Elastic wave filter device and duplexer

A balanced elastic wave filter device having an unbalanced terminal and first and second balanced terminals, comprising:

• a first elastic wave filter unit including first to third IDTs arranged in this order in an elastic wave propagation direction, the second IDT being divided into three portions in the elastic wave propagation direction so as to include first to third sub-IDT portions;
• and
• a second elastic wave filter unit including fourth to sixth IDTs arranged in this order in an elastic wave propagation direction, the fifth IDT being divided into three portions in the elastic wave propagation direction so as to include first to third sub-IDT portions;
• wherein
• one end of the first IDT, one end of the third IDT, one end of the fourth IDT, and one end of the sixth IDT are connected to the unbalanced terminal;
• the first to third IDTs and the fourth to sixth IDTs are arranged such that a phase of a signal transmitted from the unbalanced terminal to the first balanced terminal is different from a phase of a signal transmitted from the unbalanced terminal to the second balanced terminal by about 180 degrees;
• the second IDT includes a first common bus bar that commonly connects the first to third sub-IDT portions together, an end of the first sub-IDT portion and an end of the third sub-IDT portion of the second IDT that are ends opposite to the ends connected to the first common bus bar are connected to the first balanced terminal, and an end of the second sub-IDT portion that is an end opposite to the end connected to the first common bus bar is connected to a ground terminal;
• and
• the fifth IDT includes a second common bus bar that commonly connects one end of each of the first to third sub-IDT portions together, an end of the first sub-IDT portion and an end of the third sub-IDT portion of the fifth IDT that are ends opposite to the ends connected to the second common bus bar are connected to the second balanced terminal, and an end of the second sub-IDT portion that is an end opposite to the end connected to the first common bus bar is connected to a ground terminal.

A balanced elastic wave filter device having an unbalanced terminal and first and second balanced terminals, comprising:

• a first elastic wave filter unit including first to third IDTs arranged in this order in an elastic wave propagation direction, each of the first and third IDTs being divided into two portions in the elastic wave propagation direction so as to include first and second sub-IDT portions;
• and
• a second elastic wave filter unit including fourth to sixth IDTs arranged in this order in an elastic wave propagation direction, each of the fourth and sixth IDTs being divided into two portions in the elastic wave propagation direction so as to include first and second sub-IDT portions;
• wherein
• one end of the second IDT and one end of the fifth IDT are connected to the unbalanced terminal;
• the first, third, fourth, and sixth IDTs respectively include first to fourth common bus bars that commonly connect one end of the first sub-IDT portion to one end of the second sub-IDT portion;
• the other end of the first sub-IDT portion of the first IDT is commonly connected to the other end of the second sub-IDT portion of the third IDT and is connected to the first balanced terminal, and the other end of the first sub-IDT portion of the fourth IDT is commonly connected to the other end of the second sub-IDT portion of the sixth IDT and is connected to the second balanced terminal;
• the other end of the second sub-IDT portion of the first IDT, the other end of the first sub-IDT portion of the third IDT, the other end of the second sub-IDT portion of the fourth IDT, and the other end of the first sub-IDT portion of the sixth IDT are connected to a ground terminal;
• the first to sixth IDTs are arranged such that a phase of a signal transmitted from the unbalanced terminal to the first balanced terminal is different from a phase of a signal transmitted from the unbalanced terminal to the second balanced terminal by about 180 degrees.

A balanced elastic wave filter device having an unbalanced terminal and first and second balanced terminals, comprising:

• a first elastic wave filter unit including first to third IDTs arranged in this order in an elastic wave propagation direction, each of the first and third IDTs being divided into two portions in the elastic wave propagation direction so as to include first and second sub-IDT portions;
• and
• a second elastic wave filter unit including fourth to sixth IDTs arranged in this order in an elastic wave propagation direction, each of the fourth and sixth IDTs being divided into two portions in the elastic wave propagation direction so as to include first and second sub-IDT portions;
• wherein
• one end of the second IDT and one end of the fifth IDT are connected to the unbalanced terminal;
• the first, third, fourth, and sixth IDTs respectively include first to fourth common bus bars that commonly connect one end of the first sub-IDT portion to one end of the second sub-IDT portion;
• the other end of the second sub-IDT portion of the first IDT is commonly connected to the other end of the first sub-IDT portion of the third IDT and is connected to the first balanced terminal, and the other end of the second sub-IDT portion of the fourth IDT is commonly connected to the other end of the first sub-IDT portion of the sixth IDT and is connected to the second balanced terminal;
• the other end of the first sub-IDT portion of the first IDT, the other end of the second sub-IDT portion of the third IDT, the other end of the first sub-IDT portion of the fourth IDT, and the other end of the second sub-IDT portion of the sixth IDT are connected to a ground terminal;
• and
• the first to sixth IDTs are arranged such that a phase of a signal transmitted from the unbalanced terminal to the first balanced terminal is different from a phase of a signal transmitted from the unbalanced terminal to the second balanced terminal by about 180 degrees.