Optical Theorem for Transmission Lines

We present the application to transmission line systems of a new theory of the optical theorem that describes the energy budget of electromagnetic scattering in lossless wave propagation media. The insight gained by exploring this, simplest of the electromagnetic wave propagation systems from the point of view of the optical theorem, is important for understanding power budget of electromagnetic scattering due to the presence of targets in a medium, and of changes of loads due to parasitics, faults, switching, and other reasons, in transmission lines, with applications to quality control in manufacturing, self-monitoring of microwave circuits, and the detection of load changes and faults in power transmission and distribution systems. The results also apply to more general electromagnetic propagation systems and are relevant for the development of novel electromagnetic (e.g., microwave, terahertz) and optical sensors.