CN103472299A - High-resolution transient frequency stability measuring method - Google Patents
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Abstract
The invention provides a high-resolution transient frequency stability measuring method. The method comprises: first of all, the phase difference value between a reference signal and a detected signal is measured and adjusted so as to enable the value to be stabilized at the edge of a superposed detection resolution, if there are no effects of noise, the continuous detection of superposed information can be maintained, however, if there is signal noise, the phase difference change between the signals is between the inside of an edge and the outside of the edge, and the presence of phase superposed information remains variable, therefore, the phase instability degrees of the signals can be determined according to the continuity and interruption situations of the superposed information, and by detecting the change amount of the phase difference between the signals before and after a sampling time, the transient stabilization degree of a frequency source can be calculated through a formula derived from the Allan variance calculation formula.
Description
Technical field
The invention belongs to the frequency stability measurement field, relate to the measurement of the high-resolution transient state stability of frequency source, refer more particularly to the measurement that detects the high-resolution transient state stability of battle array based on phase coincidence.
Background technology
Frequency stability measurement refers to the measurement to the random fluctuation characteristic of frequency source output frequency value.Frequency stability has time domain and two kinds of characteristic manner of frequency domain.Much use the method for count measurement in the time domain frequency stability measurement, its measurement gate width usually formed is generally from 1ms to 10s.Shorter gate will make Measurement Resolution obviously reduce, as for 10MHz by measured frequency, can only count 10 numbers within the gate time of 1 μ s, be difficult to speak of the problem of precision.Yet short as far as possible measurement gate, such as until the corresponding measurement data of the gate in measured signal cycle for thering is important effect by the situations such as far-end phase noise of the method for time domain reflection frequency source intuitively.
The phase coincidence detection technique be we for many years always the development frequency and the gordian technique of phase difference measurement, especially the measurement for cyclical signals such as high-resolution frequencies plays a key effect.Can between the comparison signal identical or different at two nominal values, detect the identical information of phase value between them, as the moment of phase place zero passage appears in two signals simultaneously, just provide a specific phase coincidence information.Can become burst pulse to two signals in its " 0 " phase place place shaping, and by with method obtain phase coincidence therebetween.Realize always being difficult to occur the coincidence of " definitely " in the technology of phase coincidence.The threshold values of phase coincidence detection sensitivity has so just been arranged, and when namely signal phase difference is less than this numerical value, circuit can be exported the burst pulse that represents phase coincidence.
Any coincidence detection line all exists the resolution of detection and the stability of this resolution.Because the resolution of the detection that we often can obtain is to be greater than 1ns, and the stability of this resolution namely the stability of threshold values usually can be better than 10ps.So the phase differential between signal just has coincidence information close to ns the time and is detected.Often, at the edge of ns difference, the shake of number ps, fluctuating will cause the difference that (" 1 ") and nothing (" 0 ") are arranged detected overlapping.So, and the resolution that not bery meticulous phase coincidence detects not necessarily makes things worse, obscuring of two kinds of contrary " 0 " states avoided in its existence.The He Jin edge, this edge exactly that we will utilize is due to impact and the effect of noise, realizes the index situation by the transient state stability of the quantitative expression of different values.
Summary of the invention
Owing to using short gate will make Measurement Resolution obviously reduce in normally used method, thereby can't obtain high-resolution transient state stability.A kind of method that the purpose of this invention is to provide high resolving power instantaneous frequency stable measurement, adopt the phase coincidence detection technique of innovation to carry out the transient state stability in survey frequency source, thereby the resolution of transient state stability be significantly improved.
The technical solution adopted in the present invention is: a kind of method of high resolving power instantaneous frequency stable measurement, it is characterized in that: at first will measure and adjust the phase difference value between reference signal and measured signal, make this value can be stabilized in the edge that overlaps detection resolution, because the phase coincidence detection line has fixing coincidence detection resolution and the degree of stability of this resolution, so when the phase differential between two signals is adjusted to the edge that overlaps detection resolution, if do not have noisy impact, can keep continuous the detecting of coincidence information.But when having the noise of signal, can make phase differential between signal change the interior of this edge and outside between, just make phase coincidence information cut in and out.So we can be according to the continuity of the information of coincidence and the phase instability that the interruption situation judges signal exactly.The fastest response time can reach the periodic quantity (when nominal frequency is identical) of signal nominal frequency, or the cycle of the low frequency signal between signal (when nominal frequency is different).By the variable quantity of phase differential between the signal that detects front and back sample time, the formula that just can go out with the Allan variance formula proving calculates the instantaneous frequency degree of stability of frequency source.
