Acoustic wave device

An acoustic wave device comprising:

• first and second longitudinally-coupled resonator-type acoustic wave filters each including a piezoelectric substrate, a first IDT provided on the piezoelectric substrate, second and third IDTs arranged on either side of the first IDT in a direction in which surface waves propagate, and a pair of reflectors arranged on either side of a portion in which the first to third IDTs are provided in the direction in which the surface waves propagate;
• and
• an acoustic wave resonator provided on the piezoelectric substrate;
• wherein
• the second IDT in the first acoustic wave filter is electrically connected to the second IDT in the second acoustic wave filter and the third IDT in the first acoustic wave filter is electrically connected to the third IDT in the second acoustic wave filter to cascade the first acoustic wave filter with the second acoustic wave filter;
• the acoustic wave resonator is connected to an end of the first IDT in the first acoustic wave filter, which is opposite to the second acoustic wave filter, and NA/NB is in a range from about 2.6 to about 3.5 where NA denotes the number of electrode fingers of the first IDT in the first acoustic wave filter and NB denotes the number of electrode fingers of each of the second and third IDTs in the first acoustic wave filter;
• and
• fB/fa is in a range from about 0.995 to about 1.010 where fB denotes the end frequency of a stop band of each of the reflectors in the first and second acoustic wave filters and fa denotes an anti-resonant frequency of the acoustic wave resonator.