This paper studies analytical forms of criteria for ensuring that all
zeros of a discrete system are stable when a continuous-time, strictly
proper and low-pass plant is sampled by use of a zero order hold. Nec
essary and sufficient conditions for stable zeros of a sampled system
are developed. They are related to coefficients of a continuous-time t
ransfer function and to a sampling period. This paper also presents su
fficient conditions which are expressed in terms of coefficients of a
continuous-time transfer function.