Abstract:A novel Coplanar Waveguide(CPW) airbridge-free power divider based on CPW-slotline transition is proposed in order to solve the problem of narrow bandwidth and large size of traditional circularly polarized microstrip array antenna. By using the power divider, a compact CPW-fed circularly-polarized array antenna with high directivity is designed. Compared with traditional CPW power divider, the proposed power divider has realized energy distribution by utilizing odd mode of CPW rather than suppressing this mode, which means the power divider needs no airbridge structure. Meanwhile, since there is no need to use 1/4 wavelength matching line, the antenna size is more compact and the structure is simpler. The designed circularly-polarized antenna array is only 1 mm in thickness, the measured axial ratio bandwidth and impedance bandwidth is 4.14% and 7.03% respectively. In addition, the measured gain is 8.412 dBi at 5.8 GHz. Therefore, the proposed array antenna can simultaneously provide adequate working bandwidth and gain while ensuring low profile and small size.