Abstract
This paper describes a new astatic type automatic phase control (APC) system for a voltage-controlled crystal oscillator (VCXO). The control voltage is obtained by comparing the phase of the VCXO with that of a standard frequency oscillator operating at 40kHz. The signals from the two oscillators are supplied to a comparison circuit and the phase difference between them establishes the gate time. An auxiliary pulse generator feeds a signal to the gate circuit. The number of pulses passing through the gate is counted by a counting circuit and converted into an analog voltage which controls the VCXO.
The author has experimented with this APC system and has measured the frequency instability to be within 1.1X10-10/hour to the 40kHz frequency standard.
