Band pass type of tunable filters composed of ultra wide band SAW resonators by adjusting capacitors connected SAW resonators

Authors realized a one port surface acoustic wave (SAW) resonator composed of grooved-Cu- electrodes/4°Y-X· LiNbO₃ with an ultra wide bandwidth of 17 %. This time, the authors fabricated band pass type tunable filters using the SAW resonators instead of inductances and 2 kind of capacitors of interdigital capacitors (IDCs) and Si-diode variable capacitors. As a the result, when the IDCs were used, the tunable filter with the frequency tunable range of 6.8 % has been obtained by using 3 kinds of LiNbO₃ substrates having different capacitances of IDCs and the same designed SAW resonators. On the other hand, when the Si-diode variable capacitors were used, by applying the voltage of 1.2 V to 10 V to the Si variable capacitors (Toshiba JDV2S71E) in order to adjust the capacitance, a tunable filter with the frequency tunable range of 6.1% has been continuously obtained for the first time.