A novel design of a 1×2 and a 2×2 circularly polarized (CP) microstrip patch antenna arrays is presented in this paper. The two CP antenna arrays are fed by sequentially rotated coplanar waveguide (CPW) to slotline networks. The mechanism of circular polarization in this design is explained and the measured results shows that this kind of CPW feeding network is a good method to improve both the impedance bandwidths and 3-dB axial ratio bandwidths of CP antenna arrays. The simulated and measured impedance bandwidths and 3-dB axial ratio bandwidths of the 1×2 linear array are 3.79％ and 16.41％. Moreover, The simulated and measured impedance bandwidths and 3-dB axial ratio bandwidths of the 2×2 array are 3.61％ and 10.83％.
