Tunable RF filters using thin film barium strontium titanate based capacitors

Tunable lowpass and bandpass filters based on barium strontium titanate (BST) capacitors are reported. For the lowpass filter, 40% tunability was achieved at 9 V. Intermodulation distortion generated by the lowpass filters was also measured and predicted using a nonlinear model for the BST capacitors. The bandpass filter showed 45% tunability with an applied DC bias of 10 V.