CN105322962B - Frequency oscillator stability optimizes device and method - Google Patents
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Abstract
The present invention discloses a kind of frequency oscillator stability optimization device based on self-reference, which includes: frequency oscillator, for generating frequency signal；Phase storage unit for the phase at the frequency signal current time that storing frequencies oscillator generates, and postpones a regular time unit；Phase locking unit, the phase of the frequency signal for generating frequency oscillator, phase at the time of being locked in front of the delay time unit that phase storage unit is stored.
Description
Technical field
The present invention relates to frequency oscillator fields, and in particular to a kind of frequency oscillator stability optimization based on self-reference
Device and method.
Background technique
The development of artificial clock timing is from corona to atomic clock, after thousands of years.The timing of early stage is mainly used for astronomical phenomena
Prediction etc.；18th century mid-term, timing starts to be applied to measurement to longitude in navigation；By unremitting effort, people by
Gradually, it is realized that the main purpose of exact timing is to maintain time synchronization, and the stability of timing then becomes the decision of positioning accuracy
Factor.
Modern atomic clock timing starts from the 1950s.The birth of First cesium beam atomic frequency standard in the world,
The foundation that new " second " defines in the world in 1967 is resulted in, i.e., use is changed by " the astronomical second " that defines according to celestial bodies motion
Atomic clock reproduction " atomic second ", and started the mankind's time measure and keep time new era.
Caesium beam frequency standard is put into after practical application, either the physical characteristics such as the principle of equipment, structure or frequency
The technical indicators such as accuracy, stability are all constantly being improved.In the 1980s, people according to laser it is cooling and from
Son imprison theory develops Cesium atomic fountain clock, and stability is up to 2.8 × 10-15τ-1/2, the precision of time measurement is greatly improved,
As main timing and punctual tool.Currently, the research of light clock also has breakthrough, but still need to effort lasting for a long time.
Typical passive-type frequency standard, using the wave frequency of atom particular level transition radiation as local oscillations
The reference frequency of device carries out frequency or PGC demodulation, to obtain standard-frequency signal.Its frequency traeea-bility is inclined by Allan
Difference characterization, is represented by
Here, v0For the nominal frequency of frequency signal；<Δv2(τ) > is that the Infinite Time of the first-order difference of frequency is average；
SNR is signal-to-noise ratio；TcFor the frequency discrimination period；Q is quality factor；τ is the time of integration.The frequency standard improves the master of its stability
Wanting method is to improve Signal to Noise Ratio (SNR) or improve freely to develop time TR=Tc/2.Wherein, Signal to Noise Ratio (SNR) is proportional toN is original
Subnumber.But in practical applications, the frequency fluctuation of local oscillator is much higher than the phase noise introduced by atom decoherence,
An important factor for as frequency stability is influenced.
For active frequency standard, frequency traeea-bility is represented by
Here, kBFor Boltzmann constant；T is environment temperature；P is the actual power of frequency oscillator；When τ is integral
Between.The frequency stability depends mainly on phase fluctuation caused by thermal noise, and is proportional to
The current used frequency standard it can be seen from analyzing above, frequency stability is in the short-term time of integration
It is interior, show asFeature, i.e., continue at any time, random noise, temperature etc. will cause frequency drift,
Its stability is gradually reduced.
Summary of the invention
It is an object of the invention to propose a kind of frequency oscillator stability optimization device and method based on self-reference,
The phase of previous moment using the lasting PGC demodulation by frequency oscillator current time in fixed time apart, to change
It has been apt to frequency oscillator to continue at any time, the case where the frequency drift as caused by random noise, temperature, aging etc., frequency has been made to shake
The stability for swinging device is significantly improved.
In order to achieve the above object, the invention adopts the following technical scheme:
A kind of frequency oscillator stability optimization device based on self-reference, described device includes: frequency oscillator, is used for
Generate frequency signal；Phase storage unit for the phase at the frequency signal current time that storing frequencies oscillator generates, and is prolonged
A slow regular time unit；Phase locking unit, the phase of the frequency signal for generating frequency oscillator, is locked in phase
Phase at the time of before the delay time unit that storage unit is stored.
