Differential-fed ultra-wideband slot-loaded patch antenna with dual orthogonal polarisation

A novel dual-polarised ultra-wideband patch antenna is proposed. This antenna consists of a square ring patch and four inclined triangular-shaped patches. The vertices of the triangular patches are connected to the microstrip lines which are printed on the bottom layer of the grounded FR4 substrate. To realise the differential feed mechanism for reducing the coupling between the two polarisation ports and the cross-polarisation level, two identical tapered baluns are used to excite the antenna. The antenna prototype can provide two orthogonal polarisations with an impedance bandwidth (|S₁₁| ≤ -10 dB) of 113.2% and isolation of over 28 dB across the whole operating frequency band. The measured antenna gain varies from 2.09 to 7.66 dBi for port 1 and from 0.02 to 6.77 dBi for port 2 with a 3 dB gain bandwidth of 96.3%.