CN106885998B - Method and circuit for improving frequency measurement precision and speed of cesium optical pump magnetic resonance signals - Google Patents
Method and circuit for improving frequency measurement precision and speed of cesium optical pump magnetic resonance signals Download PDFInfo
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- CN106885998B CN106885998B CN201710133207.XA CN201710133207A CN106885998B CN 106885998 B CN106885998 B CN 106885998B CN 201710133207 A CN201710133207 A CN 201710133207A CN 106885998 B CN106885998 B CN 106885998B
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Abstract
The invention discloses a method for improving frequency measurement precision and speed of cesium optical pump magnetic resonance signals, which comprises the following steps: (1) Conditioning and shaping cesium light pump magnetic resonance signals output by the cesium light pump magneto-dependent sensor to convert the signals into signals to be measured; (2) Respectively sending the time base signal and the signal to be tested in the step (1) into an FPGA digital frequency measurement module, wherein the FPGA digital frequency measurement module processes the time base signal and the signal to be tested through a fixed gate without intermittent frequency measurement; (3) And (3) reading a processing result of the FPGA digital frequency measurement module by a controller, and performing frequency calculation on the data processed in the step (2) to obtain the frequency of the cesium optical pump magnetic resonance signal. The invention further comprises a circuit for improving the frequency measurement precision and speed of the cesium optical pump magnetic resonance signal. The invention uses the principle of fixed gate frequency measurement, adopts the mode of 'no intermittent frequency measurement' and 'eliminating frequency boundary points', greatly improves the frequency measurement precision and speed of the magnetometer, and ensures the stability of measurement precision.
Description
Technical Field
The invention relates to the technical field of earth weak magnetic field measurement, in particular to a method and a circuit for improving frequency measurement precision and speed of cesium optical pump magnetic resonance signals.
Background
The optical pump magnetometer has the advantages of high resolution, no zero drift, no need of strict orientation, capability of carrying out high-precision rapid continuous measurement under the motion condition, and the like, becomes the most important measurement means for aviation magnetic measurement and underwater magnetic measurement, and is mainly applied to the aspects of geophysical exploration, military magnetic exploration, mineral deposit exploration, and the like.
The cesium optical pump magnetometer is a weak magnetic field measuring instrument developed by optical pumping effect and optical magnetic resonance technology based on the Zeeman splitting of cesium atoms in a weak magnetic field. Cesium atoms generate zeeman energy levels under the action of an external magnetic field, and the energy difference between adjacent energy levels of the split atomic weight can be expressed by a zeeman transition frequency, namely a magnetic resonance frequency. Magnetic resonance frequency f x The ratio of the proportionality constant of the geomagnetic field strength to be measured is named cesium gyromagnetic ratio which is equal to 3.49828Hz/nT. By measuring the magnetic resonance frequency f x The measured magnetic field strength H=f can be obtained x /3.49828nT. Therefore, the frequency measurement accuracy directly determines the geomagnetic field measurement accuracy. In the geomagnetic field measuring range of 10000 nT-100000 nT, the magnetic resonance frequency is 35 KHz-350 KHz.
Because the military value of the optical pump magnetometer is high, developed countries are limited to export of the optical pump magnetometer with high sampling rate and high precision, and therefore the development of the optical pump magnetometer with high sensitivity and independent intellectual property has important significance. How to further improve the frequency measurement precision and speed of the system is a key problem to be solved by the existing optical pump magnetometer.
At present, a direct frequency measurement method (M method) and a direct frequency measurement Zhou Fa (T method) are generally adopted to measure the magnetic resonance frequency of the cesium optical pump, or the frequency measurement precision of the magnetic resonance signal of the cesium optical pump magnetometer is improved based on a FPGA (Field Programmable Gate Array) equal-precision frequency measurement method, or a phase-locked frequency measurement method is adopted to measure the magnetic resonance signal of the cesium optical pump.
However, the first method has a count error of + -1, and the noise peak of the auxiliary circuit may also cause technical errors; in the second method, because the measured gate time is discontinuous, a dead zone of frequency measurement exists, and the stability of the second method under the dynamic measurement and strong noise background is poor; the third method has the problems of large noise, insufficient sampling rate and the like, and influences the frequency measurement precision.
Disclosure of Invention
In view of the above, embodiments of the present invention provide a method and a circuit for improving the frequency measurement accuracy and speed of the magnetic resonance signal of the cesium optical pump magneto-sensor.
