Patent ID: 6570933
Filing Date: 2003-05-27
Classification: H04L

Abstract:
A method for measuring imperfections in a digital quadrature modulator operation in which an input signal of the modulator includes quadrature-phase I and Q channels, the method comprising:taking a plurality of momentary samples from an amplitude of an output signal at a rate based on a symbol clock of the modulator, the number of the plurality of samples being reduced by accepting for calculation only samples relating to symbols that are known to have a same nominal amplitude; dividing a direction angle of a transmission signal corresponding to the plurality of samples into different direction angle sectors based on data bits to be transmitted or modulator input signals; calculating magnitudes of distortions in the modulator operation from amplitude sample deviations between the different direction angle sectors or from a nominal value; and using the calculated distortion magnitudes to adjust the operation of the modulator by generating feedback loops, which correct for all the distortions in the modulator operation simultaneously in an iterative manner.