Amplitude and frequency modulators using a switchable component controlled by data signals

摘要

A modulated signal source derives its modulation information from digital data held in a data store. The digital data is arranged to operate a switch which in the case of amplitude modulation produces pulses of carrier frequency and in the case of frequency modulation introduces phase transitions into a carrier frequency. The use of the digital data and the switch enables the modulation characteristics of the signal source to be exactly predictable and reproducible and it is not degraded by non-linearities of the kind introduced by conventional mixers.