Dual-rate high order hold equivalent controllers

The paper is focused on the computation of a dual-rate high-order-hold discrete equivalent controller. We assume that the continuous-time controller has been already designed in order to meet continuous time-domain and frequency-domain specifications. Dual rate controllers are N-periodic time varying systems, and the lifting technique is utilized to express them as time invariant systems. Several different models are presented (dual-rate transfer function, dual-rate vector transfer function, dual-rate sampled-data continuous-time transfer function, discrete-time periodic algorithms) for suitable for analysis, design and/or implementation. Relations among them are presented and illustrated for the particular case of the first-order-hold circuit