Analytical Electromagnetic Field Coupling to Transmission Line Model Exploiting the Reciprocity Theorem

In this work, an analytical electromagnetic field coupling to transmission line model is proposed to efficiently evaluate the induced voltage/current responses of loads connected at the terminals. Specifically, an equivalent circuit is developed by combining the Lorentz reciprocity theorem with the classic passive transmission line model, and it is found that active contribution by impinging field could be cast in analytic form, as a function of the far-field radiation pattern and input impedance of the transmission line system in the transmitting mode. Compared with Agrawal's model, the proposed method reports concise and physical formulations without degrading the accuracy. Moreover, it is demonstrated that defining impinging field in spherical coordinates aligning parallelly with line is advantageous in revealing the wave propagation process.