Unconventional connection of ferroelectric capacitors to resonators in tunable filters

Unconventional connection of ferroelectric capacitors to resonators of tunable filters is proposed. It has increased the required minimum of capacitance value and the frequency range from ku-band to K-band. The proposed method of connection is illustrated by an example of microstrip filter, which is tunable within the frequency range 18–20 GHz. The minimum capacitance of the ferroelectric capacitor, that was obtained, was Cmin = 0.22 pF, the maximum value — Cmax = 0.31 pF. In traditional connection scheme, capacitance value is Cmin = 0.11 pF, and it is not possible to implement ferroelectric capacitors in this case. Simulation results of the frequency responses of the filter are presented.