CN106814249A - A kind of frequency measurement method for optical pumped magnetometer frequency meter - Google Patents
A kind of frequency measurement method for optical pumped magnetometer frequency meter Download PDFInfo
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- CN106814249A CN106814249A CN201710113556.5A CN201710113556A CN106814249A CN 106814249 A CN106814249 A CN 106814249A CN 201710113556 A CN201710113556 A CN 201710113556A CN 106814249 A CN106814249 A CN 106814249A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
- G01R23/02—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage
- G01R23/10—Arrangements for measuring frequency, e.g. pulse repetition rate; Arrangements for measuring period of current or voltage by converting frequency into a train of pulses, which are then counted, i.e. converting the signal into a square wave
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/032—Measuring direction or magnitude of magnetic fields or magnetic flux using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect
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- G—PHYSICS
- G04—HOROLOGY
- G04R—RADIO-CONTROLLED TIME-PIECES
- G04R20/00—Setting the time according to the time information carried or implied by the radio signal
- G04R20/02—Setting the time according to the time information carried or implied by the radio signal the radio signal being sent by a satellite, e.g. GPS
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- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Radar, Positioning & Navigation (AREA)
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- Condensed Matter Physics & Semiconductors (AREA)
- Measuring Magnetic Variables (AREA)
Abstract
The invention provides a kind of frequency measurement method for optical pumped magnetometer frequency meter, beginning and end point of the described frequency measurement method in the tested time period, it is corrected by GPS time signals, GPS time signals have been used to be modified the reference frequency source of frequency meter, frequency source error is greatly reduced, and then draw the accurate output time after being corrected by GPS time signals, then accurate frequency values are calculated by count information again, the precision of common crystals is substantially exceeded due to the precision of GPS time signals, so the frequency meter realized using this method, its precision surmounts general frequency meter precision significantly.
Description
Technical field
The present invention relates to technical field of frequency measurement, and in particular to a kind of frequency measurement for optical pumped magnetometer frequency meter
Method.
Background technology
High accuracy magnetic field detection is played at aspects such as space exploration, ground survey, seafari, human-body biological magnetic-field measurements
Important effect, so the always hot fields of every country research.Because China starts late in magnetic field detection field,
Still there is larger gap with developed country.
Optical pumped magnetometer is to utilize Zeeman splitting, energy level transition of certain Elements Atom under external magnetic field, and magnetic
The accurate magnetic field measuring instrument that resonance principle is made, has been widely used in geophysical exploration, seismic monitoring and prediction, aviation
Magnetic survey is painted, maritime affairs are salvaged and the field such as military use.
Described optical pumped magnetometer can be generally divided into two kinds, i.e. tracking optical pumping magnetometer and auto-excitation type optical pumping magnetic force
Instrument.Its operation principle is：The atomic magnetic moment arranged by optical action, in the presence of the alternating electromagnetic field of CF, and
RESONANCE ABSORPTION effect will be produced, will upset the arranging situation of atom.There is frequency and the sample institute of the electromagnetic field of RESONANCE ABSORPTION phenomenon
In the external magnetic field strength put into a proportionate relationship, therefore determining this frequency can just measure the value of external magnetic field.
At present, the frequency meter of the measurement frequency for being used on the market, its reference frequency source is all provided by crystal oscillator, time meter
Number is also to be provided by crystal oscillator, but in a practical situation, the precision of crystal oscillator is wanted to work as limited, and by environment temperature and power supply matter
The influence of amount, the precision of crystal oscillator has decline, and error is more random, therefore the output accuracy of frequency meter can be caused not high.
The content of the invention
It is an object of the present invention to overcome optical pumped magnetometer frequency meter because using crystal oscillator as reference frequency source, cause
The larger technical problem of frequency error measurement, the present invention provides a kind of frequency measurement method for optical pumped magnetometer frequency meter,
The frequency meter realized using the method for the present invention, its precision surmounts general frequency meter precision significantly.
