Patent ID: 7548591

Claim:
A quadrature modulator, comprising: a) an in-phase modulation branch receiving as an input an analog in-phase base band signal, the in-phase modulation branch including a first dc offset adjustment circuit, a first base band gain adjustment circuit, and a first mixer; b) a quadrature modulation branch receiving as an input an analog quadrature based band signal, the quadrature modulation branch including a second dc offset adjustment circuit, a second base band gain adjustment circuit, and a second mixer; c) a local oscillator means for providing a local oscillator signal to the first mixer and a phase shifted version of the local oscillator signal to the second mixer; d) a summer for summing the outputs of the first and second mixers; e) an envelope detector for detecting an output signal of the modulator and providing a signal representative of the amplitude of the output signal of the quadrature modulator; f) a band pass filter for filtering the amplitude signal; and g) a signal strength indicator circuit for measuring the strength of the filtered amplitude signal, the indicator circuit providing a compensation signal for adjusting the phase shift of the local oscillator and the dc offsets and base band gains of the in-phase and quadrature base band signals.