ELASTIC BOUNDARY WAVE RESONATOR AND LADDER FILTER

摘要

Disclosed is an elastic boundary wave resonator (1) that can provide sufficiently high impedance at the antiresonant frequency and, when used in a ladder filter, can improve the filter characteristics thereof. The intersection widths of an IDT electrode (5) are weighted such that intersection widths further outward in the direction of elastic boundary wave propagation are smaller. The inner side (11a) of a first bus bar (11) has sloped sections (11a1, 11a2) that are sloped as so to maintain a constant distance from the first bus bar (11) side of an envelope section (B1). The inner side (12a) of a second bus bar has sloped sections (12a1, 12a2) disposed as so to maintain a constant distance from the second bus bar (12) side of the envelope section (B2). For at least one of the electrode fingers (13, 15), a straight line from the tip thereof to the side (11a, 12a) of the first or second bus bar, extending in the direction of elastic boundary wave propagation, intersects a total number N of electrode fingers and dummy electrodes, N being at least 5.