To achieve the above object, a kind of frequency measurement method for optical pumped magnetometer frequency meter that the present invention is provided, bag
Include：
Step 1) GPS time signals are selected as the reference signal of frequency measurement, and provide reference with the crystal oscillator of frequency meter
Frequency signal；
Step 2) add up to obtain within the whole output cycle of GPS time signals reference frequency signal and measured signal when
Clock is counted, and the clock count of reference frequency signal is corrected using GPS time signals, when further obtaining revised reality output
Between；
Step 3) by the ratio between the clock count of measured signal and reality output time, obtain the frequency values of measured signal.
As the further improvement of above-mentioned technical proposal, the step 2) specifically include：
Step 101) after the arriving of reference signal rising edge, start to monitor the rising edge T1 of measured signal, in rising edge T1
After arriving, clock count is carried out to reference frequency signal and measured signal, after reference signal trailing edge arrives, restarted
The rising edge T2 of measured signal is monitored, after rising edge T2 arrivings, when stopping is carried out to reference frequency signal and measured signal
Clock is counted, and signal where rising edge T2 is not counted in counting；
Step 102) reference frequency signal when obtaining revised reality output for high level is calculated using following formula
Clock count T：
Wherein, R is the clock count of reference frequency signal when not correcting preceding reality output for high level, and P believes for GPS benchmark
The real output value of number cycle internal reference frequency signal clock count, W is GPS reference signal cycle internal reference frequency signal clocks
The theoretical output valve of counting；
Step 103) utilize step 102) in clock count T, calculate and obtain revised reality output time and be expressed as
T*N, wherein, N represents the clock cycle of reference frequency signal.
A kind of frequency measurement method advantage for optical pumped magnetometer frequency meter of the invention is：
The frequency measurement method that the present invention is provided, beginning and end point in the tested time period, enters by GPS time signals
Row correction, draws the real time after being corrected by GPS time signals, then calculates accurate frequency values by count information again,
The precision of common crystals is substantially exceeded due to the precision of GPS time signals, so the frequency meter realized using this method, its precision
Surmount general frequency meter precision significantly.
Brief description of the drawings
Fig. 1 is the frequency measurement method flow chart provided by the present invention for optical pumped magnetometer frequency meter.
Fig. 2 is the operation diagram for carrying out clock count to each signal using frequency measurement method of the invention.
Specific embodiment
With reference to the accompanying drawings and examples to a kind of frequency measurement for optical pumped magnetometer frequency meter of the present invention
Method is described in detail.
Described optical pumped magnetometer can be generally divided into two kinds, i.e. tracking optical pumping magnetometer and auto-excitation type optical pumping magnetic force
Instrument.By taking tracking mode laser caesium optical pumped magnetometer as an example, the pumping of caesium optical pumping produces Zeemen effect with the energy level of Cs atom in magnetic field
Based on, using RF excited caesium spectrum lamp, the spectral wavelength of generation is the D1 lines of 894nm and the D2 lines of 852nm, when wavelength is
During the light prolonged exposure of 894nm, on the Cs atom in D1 light actions to caesium absorption bubble, F=4 energy levels are pumped into, are completed former
Sub- state preparation process.
Now, if there is an applying constant external magnetic field, the space quantization orientation of atomic magnetic moment will be produced on the energy level of F=4,
Zeeman level is split into 9 strip energy levels, and this little transition between energy level is then Zeeman transition, and its jump frequency is then atomic magnetic moment
Around the Larmor frequency of applying constant external magnetic field precession, when its higher order term is ignored, size and the applying constant external magnetic field of the frequency
Size is linear, i.e.,
In above formula:f0It is Larmor's jump frequency；B is tested external magnetic field strength；γ is magnetic rotaion comparison.
For Cs atom, γ/(2 π) is 3.49857Hz/nT, then be tested external magnetic field strength B and Larmor's jump frequency f0
There is following relation：
B=f0/3.49857 (2)
Therefore the measurement to magnetic field can be realized by measurement frequency.
