Phase locking loop frequency synthesizer

Details Phase locking loop frequency synthesizer Phase locking loop frequency synthesizer

2006-03-07

2006-03-07

Vo, Nguyen T. (Department: 2685)

Telecommunications

Receiver or analog modulated signal frequency converter

Local control of receiver operation

C455S264000, C375S376000, C331S00100A

Reexamination Certificate

active

07010285

ABSTRACT:
A frequency synthesiser50comprises a VCO56whose output signal frequency is proportional to input voltage amplitude. In a first mode, the VCO output is fed via a divider24to a phase detector26which also receives a reference signal. The phase detector output passes via a loop filter28and a controller70,which is passive in the first mode, back to the VCO56to form a closed phase-locked loop. To adjust the frequency synthesiser output frequency, the controller70switches the circuit into a second mode in which the VCO56output is not fed back, and a constant voltage source is supplied to the VCO56instead so that the VCO output frequency is constant. The VCO transfer function is then altered by adjusting a variable capacitor60therein, and the circuit is then switched back to the first mode. The locking time of the synthesiser is thereby improved as output frequency changes.

REFERENCES:
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patent: 5166641 (1992-11-01), Davis et al.
patent: 5335365 (1994-08-01), Ballantyne et al.
patent: 6717484 (2004-04-01), Ben-Ayun et al.
patent: 6200 92521 (1987-04-01), None
patent: 0700 30418 (1995-01-01), None

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