ABSTRACT
MATERIAL SKI ACTION: The ferroelectric composition used in the fabrication of ferroelectric phase shifters was of Barium Strontium Titanate, with various additives, prepared by V.K. Varadan at the Penn State University or L.C. Sengupta (2) at Material Directorate, ARL. The
composition of the ferroelectric determines its Curie Point. The Barium to Strontium ratio of samples used in the development of microstrip phase shifters is in the order of .60 to .40 which has a Curie Point just below 0 degrees C, which allows for normal operation above the Curie Point in the para-electric region. The para-electric region is preferable to the true ferroelectric region below the Curie Point, in that there are lower losses and no hysteresis effects. Also, the further away operation is from the Curie Point the more temperature stable the material. Another feature of this ferroelectric composition is that generally samples with the larger changes in dielectric constant (50%) with applied voltage have higher microwave losses, and losses increase as one goes from microwave to millimeter wave frequencies.
