A dual circularly polarised Contrawound Quadrifilar Helix Antenna for land mobile satellite MIMO terminal

A dual circularly polarised contrawound quadrifilar helix antenna (CQHA) is proposed for land mobile satellite MIMO systems. The CQHA is combination of two QHAs with opposite winding rotation where one is positioned inside of the other. Low return loss and isolation of the CQHA elements is achieved by varying the radius of the outer QHA while the inner QHA is fixed. Preliminary evaluation of its MIMO capability is done by calculating the mean effective gain and analysing the polarisation correlation of each QHA. A deployment configuration of two CQHAs for land mobile satellite /DVB-SH vehicular rooftop antenna is also proposed in this paper. Mean effective gain of the CQHA configuration for a complete azimuth plane is calculated by considering Gaussian angle of arrival model for the angular distribution of the incident waves.