The Time‐space‐dependent Power Spectrum for the Description of Nonstationary and Inhomogeneous Electromagnetic Fields

Abstract

Abstract. The nonstationary analogue to the stationary Wiener Khintchine theorem is considered and applied to the multi-dimensional cam of temporally nonstationary and spatially inhoniogeneous electromagnetic fields. The time-space-dependent power spectrum of these fields is introduced, and its connection with important measurable quantities is discussed. The dispersions relations (the mutual dependence of the Fourier variables w, k belonging to the time and space coordinates t, t) are included into the consideration. The variable Fourier amplitudes are compared with the conventionally used slowly varying field amplitudes. The transition to the stationary limiting case is carried out. Das zeit-und raumabhbgige Leistungsspektrum zur