The embodiment of the invention provides a method for improving the frequency measurement precision and speed of cesium optical pump magnetic resonance signals, which comprises the following steps:
(1) Conditioning and shaping cesium light pump magnetic resonance signals output by the cesium light pump magneto-dependent sensor to convert the signals into signals to be measured;
(2) Respectively sending the time base signal and the signal to be tested in the step (1) into an FPGA digital frequency measurement module, wherein the FPGA digital frequency measurement module processes the time base signal and the signal to be tested through a fixed gate without intermittent frequency measurement;
(3) And (3) reading a processing result of the FPGA digital frequency measurement module by a controller, and performing frequency calculation on the data processed in the step (2) to obtain the frequency of the cesium optical pump magnetic resonance signal.
Further, in the step (1), the cesium optical pump magneto-sensor generates energy level transition through excitation of the high-frequency excitation circuit, and generates an optical pumping effect by a cesium simple substance, when the light intensity in the cesium optical pump magneto-sensor is unchanged, a radio-frequency magnetic field is added to a radio-frequency coil in the cesium optical pump magneto-sensor in a direction perpendicular to a magnetic field generated by the high-frequency excitation circuit, and when the frequency of the radio-frequency magnetic field is equal to the frequency of the energy level transition of the cesium atom, the cesium optical pump magneto-sensor outputs a cesium optical pump magnetic resonance signal.
Further, the high-frequency excitation circuit excites the cesium lamp in the cesium-light pump magneto-sensor to emit light and enables the cesium lamp to release photons, the photons pass through a convex lens, a filter and a polaroid in the cesium-light pump magneto-sensor and then become left-handed circularly polarized light, and the left-handed circularly polarized light excites cesium atoms to generate energy level transition and enables cesium simple substances to generate an optical pumping effect.
In the step (1), the cesium optical pump magnetic resonance signal is input into a signal conditioning circuit, the signal conditioning circuit amplifies, filters and conditions the cesium optical pump magnetic resonance signal, the conditioned cesium optical pump magnetic resonance signal is input into a hysteresis comparator, the conditioned cesium optical pump magnetic resonance signal output by the signal conditioning circuit is subjected to phase shifting by a phase shifting circuit, and then the cesium optical pump magnetic sensor outputs a continuous cesium optical pump magnetic resonance signal, and the hysteresis comparator shapes the cesium optical pump magnetic resonance signal to obtain a signal to be measured.
Further, in the step (2), the processing of the time base signal and the signal to be tested by the FPGA digital frequency measurement module through the fixed gate without intermittent frequency measurement comprises the following steps:
(2.1) multiplying the time base signal by a programmable frequency multiplier of an FPGA digital frequency measuring module to obtain a standard signal, dividing the time base signal by a programmable frequency divider to obtain a fixed gate signal, and synchronizing the signal to be measured by a first D trigger to obtain an actual gate signal;
(2.2) inverting the actual gate signal and then inverting the fixed gate signal phase to obtain a positive gate standard signal counter count signal, inverting the fixed gate signal and then inverting the actual gate signal phase to obtain a negative gate standard signal counter count signal, respectively inverting the actual gate signal and the fixed gate signal and then obtaining a mark of a controller reading standard signal count value, wherein the low level is a mark of the number of pulses of the positive gate standard signal readable by the controller, and the high level is a mark of the number of pulses of the negative gate standard signal readable by the controller;
(2.3) sending the signal to be detected, the actual gate signal and the clear signal into a first counter of the FPGA digital frequency measurement module, wherein the clear signal of the first counter is sent by a controller, the first counter is started by a first pulse of the signal to be detected after the rising edge of the pulse of the actual gate signal, and the first counter is closed by a first pulse of the signal to be detected after the falling edge of the pulse of the actual gate signal, so that the pulse number of the signal to be detected of the positive gate is obtained; starting a first counter by a first pulse of the signal to be detected after the pulse falling edge of the actual gate signal, and closing the first counter by the first pulse of the signal to be detected after the pulse rising edge of the actual gate signal to obtain the number of pulses of the signal to be detected of the negative gate;
(2.4) sending the standard signal, the count signal of the standard signal counter of the positive gate and the gate fixing signal into a second counter of the FPGA digital frequency measuring module, wherein the gate fixing signal is a zero clearing signal of the second counter, the second counter is started by a first pulse of the standard signal after the rising edge of the count signal pulse of the standard signal counter of the positive gate, and the second counter is closed by a first pulse of the standard signal after the falling edge of the count signal pulse of the standard signal counter of the positive gate, so that the pulse number of the standard signal in the asynchronous period between the gate fixing signal and the signal to be measured in the positive gate is obtained;
the method comprises the steps that a standard signal, a counting signal of a negative gate standard signal counter and a fixed gate signal are sent into a third counter of an FPGA digital frequency measuring module, the fixed gate signal is a third counter zero clearing signal, a first pulse of the standard signal after the rising edge of a signal pulse is counted by the negative gate standard signal counter, the third counter is started, a first pulse of the standard signal after the falling edge of a signal pulse is counted by the negative gate standard signal counter, the third counter is closed, and the number of pulses of the standard signal in an asynchronous period between the fixed gate signal and a signal to be measured in the negative gate is obtained;
and (2.5) the part of the edge of the actual gate signal, which is not synchronous with the edge of the signal to be detected, adopts the pulse number of the standard signal in the step (2.4), and the part of the edge of the actual gate signal, which is synchronous with the edge of the signal to be detected, adopts the pulse number of the signal to be detected in the step (2.3).
