EE5410 Signal Processing : Sampling with zero-order hold :
1. such a sytem samples x(t) at a given instant and holds that value until the NEXT instant at which a sample is taken.
2. The reconstruction of x(t) from the output of a zero-order hold can again be carried out by a lowpass filter. However, the required filter NO longer has constant gain in the passband.
3. To develop the required filter characteristic, the output x0(t) of the zero-order hold can in principle be generated by impulse-train sampling followed by an LTI system with rectangular impulse response.