In many instances the properties of a network are obstructed by an intervening network, which is required when performing measurements of the network. These intervening networks are often in the form of a mode transformer and are, in the general sense, referred to as error networks. A new analysis mechanism is developed by applying a de-embedding method that was identified as being robust. The analysis was subsequently implemented in a numerical computational software package. The analysis mechanism can then be applied to perform the characterisation of error networks. The performance of the analysis mechanism is verified using an ideal lumped-element network. The limitations of the mechanism are identified and possible ways of addressing these limitations are given. The mechanism is successfully applied to the characterisation of three different microwave networks. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Electrical, Electronic and Computer Engineering / unrestricted