Generalized Sample-Hold Functions

As we have noted in previous chapters the combination of a continuous-time plant with a digital controller raises a number of interfacing issues. Both plant input and output are continuous-time signals while the digital controller accepts and generates sequences of numbers. Sampling — the process of transforming a continuous-time signal into a sequence of numbers — and reconstruction — the process of transforming a sequence of numbers into a continuous-time signal — have been discussed in Chapter 2. However, in that chapter, these two processes have been addressed mainly from the general signal processing point of view. The main concern was to preserve, as much as possible, the information content of the signal. Hence, the sampling rates were determined by signal bandwidth; the hold filters on the reconstruction side were typically a compromise between the ideal low pass filter and technical limitations.