A kind of frequency oscillator stability optimization method based on self-reference, which comprises stored using phase single
The phase at the frequency signal current time that first storing frequencies oscillator generates, and postpone a regular time unit, while benefit
With the phase for the frequency signal that phase locking unit constantly generates frequency oscillator current time, it is locked in phase storage unit institute
The phase of the previous moment of the one delay time unit in interval of storage.
Detailed description of the invention
Fig. 1 shows the knot of the exemplary embodiments of the frequency oscillator stability optimization device of the invention based on self-reference
Structure schematic diagram.
Specific embodiment
In order to make the objectives, technical solutions and advantages of the present invention clearer, With reference to embodiment and join
According to attached drawing, the present invention is described in more detail.
Fig. 1 shows the frequency oscillator stability optimization device proposed by the present invention based on self-reference, described device packet
It includes: frequency oscillator 1, for generating frequency signal；Phase storage unit 2, the frequency letter generated for storing frequencies oscillator 1
The phase at number current time, and postpone a regular time unit；Phase locking unit 3, the frequency for generating frequency oscillator 1
The phase of rate signal is locked in the phase of the previous moment for the one delay time unit in interval that phase storage unit 2 is stored.
The phase of the frequency signal generated by frequency oscillator 1 is expressed as
Wherein, ω0For the nominal angular frequency of the frequency signal；It changes with time for the phase of the frequency signal
?.
According to the definition of Allan deviation, the stability of the frequency signal is represented by by Allan deviation
Wherein, τ is the time of integration of Allan deviation；v0=ω0/ 2 π are the nominal frequency of the frequency signal；<Δv2(τ)〉
Infinite Time for the first-order difference of frequency data is average, is defined as
Infinite Time for the first-order difference of phase change item is average, is defined as
It should be noted that under normal conditions, it can be assumed thatFor stationary random function, and ergodicity, it is unlimited
Time averagely can averagely be obtained by the time of single sample function.
By the phase value for the frequency signal that 2 storing frequencies oscillator 1 of phase storage unit is generated in t momentAnd prolong
Slow regular time unit T0Afterwards, by phase locking unit 3 by frequency oscillator 1 in t+T0The phase for the frequency signal that moment generates
PositionIt is locked in the phase for the t moment that phase storage unit 2 is storedObtain
I.e.
Here, C is the constant number of a certain determination；The process that phase locking unit 2 carries out locking phase to frequency oscillator 1 is steady mistake
Journey, δ θ (t) are random error caused by t moment phase locking process.It should be noted that under normal conditions, phase locking process generates
Random error δ θ be much smaller than variation of the frequency oscillator phase perturbation item in delay time unitI.e.
And delay time unit T0Much larger than the time needed for carrying out a phase locking process to frequency oscillator.
It should be noted that in the present invention, as long as realizing PGC demodulation of the phase at current time relative to storage,
It is essentially equal its phase is not strict with.Therefore, in order to express easily, fixed phase difference item C is omitted in the present invention, this
Sample above formula can be reduced to
Enable T0=2k π/ω0, the above formula can be simplified further as
Here, k is any constant positive integer.It should be noted that phase storage unit 2 of the present invention can produce
The delay time unit T of raw any fixation0, not in the column of discussion of the invention.
The time of integration of arbitrary Allan deviation is represented by
τ=NT0+τ′
Here, N is positive integer, 0≤τ ' < T0.When phase locking unit 3 locks, can calculate
It should be noted thatChange with the variation of τ ',For its maximum in τ ' value range
Value.For example, working asVariation be a diffusion process, i.e.,Wherein D is diffusion coefficient, thenThe Allan deviation of the frequency signal is represented by as a result,
It enables
It can obtain
As can be seen from the above equation:
As τ < < τ0When, due toThe hunting of frequency
Device 1 generate frequency signal stability byIt plays a leading role, and changes with time as σy(τ)∝1/τ；
As τ=τ0When,
As τ > > τ0When,The frequency letter that the frequency oscillator 1 generates
Number stability by δ θ2/ω0 2T0τ plays a leading role, and change with time for
The present invention also provides a kind of frequency oscillator stability optimization method based on self-reference, this method is by above
The frequency oscillator stability optimization device based on self-reference introduced is implemented.