What measuring method of the present invention adopted is to overlap to detect battle array, each phase coincidence detecting device in battle array has the degree of stability of identical coincidence detection resolution, by adding the delay phase shift to make its mutual threshold values thresholding in a road input signal, be different, the position of the strict phase coincidence point of phase deviation of the coincidence information that the most partially detects of each phase coincidence detecting device is the state that presents a kind of stepping.
What in measuring method of the present invention, adopt is passive delay device, can reach like this delay of ps magnitude, uses the wire of 1mm just can reach the delay of needed 5ps in method.
The invention has the beneficial effects as follows: utilized the cycle of signal itself to carry out coincidence detection repeatedly, thereby the variation that detects acquired information by phase coincidence is measured the instantaneous frequency degree of stability as the reflection to noise problem, and the phase noise of the detection signal that the utilization that overlaps the detection battle array can quantize rises and falls, therefore fast response time and high resolving power can be obtained.
The accompanying drawing explanation
Fig. 1 is high resolving power instantaneous frequency stable measurement functional-block diagram of the present invention.
Fig. 2 is phase coincidence detection line figure.
Fig. 3-1 is the phase coincidence detection line figure that a road input adds delay.
Fig. 3-2nd, another road input adds the phase coincidence detection line figure of delay.
Fig. 4 is that phase differential changes curve.
Fig. 5 is the phase noise of two mutual ratios of 100MHz high stability crystal oscillator.
Fig. 6 is the phase noise of two mutual ratios of 10MHz high stability crystal oscillator.
Fig. 7 is the phase noise of the poor mutual ratio of 10MHz crystal oscillator of highly stable crystal oscillator and the degree of stability of a 10MHz.
Embodiment
Below in conjunction with drawings and Examples, the present invention is further described.
Fig. 1 carries out the frame principle figure of instantaneous frequency stable measurement to two same frequency nominal value frequency sources, at first by the phase difference measurement between signal and adjustment, the adjusting offset between measured signal and reference signal is arrived to the value place, edge of the detection resolution that overlaps detection line.Calculate the instantaneous frequency degree of stability according to the interruption situation that detects coincidence information.The frequency values of two signals can equate or be the multiple relation.So just can be in the situation that a frequency nominal value frequency marking be measured a plurality of frequencies accurately.By the method for mutual frequency division, can also further widen measurement range.
The threshold values of actual phase coincidence detection line sensitivity is the ns magnitude, thus the adjusting offset between signal to the position that is slightly less than this value.From the on-off state overlap detected, the instability of coincidence detection circuit, and just can judge the instantaneous frequency Stability index by the monitoring to the phase difference measurement result etc.
Judgement about the edge value of the detection resolution of phase coincidence detection line, can adopt homology to adjust the method for phase place self-correcting.Namely adopt same frequency marking one tunnel directly to input, another road produces two of relatively-stationary phase differential input phase difference measurements equipment and compares opposite end after postponing phase shift.With this phase difference value of phase difference measurement device measuring.Detect by phase coincidence simultaneously, detect the phase coincidence state between two paths of signals.Between signal, in phase difference value variation from big to small, the phase coincidence detection line is just in stable phase coincidence state.In fact the phase difference value of now reading from phase difference measurement equipment is exactly numerical value or the edge value of the coincidence detection resolution of phase coincidence detection line.Because be the situation of homology, the situation of noise in mutual counteracting, so the coincidence after entering is stable.
