Patent ID: 7194242
Filing Date: 2007-03-20
Classification: H03C,H03D,H04B

Abstract:
1. A transmitter circuit comprising: first and second mixers; first, second and third amplifiers; a 90° phase shifter; a first oscillator; first and second voltage controlled current sources with first and second differential input terminals respectively; a switch portion for switching a direction of a differential signal on the basis of a local oscillation signal; first and second current sources; and a load in common to both mixers for picking out differential output of said first and second mixers, wherein output terminals of said first and second mixers are connected to input terminals of said first amplifier; local signal input terminals of said first and second mixers are provided for receiving local oscillation signals from said first oscillator to said first and said second mixers and; first and second output terminals of said 90° phase shifter are connected to said local signal input terminals of said first and second mixers; output terminals of said second and third amplifiers are connected to baseband signal input terminals of said first and second mixers; wherein an input terminal of said second amplifier is used as a first input terminal of said transmitter circuit; and an input terminal of said third amplifier is a second input terminal of said transmitter circuit; and an output terminal of said first amplifier is an entire output terminal for said transmitter circuit; and wherein said second and third amplifiers are provided with a variable gain circuit, wherein bias current of said first and second mixers change in proportion to an amplification factor of said second and third amplifiers, wherein said 90° phase shifter includes a divider where said first and second input terminals are a first differential output terminal and a second differential output terminal which together can output a 90° phase-shifted signal respectively, wherein said first and second mixers with said signal input terminals of said first and second mixers are differential input terminals respectively, a switch portion for switching a direction of a differential signal on the basis of a local oscillation signal, wherein said first differential output terminal and said second differential output terminal with said 90° phase-shifted signal from said divider are connected to the first differential input terminal of said switch portion respectively, wherein outputs of said first and second voltage controlled current sources and outputs of said first and second current sources are connected to a second differential input terminal of said switch portion respectively, wherein the differential output terminals of said switch portion are connected to said load in common, wherein said second and third amplifiers provided with said variable gain circuit comprising a variable attenuator having a differential input terminal and a differential output terminal respectively, wherein the differential output from said variable attenuator is connected to said differential input terminals of said first and second voltage controlled current sources, and wherein amounts of current of said first and second current sources and an attenuation level of said variable attenuator are controlled by a gain control signal.