| CPC H03H 7/463 (2013.01) [H01P 5/227 (2013.01); H03H 9/6483 (2013.01); H03H 9/725 (2013.01); H04B 1/0057 (2013.01)] | 8 Claims |
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1. A composite filter that performs at least one of a process of simultaneously inputting two signals having different frequencies within a first passband to a first terminal and a process of simultaneously inputting two signals having different frequencies within a second passband to a second terminal, the composite filter comprising:
a common terminal;
the first terminal;
the second terminal;
a first filter system connecting the common terminal and the first terminal to each other;
a second filter system connecting the common terminal and the second terminal to each other, wherein the second filter system comprises: a third filter corresponding to the second passband and connecting a second port and the second terminal to each other; and
a first 90° hybrid coupler connected to the common terminal that is shared by the first filter system and the second filter system, wherein the first 90° hybrid coupler comprises a first port that is connected to the common terminal, the second port, a third port electrically connected to the first port and the second port, and a fourth port electrically connected to the first port and the second port, the fourth port being a port to which a signal with a phase shifted by 90° relative to a phase of a signal distributed from the first port to the third port is distributed from the first port, and
wherein the first filter system comprises:
a first filter connected to the third port and corresponding to the first passband;
a second filter connected to the fourth port and corresponding to the first passband; and
a second 90° hybrid coupler connecting the first filter and the second filter to the first terminal,
wherein the second 90° hybrid coupler comprises:
a fifth port,
a sixth port,
a seventh port electrically connected to the fifth port that is connected to the first filter and the sixth port that is connected to the second filter,
an eighth port electrically connected to the fifth port, the sixth port and the first terminal, the eighth port being a port to which a signal with a phase shifted by 90° relative to a phase of a signal distributed from the fifth port to the seventh port is distributed from the fifth port, and
a termination resistor connected to the seventh port, wherein the termination resistor is located at a piezoelectric member where at least one of the first filter, the second filter, and the third filter is located
wherein the second filter system electrically connects the third port and the fourth port to the second terminal and relatively shifts a phase of a signal flowing from the third port toward the second terminal by 90° relative to a phase of a signal flowing from the fourth port toward the second terminal to change a phase difference between the two signals by 90°.
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