Signal/Quantizing-distortion ratio measurements of fast-adaptive delta modulation systems

Signal/quantizing-distortion ratio (SQDR) was measured as a function of input level at a sampling frequency of 64 kHz with a phase- and amplitude-modulated sine wave of 800 Hz as input signal for different adaptive delta modulation systems. The parameters are: the number of bits taken into account in deciding step-size changes (bit-memory length); the ratio between the number of successive identical bit repetitions after which the step size is increased and the number of consecutive bit alternations after which the step size is decreased (up/down ratio); the step-size change factor a; and the use of single or double integration. Only one parameter is changed at a time resulting in a total of 54 measurement curves of SQDR as a function of input level. An analysis of the measurements is presented in terms of an averaged SQDR and its systematic spread as a function of the parameters.