Patent ID: 6169463
Filing Date: 2001-01-02
Classification: H03C,H04L

Abstract:
A quadrature modulator comprising: an in-phase modulation branch comprising a first series arrangement of a first digital-to-analog converter, a first anti-aliasing filter, a first summing means, and a first mixer; a quadrature modulation branch comprising a second series arrangement of a second digital-to-analog converter, a second anti-aliasing filter, a second summing means, and a second mixer; a local oscillator means for providing a first local oscillator signal and a second local oscillator signal to said first and second mixers, respectively; a third summing means coupled to respective outputs of said first and second mixers, said third summing means providing a quadrature modulated signal; carrier leakage measurement means for measuring a first carrier leakage signal of said first local oscillator signal in said in-phase modulation branch, and a second carrier leakage signal of said second local oscillator signal in said quadrature modulation branch; a controllable signal generating means for generating a first monotonously increasing signal and a second monotonously increasing signal; and holding means for holding values of said first and second monotonously increasing signals, said holding means being coupled to said first and second summing means so as to form feedback paths; said carrier leakage measurement means adopting a first state in which said first and second carrier leakage signals are measured, and a second state in which said controllable signal generating means is controlled to stop generating said first and second monotonously increasing signals, said second state being adopted from said first state during measurement of said first and second carrier leakage signals.