This study proposes a method for estimating the coupling voltage between a noise source and a victim antenna using tensor function, Huygens’s principle, and reciprocity theorem. In the forward problem, tensor function is used to calculate the tangential E and H fields from the noise source to the Huygens’s box at the victim end. This approach reduces the simulation time and provides more accurate coupling voltage compared to full-wave simulation tool. Since the tensor function include both near- and far-field effects, the proposed method can estimate both near- and far-field coupling voltages in several dB$\mu$ V or smaller. The validity of the present approach and its unique advantages over naive HFSS is demonstrated through a simulation example.