An analysis of the second moment of fluctuating electromagnetic fields part II: An application to measurement

The theory of the dyadic field spectrum (DFS) of a fluctuating electromagnetic field developed in Part I is applied to the analysis of a particular experiment. The experiment is simply the measurement of the DFS by means of a two-element interferometer. The analysis includes the effect of the polarization and receiving pattern of the interferometer on the measurement and applies to the DFS of a partially polarized, partially coherent radiation field of arbitrary spectral width radiated by an incoherent source. The approach used in this calculation is that described in Section III-C of Part I. It is based on the application of the dyadic Green's function of the electric type for the interferometer. The power at the receiving terminals of the interferometer is expressed in terms of the DFS of the source and the antenna pattern of the interferometer. A method for measuring the distribution of polarization over the source is described.