Patent ID: 6504454
Filing Date: 2003-01-07
Classification: H03H

Abstract:
A longitudinally coupled double mode SAW filters using the first and the third modes are cascaded, in each of the double mode SAW filters, three IDT electrodes are disposed side by side between grating reflectors in a direction of propagation of a surface wave on the principal plane of a piezoelectric substrate, characterized in thata pitch of the IDT electrode in the center of one of the double mode SAW filters in said filter is set as L2, the number of electrode fingers of the IDT electrode is smaller than that of an IDT electrode disposed in the center of the other double mode SAW filter, and dummy electrodes having a pitch Ld are disposed of the number equal to the difference between the number of electrode fingers of the IDT electrode and that of the IDT electrode in the other double mode SAW filter, and the pitch L2 is set to be higher than an electrode finger pitch L1 of the other IDT electrodes.