Elastic wave filter device and duplexer

An elastic wave filter device comprising:

• a piezoelectric substrate;
• first to third longitudinally coupled resonator elastic wave filters including:
• first to third IDTs disposed in order in an elastic wave propagating direction on said piezoelectric substrate;
• and
• reflectors disposed at both sides in the elastic wave propagating direction of a region where said first to third IDTs are provided;
• an unbalanced signal terminal to which the respective first and third IDTs of said first to third longitudinally coupled resonator elastic wave filters are connected;
• and
• first and second balanced signal terminals defining output terminals;
• wherein
• a phase of an output signal to an input signal of said first longitudinally coupled resonator elastic wave filter differs by about 180 degrees from a phase of an output signal to an input signal of said third longitudinally coupled resonator elastic wave filter;
• said second longitudinally coupled resonator elastic wave filter includes first and second output terminals;
• a phase of a signal to be transmitted to said first output terminal from an input end of said second longitudinally coupled resonator elastic wave filter differs by about 180 degrees from a phase of a signal to be transmitted to said second output terminal from the input end of said second longitudinally coupled resonator elastic wave filter;
• a phase of the output signal corresponding to the input signal of said first longitudinally coupled resonator elastic wave filter is the same as a phase of the signal transmitted to said first output terminal from the input end of said second longitudinally coupled resonator elastic wave filter;
• a phase of the output signal corresponding to the input signal of said third longitudinally coupled resonator elastic wave filter is the same as a phase of the signal transmitted to said second output terminal from the input end of said second longitudinally coupled resonator elastic wave filter;
• the second IDT of said second longitudinally coupled resonator elastic wave filter includes a first sub-IDT portion and a second sub-IDT portion which are provided by being divided in the elastic wave propagating direction, and said first sub-IDT portion and said second sub-IDT portion is each connected to said first and second output terminals;
• the second IDT of said first longitudinally coupled resonator elastic wave filter, and the first sub-IDT portion of said second longitudinally coupled resonator elastic wave filter are connected to said first balanced signal terminal;
• and
• the second IDT of said third longitudinally coupled resonator elastic wave filter, and the second sub-IDT portion of said second longitudinally coupled resonator elastic wave filter are connected to said second balanced signal terminal.

An elastic wave filter device comprising:

• a piezoelectric substrate;
• first to sixth longitudinally coupled resonator elastic wave filters including:
• first to third IDTs disposed in order along an elastic wave propagating direction on said piezoelectric substrate;
• and
• reflectors disposed at both sides in the elastic wave propagating direction of a region where said first to third IDTs are provided;
• an unbalanced signal terminal to which each second IDT of said first to third longitudinally coupled resonator elastic wave filters is connected;
• and
• first and second balanced signal terminals defining output terminals;
• wherein
• the first and third IDTs of said first longitudinally coupled resonator elastic wave filter are connected to the first and third IDTs of said fourth longitudinally coupled resonator elastic wave filter by first and second signal lines, respectively;
• the first and third IDTs of said second longitudinally coupled resonator elastic wave filter are connected to the first and third IDTs of said fifth longitudinally coupled resonator elastic wave filter by third and fourth signal lines, respectively;
• the first and third IDTs of said third longitudinally coupled resonator elastic wave filter are connected to the first and third IDTs of said sixth longitudinally coupled resonator elastic wave filter by fifth and sixth signal lines, respectively;
• signals which flow to said first, third, and fifth signal lines have the same phase, signals which flow to said second, fourth, and sixth signal lines have the same phase, the phase of the signals which flow to said first, third, and fifth signal lines differs by about 180 degrees from the phase of the signals which flow to said second, fourth, and sixth signal lines;
• the second IDT of said fifth longitudinally coupled resonator elastic wave filter includes a first sub-IDT portion and a second sub-IDT portion which are provided by being divided in the elastic wave propagating direction;
• the second IDT of said fourth longitudinally coupled resonator elastic wave filter, and the first sub-IDT portion of said fifth longitudinally coupled resonator elastic wave filter are connected to said first balanced signal terminal;
• the second IDT of said sixth longitudinally coupled resonator elastic wave filter, and the second sub-IDT portion of said fifth longitudinally coupled resonator elastic wave filter are connected to said second balanced signal terminal;
• the respective first to third IDTs of said first to sixth longitudinally coupled resonator elastic wave filters are configured such that balanced output can be taken out from said first and second balanced signal terminals.