| CPC H03H 7/09 (2013.01) [H03H 7/0115 (2013.01)] | 19 Claims |

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1. A filter, comprising:
a first input/output terminal;
a second input/output terminal;
a third input/output terminal;
a fourth input/output terminal;
a first stage resonant circuit connected between the first input/output terminal and the second input/output terminal;
at least one intermediate stage resonant circuit; and
a final stage resonant circuit connected between the third input/output terminal and the fourth input/output terminal; wherein
the first stage resonant circuit and the final stage resonant circuit each include an inductor;
the at least one intermediate stage resonant circuit includes an inductor and a capacitor connected in parallel to each other, and one end of the inductor and one end of the capacitor connected in parallel to the inductor are connected to a reference potential; and
at least two of the first stage resonant circuit, the at least one intermediate stage resonant circuit, and the final stage resonant circuit are coupled to each other.
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