Measurement and analysis of electromagnetic field-field correlation functions

Increasing frequency and complexity of operation make modern digital systems stochastic sources of electromagnetic radiation. We present a theory based on the Wigner function, a wave dynamical phase-space representation, to propagate the correlation tensor of vector fields from spatially distributed and broadband stochastic sources in free-space. The theory accounts for polarization effects and it is suited for propagation through reflecting environments. Near-field measurements of the field-field correlation function constitute the input of this procedure. We describe an efficient experimental procedure to carry out such measurements. The issues of phase reference and number of required sample points are addressed. The shape of the Wigner function is shown for the radiation of a mode-stirred cavity backed aperture in both the near- and the far-field regimes beyond the aperture. Results can be of interest for metrology techniques in electromagnetic compatibility, and for remote sensing in aerospace.