Fujitsu Semiconductor Limited

Fujitsu Corporation

Shingo Sakamoto

Kazuaki Oishi

Kotaro Murakami

Kentaro Uchida

Jialin Ren

A mixer circuit includes: a mixer circuit including a first transistor pair to output a first differential input signal and a second transistor pair to output a second differential input signal by inversing the first differential signal; a local signal supply circuit to supply a pair of local signals to gates of the first transistor pair and the second transistor pair; an operational amplifier including an input pair coupled to an output pair of the mixer circuit and an output pair coupled to the input pair via feedback resistors, the operational amplifier to amplify the first differential input signal and output a differential output signal; a common mode feedback circuit to control a center voltage of the differential output signal so that the center voltage maintains a common voltage; and a common voltage generator circuit to generate the common voltage according to an amplitude of the local signal.

Mixer circuit and method for adjusting common voltage of mixer circuit

A quadrature demodulation circuit includes: first to fourth mixers to receive a modulation signal; a phase shifter to supply to the first and third mixers a first local frequency signal, to supply to the second mixer a second local frequency signal having a designated phase difference relative to the first local frequency signal, and to supply to the fourth mixer a third local frequency signal that is an inverse in phase to the second local frequency signal; a first adder to add a signal output from the first mixer and a signal output from the second mixer and to output a first demodulation signal; and a second adder to add a signal output from the third mixer and a signal output from the fourth mixer and to output a second demodulation signal.

Quadrature modulation demodulation circuit

A noise cancellation circuit, which reduces noise in an output signal of an amplifier having an input resistance, a feedback resistance, and an operational amplifier, has: a first mixer circuit, which input an input signal across a first input terminal and a second input terminal of the operational amplifier, and performs frequency conversion of the input signal according to a first frequency signal; a noise cancellation amplifier, which amplifies an output signal of the first mixer circuit; a second mixer circuit, which performs frequency conversion of an output signal of the noise cancellation amplifier according to the first frequency signal; and a signal supply circuit, which supplies an output signal of the second mixer circuit to the first input terminal of the operational amplifier via an output resistance.

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Yokohama, Japan

Shingo Sakamoto