Further, in the step (3), when the controller performs frequency calculation on the data processed in the step (2), in order to eliminate the frequency boundary points, the controller divides a frequency updating period into n frequency division gates, and if the frequency boundary points appear in the a-th frequency division gate, the next frequency boundary point appears in the a+n-th frequency division gate, so that the frequency division gate where each frequency boundary point is located can be found.
Further, in the step (3), a frequency calculation formula of the cesium optical pump magnetic resonance signal is:
wherein: f (f) x For the frequency of the signal to be measured, f 0 For the frequency of the standard signal, n xi For the pulse number of the part of standard signals of which the edges of the ith actual gate signal are not synchronous with the edges of the signal to be detected, n xi+1 For the pulse number of the part of standard signals of which the edges of the (i+1) th actual gate signal are not synchronous with the edges of the signal to be detected, N xi For the number of signal pulses to be detected in the actual gate signal, N 0i The standard signal pulse number in the actual gate signal is the frequency division gate number, the actual gate signal is generated by synchronizing the fixed gate signal and the signal to be detected, and the fixed gate signal and the standard signal are generated by the same time base signal.
The circuit for improving the frequency measurement precision and speed of the cesium optical pump magnetic resonance signal comprises a high-frequency excitation circuit, a cesium optical pump magnetic resonance sensor, a signal conditioning circuit, a hysteresis comparator, a phase shifting circuit, a crystal oscillator circuit, an FPGA digital frequency measurement module, a controller and a storage unit, wherein the input end of the cesium optical pump magnetic resonance sensor is connected with the high-frequency excitation circuit, the high-frequency excitation circuit excites the cesium optical pump magnetic resonance sensor to output a cesium optical pump magnetic resonance signal, the output end of the cesium optical pump magnetic resonance sensor is connected with the signal conditioning circuit, the signal conditioning circuit is connected with the phase shifting circuit and the hysteresis comparator, the conditioned cesium optical pump magnetic resonance signal is input into the hysteresis comparator, the phase shifting circuit, the signal conditioning circuit and the cesium optical pump magnetic resonance sensor form a feedback loop, the conditioned cesium optical pump magnetic resonance signal output by the signal conditioning circuit passes through the circuit and then enables the cesium optical pump magnetic resonance sensor to output a continuous cesium optical pump magnetic resonance signal, the phase shifting circuit is connected with the FPGA digital frequency measurement module to output a time-frequency measurement module, the phase shifting circuit is connected with the FPGA digital frequency measurement module to calculate the result, and the result is processed by the FPGA digital frequency measurement module, and the result is stored by the FPGA digital frequency measurement module.
Further, the FPGA digital frequency measurement module comprises a control signal part, a counting part, a latching part and a data transmission part, wherein the control signal part, the counting part, the latching part and the data transmission part are mutually connected; the control signal part comprises a programmable frequency multiplier, a programmable frequency divider, a D trigger, a plurality of AND gates and a plurality of NOT gates, wherein the programmable frequency divider adjusts the frequency multiplication ratio according to actual conditions, and the programmable frequency divider adjusts the frequency division ratio according to the actual conditions; the counting part comprises a first counter, a second counter and a third counter; the latch part comprises two latches, the data transmission part comprises a multiplexer, the latches are connected with the multiplexer, and the multiplexer is a 48-choice 8-multiplexer.
