Patent ID: 7919975

Claim:
A differential signaling system comprising: a differential signal line having a first wiring and a second wiring coupled between a sending end and a receiving end of the system; a termination resistor coupled between the first wiring and the second wiring in the receiving end side of the system; and a test circuit coupled to the termination resistor in parallel to amplify and detect a variation of a differential impedance due to the differential signal line, wherein the test circuit includes: a differential test amplifier to amplify the variation in the differential impedance of the first wiring or the second wiring, a switching unit installed at an input terminal of the differential test amplifier used for controlling an operation of the differential test amplifier, a peak detector to convert an output signal of the differential test amplifier into a direct current component, and a phase detector connected to the first wiring and the second wiring of the differential signal line to detect a phase difference of a differential signal transmitted in the differential signal line.