CN109633759B - Ground magnetic resonance signal rapid extraction device and method based on phase-locked amplification technology - Google Patents

Ground magnetic resonance signal rapid extraction device and method based on phase-locked amplification technology Download PDF

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CN109633759B
CN109633759B CN201811516744.3A CN201811516744A CN109633759B CN 109633759 B CN109633759 B CN 109633759B CN 201811516744 A CN201811516744 A CN 201811516744A CN 109633759 B CN109633759 B CN 109633759B
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CN109633759A (en
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张洋
张博
皮帅
陈思博
孙德立
李苏杭
林婷婷
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Jilin University
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Abstract

The invention relates to the technical field of nuclear magnetic resonance underground water detection, in particular to a ground magnetic resonance signal rapid extraction device and method based on a phase-locked amplification technology, which comprises the following steps: a receiving coil for inducing a magnetic resonance signal generated from the underground water; the band-pass filter with the adjustable central frequency of 200Hz of bandwidth adjusts the central frequency to be Larmor frequency through the main control module and receives magnetic resonance signals; the master control module controls the signal generator to generate a cosine signal with Larmor frequency, and the signal is used as a reference signal and an output signal of a center frequency adjustable band-pass filter with the bandwidth of 200Hz to realize frequency relocation through an in-phase channel; the main control module controls the signal generator to generate a cosine signal with Larmor frequency, the cosine signal is converted into a sine signal through the 90-degree phase shifter, and the sine signal serves as a reference signal and is subjected to frequency relocation through an orthogonal channel together with an output signal of a center frequency adjustable band-pass filter with the bandwidth of 200 Hz; can realize rapid extraction.

Description

Ground magnetic resonance signal rapid extraction device and method based on phase-locked amplification technology
Technical Field
The invention relates to the technical field of nuclear magnetic resonance underground water detection, in particular to a ground magnetic resonance signal rapid extraction device and method based on a phase-locked amplification technology.
Background
The ground magnetic resonance technology can directly detect underground water and has the advantages of qualitative and quantitative detection. However, the ground magnetic resonance signal is very weak, only has a nanovolt level, is easily interfered by noise, and has low signal-to-noise ratio. Especially in the area with serious interference of man-made noise, the problem that the amplifier is saturated and the effective signal can not be extracted occurs.
The nuclear magnetic resonance underground water detection system with the reference coil and the detection method disclosed in CN102053280A, however, the method can only eliminate the power frequency harmonic noise with correlation, and the noise elimination effect is greatly affected by the structure, the laying position and the noise mutation of the two coils.
CN104614778A discloses "a nuclear magnetic resonance underground water detection signal noise elimination method based on ICA", which utilizes the ICA algorithm to attenuate random noise. In a real noisy environment, however, it is difficult to achieve reliable suppression of colored noise.
CN108254794A discloses a magnetic resonance noise reduction method based on modeling inverse recovery technology, which suppresses noise by using extremely narrow low-pass filtering, and recovers the original signal by late laplace and derivative transformation. However, the method is realized on software, so that the problem of saturation of an amplifier of the acquisition device cannot be solved, and the data operation is complex and the signal is difficult to be quickly extracted in an on-chip embedded system.
At present, most of traditional noise elimination algorithms for detecting nuclear magnetic resonance signals aim at single noise to eliminate noise, and complex environment noise of actual work cannot be effectively responded. In addition, the three methods cannot inhibit the problem of saturation of an amplifier of the acquisition device, and cannot extract signals in real time on site because of noise elimination of subsequent software. Therefore, the research on a new technology which has the anti-saturation function and can quickly extract the ground magnetic resonance signal in a field work site has important significance.
Disclosure of Invention
The technical problem to be solved by the present invention is to provide a device for rapidly extracting a ground magnetic resonance signal based on a phase-locked amplification technique, and to provide a method for rapidly extracting a ground magnetic resonance signal based on a phase-locked amplification technique.
