Reflectometer calibration with a pair of partially known standards

We present a closed form solution to reflectometer self-calibration that allows for two partially known standards. The solution is developed explicitly for a pair lossless reflects standards, but could be applied to any calibration set with similar constraints. Related techniques presented previously are simplified in the new formulation and shown to be special cases of a more general solution. The procedure is based upon the cross-ratio invariance of a Möbius transformation.