Electric circuits, which produce oscillations at widely separated time scales, cause a huge computational effort in a numerical simulation of the mathematical model based on differential-algebraic equations (DAEs). Alternatively, a multidimensional signal model yields a description via multirate partial differential-algebraic equations (MPDAEs). Initialboundary value problems of the MPDAE system reproduce solutions of the underlying DAE system. In case of frequency modulation, an additional function arises in the MPDAE model, which represents a degree of freedom in the multivariate description of the signals. We present two minimisation strategies, which are able to identify the additional parameters such that the resulting solutions exhibit an elementary structure. Thus numerical schemes can apply relatively coarse grids and an efficient simulation is achieved.