The invention is realized in this way, a ground magnetic resonance signal rapid extraction device based on the phase-locked amplification technology, the device includes: the device comprises a receiving coil, a band-pass filter with the bandwidth of 200Hz and the center frequency adjustable, a signal generator, a 90-degree phase shifter, an in-phase channel, a quadrature channel and a main control module;
the receiving coil is used for inducing magnetic resonance signals generated by underground water;
the band-pass filter with the adjustable central frequency of 200Hz of bandwidth adjusts the central frequency to be Larmor frequency through the main control module and receives magnetic resonance signals;
the master control module controls the signal generator to generate a cosine signal with Larmor frequency, and the signal is used as a reference signal and an output signal of a center frequency adjustable band-pass filter with the bandwidth of 200Hz to realize frequency relocation through an in-phase channel;
the master control module controls the signal generator to generate a cosine signal with Larmor frequency, the cosine signal is converted into a sine signal through the 90-degree phase shifter, and the sine signal serves as a reference signal and is frequency shifted through an orthogonal channel with an output signal of a center frequency adjustable band-pass filter with the bandwidth of 200 Hz;
the main control module collects signals of an in-phase channel and a quadrature channel and extracts a ground magnetic resonance signal.
Further, still include: the magnetic resonance circuit comprises an LC matching network and a preamplifier, wherein the LC matching network receives a magnetic resonance signal of a receiving coil, realizes resonance to improve signal amplitude and suppresses noise interference;
the preamplifier amplifies the signal passing through the LC matching network for the first time and transmits the amplified signal to a center frequency adjustable band-pass filter with the bandwidth of 200 Hz.
Furthermore, the in-phase channel comprises an orthogonal vector type phase-locked amplifier and an in-phase secondary amplifier, the orthogonal vector type phase-locked amplifier and the in-phase secondary amplifier are composed of a first multiplier and a first low-pass filter, the orthogonal vector type phase-locked amplifier receives a band-pass filter with a central frequency of 200Hz of a bandwidth, and is connected with the signal generator, the frequency shifting is realized by the cosine signal of the Larmor frequency and the output signal of the band-pass filter with the central frequency of 200Hz of the bandwidth through the first multiplier, the high-frequency component and most of noise are eliminated through the first low-pass filter.
Furthermore, the orthogonal channel comprises an orthogonal vector type lock-in amplifier and an orthogonal secondary amplifier which are formed by a second multiplier and a second low-pass filter, a cosine signal with the Larmor frequency is converted into a sine signal through a 90-degree phase shifter, the sine signal is used as a reference signal, the frequency shift is realized through the second multiplier with an output signal of a center frequency adjustable band-pass filter with the bandwidth of 200Hz, the high-frequency component and most of noise are eliminated through the second low-pass filter, and the sine signal is further amplified through the orthogonal secondary amplifier.
The main control module controls the A/D acquisition card to acquire signals of an in-phase channel and acquires original data of the in-phase channel; and controlling an A/D acquisition card to acquire a channel signal and acquiring the original data of the orthogonal channel.
Further, the first low-pass filter and the second low-pass filter both adopt a first-order low-pass filter with a cut-off frequency of 20 Hz.
Further, the second low-pass filters are first-order low-pass filters with the cut-off frequency of 20 Hz.
A ground magnetic resonance signal fast extraction method based on a phase-locked amplification technology comprises the following steps:
inducing a magnetic resonance signal generated by underground water through a receiving coil;
magnetic resonance signals pass through a band-pass filter with the bandwidth of 200Hz and the center frequency of the magnetic resonance signals is adjustable, and the center frequency is the Larmor frequency;
generating a cosine signal with Larmor frequency, wherein the signal is used as a reference signal and realizes frequency relocation through an in-phase channel with an output signal of a center frequency adjustable band-pass filter with a bandwidth of 200 Hz;
generating a cosine signal with Larmor frequency, converting the cosine signal into a sine signal through 90-degree phase shift, and realizing frequency relocation by taking the sine signal as a reference signal and an output signal of a center frequency adjustable band-pass filter with the bandwidth of 200Hz through an orthogonal channel;
and acquiring signals of an in-phase channel and a quadrature channel, and extracting a ground magnetic resonance signal.
Further, the raw data of the in-phase channel is formulated as
Figure BDA0001902162040000041
When the acquisition time is more than 10ms, exp (-T/T)2*)>>exp(-ωct), the raw data of the collected same-phase channel is reduced to
Figure BDA0001902162040000042
Logarithm of the above formula to obtain a linear equation
Figure BDA0001902162040000043
Solving for T through linear equation slope k2And obtaining a linear equation of two primary variables by a longitudinal intercept I (0) of a linear equation:
in the same way, a linear equation of two elements of the orthogonal channel is obtained:
Figure BDA0001902162040000051
q (0) is the longitudinal intercept of the linear equation after the logarithm of the orthogonal channel is solved, equations (4) and (5) are combined to establish an equation set, and the initial amplitude E is solved0And a phase theta.
