Patent ID: 7295087

Claim:
A signal transmission circuit having a characteristic impedance and comprising: a common mode filter including a core, and first and second signal lines wound in a spiral around the core, the first signal line having a first input and a first output, the second signal line having a second input and a second output, wherein signals in reverse phase are input to the first input and the second input; a first capacitive element having a first terminal; a first connection line having a first end and a second end, the first connection line being connected to the first output only at the first end, the first connection line being connected to the first terminal only at the second end, wherein the first connection line has a first length; a second capacitive element having a second terminal; and a second connection line having a primary end and a secondary end, the second connection line being connected to the second output only at the primary end, the second connection line being connected to the second terminal only at the secondary end, wherein the second connection line has a second length, wherein each of the first length and the second length is within 3 mm to change the characteristic impedance.