A High Gain Circularly Polarized Microstrip Array Antenna At Millimeter-Wave Band

This paper presents the design of a
$\mathrm{4} \times \mathrm{4}$
elements circularly polarized microstrip patch array at millimeter-wave band. The sequential rotation method and series-parallel feed network are employed in the power distribution circuit for antenna performance improvement. The feed network is integrated on the same substrate layer of the antenna array in order to facilitate processing and manufacturing, and the total size of the design is
$\mathrm{10} \text{mm}\times \mathrm{12} \text{mm}\times \mathrm{0.127} \text{mm}$
. The simulated return loss exhibits an impedance bandwidth of 7%, and the 3-dB axial ratio bandwidth of 10% with respect to 78.5 GHz is obtained. Besides, the maximal gain is 17.6dBi at 78.5GHz.