Compared with the prior art, the invention has the beneficial effects that:
(1) according to the device and the method for rapidly extracting the ground magnetic resonance signal based on the phase-locked amplification technology, provided by the invention, the signal can be extracted on site in real time through low computation amount of data acquired through the orthogonal channel and the in-phase channel.
(2) The ground magnetic resonance signal rapid extraction device based on the phase-locked amplification technology provided by the invention adopts the LC matching network to improve the detection sensitivity and effectively solves the problem of preamplifier saturation;
(3) according to the ground magnetic resonance signal rapid extraction device based on the phase-locked amplification technology, the multistage hardware filtering is adopted, especially the first low-pass filter and the second low-pass filter based on the low cut-off frequency can effectively inhibit the saturation of the secondary amplifier, the full amplification of the secondary amplifier can be realized, an A/D acquisition card with high conversion digit is not required, and the cost is reduced;
additional aspects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
Fig. 1 is a ground magnetic resonance signal fast extraction device based on a phase-locked amplification technique according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a main control module according to the present invention.
Fig. 3 is a circuit diagram of an LC matching network of the present invention.
FIG. 4 shows a testing apparatus according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Referring to fig. 1, a schematic block diagram of a ground magnetic resonance signal fast extraction device based on a phase-locked amplification technology is shown; a ground magnetic resonance signal fast extraction device based on a phase-locked amplification technology comprises: the device comprises a receiving coil, an LC matching network, a preamplifier, a center frequency adjustable band-pass filter with the bandwidth of 200Hz, a signal generator, a 90-degree phase shifter, a first multiplier, a second multiplier, a first low-pass filter, a second low-pass filter, an in-phase secondary amplifier, a quadrature secondary amplifier, an A/D acquisition card and a main control module.
Referring to FIG. 2, there is shown a schematic block diagram of the master control module of the present invention; the main control module comprises a DSP module, an FPGA module, a key and a display.
The receiving coil 1 is connected with a preamplifier 3 through an LC matching network 2 in connection relation, the preamplifier 3 is respectively connected with a first multiplier 7 and a second multiplier 8 through a bandwidth 200Hz center frequency adjustable band-pass filter 4, the first multiplier 7 is connected with an in-phase secondary amplifier 11 through a first low-pass filter 9, the second multiplier 8 is connected with an orthogonal secondary amplifier 12 through a second low-pass filter 10, the in-phase secondary amplifier 11 and the orthogonal secondary amplifier 12 are respectively connected with an A/D (analog-to-digital) acquisition card 13, the A/D acquisition card 13 is respectively connected with a signal generator 5 and a width 200Hz center frequency adjustable band-pass filter 4 through a main control module 14, the signal generator 5 is respectively connected with the first multiplier 7 and a 90-degree phase shifter 6, the 90-degree phase shifter 6 is connected with the second multiplier 8, and the DSP module 15 is respectively connected with an FPGA (field programmable gate array) module 16, a key 17 and a display.
