US3921095A
Expired / Lapsed
US
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Startable phase-locked loop oscillator
Assignee: HP Inc
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Filing: 1974-11-14
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Granted: 1975-11-18
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Expires: 1994-11-14
Abstract
Abstract A startable oscillator is provided whose frequency can be locked to a reference frequency and whose initial phase at the instant of start can be maintained indefinitely with a known precision. More particularly, the frequency of a tunable oscillator is locked to the reference frequency by means of a phase-locked loop. When a start signal is applied to the loop, the tunable oscillator is momentarily stopped and then restarted a fixed time later with a new phase as a result of the interruption. Simultaneously the inputs to a phase detector in the loop are withheld so that the phase detector will not produce any error correction signal to retune the frequency of the oscillator as a result of the change in oscillator phase. Large variations in the frequency of the tunable oscillator which would destroy the initial phase information are therefore avoided. Although the signals to the phase detector input are withheld from the phase detector, they are monitored and adjusted in phase. At an appropriate time at which the phases resemble the conditions prior to the start/restart interruption, the inputs are released to the phase detector. The phase detector thus experiences only locked conditions both before and after the restart. After the restart, however, the loop is locked at the new phase of the oscillator. The phase-locked loop thus behaves as though no interruption had occurred so that the tunable oscillator will continue operating at a frequency locked to the reference frequency but having the new phase preserved indefinitely.
Inventors
- 👤 David Chau-Kwong Chu
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 12:35
CPC Classifications
H; H03; H03L; H03L7/00; H03L7/06; H03L7/16; H03L7/18; H03L7/197; H03L7/199
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
253 words
A phase-locked oscillator comprising: frequency generating means for producing an output signal of a frequency responsive to the level of an input signal; scaling means for producing a divided signal output having a pulse spacing equal to the total spacing of N pulses of a signal appearing at the input of the scaling means, where N is a predetermined integer; mixing means responsive to the output signal of the frequency generating means and to a reference frequency for producing a beat signal output; phase comparison means for comparing the phases of the divided signal output from the scaling means and the beat signal output from the mixing means and generating an error signal indicative of a phase difference therebetween, said error signal supplying the input signal to the frequency generating means to thereby vary the frequency of the output signal from the frequency generating means to lock this frequency in a fixed relation with the reference frequency; restart means for generating a restart signal which momentarily shuts down and restarts the frequency generating means; and inhibit and phase shift means for responding to the restart signal by inhibiting the phase comparison means from causing perturbations in the input signal to the frequency generating means and altering the phase of the scaling means output to match a change in phase if any of the beat signal arising from the restart of the frequency generating means, and for reactivating the phase comparison means upon the occurrence of a predetermined phase in the beat signal output.
Claim 2
Dependent Claim
253 words
A phase-locked oscillator comprising: frequency generating means for producing an output signal of a frequency responsive to the level of an input signal; scaling means for producing a divided signal output having a pulse spacing equal to the total spacing of N pulses of a signal appearing at the input of the scaling means, where N is a predetermined integer; mixing means responsive to the output signal of the frequency generating means and to a reference frequency for producing a beat signal output; phase comparison means for comparing the phases of the divided signal output from the scaling means and the beat signal output from the mixing means and generating an error signal indicative of a phase difference therebetween, said error signal supplying the input signal to the frequency generating means to thereby vary the frequency of the output signal from the frequency generating means to lock this frequency in a fixed relation with the reference frequency; restart means for generating a restart signal which momentarily shuts down and restarts the frequency generating means; and inhibit and phase shift means for responding to the restart signal by inhibiting the phase comparison means from causing perturbations in the input signal to the frequency generating means and altering the phase of the scaling means output to match a change in phase if any of the beat signal arising from the restart of the frequency generating means, and for reactivating the phase comparison means upon the occurrence of a predetermined phase in the beat signal output.
Claim 3
Dependent Claim
94 words
A phase-locked oscillator as in claim 1 wherein the inhibit and phase shift means is adapted for inhibiting the divided signal and the beat signal outputs from presentation at the input of the phase comparison means in response to the restart signal and altering the phase of the scaling means output to match a change in phase if any of the beat signal arising from the restart of the frequency generating means, and for reactivating the inputs to the phase comparison means upon the occurrence of a predetermined phase in the beat signal output.
Claim 4
Dependent Claim
55 words
A phase-locked oscillator as in claim 2 wherein the inhibit and phase shift means is operable for altering the phase of the scaling means output by resetting and holding the scaling means in response to the restart signal and releasing the scaling means upon the occurrence of a predetermined phase in the beat signal output.
Claim 5
Dependent Claim
54 words
A phase-locked oscillator as in claim 3 wherein: said inhibit and reset means releases the scaling means and at the same time reenables the inputs to the phase comparison means in response to the first natural transition in the beat signal output of the mixing means after the frequency generating means has been restarted.
Claim 6
Dependent Claim
158 words
A startable phase-locked oscillator as in claim 2 wherein said inhibit and reset means comprises: first gating means at the input of the phase comparison means for gatIng the divided signal output from the scaling means; second gating means at the input of the phase comparison means for gating the beat signal output from the mixing means; coincidence means for monitoring the beat signal output of the mixing means and generating a coincidence signal response to the occurrence of the first natural transition in the beat signal output after the frequency generating means has been restarted; third gating means for generating an inhibit signal in response to the signal which momentarily shuts down the frequency generating means to inhibit the first and second gating means and reset the scaling means, and generating an enable signal in response to the coincidence signal from the coincidence means to enable the first and second gating means and restart the scaling means.
Claim 7
Dependent Claim
41 words
A phase-locked oscillator as in claim 1 wherein the scaling means is responsive to the output signal of the frequency generating means for producing a divided signal output whose frequency is a subharmonic of the frequency of the frequency generating means.
References Cited (Backward Citations)
US3619804A
Cited
US3638135A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-11-17 | 1979-05-19 | 1979-11-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-17 | 1983-05-19 | 1983-11-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-17 | 1987-05-19 | 1987-11-18 | $7700.00 | Window Closed / Lapsed |