Electromagnetic Field Coupling to a Transmission Line - A Reciprocity-Based Approach

The electromagnetic (EM) reciprocity theorem of the time-convolution type is systematically applied to describe an EM-field-to-line coupling model interrelating the (actual) induced voltage and current quantities at the ends of a transmission line with the (testing) ones pertaining to the situation when the line operates as a transmitter. It is demonstrated that under certain conditions, the reciprocity-based coupling model is fully equivalent to the classic models of Agrawal, Taylor, and Rachidi. Furthermore, it is shown for the case of plane-wave incidence that the far-field amplitude radiated in the testing state can be used to replace the forcing functions that are traditionally expressed in terms of the excitation-field distribution along the transmission line. The reciprocity-based formulation is finally validated both analytically and numerically.