Further, the controller is an STM32 controller, and the storage unit is an SD card.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention uses the principle of fixed gate frequency measurement, adopts the mode of 'intermittent frequency measurement' and 'eliminating frequency boundary points', adopts double counters to continuously and alternately count in positive and negative gate time respectively, eliminates frequency measurement dead zones, realizes intermittent continuous frequency measurement, and greatly improves the frequency measurement precision and speed of the magnetometer; the mode of eliminating the frequency intersection points adopts a controller to analyze the acquired data, so as to find and eliminate the dynamic frequency change intersection points, thereby ensuring the stability of measurement accuracy;
2. each sub-module of the frequency measurement module is integrated in the FPGA digital frequency measurement module, so that the circuit is easy to realize, the reliability is high, and the later frequency measurement scheme is more convenient to upgrade;
3. the method can adjust the corresponding software lap joint and chip selection according to actual conditions, and reduces the transformation cost.
Drawings
Fig. 1 is a schematic diagram of a circuit for improving frequency measurement accuracy and speed of cesium optical pump magnetic resonance signals according to an embodiment of the present invention.
Fig. 2 is a circuit diagram of the FPGA digital frequency measurement module of fig. 1.
Figure 3 is a flowchart of the operation of one embodiment of a method of the present invention for improving the frequency measurement accuracy and speed of cesium optical pump magnetic resonance signals.
Fig. 4 is a flowchart of the fixed gate non-intermittent frequency measurement operation in fig. 3.
Fig. 5 is a schematic waveform diagram of an embodiment of a method of improving the frequency measurement accuracy and speed of the magnetic resonance signal of the cesium optical pump of the present invention in fig. 3.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be further described with reference to the accompanying drawings.
Referring to fig. 1 and 2, an embodiment of the present invention provides a circuit for improving frequency measurement accuracy and speed of a magnetic resonance signal of a cesium optical pump, which includes a high-frequency excitation circuit 1, a cesium optical pump magneto-sensor 2, a signal conditioning circuit 3, a hysteresis comparator 4, a phase shift circuit 5, a crystal oscillator circuit 6, an FPGA digital frequency measurement module 7, a controller 8 and a storage unit 9.
The input end of the cesium light pump magneto-dependent sensor 2 is connected with a high-frequency excitation circuit 1, the high-frequency excitation circuit 1 excites the cesium light pump magneto-dependent sensor 2 to output a cesium light pump magnetic resonance signal, and the output end of the cesium light pump magneto-dependent sensor 2 is connected with a signal conditioning circuit 3.
The signal conditioning circuit 3 is connected with the phase shifting circuit 5 and the hysteresis comparator 4, the signal conditioning circuit 3 conditions the cesium optical pump magnetic resonance signal output by the cesium optical pump magnetic sensor 2, the conditioned cesium optical pump magnetic resonance signal is input into the hysteresis comparator 4, the phase shifting circuit 5, the signal conditioning circuit 3 and the cesium optical pump magnetic sensor 2 form a feedback loop, and the conditioned cesium optical pump magnetic resonance signal output by the signal conditioning circuit 3 is subjected to phase shifting by the phase shifting circuit 5 to enable the cesium optical pump magnetic sensor 2 to output continuous cesium optical pump magnetic resonance signals.
The output ends of the hysteresis comparator 4 and the crystal oscillator circuit 6 are both connected with the FPGA digital frequency measuring module 7, the crystal oscillator circuit 6 outputs time base signals to the FPGA digital frequency measuring module 7, and the hysteresis comparator 4 processes the conditioned cesium optical pump magnetic resonance signals and outputs signals to be measured to the FPGA digital frequency measuring module 7.
The FPGA digital frequency measuring module 7 processes the time base signal and the signal to be measured, and in one embodiment, the FPGA digital frequency measuring module 7 includes a control signal portion 71, a counting portion 72, a latch portion 73, and a data transfer portion 74, and the control signal portion 71, the counting portion 72, the latch portion 73, and the data transfer portion 74 are connected to each other.
