Analysis of Antenna Mutual Coupling in the X-Type Polarization Diversity System

Polarization diversity gain of the X-type polarization diversity system is determined by two factors: spatial correlation and average power ratio. These two factors are affected by mutual coupling (MC) greatly. Base on the polarization diversity antenna construction, a precise expression of MC, that is, mutual impedance is derived in this document. Combined with the equivalent MC network, the effects of MC on the spatial correlation and on the average power ratio are investigated firstly; next the effects of MC on the final polarization diversity gain through these two factors are further analyzed. Theoretical analysis plus numerical simulations are both presented. It is finally concluded that MC can raise the spatial correlation but also decrease the average power difference between the two array elements, thus changing the performance of polarization diversity system.