Frequency oscillator stability optimization method based on self-reference of the invention is comprising steps of utilize phase storage unit
The phase at the frequency signal current time that 2 storing frequencies oscillators 1 generate, and postpone a regular time unit, while benefit
With the phase for the frequency signal that phase locking unit 3 constantly generates 1 current time of frequency oscillator, it is locked in phase storage unit
The phase of the previous moment of the 2 one delay time unit in interval stored.
In conclusion the present invention is directed to protect a kind of device that the frequency oscillator stability based on self-reference optimizes and side
Method is avoided the PGC demodulation at frequency oscillator current time in the phase of the previous moment of fixed time apart by continuing
With the continuity of time, the case where due to caused by random noise, temperature, aging etc. frequency drift.Compared with prior art,
The present invention has the following advantages and effects:
(1) when described device locks, in time of integration τ0The stability of place's frequency oscillator exists Under normal conditions, the short-term stability feature of the frequency oscillator of free-running is shown as If it is in τ0The stability at place can reachIt can be calculated in T0The stability at place needs
ForRandom error δ θ caused by phase locking process is considered, if only comprising to phase measurement
Uncertainty can minimize to thermal noise, be expressed as
Here, kBFor Boltzmann constant；T is environment temperature；P is the actual power of frequency oscillator.Take accepted value ω0
=2 π × 10GHz, T0=1ms, P=7dBm (5mW), calculate
At τ=1s, stability isThis index is in current technology water
It is flat to be extremely difficult to.Heretofore described device and method, since the time of integration is in τ0Before, stability change with time for
σy1/ τ of (τ) ∝, so that the frequency oscillator poor using short-term stability, can be realized in τ0The stability at place reachesIn other words, when described device locks, the short-term stability of frequency oscillator, which has, to be obviously improved.
(2) when described device locks, the frequency stability of frequency oscillator is in τ < < τ0Place, shows as σy(τ)∝1/τ；
In τ > > τ0Place, shows asIts turning point corresponding time of integration It can lead to
Cross changeValue adjust.The frequency oscillator poorer for short-term stability,Corresponding value is bigger, turns
The corresponding time of integration τ of break0Also bigger, the frequency stability σ at corresponding turning pointy(τ0) and its time of integration later
The optimization that corresponding frequency stability obtains also can be bigger.
It should be understood that above-mentioned specific embodiment of the invention is used only for exemplary illustration or explains of the invention
Principle, but not to limit the present invention.Therefore, that is done without departing from the spirit and scope of the present invention is any
Modification, equivalent replacement, improvement etc., should all be included in the protection scope of the present invention.In addition, appended claims purport of the present invention
Covering the whole variations fallen into attached claim scope and boundary or this range and the equivalent form on boundary and is repairing
Change example.
Claims (8)
1. a kind of frequency oscillator stability optimizes device, which includes:
Frequency oscillator, for generating frequency signal；
Phase storage unit for the phase at the frequency signal current time that storing frequencies oscillator generates, and postpones one admittedly
Fixed time quantum；
Phase locking unit, the phase of the frequency signal for generating frequency oscillator are locked in what phase storage unit was stored
Phase at the time of before one delay time unit；
As τ < < τ0When, the stability for the frequency signal that the frequency oscillator generates changes with time as σy(τ)∝1/τ；
Wherein,
T0For one regular time unit of the delay, δθFor phase locking process generate random error,D is
Diffusion coefficient；τ is the time of integration of Allan deviation.
2. the apparatus according to claim 1, which is characterized in that the phase meter for the frequency signal that the frequency oscillator generates
It is shown as
Wherein, ω0For the nominal angular frequency of the frequency signal,It changes with time item for the phase of the frequency signal, root
According to the definition of Allan deviation, the stability of the frequency signal may be expressed as: by Allan deviation
Wherein, τ is the time of integration of Allan deviation, υ0=ω0/ 2 π are the nominal frequency of the frequency signal, < Δ v2(τ) > is frequency
The Infinite Time of the first-order difference of rate data is average, is defined as:
Infinite Time for the first-order difference of phase change item is average, is defined as:
It is assumed thatFor stationary random function, and ergodicity, Infinite Time is average to be averaged by the time of single sample function
It obtains.
