Method and apparatus for characterizing homodyne transmitters and receivers

A system that corrects for linear distortions in a homodyne system, said system comprising:

• a homodyne system that is characterized by linear distortions;
• and
• a data processing system that receives a time domain signal, x1(t), to be processed by said homodyne system, a modulation format that is to be applied to said x1(t), generates a frequency spectrum, X1(f) from said x1(t), and generates an ideal output spectrum, Y1(f), representing a frequency spectrum of an output signal that would be produced by said homodyne system in the absence of said linear distortions in said homodyne system, wherein
• said data processing system stores a model of said homodyne system that maps Y1(f) to a frequency spectrum X2(f), computes an inverse Fourier transformation of X2(f) to arrive at a time domain signal, x2(t), and causes x2(t) to be input to said homodyne system.

A system that measures distortions in a homodyne system that processes a multi-tone time domain signal, x(t) to generate an output signal, y(t), said system comprising:

• a first port that receives said x(t) and generates a frequency spectrum X(f) therefrom;
• a second port that receives said y(t) and generates a frequency spectrum Y(f) therefrom;
• a data processing system that determines a plurality of parameters of a model that represents a linear frequency response of said homodyne system when operating on X(f) to arrive at Y(f) by fitting said model to Y(f) and X(f);
• and
• applies said model to X(f) and Y(f) to estimate said distortions.