Ferroelectric phase shifters and their performance in microwave phased array antennas

Abstract

Recent advances in the development of Barium Strontium Titanate ferroelectric composition has made possible reasonable performance of ferroeletric phase shifters to frequencies up to 10 GHz. These material improvements, coupled with phase shifter circuit design changes have resulted in phase shifts greater than 360 degrees with less than 6 dB insertion loss. In particular additives to the BaxSr1-_xTiO₃ composition have been shown to exhibit a consistent electrical phase shift verses DC potential over parameters of temperature and humidity. These ferroelectric material improvements and circuit design changes, included with the development of multiple ferroelectric phase shifters makes possible the fabrication of a low cost electronic scanning antenna. A single four element phase shifter was used with a one dimensional linear antenna array which was constructed on three layers and used an aperture coupled distribution technique. Individual elements of this multiple four element phase shifter were evaluated with respect to uniformity phase shift and insertion loss. The four element antenna was fed by four ferroelectric phase shifters and the phase shifters are corporately fed by the microwave source. The ferroelectric phase shifters are controlled via a dedicated microcontroller which calibrates out element phase variations and provides a real time scan capability for the antenna assembly.