The control signal portion 71 includes a programmable frequency multiplier 711, a programmable frequency divider 712, a D flip-flop 713, and a plurality of and gates 714 and a plurality of not gates 715, the programmable frequency multiplier 711 adjusts the frequency multiplication ratio according to the actual situation, and the programmable frequency divider 712 adjusts the frequency division ratio according to the actual situation.
The counting section 72 includes a first counter (CNT 1) 721, a second counter (CNT 2) 722, and a third counter (CNT 3) 723; the latch section 73 includes two latches 731, and the data transfer section 74 includes a multiplexer 741, the latches 731 being connected to the multiplexer 741, the multiplexer 741 preferably being a 48-choice 8 multiplexer.
The controller 8 reads the processing result of the FPGA digital frequency measurement module 7, in an embodiment, the controller is preferably an STM32 controller, and calculates the frequency of the cesium optical pump magnetic resonance signal, and the storage unit 9 stores the calculation result, in an embodiment, the storage unit 9 is preferably an SD card.
Referring to fig. 3, a method for improving frequency measurement accuracy and speed of cesium optical pump magnetic resonance signals includes the following steps:
(1) Conditioning and shaping cesium light pump magnetic resonance signals output by the cesium light pump magneto-dependent sensor 2 to convert the signals into signals to be measured;
the high-frequency excitation circuit 1 excites the cesium lamp in the cesium-light pump magnetic sensor to emit light and enable the cesium lamp to release photons, the photons pass through a convex lens (not shown in the figure), a light filter (not shown in the figure) and a polarizing plate (not shown in the figure) in the cesium-light pump magnetic sensor and then become left-handed circularly polarized light, the left-handed circularly polarized light excites cesium atoms to generate energy level transition, and enable cesium simple substances to generate optical pumping effect, when the light intensity in the cesium-light pump magnetic sensor is unchanged, a radio-frequency magnetic field is applied to a radio-frequency coil (not shown in the figure) in the cesium-light pump magnetic sensor in the direction perpendicular to the magnetic field generated by the high-frequency excitation circuit 1, when the frequency of the radio-frequency magnetic field is equal to the frequency of the cesium atomic energy level transition, the cesium-light pump magnetic resonance sensor outputs cesium-light pump magnetic resonance signals, the cesium-light pump magnetic resonance signals are input into the signal conditioning circuit 3, the conditioned cesium-light-pump magnetic resonance signals are amplified and filtered, the conditioned cesium-light-pump magnetic resonance signals are input into the comparator 4, and the conditioned cesium-light-pump magnetic resonance signals are continuously subjected to the phase-shift circuit 5 to obtain the cesium-pump magnetic resonance signals after the cesium-resonance signals are subjected to phase-shift and the phase-modulated by the phase-change circuit.
(2) Respectively sending the time base signal and the signal to be tested in the step (1) into an FPGA digital frequency measurement module, wherein the FPGA digital frequency measurement module processes the time base signal and the signal to be tested through a fixed gate without intermittent frequency measurement;
referring to fig. 4 and 5, the fpga digital frequency measurement module processes a time-based signal and a signal to be measured by non-intermittent frequency measurement through a fixed gate, and includes the following steps:
(2.1) multiplying the time base signal by a programmable frequency multiplier of an FPGA digital frequency measuring module to obtain a standard signal, dividing the time base signal by a programmable frequency divider to obtain a fixed gate signal, and synchronizing the signal to be measured by a first D trigger to obtain an actual gate signal;
(2.2) inverting the actual gate signal and then inverting the fixed gate signal phase to obtain a positive gate standard signal counter count signal, inverting the fixed gate signal and then inverting the actual gate signal phase to obtain a negative gate standard signal counter count signal, respectively inverting the actual gate signal and the fixed gate signal and then obtaining a mark of a controller reading standard signal count value, wherein the low level is a mark of the number of pulses of the positive gate standard signal readable by the controller, and the high level is a mark of the number of pulses of the negative gate standard signal readable by the controller;
(2.3) sending the signal to be detected, the actual gate signal and the clear signal into a first counter of the FPGA digital frequency measurement module, wherein the clear signal of the first counter is sent by the controller 8, the first counter is started by a first pulse of the signal to be detected after the rising edge of the pulse of the actual gate signal, and the first counter is closed by a first pulse of the signal to be detected after the falling edge of the pulse of the actual gate signal, so that the pulse number of the signal to be detected of the positive gate is obtained; starting a first counter by a first pulse of the signal to be detected after the pulse falling edge of the actual gate signal, and closing the first counter by the first pulse of the signal to be detected after the pulse rising edge of the actual gate signal to obtain the number of pulses of the signal to be detected of the negative gate;
