Polarized Antenna Array with Wide Gain and Axial Ratio Bandwidth

In this paper, the design, simulation and measurement results of a 2x2 circularly polarized microstrip antenna sub-array at Ka-band are presented. The proposed antenna sub-array employs the sequential rotation technique for improvement of AR bandwidth with high circular polarization purity without degrading the circularly polarized gain. The 3-dB gain reduction due to using sequential rotation technique is compensated by employing an antenna element with wide axial ratio bandwidth. The antenna array has a wide impedance bandwidth (S11< -10 dB) of 6.5 GHz from 26-32.5 GHz. The antenna has a wide axial ratio bandwidth (AR< 3 dB) of 6.2 GHz from 25.4-31.6 GHz with high circular polarization purity. The 3-dB gain bandwidth of the antenna is from 25.5-31.2 GHz and the peak gain is 12.1 dBic. The antenna is fabricated through multilayer printed circuit board process and has a size of 18.5 mm x 18.5 mm x 1.02 mm.