CN103823244B - Magnetic resonance three-component noise removing device and noise removing method - Google Patents
Magnetic resonance three-component noise removing device and noise removing method Download PDFInfo
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- CN103823244B CN103823244B CN201410088813.0A CN201410088813A CN103823244B CN 103823244 B CN103823244 B CN 103823244B CN 201410088813 A CN201410088813 A CN 201410088813A CN 103823244 B CN103823244 B CN 103823244B
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Abstract
The invention relates to a magnetic resonance three-component noise removing device. The magnetic resonance three-component noise removing device is formed through a structure. The structure is characterized in that an upper computer is connected with a transmitting coil through a control system, a transmitting circuit and a resonance matching capacitor; the transmitting circuit is connected with a power supply; the control system is connected with a receiving coil and a reference coil respectively through an A/D (Analog to Digital) collection and amplification circuit and a conditioning circuit. The magnetic resonance three-component noise removing device is applicable to a detection area with complex and changeable environment noise and uneven space distribution of the noise; due to the adoption of relevance between x-component signals, y-component signals and z-component signals which are sensed by coils paved in the same detection place, the z-component noise is removed, then filtered and processed to obtain reliable magnetic resonance signals, so that the wiring space is greatly saved and the processing result is flexible and accurate; in particular, when sharp-peak noise with great amplitude exists, the noise removing effect is excellent. Through the magnetic resonance three-component noise removing device, the influence of strong electromagnetic interference near the cities, the villages and the water-deficient areas is eliminated, and the problem of limited application of a nuclear magnetic resonance underground water detection method is solved.
Description
Technical field:
The present invention relates to a kind of geophysical prospecting method and data interpretation thereof, in particular for gathering nuclear magnetic resonance (Nuclear Magnetic Resonance, NMR) three-component underground water detection method and utilizing the data processing method of magnetic resonance three-component stress release treatment.
Background technology:
Nuclear magnetic resonance underground water detection method has as a kind of method of direct detection underground water that resolution is high, efficiency is high, the advantage such as informative and uniqueness of solution.But the signal received due to instrument very faint (receive and lie prostrate level), highly sensitive receiving trap is very easily subject to the interference of ambient noise composition.Chinese population is intensive, electrical network is flourishing, line of electric force and power equipment are covered with cities and towns and village, electromagnetic interference (EMI) situation is serious, and water-deficient area major part is in these strong jamming areas such as near cities and village, this makes the application of nuclear magnetic resonance underground water detection method be restricted, and sometimes even can not obtain reliable NMR signal.Noise to received signal carries out effective filtering and becomes accurate inversion interpretation hydrogeological parameter result important prerequisite with the reliable extraction realizing NMR signal.
CN101251606A discloses one " in Testing of Feeble Signals instrument in useful signal frequency band industrial frequency harmonic codan ", is utilize frequency, phase place, amplitude to follow the tracks of industrial frequency harmonic in useful signal frequency band to cause the compensating circuit of interference comprehensively.The connecting and disconnecting of master microprocessor control signal sensor and impedance matching network, impedance matching network is connected with programmable amplifier through prime amplifier, broadband filter, output signal envelope detecting device is connected with from microprocessor with data bus by control line, and programmable amplifier connects DDS signal generator through phaselocked loop.This circuit effectively suppresses the industrial frequency harmonic in detecting instrument in useful signal frequency band to disturb, follow the tracks of the frequency of this interference, phase place and amplitude in real time, by its filtering from Received signal strength, and do not affect other useful signal, do not affect the useful signal frequency content with this interfering frequency overlap.
CN102053280A discloses one " nuclear magnetic resonance underground water detection system and detection method with reference coil ", by the Full wave shape data of noise signal in the NMR signal in multi-channel A/D collecting unit synchronous acquisition transmitting/receiving coil and reference coil, the noise signal gathered by computing reference coil and the maximum correlation with magnetic resonance signal, realize the laying of reference coil optimum position and quantity, when signal and noise statistics the unknown, adopt variable step size adaptive algorithm, offset the noise in transmitting/receiving coil acquisition NMR signal to greatest extent, realize the complicated very noisy of many field sources and disturb extraction that is lower and magnetic resonance signal, improve equipment anti-interference ability, for searching ground water provides a kind of sniffer and method reliably.
The industrial frequency harmonic codan of foregoing invention can only solve the filtering of the some industrial frequency harmonics in useful signal frequency band, then helpless for other electromagnetic interference (EMI) such as industrial frequency harmonic and unusual noise; Underground water detection method with reference coil requires that in reference coil, noise signal and magnetic resonance signal have good correlativity, thus the distance between reference coil and main coil is at least greater than two times of wire diameters, add wiring space, and due to the unevenness of the complicacy of neighbourhood noise, polytrope and space distribution, sometimes desirable denoising effect can not be obtained.
