The theory of static wideband transformers has been applied to the design of a VHF rotary coupler that has a bandwidth ratio of 1000:1, and that requires no physical contact between the stator and rotor. A combination of balanced and unbalanced transmission line theory has been used to predict the performance of the coupler, and measurements on the prototype model showed excel lent agreement with predicted values. Input impedance and insertion loss were shown to be essentially independent of rotation over a wide frequency range. A significant aspect of this work is the analysis of the rotating turn in terms of two transmission line segments of variable length. This, coupled with the unbalanced-line theory from Sato [12J, led to a complex analysis that resulted in a system of 20 simultaneous equations to describe the 5-turn transformer. Thus, a computer solution was the only feasible method to predict the coupler performance. / Ph. D.