Digital Techniques in Delta Modulation

The use of digital techniques in delta modulation is described. Two delta modulators are described, firstly a nonlinear digital delta modulation (NDDM) system, which uses instantaneous companding and secondly, a digital syllabic companded delta modulation (DSCDM) system, which uses syllabic companding. Both these delta modulators have the following properties. 1) Digital techniques are used for most of the circuitry, an
RC
integrator and a comparator being the only analogue components used. 2) The delta modulators are similar to a single integration delta modulator (SIDM) but use switched resistors in the
RC
integrators. Logic circuitry is used to connect one or more resistors to either the positive or negative supply, charging or discharging the capacitor. The relative ratio of the resistors and the order in which they are switched determines the signal-to-quantization-noise ratio, the dynamic range, and whether the system has instantaneous or syllabic companding.