This paper explains the principles of operation of an interpolation device, which transforms a discretely defined signal into a continuous one. The conditions for designing an interpolating parabola, which is going through (m + 1) discrete points for the m-th order of interpolation, are given. By the selection of a parameter 1 it is possible to ohoose the allocation of a working interval, along which the created parabola is valid. The case of cubic interpolation, using the third interval as the working interval, is used to illustrate the synthesis of the required overall transfer function and the transfer function of the forward and the feedback block. These transfer functions are implemented by rather simple circuitry, which may be designed, for example, on general purpose analog computer. The circumstances limiting the order of interpolation in these types of interpolating circuits are explained. At the end, a survey of transfer functions, together with actual circuits is given for first, second and third order interpolation. Some practical results achieved are discussed and an example of utilization is presented.
