Investigation of Using Ferroelectric Materials in High Power Fast Rf Phase Shifters for Rf Vector Modulation*

A fast ferroelectric phase shifter controlled by an electric field bias is being investigated for high-power fast RF phase shifters to be used for vector modulation. Such a device could find applications in particle accelerators, allowing vector control of the RF power divided and delivered to accelerating cavities from a power amplifier. Bulk ferroelectric materials, particularly those based on barium-strontium titanate (BST) compounds, have shown promise in high-power applications because of their low loss tangent and high dielectric strength. Use of BST compounds is investigated in a coaxial phase shifter prototype for frequencies in the 400 MHz – 800 MHz range that could be adapted for future large-scale accelerator projects. Designs of subsystems such as the DC block and matching structure are discussed. Since BST is a nonlinear dielectric compound, preliminary study on the nonlinear propagation effects is also conducted through computer simulation.