Vol. 51, Issue 3, pp. 321-333
far-field extrapolation, Stratton–Chu formula, Gauss’s law
The extrapolation of the electric field is studied theoretically both in frequency domain and time domain. Combining Gauss’s law with the approximation method in engineering, two new formulas for the scattering field calculation are derived from different logical ideas based on Stratton–Chu formula. The consistency property of the derived formulas is investigated, and the third formula for the scattering field calculation is further obtained. Finally, the time-domain extrapolation is discussed based on the formulas, followed by a simple numerical example. The results obtained are characterized by a simple form and intuitive physical meaning, and are helpful to calculate certain engineering problems.