Tunable transversal and resonator filters using the variable velocity inter-digital transducers with the variable capacitors and gaps

In order to obtain the high performance of Surface Acoustic Wave (SAW) devices, the tunable Inter-Digital Transducer (IDT) and IDT resonators are very important. We propose the new configuration of tunable interdigital transducers and resonators using the one of IDTs connected alternately to the only variable capacitance (impedance) and the other one of IDTs connected alternately to sending and receiving electrode, or the one of IDT with the gap control between the shorted electrode and IDTs and the other one of IDTs connected alternately to sending and receiving electrode with collinear arrangement. The center frequency changes were 2% and 13% for using 128° YX LiNbO₃ with k²=0.055 and SiO₂ YX-LiNbO₃ with k²=0.3.