(2.4) sending the standard signal, the count signal of the standard signal counter of the positive gate and the fixed gate signal to a second counter of the FPGA digital frequency measuring module, wherein the fixed gate signal is a zero clearing signal of the second counter, the second counter is started by a first pulse of the standard signal after the rising edge of the count signal pulse of the standard signal counter of the positive gate, and the second counter is closed by a first pulse of the standard signal after the falling edge of the count signal pulse of the standard signal counter of the positive gate, so that the pulse number of the standard signal in the asynchronous period between the fixed gate signal and the signal to be measured in the positive gate is obtained;
the method comprises the steps that a standard signal, a counting signal of a negative gate standard signal counter and a fixed gate signal are sent into a third counter of an FPGA digital frequency measuring module, the fixed gate signal is a third counter zero clearing signal, a first pulse of the standard signal after the rising edge of a signal pulse is counted by the negative gate standard signal counter, the third counter is started, a first pulse of the standard signal after the falling edge of a signal pulse is counted by the negative gate standard signal counter, the third counter is closed, and the number of pulses of the standard signal in an asynchronous period between the fixed gate signal and a signal to be measured in the negative gate is obtained;
and (2.5) the part of the edge of the actual gate signal, which is not synchronous with the edge of the signal to be detected, adopts the pulse number of the standard signal in the step (2.4), and the part of the edge of the actual gate signal, which is synchronous with the edge of the signal to be detected, adopts the pulse number of the signal to be detected in the step (2.3).
(3) And (3) reading a processing result of the FPGA digital frequency measurement module 7 by a controller 8, and performing frequency calculation on the data processed in the step (2) to obtain the frequency of the cesium optical pump magnetic resonance signal.
In practice, the frequency dividing gate and the frequency updating rate to be measured are not generated in the same time base, the frequency crossing points drift relative to the frequency dividing gate due to long-time measurement, so that the judgment error of the frequency crossing points is caused, in order to eliminate the frequency crossing points and smaller errors, the controller 8 divides one frequency updating period into n frequency dividing gates, if the frequency crossing points appear in the A-th frequency dividing gate, the next frequency crossing point appears in the A+n-th frequency dividing gate, and therefore, the frequency dividing gate where each frequency crossing point is can be found, and standard signal counting errors of plus or minus one period are allowed to appear.
The frequency calculation formula of the cesium optical pump magnetic resonance signal is as follows:
wherein: f (f) x For the frequency of the signal to be measured, f 0 For the frequency of the standard signal, n xi For the pulse number of the part of standard signals of which the edges of the ith actual gate signal are not synchronous with the edges of the signal to be detected, n xi+1 For the pulse number of the part of standard signals of which the edges of the (i+1) th actual gate signal are not synchronous with the edges of the signal to be detected, N xi For the number of signal pulses to be detected in the actual gate signal, N 0i And n is the number of frequency division gates, which is the number of standard signal pulses in the actual gate signal.
Wherein the actual gate signal is generated by synchronizing the fixed gate signal and the signal to be detected, and the fixed gate signal and the standard signal are generated by the same time base signal, so the number N of standard signal pulses in the actual gate signal 0i Can be directly converted.
When n is set to 5, the signal f to be tested x The start-stop time of the counting of (a) is triggered by the rising edge or the falling edge of a fixed gate signal, and f is counted in the gate time tau x Is error free; for standard signal f 0 The counts of (2) differ by at most one number of errors, so the relative errors measured are:
the accuracy of the measured frequency is independent of the signal to be measured and is only dependent on the gate time and the frequency of the standard signal. Compared with the traditional gate fixing method, the method increases the sampling rate and improves the accuracy and the speed of the measurement result.
The invention uses the principle of fixed gate frequency measurement, adopts the mode of 'intermittent frequency measurement' and 'eliminating frequency boundary points', adopts double counters to continuously and alternately count in positive and negative gate time respectively, eliminates frequency measurement dead zones, realizes intermittent continuous frequency measurement, and greatly improves the frequency measurement precision and speed of the magnetometer; the mode of eliminating the frequency intersection points adopts a controller to analyze the acquired data, so as to find and eliminate the dynamic frequency change intersection points, thereby ensuring the stability of measurement accuracy; each sub-module of the frequency measurement module is integrated in the FPGA digital frequency measurement module, so that the circuit is easy to realize, the reliability is high, and the later frequency measurement scheme is more convenient to upgrade; the method can adjust the corresponding software lap joint and chip selection according to actual conditions, and reduces the transformation cost.
