High port-to-port isolation dual circularly polarised microstrip patch antenna with multifunction DGS

Abstract

A two-port planar dual circularly polarised microstrip patch antenna is presented. The designed antenna has two groups of patches, each for transmission and reception. In one such group, only the central patch with truncated opposite corners is probe-fed whereas the surrounding patches act as parasitic patches for bandwidth and gain enhancement. A defected ground structure (DGS) consisting 4 units of complementary square spiral resonators is used to enhance the port-to-port isolation as well as the axial ratio (AR) bandwidth. Based on the measured data of the fabricated prototype, the antenna is seen to have an impedance bandwidth of 900 MHz with the centre frequency of f0 = 6.40 GHz. Moreover, the AR bandwidth is measured to be 600 MHz at fAR = 6.36 GHz, whereas the peak gain within this band is found to be ranging from 6.8 to 7.9 dBic. It is also noted that the AR bandwidth lies entirely within the impedance bandwidth and the cross-polarisation discrimination is 20 dB in the boresight direction.