TRANSVERSE DOUBLE MODE SAW FILTER

摘要

A transverse double mode SAW filter using a surface acoustic wave comprises two SAW resonators each having interdigital electrodes and a pair of reflectors arranged on both sides of the interdigital electrodes and provided close to each other on a piezoelectric flat plate parallel to the direction of propagation of an acoustic surface wave (SAW). The interdigital electrodes of each SAW resonator have first, second, and third feed conductors. The first feed conductor has electrode fingers of electrically positive polarity oriented toward the second and third feed conductors. The second and third feed conductors have electrode fingers of electrically negative polarity corresponding to the electrode fingers of positive polarity and oriented toward the first feed conductor. Thus, the passband width is increased greatly compared with conventional ones by making use of the frequency difference between the first-order symmetric mode S1 and the first-order oblique symmetric mode A1 excited by the interdigital electrodes.