Tiny voltage-tuned phase shifters are among the first components
offered by a company with unique thin-film ferroelectric
technology. Tuning a high-frequency circuit usually involves
trimming a variable capacitor or turning a mechanical tuner. By
using innovative circuit materials formed of barium-strontium-
titanate (BST) dielectric, however, Agile Materials &
Technologies (Goleta, CA) offers components that can be tuned
with an applied voltage. The company's thin-film ferroelectric
technology offers tuning benefits at RF through millimeter-wave
frequencies for commercial and military applications, including
for antennas, filters, phase shifters, and linearization
circuitry. Since the dielectric constant of BST-based substrate
materials changes with applied DC voltage, circuits can be
readily fabricated with voltage-tunable capacitances. As with
trimmer capacitors, as the capacitance is varied, the impedance
and phase responses of an active or passive circuit are adjusted
in a predictable way. In the case of