Printed log-periodic antenna fed by UWB balun for multi-polarization operation

A microstrip-fed log-periodic antenna integrated with a planar ultra-wideband balun printed on the same PCB is presented. The UWB balun feed is particularly designed using a compensated scheme that provides a stable main beam direction and gain level and a fixed phase center over the entire bandwidth (1~6GHz). The antenna operates in two orthogonal linear polarizations with two separate ports. The characteristic of polarization diversity can be configured in MIMO system with wideband frequency response. Simulation and experimental results show that the antenna has stable impedances and radiation gain patterns with a very good cross-polarization discrimination (XPD) of 20dB over the entire bandwidth. The novel design of the meander shape along the quasi-transmission line in the antenna is also included in this study.