A receiving coil 1 for inducing a magnetic resonance signal generated from underground water and transmitting the signal to an LC matching network 2;
referring to fig. 3, a circuit diagram of the LC matching network of the present invention is shown, where the LC matching network 2 is composed of a matching capacitor C and an LC passive filter, the LC passive filter is a 3-order Π -type filter composed of L1, C1, L2, C2, L3, and C3, the matching capacitor and the receiving coil realize resonance to improve signal amplitude, and the LC passive filter suppresses noise interference to prevent saturation of the preamplifier 3;
the preamplifier 3 amplifies the signal for the first time and transmits the amplified signal to a center frequency adjustable band-pass filter 4 with the bandwidth of 200 Hz;
the band-pass filter 4 with the adjustable central frequency of 200Hz is a band-pass filter with the adjustable central frequency and the adjustable bandwidth of 200Hz, the central frequency is adjusted by the main control module 14 to be Larmor frequency, the bandwidth of 200Hz ensures that the ground magnetic resonance signal can be obtained without distortion, and the noise is further suppressed;
the first multiplier 7 and the first low-pass filter 9 form an in-phase channel of the orthogonal vector type lock-in amplifier, the main control module 14 generates a cosine signal with larmor frequency through the control signal generator 5, the signal is taken as a reference signal and is shifted with the frequency of the output signal of the band-pass filter 4 with the central frequency of 200Hz through the first multiplier, the noise-eliminating high-frequency component and most of noise are eliminated through the first low-pass filter 9, and finally, the main control module controls the A/D acquisition card 13 to acquire a signal which is further amplified by the in-phase secondary amplifier 11 and acquires original data of the in-phase channel;
the second multiplier 8 and the second low-pass filter 10 form an orthogonal channel of the orthogonal vector type lock-in amplifier, the main control module 14 generates a cosine signal with larmor frequency through the control signal generator 5, the cosine signal is converted into a sine signal through the 90-degree phase shifter 6, the frequency of the sine signal serving as a reference signal and an output signal of the central frequency adjustable band-pass filter 4 with the bandwidth of 200Hz are shifted through the second multiplier 8, the noise high-frequency component and most of noise are eliminated through the second low-pass filter 10, and finally the main control module controls the A/D acquisition card 13 to acquire a signal further amplified by the orthogonal secondary amplifier 12 and acquire original data of the orthogonal channel;
the first low-pass filter 9 and the second low-pass filter 10 both adopt a first-order low-pass filter with the cut-off frequency of 20Hz, and because the pass band range is small, noise and signals outside the frequency band are effectively filtered, so that the problem of saturation of a secondary amplifier is effectively solved, and the signals output by the low-pass filters mainly comprise ground magnetic resonance signals and can be further amplified to a range which can be identified by low conversion digit A/D (analog/digital) through the secondary amplifier, so that the device cost is further reduced.
The main control module 14 is composed of a DSP module 15, an FPGA module 16, a key 17 and a display 18, human-computer interaction is realized through the key 17 and the display 18, besides the regulation and control work is completed, a ground magnetic resonance signal fast extraction method based on a phase-locked amplification technology is realized on the main control module 14, the collected original data of an in-phase channel and the collected original data of an orthogonal channel are processed in real time to extract signals fast, and the extracted signals are displayed on the display 18.
A ground magnetic resonance signal fast extraction method based on a phase-locked amplification technology comprises the following steps:
inducing a magnetic resonance signal generated by underground water through a receiving coil;
magnetic resonance signals pass through a band-pass filter with the bandwidth of 200Hz and the center frequency of the magnetic resonance signals is adjustable, and the center frequency is the Larmor frequency;
generating a cosine signal with Larmor frequency, wherein the signal is used as a reference signal and realizes frequency relocation through an in-phase channel with an output signal of a center frequency adjustable band-pass filter with a bandwidth of 200 Hz;
generating a cosine signal with Larmor frequency, converting the cosine signal into a sine signal through 90-degree phase shift, and realizing frequency relocation by taking the sine signal as a reference signal and an output signal of a center frequency adjustable band-pass filter with the bandwidth of 200Hz through an orthogonal channel;
and acquiring signals of an in-phase channel and a quadrature channel, and extracting a ground magnetic resonance signal.
The raw data formula of the in-phase channel can be expressed as
Figure BDA0001902162040000095
Three key parameters of the magnetic resonance signal include the initial amplitude E0Average relaxation time T2Sum phase θ, due to mean relaxation time of magnetic resonance signal 30 ≦ T21000ms or less, i.e. 1<1/T2*<33.3 and the cut-off frequency of the low-pass filter is 20Hz, corresponding to a cut-off angular frequency of ωc125.65rad/s, exp (-T/T) when acquisition time is greater than 10ms2*)>>exp(-ωct), the formula of the raw data of the same-phase channel collected at this time can be simplified to
Figure BDA0001902162040000091
Logarithm of the above formula to obtain a linear equation
Figure BDA0001902162040000092
First, T can be obtained by the slope k of the linear equation2Obtaining a linear equation of two primary variables by the vertical intercept I (0) of the linear equation
Figure BDA0001902162040000093
Similarly, a linear equation of two in the orthogonal channel can be obtained
Q (0) is the longitudinal intercept of the linear equation after the logarithm of the orthogonal channel is solved, and the simultaneous formulas (4) and (5) are establishedEquation set, can find E0And phase θ, i.e., the effective ground magnetic resonance signal is quickly extracted by simple calculation.
