Numerical adaptive delta modulation-a technique for digital signal representation in ASIC applications

A fully digital adaptive delta modulation (ADM), called numerical adaptive delta modulation (NADM), is discussed. In contrast to conventional ADM systems, both step size adaptation and integration are performed numerically by an arithmetic logic unit. The hardware realization of the NADM is made up almost completely of logical gates. Hence the system is well suited to circuit integration. Since the clock frequency of the system is equal to the sampling rate, the power consumption is at a minimum. As an application example, the NADM system is used for speech signal transmission in a neural stimulator for electrical stimulation of the acoustic nerve