Tunable Bandstop Resonator and Filter on Si-Substrate with PST Thin Film by Sol-Gel Deposition

Tunable bandstop resonators and filters are fabricated and measured. Lead strontium titanate (PST-Pb
_0.4
Sr
_0.6
(Ti
_1-x
Mn
_x
)O
₃
) thin film on a high-resistivity Si substrate is used for an application of low loss tunable circuits at microwave frequency band. Parallel plated PST varactors tune resonators and 3-pole bandstop filters which resonate at the center frequency of 4.23 and 7.1 GHz and its maximum rejection is more than 13.8 dB at the stop band while the insertion loss at the pass band is less than 3 dB.