Patent ID: 8508277

Claim:
A phase interpolator comprising: a first signal generation circuit that generates a first output signal that has a phase corresponding to a phase of a first periodic signal that has been input; a second signal generation circuit to which a second periodic signal having a phase different from that of the first periodic signal is input, the second signal generation circuit generating a second output signal that has a phase corresponding to a phase of the second periodic signal; a third signal generation circuit that generates a third periodic signal by synthesizing the first output signal and the second output signal; a delay circuit that provides a variable delay amount to the first periodic signal; a detection circuit that detects a value of the third periodic signal at a timing corresponding to the phase of the first periodic signal that is delayed by the delay circuit; an optimum delay amount obtaining circuit that compares the value of the third periodic signal detected by the detection circuit according to the first periodic signal that has the delay amount with the value of the third periodic signal detected by the detection circuit according to the first periodic signal that has the different delay amount and obtains as an optimum delay amount the delay amount at which the detected value of the third periodic signal is a maximum or a minimum; and an amplitude adjustment circuit that, in a state of the optimum delay amount being set to the delay circuit, adjusts an amplitude of the third periodic signal in such a manner that the value of the third periodic signal detected by the detection circuit falls within a predetermined range.