In order to realize the high-acruracy survey of Larmor's jump frequency, optical pumped magnetometer frequency to be used for the invention provides one kind
The frequency measurement method of meter.The method use GPS time signals to be modified the reference frequency source of frequency meter, by frequency source
Error is greatly reduced.
For the method that most frequency meter is used, be all by measured signal and reference signal carry out contrast draw it is tested
The cycle time of signal, specific method is：(this time can freely set according to actual conditions to be spaced about 20 milliseconds in measured signal
It is fixed) two rising edges between time period in, counted by reference frequency signal, reference frequency by frequency meter crystalline substance
Shake offer, and measured signal periodicity is counted, draw the time that the measured signal cycle consumed, it is tested so as to calculate
The frequency of signal.
And in the frequency measurement method that the present invention is provided, beginning and end point in the tested time period, by GPS time services
The time signal that signal receiving chip is received is corrected, and draws the real time after being corrected by GPS time signals, Ran Houzai
Accurate frequency values are calculated by count information, the precision of common crystals is substantially exceeded due to the precision of GPS time signals, so
Surmount general frequency meter precision significantly using the frequency meter precision of this method.
As shown in figure 1, a kind of frequency measurement method for optical pumped magnetometer frequency meter that the present invention is provided, the method tool
Body includes：
Step 1) GPS time signals are selected as the reference signal of frequency measurement, and provide reference with the crystal oscillator of frequency meter
Frequency signal；
Step 2) add up to obtain within the whole output cycle of GPS time signals reference frequency signal and measured signal when
Clock is counted, and the clock count of reference frequency signal is corrected using GPS time signals, when further obtaining revised reality output
Between；
Step 3) by the ratio between the clock count of measured signal and reality output time, obtain the frequency values of measured signal.
Based on said frequencies measuring method, the step 2) specifically include：
Step 101) after the arriving of reference signal rising edge, start to monitor the rising edge T1 of measured signal, in rising edge T1
After arriving, clock count is carried out to reference frequency signal and measured signal, after reference signal trailing edge arrives, restarted
The rising edge T2 of measured signal is monitored, after rising edge T2 arrivings, when stopping is carried out to reference frequency signal and measured signal
Clock is counted, and signal where rising edge T2 is not counted in counting；
Step 102) reference frequency signal when obtaining revised reality output for high level is calculated using following formula
Clock count T：
Wherein, R is the clock count of reference frequency signal when not correcting preceding reality output for high level, and P believes for GPS benchmark
The real output value of number cycle internal reference frequency signal clock count, W is GPS reference signal cycle internal reference frequency signal clocks
The theoretical output valve of counting；
Step 103) utilize step 102) in clock count T, calculate and obtain revised reality output time and be expressed as
T*N, wherein, N represents the clock cycle of reference frequency signal.
Embodiment one
In the present embodiment, by taking the output frequency of laser caesium optical pumped magnetometer as an example, the method pair provided using the present invention
Larmor precession frequencies realize that high accuracy is changed.By caesium optical pumping output frequency in sending into FPGA after light-coupled isolation, to input
Signal carries out high-precision timing and counting, and the GPS clock signal received by GPS receiver chip is carried out to reference clock
Amendment, to reduce due to the clock frequency error that environmental change is caused.Specific operating instruction is as follows：
First by High Precision Crystal Oscillator high-quality frequency source is provided to FPGA.As shown in Fig. 2 reference frequency is brilliant using 20M
Shake to provide frequency source, be tested frequency signal between 30KHz -300KHz, reference signal is 20Hz signals, its signal source is
Gps signal.
After the arriving of reference signal rising edge, start to monitor measured signal rising edge T1, after measured signal rising edge arrives,
Clock count is proceeded by reference frequency signal and measured signal, after reference signal trailing edge arrives, restarts prison
Measured signal rising edge T2 is surveyed, after T2 arrives, is stopped to reference frequency signal and the clock count of measured signal, last
Signal where rising edge T2 is not counted in counting.
