Time domain characterization of circular polarization selective structures

This paper investigates how typical frequency domain concepts such as circular polarization and axial ratio can be given a useful meaning in the time domain. The relationship between the linear polarizations of a circularly polarized time dependent signal is shown to be the Hilbert transform, and the instantaneous axial ratio can be computed from envelope functions, obtained from corresponding analytical signals. The analysis is applied to a recently published wideband circular polarization selective structure.