Patent ID: 8093960

Claim:
A filter comprising: a filter section that is provided with a balanced input terminal including a terminal 1 and a terminal 2 and a balanced output terminal including a terminal 3 and a terminal 4 , and that passes a signal in a passband out of balanced signals input from the balanced input terminal and outputs the signal from the balanced output terminal; and a balanced-to-unbalanced converter that is connected between the balanced input terminal of the filter section and a single terminal, and that divides a signal input from the single terminal into two signals of opposite phase and inputs the two signals respectively to the terminal 1 and the terminal 2 of the balanced input terminal, or a balanced-to-unbalanced converter that is connected between the balanced output terminal and a single terminal, and that combines balanced signals output from the terminal 3 and the terminal 4 of the balanced output terminal and outputs the combined signal to the single terminal, wherein in the filter section, a frequency transfer characteristic between the terminals 1 and 3 differs from a frequency transfer characteristic between the terminals 2 and 4 , wherein in the filter section, a single-ended filter 1 is connected between the terminals 1 and 3 , a single-ended filter 2 is connected between the terminals 2 and 4 , and frequency transfer characteristics of the single-ended filter 1 and the single-ended filter 2 mutually differ.