Voltage-Controlled Ku-Band and X-Band Tunable Combline Filters Using Barium-Strontium-Titanate

Tunable X-band and Ku-band combline bandpass filters using barium-strontium-titanate capacitors fabricated on alumina substrates with through-substrate CuW vias are reported. Under a 0-100 V bias, the X-band filter changes center frequency from 8.75 GHz to 10.96 GHz with 4-8 dB of loss while the Ku-band filter changes center frequency from 11.7 GHz to 14.3 GHz with 6-10 dB of loss. Advances in processing and integration related to the filter fabrication and design are discussed.