Adopt commercial time interval measuring instrucment device (as SR620), and adopt the method for multiple averaging, measurement and the processing resolution close to 5ps can obtain like this.Because the threshold values of the phase coincidence detection line of the reality measured is the ns magnitude, thus the adjusting offset between signal to the position that is slightly less than this value.(in the process of measuring, the drift of signal at least is not more than 1/10 of threshold values.) and coincidence detection circuit itself has the stability indicator that is less than 10ps.Like this, when the impact of phase noise causes phase difference value between signal to be greater than the changing inversely of several ps, just likely make to overlap to detect can not produce.Therefore, from the on-off state overlap detected, the instability of coincidence detection circuit, and just can judge the instantaneous frequency Stability index by the monitoring to the phase difference measurement result etc.In fact the resolution of measuring depend on the instability of several ps of coincidence detection circuit.The key that further improves Measurement Resolution will obtain better this degree of stability exactly.
In Fig. 2, be exactly the phase coincidence detection line figure that we use, what the present invention adopted is the d type flip flop method, when phase coincidence appears in measured signal and reference signal, can trigger.The function of d type flip flop is exactly with f
0the rising edge of waveform, as clock signal, gathers now f
xstate as output signal.Because the phase differential between two signals has been adjusted to the edge that overlaps detection resolution, so, if do not have noisy impact, just can keep a kind of level state to continue output.But when having the noise of signal, can make phase differential between signal change the interior of this edge and outside between, low when high while just making the phase coincidence level.
In Fig. 3-1 and Fig. 3-2, be exactly that our phase coincidence that uses detects the phase coincidence detection line figure that a needed road input in battle array adds delay.To use a large amount of identical phase coincidence detection means to form phase coincidence and to detect the intension that gust phase differential variation information that is exactly the signal in order making to gather has more standby " amount ".Each phase coincidence detecting device in battle array has the degree of stability of identical coincidence detection resolution, as close to 1ps; But its mutual threshold values thresholding is different.Namely by a road input signal, adding the delay phase shift, making the position of the strict phase coincidence point of phase deviation of the coincidence information that the most partially detects of each phase coincidence detecting device is the state that presents a kind of stepping.According to the noise amplitude difference of measured signal, this overlaps the detection battle array height of level can selectively occur according to the size cases of noise under the effect of same larger noise.And different detection line level height are different in the implication aspect amount.On the basis of this sampling, just can detect the size of noise amplitude.
Because active delay device all can only postpone the ns magnitude, with our desired ps magnitude, differ greatly, so adopt passive delay device here, used in the present invention is wire, the transmission delay of wire is more stable.The velocity of propagation of general signal in wire is 200,000 kilometers per seconds, so ratio is calculated the short delay that the wire that can obtain 0.2mm can reach 1ps in due order, here the delay of needed 5ps, only needs to use the wire of 1mm just can reach requirement.In phase coincidence detection battle array, the length of delay of the lag line of the correspondence of every trigger used presents the multiple relation, and the selection of line length also will be considered the difference of the phase coincidence detection resolution that each device just exists originally.
Fig. 4 is the curve that the phase differential of short time of restoring changed along with the time, according to the sample interval τ intercepting curve of selecting, can access the variable quantity of corresponding phase differential, the average frequency value of τ time is obtained, and corresponding frequency stability index can be obtained.The general Unified Characterization amount of the root value of Allan variance as the time domain frequency stability that adopt.Allan variance computing formula commonly used is
Consider the relation of frequency and phase place:
just can derive (2) formula by (1) formula.
The parameter wherein occurred has comprised the information Δ T that represents the phase differential variation and has changed corresponding duration τ with this.This formula is originally the computing formula to degree of stability of the measurement result that the method for comparing by phase place between same frequency nominal value signal obtains.Its deduction and variation are just for utilizing the processing that overlaps detection zone information to obtain the important foundation of frequency stability.If consider the cycle correspondence of lower frequency person between response time and comparison signal, the cycle that coincidence detects is the period tau of low frequency signals exactly; Whether by the detection of the continuation to coincidence status, obtain Δ T changes.Δ T wherein
iit is the variable quantity of phase differential between the signal before and after the τ time.
