Patent ID: 6687312
Filing Date: 2004-02-03
Classification: H03F

Abstract:
An apparatus for modulating a carrier signal on the basis of an input signal to generate an output signal, said apparatus comprising a control loop having a forward path and a feedback path,said forward path comprising: means for converting the input signal into a pair of signal components whose phases are orthogonal to each other; first combining means for combining each of the pair of the orthogonal signal components with a respective different one of a pair of demodulated feedback signals to generate a pair of error signals; modulating means for modulating a carrier wave on the basis of the pair of error signals to form a pair of modulated signals; and second combining means for combining the pair of modulated signals to form the output signal, and said feedback path comprising: a feedback coupler for coupling a portion of the output signal into the feedback path; means for splitting the coupled signal into a pair of orthogonal feedback signals whose phases are orthogonal to each other; and demodulating means for demodulating the pair of orthogonal feedback signals to form the said pair of demodulated feedback signals, whereby said forward path further comprises a phase-shift control means operable to introduce a phase shift from 0-360Â° into the said pair of error signals.