3. the apparatus of claim 2, which is characterized in that by phase storage unit storing frequencies oscillator in t moment
The phase value of the frequency signal of generationAnd postpone a regular time unit T0Afterwards, by phase locking unit by hunting of frequency
Device is in t+T0The phase for the frequency signal that moment generatesIt is locked in the t moment that phase storage unit 2 is stored
PhaseObtain
I.e.
Wherein C is the constant number of a certain determination, and the process that phase locking unit carries out locking phase to frequency oscillator is stationary process, δ θ
It (t) is random error caused by t moment phase locking process.
4. device according to claim 3, which is characterized in that
It willSimplify are as follows: Enable T0=2k π/ω0, the above formula can be simplified further as: K is any constant positive integer, and the time of integration of arbitrary Allan deviation indicates are as follows:
τ=NT0+τ′
N is positive integer, 0≤τ ' < T0, when phase locking unit locking, can calculate:
Change with the variation of τ ',For its maximum value in τ ' value range, the frequency as a result,
The Allan deviation of signal is represented by
It enables
It can obtain
As τ < < τ0When, due to The frequency oscillator generates
Frequency signal stability byIt plays a leading role, and changes with time as σy(τ)∝1/τ；
As τ=τ0When,
As τ > > τ0When,The frequency signal that the frequency oscillator generates it is steady
Fixed degree is by δ θ2/ω0 2T0τ plays a leading role, and change with time for
5. a kind of frequency oscillator stability optimization method based on self-reference, this method comprises: being deposited using phase storage unit
The phase at the frequency signal current time that frequency oscillator generates is stored up, and postpones a regular time unit, while utilizing lock
The phase for the frequency signal that phase element constantly generates frequency oscillator current time is locked in phase storage unit and is stored
The one delay time unit in interval previous moment phase；
As τ < < τ0When, the stability for the frequency signal that the frequency oscillator generates changes with time as σy(τ)∝1/τ；
Wherein,
T0For one regular time unit of the delay, δ θ is the random error that phase locking process generates,D is
Diffusion coefficient；τ is the time of integration of Allan deviation.
6. according to the method described in claim 5, it is characterized in that, the phase meter for the frequency signal that the frequency oscillator generates
It is shown as
Wherein, ω0For the nominal angular frequency of the frequency signal,It changes with time item for the phase of the frequency signal, root
According to the definition of Allan deviation, the stability of the frequency signal may be expressed as: by Allan deviation
Wherein, τ is the time of integration of Allan deviation, υ0=ω0/ 2 π are the nominal frequency of the frequency signal, < Δ v2(τ) > for frequently
The Infinite Time of the first-order difference of rate data is average, is defined as:
Infinite Time for the first-order difference of phase change item is average, is defined as:
It is assumed thatFor stationary random function, and ergodicity, Infinite Time is average to be averaged by the time of single sample function
It obtains.
7. according to the method described in claim 6, it is characterized in that, by phase storage unit storing frequencies oscillator in t moment
The phase value of the frequency signal of generationAnd postpone a regular time unit T0Afterwards, by phase locking unit by hunting of frequency
Device is in t+T0The phase for the frequency signal that moment generatesIt is locked in the t moment that phase storage unit 2 is stored
PhaseObtain
I.e.
Wherein C is the constant number of a certain determination, and the process that phase locking unit carries out locking phase to frequency oscillator is stationary process, δ θ
It (t) is random error caused by t moment phase locking process.
