Dual-Rate Control Ripple Detection by an Approximate Frequency Response Methodology

In this work a new methodology for tracing the frequency response of a multirate system is presented, a multirate system being that in which different blocks appear operating with different sampling periods. Normally, lifting techniques are used to model this kind of system leading to multivariable systems and, in this way, the procedures from this environment are used to obtain the frequency response. It was possible to demonstrate that this methodology is extremely conservative and is also incapable of explaining specific cases of dual-rate controls. The proposed method is applied to the study of the intersample ripple of a multirate control system.