PLL varicap diode piezoelectric oscillator - has digital frequency divider feeding phase comparator supplied with reference to select correction speed

摘要

The device includes an oscillator circuit (2), whose output is fed to a digital signal shaping circuit (10) followed by a frequency divider (11). The output from this divider is applied to one input of a digital phase comparator (12) which also receives a reference signal (13). The output of this passes to a digital speed correction selecting circuit (14), and then on to a controlled switch (9). The controlled switch has one terminal connected to earth, and the other connected to an additional capacitor (8) linked to the piezo-electric element (4). The speed correction selecting circuit is also connected (15) to a cutting signal. The oscillator is able to remain synchronised within the range of frequencies determined by the additional capacitor (8).