Sampling of stochastic electromagnetic fields

Stochastic electromagnetic fields can be described by the auto- and cross correlation spectra of the electric and magnetic field values at pairs of points in space. In this work the characterization of noisy electromagnetic fields by sampling the field values in pairs of sampling points is discussed. Sampling of the electric or magnetic field values in all pairs of a set of sampling points yields the correlation matrix of the field samples. If the near-field in a surface of reference enclosing the stochastic field sources is sampled and characterized by its correlation matrix the field radiated in the space outside the surface of reference can be calculated and described by the field correlation spectra. Depending on the number of statistically independent field sources the eigenvalue decomposition of the correlation matrix yields a compact description of the measured EM noise field.