This book is devoted to the problems of measuring electrical parameters of microwave devices, circuits and systems by comparing the measured values of a quantity with known values of the quantity as represented by a reference microwave standard. The author has tried to cover quite a wide group of microwave measuring techniques in the study, since up to now comparison measurements have appeared only in periodicals, handbooks of microwave measuring techniques or in various manuals describing the standard measuring procedures. This broad-based approach offers the possibility of abstracting the principles which are common to all partial comparison techniques and their modifications, as well as deriving the general rules for the optimum design, set-up and use of corresponding measurement networks.