About the problem in sampling time, can detect the stable measurement of realizing near this cycle length according to the continuous coincidence that the cycle according to signal is interval.As the measurement that can respond near the degree of stability of 100ns the 10MHz signal.To the stable measurement of 1 μ s, 10 μ s, 100 μ s signals, it is the variation that will consider the interior phase differential of time in 10,100 and 1000 cycles.Namely should detect in a plurality of all period interval of correspondence the total variation of phase differential between the signal before and after sample time.So need to be converted into the interrupted information of the coincidence of the wide region of phase coincidence the variation of the phase differential between signal.
About the experiment of this method, the accepted standard signal is ultra-high stable degree crystal oscillator, and different measured signals is respectively crystal oscillator and the obvious poor constant-temperature crystal oscillator of index of high stability.Low make an uproar mutually, the oscillator of high stability has the continuity of obvious coincidence status, make an uproar mutually and the poor oscillator of Stability index there is the scope of the discontinuity of obvious coincidence status and interruption can be larger.It is below the result to the actual measurement of a plurality of oscillators.Measurement with comparison corresponding transient state stability of signal period for each simultaneously, adopt (import) PN8010 phase noise measurement system again than the phase noise between right signal in addition.The transient state stability of measuring is the result of calculation of the Allan variance of corresponding sample time 100ns, and measured phase noise is from departing from carrier frequency 1Hz until 1MHz.From corresponding measurement result, the phase noise measurement result of relatively near carrier frequency and the transient state stability measurement result correspondence corresponding with far-end phase noise situation more are quite clear and definite.
The transient state stability of testing between the high stability crystal oscillator SOXO13FF100MDSGU of 1: two 100MHz is measured, and measures respectively 10 groups of data, and the frequency stability result of calculation that obtains the Allan variance of 10ns is respectively: 1.25813 * 10
-4, 1.17495 * 10
-4, 1.15322 * 10
-4, 1.15322 * 10
-4, 1.15322 * 10
-4, 1.15322 * 10
-4, 1.15322 * 10
-4, 1.15322E * 10
-4, 1.15322 * 10
-4, 1.15322 * 10
-4.Phase noise measurement result between two signals as shown in Figure 5.
The transient state stability of testing between 2: two 10MHz high stability crystal oscillators is measured.Measure respectively 10 groups of data, the frequency stability result of calculation of the Allan variance of the 100ns obtained is respectively: 7.22587 * 10
-4, 7.19175 * 10
-4, 7.19175 * 10
-4, 7.15718 * 10
-4, 7.01721 * 10
-4, 6.91772 * 10
-4, 6.81641 * 10
-4, 6.66839 * 10
-4, 6.56296 * 10
-4, 6.45541 * 10
-4.Phase noise measurement result between two signals as shown in Figure 6.
The transient state stability of testing between the poor 10MHz crystal oscillator of the highly stable crystal oscillator of 3: one 10MHz and degree of stability is measured.Measure respectively 10 groups of data, the frequency stability result of calculation of the Allan variance of the 100ns obtained is respectively: 3.96571 * 10
-3, 3.96571 * 10
-3, 3.96571 * 10
-3, 3.96571 * 10
-3, 3.96571 * 10
-3, 3.96571 * 10
-3, 3.96571 * 10
-3, 3.96571 * 10
-3, 3.96571 * 10
-3, 3.43645 * 10
-3.Phase noise measurement result between two signals as shown in Figure 7.
By experiment can find out when between signal when stablizing specific phase state, thereby the variation that can detect acquired information by phase coincidence is as the measurement of the reflection to noise problem transient state stability.The present invention, because the cycle of having utilized signal itself is carried out coincidence detection repeatedly, can quantize to explain and overlap the utilization that detects battle array the phase noise fluctuating that is detected signal, and therefore fast response time and high resolving power can be obtained.This method has further value of exploiting and utilizing in the precision measurement of the phase noise time domain of frequency source and frequency domain.
It should be noted that: the foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, although with reference to previous embodiment, the present invention is had been described in detail, for a person skilled in the art, its technical scheme that still can put down in writing previous embodiment is modified, or part technical characterictic is wherein replaced on an equal basis.
Within the spirit and principles in the present invention all, any modification of making, be equal to replacement, improvement etc., within all should being included in protection scope of the present invention.