Example (b):
the device and the method for rapidly extracting the ground magnetic resonance signal based on the phase-locked amplification technology provided by the invention are tested by using the measuring device shown in fig. 4. The programmable signal source generates an E in the signal coil via the voltage attenuator0＝200nV,fL＝2000Hz,T2150ms and theta 30 DEG, wherein the expression is e (t) 200exp (-t/0.15) cos (2 pi × 2000 × t +30 DEG), because the receiving coil and the signal coil are arranged in parallel and adopt the same turns, wire diameters and structures, the same magnetic resonance signal is coupled in the receiving coil, meanwhile, the receiving coil is coupled with space electromagnetic noise, and the controller starts the programmable signal source to output a signal through the synchronous trigger and simultaneously starts the quick extraction device provided by the invention.
Adjusting the reference signals output by the signal generator and the 90 DEG phase shifter to have a frequency fLCosine signal and sine signal of 2000Hz, order 1 and cut-off angle frequency omega of two low-pass filtersc125.67 rad/s. Displaying the extracted key parameters of the magnetic resonance signals on site, wherein the result is E0＝194.65nV,T2152.78ms and θ 29.32 °, compare E to the original signal0,T2The accuracies of x and θ are 97.32%, 98.14% and 97.73%, respectively, a valid signal is acquired, and the results can be processed and displayed in real time.

Claims (8)

1. A ground magnetic resonance signal rapid extraction device based on a phase-locked amplification technology is characterized by comprising: the device comprises a receiving coil, a band-pass filter with the bandwidth of 200Hz and the center frequency adjustable, a signal generator, a 90-degree phase shifter, an in-phase channel, a quadrature channel and a main control module;
the receiving coil is used for inducing magnetic resonance signals generated by underground water;
the band-pass filter with the adjustable central frequency of 200Hz of bandwidth adjusts the central frequency to be Larmor frequency through the main control module and receives magnetic resonance signals;
the master control module controls the signal generator to generate a cosine signal with Larmor frequency, and the signal is used as a reference signal and an output signal of a center frequency adjustable band-pass filter with the bandwidth of 200Hz to realize frequency relocation through an in-phase channel;
the master control module controls the signal generator to generate a cosine signal with Larmor frequency, the cosine signal is converted into a sine signal through the 90-degree phase shifter, and the sine signal serves as a reference signal and is frequency shifted through an orthogonal channel with an output signal of a center frequency adjustable band-pass filter with the bandwidth of 200 Hz;
the main control module collects signals of an in-phase channel and a quadrature channel and extracts a ground magnetic resonance signal;
the extraction of the ground magnetic resonance signal comprises the steps of formulating the original data of the in-phase channel into
Wherein the content of the first and second substances,
Figure FDA0002244336710000012
to mean relaxation time, ωcIn order to cut off the angular frequency of the antenna,
when the acquisition time is greater than 10ms,
Figure FDA0002244336710000013
the collected original data of the same-phase channel is reduced to
Figure FDA0002244336710000014
Logarithm of the above formula to obtain a linear equation
Figure FDA0002244336710000021
By the slope k of the linear equation
Figure FDA0002244336710000022
Then obtaining a linear equation of two-dimensional through the longitudinal intercept I (0) of the linear equation:
Figure FDA0002244336710000023
in the same way, a linear equation of two elements of the orthogonal channel is obtained:
q (0) is the longitudinal intercept of the linear equation after the logarithm of the orthogonal channel is solved, equations (4) and (5) are combined to establish an equation set, and the initial amplitude E is solved0And a phase theta.
2. The apparatus of claim 1, further comprising: the magnetic resonance circuit comprises an LC matching network and a preamplifier, wherein the LC matching network receives a magnetic resonance signal of a receiving coil, realizes resonance to improve signal amplitude and suppresses noise interference;
the preamplifier amplifies the signal passing through the LC matching network for the first time and transmits the amplified signal to a center frequency adjustable band-pass filter with the bandwidth of 200 Hz.
