Low-profile ultra-wideband polarisation diversity antenna with high isolation

A low-profile single-layer printed dual-port antenna with high isolation is presented for broadband polarisation diversity applications. The proposed antenna comprises a pair of the same monopoles that are orthogonally fed by two coplanar waveguide lines. Each monopole consists of a hexagonal radiator and a staircase-like ground plane. To accomplish a wideband polarisation diversity performance with a compact size, the geometrical parameters of the radiator and ground plane were optimised by using Ansoft HFSS. The designed antenna with the total area of 25x50mm(2) was fabricated and tested. Measured results show that the antenna covers the frequency ranges of 2.4-17.1 and 2.6-16.8GHz (|S-11| and |S-22|<-10dB), for ports 1 and 2, respectively. Also, the isolation between the two ports is better than 25dB over the entire working band. The proposed antenna features not only nearly omnidirectional radiation patterns, but also reasonable gain and radiation efficiency. Besides, the envelope correlation coefficient reveals a good diversity performance across the whole bandwidth. Finally, the distortionless time-domain performance of the antenna is verified by measurement of the group delay. The experimental results in both frequency and time domain show the suitability of the antenna for broadband dual-polarised applications.