Tri-polarised antenna – a virtual rotatable dual-polarised antenna used in polarised beampattern synthesis

Tri-polarised antennas are exploited to synthesise the optimal polarised beampattern in this study. First, the characteristics of a single tri-polarised antenna are studied with an infinite current sheet model. Using the cross-product algorithm, the authors find that three co-located orthogonal current sheets are equivalent to a pair of orthogonal current sheets in a particular orientation. It implies that the tri-polarised antenna is just virtually equivalent to a rotatable dual-polarised antenna. Then by formulating the problem in a convex form, they adopt the convex optimisation algorithm to synthesise optimal polarised beampattern of the tri-polarised array. The simulation results show that due to the increased orientation degree of freedom, the sidelobe and cross-polarisation level of tri-polarised array are significantly lower than the dual-polarised array.