Claims (3)
1. the method for a high resolving power instantaneous frequency stable measurement, it is characterized in that: the phase difference value between reference signal and measured signal will be measured and adjust to this measuring method at first, make this value can be stabilized in the edge that overlaps detection resolution, according to the continuity of the information of coincidence and the phase instability that the interruption situation judges signal exactly, by the variable quantity of phase differential between the signal that detects front and back sample time, the formula gone out with the Allan variance formula proving calculates the transient state stability of frequency source.
2. the method for high-resolution instantaneous frequency stable measurement according to claim 1, it is characterized in that: what this measuring method adopted is to overlap to detect battle array, each phase coincidence detecting device in battle array has the degree of stability of identical coincidence detection resolution, by adding the delay phase shift to make its mutual threshold values thresholding in a road input signal, be different, the position of the strict phase coincidence point of phase deviation of the coincidence information that the most partially detects of each phase coincidence detecting device is the state that presents a kind of stepping.
3. the method for high-resolution instantaneous frequency stable measurement according to claim 1, it is characterized in that: what in this measuring method, adopt is passive delay device, can reach the delay of ps magnitude like this, use the wire of 1mm just can reach the delay of needed 5ps in method.
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Cited By (7)
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| CN106841777A (en) * | 2016-12-19 | 2017-06-13 | 江汉大学 | A kind of measurement apparatus of high accuracy frequency domain stability |
| CN107247181A (en) * | 2017-04-24 | 2017-10-13 | 西安电子科技大学 | A kind of digitization frequencies stable measurement method of total reponse time |
| CN108710026A (en) * | 2018-06-14 | 2018-10-26 | 东南大学 | Frequency stability measurement method based on high-precision phase frequency analysis and system |
| CN108732422A (en) * | 2017-04-14 | 2018-11-02 | 奇景光电股份有限公司 | Abnormal frequency detection method and its circuit |
| CN110007150A (en) * | 2019-03-28 | 2019-07-12 | 河北远东通信***工程有限公司 | A kind of linear ratio phase method of Direct Digital Phase Processing |
| CN110007149A (en) * | 2019-03-28 | 2019-07-12 | 河北远东通信***工程有限公司 | A kind of linear ratio phase method of digitlization phase shift auxiliary |
| CN111999559A (en) * | 2020-08-28 | 2020-11-27 | 西安电子科技大学 | Digital linear phase comparison method based on double ADCs |
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Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN106841777A (en) * | 2016-12-19 | 2017-06-13 | 江汉大学 | A kind of measurement apparatus of high accuracy frequency domain stability |
| CN108732422A (en) * | 2017-04-14 | 2018-11-02 | 奇景光电股份有限公司 | Abnormal frequency detection method and its circuit |
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| CN107247181A (en) * | 2017-04-24 | 2017-10-13 | 西安电子科技大学 | A kind of digitization frequencies stable measurement method of total reponse time |
| CN107247181B (en) * | 2017-04-24 | 2019-09-03 | 西安电子科技大学 | A kind of digitization frequencies stable measurement method of total reponse time |
| CN108710026A (en) * | 2018-06-14 | 2018-10-26 | 东南大学 | Frequency stability measurement method based on high-precision phase frequency analysis and system |
| CN108710026B (en) * | 2018-06-14 | 2020-05-05 | 东南大学 | Frequency stability measuring method and system based on high-precision phase frequency analysis |
| CN110007150A (en) * | 2019-03-28 | 2019-07-12 | 河北远东通信***工程有限公司 | A kind of linear ratio phase method of Direct Digital Phase Processing |
| CN110007149A (en) * | 2019-03-28 | 2019-07-12 | 河北远东通信***工程有限公司 | A kind of linear ratio phase method of digitlization phase shift auxiliary |
| CN111999559A (en) * | 2020-08-28 | 2020-11-27 | 西安电子科技大学 | Digital linear phase comparison method based on double ADCs |
| CN111999559B (en) * | 2020-08-28 | 2021-08-31 | 西安电子科技大学 | Digital linear phase comparison method based on double ADCs |
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