Patent ID: 7606323
Filing Date: 2009-10-20
Classification: H04B

Abstract:
1. A transmitter circuit that outputs a first signal having information in a phase and an amplitude, the transmitter circuit comprising: a mixer that modulates a carrier signal according to an input signal; a detector that detects a DC offset of the mixer; and an adder that adds a DC voltage which corrects the detected DC offset to the input signal of the mixer, wherein the mixer comprises a double balanced mixer that includes two first resistors for differential output, wherein the transmitter circuit further comprises: a second resistor that is connected between a node of the two first resistors and a power supply; a limiter amplifier that amplifies a second signal that appears at the node when potentials of a pair of input terminals that input differential input signals of the double balanced mixer are alternately set to a first potential and a second potential; and a control unit that changes the first potential and the second potential by using a third signal that is outputted by the limiter amplifier, wherein a feedback loop that reduces the amplitude of the second signal by changing the first potential and the second potential, and wherein the first potential and the second potential which are converged in the feedback loop is a potential of the DC voltage which corrects the DC offset.