Radiators in Time Domain–Part I: Electric, Magnetic, and Radiated Energies

Closed form expressions are derived in time domain to calculate the electric and magnetic energy linked to the electromagnetic field surrounding an electromagnetic device. The expressions are rigorous, general, and explicit in terms of the time dependent currents flowing on the device. They are computationally very efficient since they involve integrals solely over the device generating the field. The expressions can also be applied to and interpreted in frequency domain. This will lead to a new interpretation of stored energy in the frequency domain.