Because 20Hz signal sources are gps signal, within each reference signal cycle, the signal mathematics opinion of 20M reference frequencies
Upper is 1M, but due to the reason such as environmental change and the limitation of crystal oscillator itself precision, when crystal oscillator frequency and long term drift performance are with GPS
Clock precision still has certain gap.So being modified to the clock count of reference frequency signal using gps time signal, correct
Method is formula (3).
Wherein, R is the clock count of reference frequency signal when not correcting preceding reality output for 1 (high level), and P is GPS bases
Calibration signal cycle internal reference frequency clock count real output value, T be when revised reality output is 1 reference frequency when
Clock number.
Then calculate T*50ns and be the revised reality output time.So what is actually obtained is by measured frequency：
Wherein, C is the clock count of measured signal.
By can be calculated, if GPS time signals are accurate, crystal oscillator output frequency is linear, and max value of error is 20Hz/
20M, i.e. 1ppm.
The present invention carries out high precision test using FPGA by actual verification to caesium optical pumping output frequency, and by gps time
System is calibrated, high-precision magnetic-field measurement data are can obtain.By multiple authentication, frequency measurement method energy of the invention
Estimated performance is enough reached, can carry out stablizing high-precision conversion for caesium optical pumping Larmor precession frequencies, and use fpga chip
It is A3P060, enables to hardware circuit more simple, area occupied is small, and reliability is high, in that context it may be convenient to be integrated into it
In his system.
It should be noted last that, the above embodiments are merely illustrative of the technical solutions of the present invention and it is unrestricted.Although ginseng
The present invention has been described in detail according to embodiment, it will be understood by those within the art that, to technical side of the invention
Case is modified or equivalent, and without departure from the spirit and scope of technical solution of the present invention, it all should cover in the present invention
Right in the middle of.
Claims (2)
1. a kind of frequency measurement method for optical pumped magnetometer frequency meter, it is characterised in that including：
Step 1) GPS time signals are selected as the reference signal of frequency measurement, and provide reference frequency with the crystal oscillator of frequency meter
Signal；
Step 2) add up to obtain the clock meter of reference frequency signal and measured signal within the whole output cycle of GPS time signals
Number, the clock count of reference frequency signal is corrected using GPS time signals, further obtains the revised reality output time；
Step 3) by the ratio between the clock count of measured signal and reality output time, obtain the frequency values of measured signal.
2. the frequency measurement method for optical pumped magnetometer frequency meter according to claim 1, it is characterised in that the step
It is rapid 2) to specifically include：
Step 101) after the arriving of reference signal rising edge, start to monitor the rising edge T1 of measured signal, arrive in rising edge T1
Afterwards, clock count is carried out to reference frequency signal and measured signal, after reference signal trailing edge arrives, restarts monitoring
The rising edge T2 of measured signal, after rising edge T2 arrivings, stopping enters row clock meter to reference frequency signal and measured signal
Number, and signal where rising edge T2 is not counted in counting；
Step 102) clock for obtaining reference frequency signal when revised reality output is high level is calculated using following formula
Count T：
Wherein, R is the clock count of reference frequency signal when not correcting preceding reality output for high level, and P is GPS reference signals week
The real output value of phase internal reference frequency signal clock count, W is GPS reference signal cycle internal reference frequency signal clock counts
Theoretical output valve；
Step 103) utilize step 102) in clock count T, calculate and obtain revised reality output time and be expressed as T*N,
Wherein, N represents the clock cycle of reference frequency signal.
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Cited By (2)
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| CN107870262A (en) * | 2017-11-01 | 2018-04-03 | 中国科学院上海微***与信息技术研究所 | A kind of high-precision optical pumped magnetometer meter frequency device and method based on GPS time services |
| CN110297199A (en) * | 2019-07-05 | 2019-10-01 | 中国地质大学（武汉） | A kind of caesium optical pumped magnetometer frequency measurement method and system based on whole phase FFT |
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Application publication date: 20170609 |