SINUSOIDAL SIGNAL GENERATOR, THE FREQUENCY OF WHICH IS DEPENDENT UPON A BINARY SIGNAL, IN PARTICULAR FOR A MODEM

摘要

A sinusoidal signal generator having a frequency variable as a function of a selection signal applied to the generator. A clock generator (1, 2) is programmable as a function of the selection signal and adapted to provide a plurality of clock signals having variable frequencies. A D/A converter (7) generates from a difference fixed potential (Vss, Vr), as a function of the clock signals utilized as sampling signals, a step signal having a sinusoidal envelope, of which the fundamental frequency is a function of the selection signal. A low pass filter (10) having transfer function which is dependent on the change in the fundamental frequency of the sinusoidal envelope (as controlled by the clock signals) rejects the harmonics contained in the step signal produced by the convertor (17), and provides a sinusoidal signal having a low harmnonic distortion.