8. the method according to the description of claim 7 is characterized in that
It willSimplify are as follows: Enable T0=2k π/ω0, the above formula can be simplified further as: K is any constant positive integer, and the time of integration of arbitrary Allan deviation indicates are as follows:
τ=NT0+τ′
N is positive integer, 0≤τ ' < T0, when phase locking unit locking, can calculate:
Change with the variation of τ ',For its maximum value in τ ' value range, the frequency as a result,
The Allan deviation of signal is represented by
It enables
It can obtain
As τ < < τ0When, due toThe frequency oscillator produces
The stability of raw frequency signal byIt plays a leading role, and changes with time as σy(τ)∝1/τ；
As τ=τ0When,
As τ > > τ0When,The frequency signal that the frequency oscillator generates it is steady
Fixed degree is by δ θ2/ω0 2T0τ plays a leading role, and change with time for
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4873491A (en) * | 1987-10-19 | 1989-10-10 | Wilkins Jeffrey K | Phase shift circuit utilizing a variable time delay line |
| US6326812B1 (en) * | 1997-05-23 | 2001-12-04 | Altera Corporation | Programmable logic device with logic signal delay compensated clock network |
| CN1768479A (en) * | 2003-04-03 | 2006-05-03 | 艾利森电话股份有限公司 | Method and system of jitter compensation |
| US7659783B2 (en) * | 2007-07-16 | 2010-02-09 | Micrel, Inc. | System and method for phase-locked loop (PLL) for high-speed memory interface (HSMI) |
| CN102098045A (en) * | 2009-12-10 | 2011-06-15 | Nxp股份有限公司 | Electronic circuit frequency generation |
| US7969252B2 (en) * | 2007-12-17 | 2011-06-28 | Micron Technology, Inc. | System and method for reducing lock time in a phase-locked loop |
| EP2110951A3 (en) * | 2008-04-11 | 2012-03-07 | Fujitsu Ltd. | Phase controlling apparatus, phase-control printed board, and controlling method |
| CN103633999A (en) * | 2012-08-20 | 2014-03-12 | 南亚科技股份有限公司 | Phase-locked loop and method for clock delay adjustment |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19840241C1 (en) * | 1998-09-03 | 2000-03-23 | Siemens Ag | Digital PLL (Phase Locked Loop) frequency synthesizer |
| US6778027B2 (en) * | 2002-04-12 | 2004-08-17 | Sun Microsystems, Inc. | Phase locked loop input receiver design with delay matching feature |
| KR100594297B1 (en) * | 2004-10-12 | 2006-06-30 | 삼성전자주식회사 | Delay locked loop using an oscillator obeying an external clock signal frequency and method thereof |
| US7355464B2 (en) * | 2005-05-09 | 2008-04-08 | Micron Technology, Inc. | Apparatus and method for controlling a delay- or phase-locked loop as a function of loop frequency |
| JP4271244B2 (en) * | 2007-03-26 | 2009-06-03 | 株式会社半導体理工学研究センター | Analog-digital (AD) converter and analog-digital conversion method |
-
2014
- 2014-07-03 CN CN201410314762.9A patent/CN105322962B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4873491A (en) * | 1987-10-19 | 1989-10-10 | Wilkins Jeffrey K | Phase shift circuit utilizing a variable time delay line |
| US6326812B1 (en) * | 1997-05-23 | 2001-12-04 | Altera Corporation | Programmable logic device with logic signal delay compensated clock network |
| CN1768479A (en) * | 2003-04-03 | 2006-05-03 | 艾利森电话股份有限公司 | Method and system of jitter compensation |
| US7659783B2 (en) * | 2007-07-16 | 2010-02-09 | Micrel, Inc. | System and method for phase-locked loop (PLL) for high-speed memory interface (HSMI) |
| US7969252B2 (en) * | 2007-12-17 | 2011-06-28 | Micron Technology, Inc. | System and method for reducing lock time in a phase-locked loop |
| EP2110951A3 (en) * | 2008-04-11 | 2012-03-07 | Fujitsu Ltd. | Phase controlling apparatus, phase-control printed board, and controlling method |
| CN102098045A (en) * | 2009-12-10 | 2011-06-15 | Nxp股份有限公司 | Electronic circuit frequency generation |
| CN103633999A (en) * | 2012-08-20 | 2014-03-12 | 南亚科技股份有限公司 | Phase-locked loop and method for clock delay adjustment |
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