The embodiments described above and features of the embodiments herein may be combined with each other without conflict.
The foregoing description of the preferred embodiments of the invention is not intended to limit the invention to the precise form disclosed, and any such modifications, equivalents, and alternatives falling within the spirit and scope of the invention are intended to be included within the scope of the invention.
Claims (6)
1. The method for improving the frequency measurement precision and speed of the cesium optical pump magnetic resonance signal is characterized by comprising the following steps of:
(1) Conditioning and shaping cesium light pump magnetic resonance signals output by the cesium light pump magneto-dependent sensor to convert the signals into signals to be measured;
(2) Respectively sending the time base signal and the signal to be tested in the step (1) into an FPGA digital frequency measurement module, wherein the FPGA digital frequency measurement module processes the time base signal and the signal to be tested through a fixed gate without intermittent frequency measurement;
in the step (2), the processing of the time base signal and the signal to be tested by the FPGA digital frequency measurement module through the fixed gate without intermittent frequency measurement comprises the following steps:
(2.1) multiplying the time base signal by a programmable frequency multiplier of an FPGA digital frequency measuring module to obtain a standard signal, dividing the time base signal by a programmable frequency divider to obtain a fixed gate signal, and synchronizing the signal to be measured by a first D trigger to obtain an actual gate signal;
(2.2) inverting the actual gate signal and then inverting the fixed gate signal phase to obtain a positive gate standard signal counter count signal, inverting the fixed gate signal and then inverting the actual gate signal phase to obtain a negative gate standard signal counter count signal, respectively inverting the actual gate signal and the fixed gate signal and then obtaining a mark of a controller reading standard signal count value, wherein the low level is a mark of the number of pulses of the positive gate standard signal readable by the controller, and the high level is a mark of the number of pulses of the negative gate standard signal readable by the controller;
(2.3) sending the signal to be detected, the actual gate signal and the clear signal into a first counter of the FPGA digital frequency measurement module, wherein the clear signal of the first counter is sent by a controller, the first counter is started by a first pulse of the signal to be detected after the rising edge of the pulse of the actual gate signal, and the first counter is closed by a first pulse of the signal to be detected after the falling edge of the pulse of the actual gate signal, so that the pulse number of the signal to be detected of the positive gate is obtained; starting a first counter by a first pulse of the signal to be detected after the pulse falling edge of the actual gate signal, and closing the first counter by the first pulse of the signal to be detected after the pulse rising edge of the actual gate signal to obtain the number of pulses of the signal to be detected of the negative gate;
(2.4) sending the standard signal, the count signal of the standard signal counter of the positive gate and the gate fixing signal into a second counter of the FPGA digital frequency measuring module, wherein the gate fixing signal is a zero clearing signal of the second counter, the second counter is started by a first pulse of the standard signal after the rising edge of the count signal pulse of the standard signal counter of the positive gate, and the second counter is closed by a first pulse of the standard signal after the falling edge of the count signal pulse of the standard signal counter of the positive gate, so that the pulse number of the standard signal in the asynchronous period between the gate fixing signal and the signal to be measured in the positive gate is obtained;
the method comprises the steps that a standard signal, a counting signal of a negative gate standard signal counter and a fixed gate signal are sent into a third counter of an FPGA digital frequency measuring module, the fixed gate signal is a third counter zero clearing signal, a first pulse of the standard signal after the rising edge of a signal pulse is counted by the negative gate standard signal counter, the third counter is started, a first pulse of the standard signal after the falling edge of a signal pulse is counted by the negative gate standard signal counter, the third counter is closed, and the number of pulses of the standard signal in an asynchronous period between the fixed gate signal and a signal to be measured in the negative gate is obtained;
(2.5) the part of the edge of the actual gate signal, which is not synchronous with the edge of the signal to be detected, adopts the pulse number of the standard signal in the step (2.4), and the part of the edge of the actual gate signal, which is synchronous with the edge of the signal to be detected, adopts the pulse number of the signal to be detected in the step (2.3);
(3) And (3) reading a processing result of the FPGA digital frequency measurement module by a controller, and performing frequency calculation on the data processed in the step (2) to obtain the frequency of the cesium optical pump magnetic resonance signal.
