Phase interpolator

A phase interpolator comprising:

• a mixer configured to synthesize phases of a plurality of input cosine-wave or sine-wave signals whose phases are different from each other;
• and
• a bias generator configured to output a bias signal in accordance with a phase control signal to the mixer,
• wherein the mixer outputs a signal with a phase in accordance with the phase control signal, wherein:
• the mixer has:
• first to fourth input terminals to which four cosine-wave or sine-wave input signals whose phases are different from each other are input respectively;
• first and second output terminals which each output a differential signal with the phase in accordance with the phase control signal;
• a first differential pair to which the input signals of the first input terminal and the second input terminal are input;
• a second differential pair to which the input signals of the first input terminal and the second input terminal are input;
• a third differential pair to which an output signal of the first differential pair is input and which outputs a signal to the first output terminal and the second output terminal;
• a fourth differential pair to which an output signal of the second differential pair is input and which outputs a signal to the second output terminal and the first output terminal;
• a fifth differential pair to which the input signals of the third input terminal and the fourth input terminal are input;
• a sixth differential pair to which the input signals of the third input terminal and the fourth input terminal are input;
• a seventh differential pair to which an output signal of the fifth differential pair is input and which outputs a signal to the first output terminal and the second output terminal;
• and
• an eighth differential pair to which an output signal of the sixth differential pair is input and which outputs a signal to the second output terminal and the first output terminal;
• the first differential pair, the third differential pair, the fifth differential pair, and the seventh differential pair each have a current source in which a current based on the bias signal with a cosine value or a sine value flows;
• and
• the second differential pair, the fourth differential pair, the sixth differential pair, and the eighth differential pair each have a current source in which a constant current flows.

A phase interpolator comprising:

• a mixer configured to synthesize phases of a plurality of input cosine-wave or sine-wave signals whose phases are different from each other;
• and
• a bias generator configured to output a bias signal in accordance with a phase control signal to the mixer,
• wherein the mixer outputs a signal with a phase in accordance with the phase control signal, wherein the bias generator has:
• a control circuit which outputs first to third control signals in accordance with the phase control signal;
• a first current mirror circuit whose current mirror ratio is controlled in accordance with the first control signal;
• a second current mirror circuit which is connected to a subsequent stage of the first current mirror circuit, whose current mirror ratio is controlled in accordance with the second control signal, and which generates a cosine value current;
• and
• a third current mirror circuit which is connected to a subsequent stage of the first current mirror circuit, whose current mirror ratio is controlled in accordance with the third control signal, and which generates a sine value current.