Polarization-Tracking Phased Array Antenna Based on Liquid Crystal Material

A compact polarization tracking phased array antenna based on liquid crystal material for satellite communication is presented. In contrast with conventional mechanically tracking antennas, the approach presented here meets the requirements of beam tracking and polarization tracking simultaneously without any servo components. The aperture coupled microstrip antenna feeding by liquid crystal phase shifter is used as radiation element. The cross-polarization level of the element is better than −21.5dB. The liquid crystal phase shifter has the advantage of low dispersion with ±8.5° phase shift error from 9 GHz to 10 GHz. A 45° and −45° orthogonal polarization phased array with three-stage phase shifter network is designed and fabricated. The first stage phase shifter and the second stage phase shifter control the beam scanning in xz-plane and yz-plane respectively, while the third stage phase shifter control the polarization tracking. The measured polarization tracking patterns of the array are given. The gain is no less than 15dB with radiation efficiency of more than 66%. The sidelobe of the pattern is lower than −16.5dB.