A wigner function approach for describing the radiation of complex sources

The radiation of complex electromagnetic sources in free space is described using a propagator of field-field correlation functions. We exploit a wave kinematic analogy to predict the evolution of correlation functions in terms of the propagation of density functions in the phase space associated with ray tracing. The Wigner distribution function formalism is used to derive propagation rules for these densities. The problem is reduced to tracing ray families in phase space for near-homogeneous sources. Numerical results are presented, and the correlation spreading predicted from the Van Cittert-Zernike theorem of statistical optics is retrieved as a special case. An application of the method to evaluate mechanical stirrers used in reverberation chambers is presented and discussed. These results serve as a proof-of-principle for understanding and predicting emissions from sources in more complicated environments.