### Reflectance of an Impedance

Let denote the driving-point impedance of an arbitrary continuous-time LTI system. Then, by definition, where and denote the Laplace transforms of the applied force and resulting velocity, respectively. The wave variable decomposition in Eq.(C.74) givesWe may call the

*reflectance*of impedance relative to . For example, if a transmission line with characteristic impedance were terminated in a lumped impedance , the reflection transfer function at the termination, as seen from the end of the transmission line, would be .

We are working with reflectance for

*force waves.*Using the elementary relations Eq.(C.73),

*i.e.*, and , we immediately obtain the corresponding

*velocity-wave reflectance:*

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Power-Normalized Waveguide Filters