Digital signal modulator for MODEM - has independent memories store differences in successive signal samples over different durations equal to integral time periods of signal

摘要

The device transforms digital data which is transmitted with a Baud rate and a binary rate d2=kd1 (where k is a positive integer) into a digital signal. This digital signal is equivalent to the signal which would be obtained by sampling with a frequency f. The device then codes an analogue signal which, for a frequency equal to the Baud rate, contains phase discontinuities. These phase discontinuities would reproduce, according to a predetermined modulation law, the state changes of the digital data, at the above frequency. The modulation and the usual filtering operations are performed simultaneously so that the sampling frequency can be lowered and the processing capacity of the modulation device increased. A memory stores the differences between successive samples when validated by the detector.