Phase detection reset in phase locked loops used for direct VCO modulation
First Claim
1. A phase-lock loop (PLL) in which the loop is selectively opened and then re-closed to re-achieve phase-lock with a reference signal within a selectively predetermined phase-settling time interval, comprising:
- frequency-tunable oscillator means for selectively receiving a PLL tuning signal and in accordance therewith providing a closed-loop oscillator signal, and for providing an open-loop oscillator signal which includes a plurality of open-loop carrier frequencies when said PLL tuning signal is not being received, wherein initially upon said receiving of said PLL tuning signal said closed-loop oscillator signal includes a plurality of phase-unlocked closed-loop carrier frequencies and phases, and after said phase-settling time interval includes a phase-locked closed-loop carrier frequency and phase;
signal comparator means, coupled to said frequency-tunable oscillator means, for receiving said closed-loop oscillator signal and a reference oscillator signal which includes a reference carrier frequency and phase, and for comparing said closed-loop oscillator signal with said reference oscillator signal and in accordance therewith providing to said frequency-tunable oscillator means a closed-loop tuning signal as said PLL tuning signal, and further for receiving a comparator initialization signal in accordance with which said phase-settling time interval can be selectively predetermined, wherein said signal comparator means comprises signal disabler means for receiving a loop command signal and in accordance therewith enabling and disabling said providing of said PLL tuning signal to said frequency-tunable oscillator means, and wherein said signal disabler means comprises carrier holder means for receiving said loop command signal and in accordance therewith providing during a hold time interval a tuning hold signal substantially equal to said PLL tuning signal as provided immediately prior to said receiving of said loop command signal, wherein said phase-locked closed-loop carrier phase of said closed-loop oscillator signal is phase-locked to said reference oscillator signal, and wherein during said hold time interval each one of said plurality of open-loop carrier frequencies is approximately equal to said phase-locked closed-loop carrier frequency.
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Accused Products
Abstract
A phase-lock loop (PLL) includes a switch for opening the loop (e.g. for direct modulation of its voltage-controlled oscillator (VCO) during transmission of an intermittent signal such as data bursts) and has a phase comparator which can be selectively initialized (e.g. by setting to a programmed value or resetting to zero or terminal count value the reference and/or feedback signal frequency dividers) so that upon "re-closing" of the loop the PLL will achieve phase-lock within a predetermined amount of time. When the loop is opened, the VCO'"'"'s dc ("phase-lock") control voltage can be maintained so as to help ensure that phase-lock will be achieved within the desired amount of time.
31 Citations
24 Claims
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1. A phase-lock loop (PLL) in which the loop is selectively opened and then re-closed to re-achieve phase-lock with a reference signal within a selectively predetermined phase-settling time interval, comprising:
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frequency-tunable oscillator means for selectively receiving a PLL tuning signal and in accordance therewith providing a closed-loop oscillator signal, and for providing an open-loop oscillator signal which includes a plurality of open-loop carrier frequencies when said PLL tuning signal is not being received, wherein initially upon said receiving of said PLL tuning signal said closed-loop oscillator signal includes a plurality of phase-unlocked closed-loop carrier frequencies and phases, and after said phase-settling time interval includes a phase-locked closed-loop carrier frequency and phase; signal comparator means, coupled to said frequency-tunable oscillator means, for receiving said closed-loop oscillator signal and a reference oscillator signal which includes a reference carrier frequency and phase, and for comparing said closed-loop oscillator signal with said reference oscillator signal and in accordance therewith providing to said frequency-tunable oscillator means a closed-loop tuning signal as said PLL tuning signal, and further for receiving a comparator initialization signal in accordance with which said phase-settling time interval can be selectively predetermined, wherein said signal comparator means comprises signal disabler means for receiving a loop command signal and in accordance therewith enabling and disabling said providing of said PLL tuning signal to said frequency-tunable oscillator means, and wherein said signal disabler means comprises carrier holder means for receiving said loop command signal and in accordance therewith providing during a hold time interval a tuning hold signal substantially equal to said PLL tuning signal as provided immediately prior to said receiving of said loop command signal, wherein said phase-locked closed-loop carrier phase of said closed-loop oscillator signal is phase-locked to said reference oscillator signal, and wherein during said hold time interval each one of said plurality of open-loop carrier frequencies is approximately equal to said phase-locked closed-loop carrier frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A phase-lock loop (PLL) in which the loop is selectively opened and then re-closed to re-achieve phase-lock with a reference signal within a selectively predetermined phase-settling time interval, comprising:
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a frequency-tunable oscillator which selectively receives a PLL tuning signal and in accordance therewith provides a closed-loop oscillator signal, and which provides an open-loop oscillator signal including a plurality of open-loop carrier frequencies when said PLL tuning signal is not being received, wherein initially upon said receiving of said PLL tuning signal said closed-loop oscillator signal includes a plurality of phase-unlocked closed-loop carrier frequencies and phases, and after said phase-settling time interval includes a phase-locked closed-loop carrier frequency and phase; a signal comparator, coupled to said frequency-tunable oscillator, which receives said closed-loop oscillator signal and a reference oscillator signal including a reference carrier frequency and phase, and which compares said closed-loop oscillator signal with said reference oscillator signal and in accordance therewith provides to said frequency-tunable oscillator a closed-loop tuning signal as said PLL tuning signal, and which further receives a comparator initialization signal in accordance with which said phase-settling time interval can be selectively predetermined, wherein said signal comparator comprises a signal disabler which receives a loop command signal and in accordance therewith enables and disables said providing of said PLL tuning signal to said frequency-tunable oscillator, and wherein said signal disabler comprises a carrier holder which receives said loop command signal and in accordance therewith provides during a hold time interval a tuning hold signal substantially equal to said PLL tuning signal as provided immediately prior to said receiving of said loop command signal, wherein said phase-locked closed-loop carrier phase of said closed-loop oscillator signal is phase-locked to said reference oscillator signal, and wherein during said hold time interval each one of said plurality of open-loop carrier frequencies is approximately equal to said phase-locked closed-loop carrier frequency. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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17. A method of operating a phase-lock loop (PLL) in which the loop is selectively opened and then re-closed to re-achieve phase-lock with a reference signal within a selectively predetermined phase-settling time interval, comprising the steps of:
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selectively receiving a PLL tuning signal and in accordance therewith generating a closed-loop oscillator signal, wherein initially upon said receiving of said PLL tuning signal said closed-loop oscillator signal includes a plurality of phase-unlocked closed-loop carrier frequencies and phases, and after said phase-settling time interval includes a phase-locked closed-loop carrier frequency and phase; generating an open-loop oscillator signal which includes a plurality of open-loop carrier frequencies when said PLL tuning signal is not being received; receiving a loop command signal and in accordance therewith enabling and disabling said receiving of said PLL tuning signal by receiving said loop command signal and in accordance therewith providing during a hold time interval a tuning hold signal substantially equal to said PLL tuning signal as provided immediately prior to said receiving of said loop command signal, wherein said phase-locked closed-loop carrier phase of said closed-loop oscillator signal is phase-locked to said reference oscillator signal, and wherein during said hold time interval each one of said plurality of open-loop carrier frequencies is approximately equal to said phase-locked closed-loop carrier frequency; receiving a reference oscillator signal which includes a reference carrier frequency and phase; comparing said closed-loop oscillator signal with said reference oscillator signal and in accordance therewith generating a closed-loop tuning signal as said PLL tuning signal; and receiving an initialization signal and in accordance therewith preselecting said phase-settling time interval. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
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Specification