2. The method for improving the frequency measurement precision and speed of the cesium optical pump magnetic resonance signal according to claim 1, wherein in the step (1), the cesium optical pump magnetic sensor generates energy level transition by excitation of a high-frequency excitation circuit and generates an optical pumping effect by cesium simple substance, when the light intensity in the cesium optical pump magnetic sensor is unchanged, a radio-frequency magnetic field is added to a radio-frequency coil in the cesium optical pump magnetic sensor in a direction perpendicular to a magnetic field generated by the high-frequency excitation circuit, and when the frequency of the radio-frequency magnetic field is equal to the frequency of the energy level transition of the cesium atom, the cesium optical pump magnetic sensor outputs the cesium optical pump magnetic resonance signal.
3. The method for improving the frequency measurement precision and speed of cesium optical pump magnetic resonance signals according to claim 2, wherein the high-frequency excitation circuit excites a cesium lamp in the cesium optical pump magnetic sensor to emit light and enables the cesium lamp to release photons, the photons pass through a convex lens, a filter and a polaroid in the cesium optical pump magnetic sensor and then become left-handed circularly polarized light, and the left-handed circularly polarized light excites cesium atoms to generate energy level transition and enables cesium simple substances to generate an optical pumping effect.
4. The method for improving the frequency measurement precision and the speed of the cesium optical pump magnetic resonance signal according to claim 1, wherein in the step (1), the cesium optical pump magnetic resonance signal is input into a signal conditioning circuit, the signal conditioning circuit amplifies and filters and conditions the cesium optical pump magnetic resonance signal, the conditioned cesium optical pump magnetic resonance signal is input into a hysteresis comparator, the conditioned cesium optical pump magnetic resonance signal output by the signal conditioning circuit is subjected to phase shift by a phase shift circuit, and then the cesium optical pump magnetic resonance signal is output by a cesium optical pump magneto-sensor continuously, and the hysteresis comparator shapes the cesium optical pump magnetic resonance signal to obtain a signal to be measured.
5. The method for improving the frequency measurement accuracy and speed of the magnetic resonance signal of the cesium optical pump according to claim 1, wherein in the step (3), when the controller performs frequency calculation on the data processed in the step (2), in order to eliminate the frequency boundary points, the controller divides a frequency update period into n frequency division gates, if the frequency boundary point appears in the a-th frequency division gate, the next frequency boundary point appears in the a+n-th frequency division gate, so that the frequency division gate where each frequency boundary point is can be found.
6. The method for improving the frequency measurement accuracy and speed of the cesium optical pump magnetic resonance signal according to claim 1, wherein in the step (3), the frequency calculation formula of the cesium optical pump magnetic resonance signal is:
wherein: f (f) x For the frequency of the signal to be measured, f 0 For the frequency of the standard signal, n xi For the pulse number of the part of standard signals of which the edges of the ith actual gate signal are not synchronous with the edges of the signal to be detected, n xi+1 Is the (i+1) th time of practiceThe pulse number, N, of the partial standard signal with the edge of the inter-gate signal not synchronous with the edge of the signal to be measured xi For the number of signal pulses to be detected in the actual gate signal, N 0i The standard signal pulse number in the actual gate signal is the frequency division gate number, the actual gate signal is generated by synchronizing the fixed gate signal and the signal to be detected, and the fixed gate signal and the standard signal are generated by the same time base signal.
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| CN109541500B (en) * | 2018-12-07 | 2021-08-13 | 中国人民解放军国防科技大学 | Co-magnetometer based on alkali metal atom hyperfine energy level Zeeman splitting |
| CN110297198A (en) * | 2019-06-28 | 2019-10-01 | 中国地质大学（武汉） | A kind of system and method for the measurement of caesium pumped magnetic resonance signal frequency |
| CN110297199B (en) * | 2019-07-05 | 2021-08-27 | 中国地质大学（武汉） | Frequency measurement method and system for cesium optical pump magnetometer based on full-phase FFT |
| CN110850349B (en) * | 2019-11-08 | 2021-10-01 | 中国科学技术大学 | Method for aligning ground state spin energy levels |
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