Surface acoustic wave filter device and duplexer

A surface acoustic wave filter device comprising:

• a piezoelectric substrate;
• a first surface acoustic wave filter provided on the piezoelectric substrate;
• and
• a second surface acoustic wave filter provided on the piezoelectric substrate;
• wherein
• the first surface acoustic wave filter includes a longitudinally coupled resonator-type first filter section and a longitudinally coupled resonator-type second filter section, the second filter section being electrically connected in parallel or series with the first filter section on at least one of an input signal side and an output signal side;
• the first filter section includes a first IDT group including three IDTs arranged in a line in a surface acoustic wave propagation direction and a pair of first reflectors arranged on either side of the first IDT group in the surface acoustic wave propagation direction;
• the second filter section includes a second IDT group including three IDTs arranged in a line in the surface acoustic wave propagation direction and a pair of second reflectors arranged on either side of the second IDT group in the surface acoustic wave propagation direction;
• and
• the second surface acoustic wave filter includes a third IDT group that is cascade connected to the first filter section and the second filter section and includes a first IDT, a second IDT, a third IDT, a fourth IDT and a fifth IDT arranged in order in a line in the surface acoustic wave propagation direction, and a pair of third reflectors arranged on either side of the third IDT group in the surface acoustic wave propagation direction.