3. The device according to claim 1, wherein the in-phase channel comprises a quadrature vector type lock-in amplifier and an in-phase secondary amplifier which are composed of a first multiplier and a first low-pass filter, the quadrature vector type lock-in amplifier receives a center frequency tunable band-pass filter with a bandwidth of 200Hz and is connected with the signal generator, the frequency shift between the cosine signal of the larmor frequency and the output signal of the center frequency tunable band-pass filter with the bandwidth of 200Hz is realized through the first multiplier, the high-frequency component and most of noise are eliminated through the first low-pass filter, and the signals are further amplified through the in-phase secondary amplifier.
4. The apparatus of claim 1, wherein the quadrature channel comprises a quadrature vector type lock-in amplifier and a quadrature two-stage amplifier, the second multiplier and the second low-pass filter constitute a quadrature vector type lock-in amplifier, a cosine signal with larmor frequency is converted into a sine signal through a 90 ° phase shifter, the sine signal is used as a reference signal, the frequency shift is realized through the second multiplier with an output signal of a center frequency adjustable band-pass filter with a bandwidth of 200Hz, the high frequency component and most of noise are eliminated through the second low-pass filter, and the signal is further amplified through the quadrature two-stage amplifier.
5. The device according to claim 1, wherein the device further comprises an a/D acquisition card, and the main control module controls the a/D acquisition card to acquire signals of an in-phase channel and acquire original data of the in-phase channel; and controlling an A/D acquisition card to acquire a channel signal and acquiring the original data of the orthogonal channel.
6. The apparatus according to claim 3, wherein the first low-pass filter is a first-order low-pass filter having a cutoff frequency of 20 Hz.
7. The apparatus according to claim 4, wherein the second low-pass filters each employ a first-order low-pass filter having a cutoff frequency of 20 Hz.
8. A ground magnetic resonance signal fast extraction method based on a phase-locked amplification technology is characterized by comprising the following steps:
inducing a magnetic resonance signal generated by underground water through a receiving coil;
magnetic resonance signals pass through a band-pass filter with the bandwidth of 200Hz and the center frequency of the magnetic resonance signals is adjustable, and the center frequency is the Larmor frequency;
generating a cosine signal with Larmor frequency, wherein the signal is used as a reference signal and realizes frequency relocation through an in-phase channel with an output signal of a center frequency adjustable band-pass filter with a bandwidth of 200 Hz;
generating a cosine signal with Larmor frequency, converting the cosine signal into a sine signal through 90-degree phase shift, and realizing frequency relocation by taking the sine signal as a reference signal and an output signal of a center frequency adjustable band-pass filter with the bandwidth of 200Hz through an orthogonal channel;
collecting signals of an in-phase channel and a quadrature channel, and extracting a ground magnetic resonance signal;
the raw data of the in-phase channel is formulated as
Figure FDA0002244336710000041
Wherein the content of the first and second substances,
Figure FDA0002244336710000042
to mean relaxation time, ωcIn order to cut off the angular frequency of the antenna,
when the acquisition time is greater than 10ms,
Figure FDA0002244336710000043
the collected original data of the same-phase channel is reduced to
Figure FDA0002244336710000044
Logarithm of the above formula to obtain a linear equation
Figure FDA0002244336710000045
By the slope k of the linear equationThen obtaining a linear equation of two-dimensional through the longitudinal intercept I (0) of the linear equation:
Figure FDA0002244336710000047
in the same way, a linear equation of two elements of the orthogonal channel is obtained:
Figure FDA0002244336710000048
q (0) is the longitudinal intercept of the linear equation after the logarithm of the orthogonal channel is solved, equations (4) and (5) are combined to establish an equation set, and the initial amplitude E is solved0And a phase theta.
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CN206211979U (en) * 2016-12-14 2017-05-31 吉林大学 A kind of ground nuclear magnetic resonance signal locking amplifying device
CN108152767A (en) * 2017-11-30 2018-06-12 华东师范大学 A kind of magnetic resonance signal real-time processing method based on FPGA
CN108254794B (en) * 2018-01-26 2020-01-14 吉林大学 Magnetic resonance denoising method and device based on modeling reverse recovery technology
CN208026853U (en) * 2018-04-02 2018-10-30 华东师范大学 The magnetic resonance signal real time processing system of bandwidth varying based on FPGA
CN108458654B (en) * 2018-05-11 2022-02-18 哈尔滨工业大学 Optical nonlinear error measuring method and device based on two-channel quadrature phase-locked demodulation

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