Stochastic Analysis of Wideband Near-Field Emissions From Dipole Antennas and Integrated Circuits

A statistical method is developed for characterizing wideband emissions from planar antennas and circuits containing multiple radiating elements. It is shown how the space-time and space-frequency correlation functions for source currents can be deduced from near-field measurements. These correlations produce additional spectral distortion of the emitted near field, over and above the far-field spectra of individual elements and their combined spectrum for uncorrelated sources. For an arbitrary configuration and number of emitting dipoles, the contribution to this distortion by pairwise correlations is fully calculable from the second-order covariance theory. Simulation results for a 2 ×2 dipole array and near-field measurements on an L-shaped microstrip antenna with wide-band excitation demonstrate and validate the feasibility of the method and the theoretically predicted spectral distortion based on pairwise correlations only.