A time-varying difference equation for nonperiodic sampling systems

It is shown that nonperiodic discrete-continuous sampling systems may be modeled in the time domain by a difference matrix equation which may be manipulated in the same way as in the case of periodic sampling. The output sequence may be computed by means of finite combinations of previous inputs and outputs using a finite set of time-varying parameters which are dependent on the parameters of the continuous transfer matrix and on a finite set of previous sampling periods equal to the order of the system.