SOME MICROWAVE APPLICATIONS OF BASRTIO3 AND HIGH-TEMPERATURE SUPERCONDUCTORS

The group at the University of Colorado has been working on the applic ations of BaSrTiO3 and high temperature superconductors to microwave c ircuits and systems with support from Superconducting Core Technologie s, NASA and ONR. This work has included the development of a voltage t unable oscillator, a phase shifter, and a voltage tunable phased array antenna system. An important aspect of this program is the lattice ma tch between the high temperature superconductor and the ferroelectric materials which enables us to grow thin films of either material on ea ch other. By choosing the appropriate barium stronium ratio we are abl e to obtain changes in the dielectric constant of 5 to 1 in bulk capac itors at 77 K, the liquid nitrogen boiling temperature. Phase shifts o f a little less than 126 degrees at 10 Ghz have been obtained by apply ing 5 volts on a one centimeter coplanar line. The proposed phased arr ay systems should enable us to point the beam radiated from the antenn a in an arbitrary direction using two control voltages of less than 50 volts. We believe this approach leads to the possibility of inexpensi ve electronically scannable antenna systems which could be used for mo bile communications with satellites and cellular systems.