Noise filter and transmission device

摘要

A noise filter can reliably reject an in-phase component included in a differential signal without generating anti-resonance at a target frequency reject and, a transmission device including such a noise filter.;Ends of a pair of coils are connected to a pair of transmission lines in the vicinity of the transmitting circuit, and other ends are short-circuited. The coils are magnetically coupled so that the magnetic flux is cancelled regarding the in-phase component that transmits the pair of transmission lines, and the magnetic flux is increased regarding an opposite-phase component that transmits the pair of transmission lines. A series circuit, which includes an inductor and a capacitor connected in series, is connected to the pair of coils and ground. Each value of the pair of coils, the inductor, and the capacitor is set so that a resonance frequency of the in-phase component is a target frequency.

主权项

1. A filter provided on a pair of transmission lines connecting a transmitting circuit configured to transmit a differential signal and a receiving circuit configured to receive the differential signal, the filter comprising:
a pair of coils; an inductor; and a capacitor; wherein one end of one coil of the pair of coils is connected to one transmission line of the pair of transmission lines in the vicinity of the transmitting circuit; wherein one end of the other coil of the pair of coils is connected to the other transmission line of the pair of transmission lines in the vicinity of the transmitting circuit; wherein respective other ends of the pair of coils are short-circuited, wherein the pair of coils are in a magnetic coupling state in which magnetic fluxes of an in-phase component that is transmitted on the pair of transmission lines are cancelled with each other and magnetic fluxes of an opposite-phase component that is transmitted on the pair of transmission lines are increased with each other, wherein the inductor and the capacitor are a series circuit connected in series with the pair of coils and a ground, wherein a resonance frequency of the in-phase component of the pair of coils and the series circuit is set within a frequency band, the frequency band including a frequency corresponding to a one bit period of the differential signal, and having a bandwidth of 10% of the frequency corresponding to the one bit period of the differential signal, or the frequency band including an integer multiple of the one bit period of the differential signal, and having a bandwidth of 10% of the integer multiple of the one bit period of the differential signal.