Abstract: A novel millimeter-wave broadband circularly polarized microstrip truncated-corner patch antenna fed by H shape aperture coupling is proposed , the influence of the key parameters to axial ratio(AR) is analyzed. A 4伊4 milimeter wave broadband circularly polarized microstrip antenna array based on this novel element is designed. The simulated result shows that the antenna array has good circular polarized characteristic. Compared with the traditional antenna array, the im pedance bandwidth(S11 <-10dB) and the AR bandwidth(AR<3dB) are 25. 9%(32. 2 ~41. 8GHz) and 20. 4%(32. 6 ~39. 9GHz)respectively, which has been improved greatly by 15% and 9. 7%. The maxim gain is 19dB, in the bandwidth, the antenna gain is upper than 15 dB, the side lobe level and the cross polarized level are low.