Phase lock control system for a voltage controlled oscillator
A phase lock control system is presented for controlling a voltage controlled oscillator. The system includes a voltage controlled oscillator that produces a frequency signal exhibiting an output frequency that varies dependent upon the value of a control voltage applied thereto. A frequency deviation determining system employs a counter intermittently triggered ON for a fixed time by successive timing pulses received from a reference source and a comparator that determines any frequency deviation of the output frequency relative to a preset frequency. An error filter monitors the comparator for any frequency deviation for a plurality of samples of the frequency deviation determinations. A controller varies the control voltage to vary the output frequency in a direction to eliminate any frequency deviation.
1. A phase lock control system for controlling the output frequency of a voltage controlled oscillator comprising:
a voltage controlled oscillator that produces a frequency signal exhibiting an output frequency that varies dependent upon the value of a control voltage applied thereto;
a frequency deviation determining system that employs a counter intermittently triggered ON for a fixed time by successive timing pulses received from a reference source and a comparator that determines any frequency deviation of said output frequency relative to a preset frequency;
an error filter that monitors the comparator for any said frequency deviation for a plurality of samples of said frequency deviation determinations; and
a controller that varies said control voltage to vary said output frequency in a direction to eliminate any said frequency deviation.
2. A system as set forth in claim 1 wherein said voltage controlled oscillator is an oven controlled crystal oscillator (OCXO).
3. A system as set forth in claim 1 wherein said reference source is a global positioning system (GPS).
4. A system as set forth in claim 3 wherein said voltage controlled oscillator is an oven-controlled crystal oscillator (OCXO).
5. A system as set forth in claim 1 wherein said error filter is a moving average filter.
6. A system as set forth in claim 5 wherein said voltage controlled oscillator is an oven-controlled crystal oscillator (OCXO).
7. A system as set forth in claim 6 wherein said reference source is a global positioning system (GPS).
8. A system as set forth in claim 3 wherein said error filter is a moving average filter.
9. A system as set forth in claim 1 wherein said controller includes multiple stage variations of said control voltage to achieve variations in the speed of reducing any said frequency deviation.
10. A system as set forth in claim 9 wherein said multiple stage variations of said control voltage are dependent upon the value of any said frequency deviation.
11. A system as set forth in claim 10 wherein said multiple stage variations includes a first response stage for quickly reducing any said frequency deviation greater than a first predetermined level.
12. A system as set forth in claim 11 wherein said multiple stage variations includes a second response stage for reducing any said frequency deviation which is of a level between that of said first predetermined level and a second predetermined level.
13. A system as set forth in claim 12 wherein said multiple stage variations includes a third response stage for reducing any said frequency deviation of a level which is less than that of said second predetermined level.