For the noise problem in magnetic resonance signal, by laying special shape coil, the methods such as method, block opposition method, sinusoidal opposition method and the notch filter increasing Signal averaging number of times are adopted also to be used to the filtering of electromagnetic noise, these methods obtain good effect under certain precondition, but when noise intensity is large, interference component is complicated, signal center frequency and Hz noise frequency difference less time, be difficult to obtain good filter effect.
Summary of the invention:
Object of the present invention is just for above-mentioned the deficiencies in the prior art, one is provided to be applicable to neighbourhood noise complexity, the magnetic resonance three-component noise-eliminating method of test operation limited space, thus to received signal in noise carry out effective filtering to realize the reliable extraction of NMR signal, to accurate inversion interpretation hydrogeological parameter, there is vital role and beyond thought effect.
The object of the invention is to be achieved through the following technical solutions:
Magnetic resonance three-component noise cancellation apparatus, through control system 2, radiating circuit 3 with join humorous electric capacity 5 and be connected with transmitting coil 6 by host computer 1, radiating circuit 3 is connected with power supply 4, and control system 2 connects and composes respectively at receiving coil 7, reference coil 8 and reference coil 9 through A/D collection 12, amplifying circuit 11 and modulate circuit 10.
Along the orthogonal laying reference coil 8 of X, Y, Z axis, reference coil 9 and receiving coil 7 centered by point of fixity O.
Host computer 1 arranges emission parameter to control system 2, comprises and excites duration and stimulating frequency.By radiating circuit 3 to the sine pulse equal with local Larmor frequency of transmission frequency in transmitting coil 6.NMR signal is spatially made up of x, y, z three components, receives nuclear magnetic resonance z component signal with receiving coil 7, receives nuclear magnetic resonance x component with reference coil 8, receives nuclear magnetic resonance y component signal with reference coil 9.Wherein, receiving coil 7, reference coil 8 and reference coil 9 are three coils of orthogonal laying centered by a certain point of fixity O.The signal received is by after signal conditioning circuit 10 and amplifying circuit 11, gathered by A/D acquisition module 12, finally pass to host computer 1, preserve data and start to process this three components, utilize magnetic resonance three-component with reference to noise-eliminating method stress release treatment, obtain reliable NMR signal.
Magnetic resonance three-component, with reference to noise-eliminating method, comprises the following steps:
A, survey district in select detection place, lay transmitting coil 6;
B, be that normal vector lays receiving coil 7 with vertical direction, being that normal vector lays reference coil 8 with North and South direction, is that normal vector lays reference coil 9 with east-west direction.Receiving coil 7, the orthogonal laying on locus centered by O point of reference coil 8 and reference coil 9, and transmitting coil 6 and receiving coil 7, reference coil 8 and reference coil 9 must be arranged and be laid on same place;
C, first a measurement noise, open magnetic resonance three component seismic data acquisition system, host computer 1 sends control word to control system 2, comprises the information exciting duration and stimulating frequency.Control system 2 produces control signal and controls radiating circuit 3, and radiating circuit 3 does not produce transmitter current to transmitting coil 6, and this is emitted as pseudo-transmitting.
D, receiving coil 7, reference coil 8 and reference coil 9 receive signal after puppet being launched and are gathered by A/D acquisition module 12 after three-channel modulate circuit 10 carries out signal condition and three-channel amplifying circuit 11 amplifies;
E, acquiescence North and South direction are x-axis direction, and the signal that reference coil 8 receives is x component noise; East-west direction is y-axis direction, and the signal that reference coil 9 receives is y component noise; Vertical direction is z-axis direction, and the signal that receiving coil 7 receives is z component noise;
F, measurement magnetic resonance signal, now host computer 1 sends control word to control system 2 again, comprises the information exciting duration and stimulating frequency.Control system 2 produces control signal and controls radiating circuit 3, and radiating circuit 3 produces by joining humorous electric capacity 5 exchange current that frequency is local Larmor frequency in transmitting coil 6;
G, receiving coil 7, gathered by A/D acquisition module 12 after three-channel modulate circuit 10 carries out signal condition and three-channel amplifying circuit 11 amplifies after reference coil 8 and reference coil 9 sense signal, the signal now received is respectively magnetic resonance x component signal, magnetic resonance y component signal and magnetic resonance z component signal;
H, with the handling object of the clock signal of record three components simultaneously, time-domain filtering algorithm is proposed:
h
z(t)=[h
x(t)*X(t)]+[h
y(t)*Y[t)]
Wherein h
x, h
yand h
zfor x, y and z component noise, X and Y is x and y component signal, and * is convolution algorithm;
I, obtain z component noise according to above-mentioned time-domain filtering algorithm, that from z component signal, removes that z component noise obtains is reliable magnetic resonance signal;
J, change transmitter current size, obtaining different pulses apart from detecting different depth of stratums, repeating c-i process, obtaining second group of magnetic resonance signal after process;
K, above-mentioned j process can be repeated, repeatedly detect, contrasting repeatedly processing the magnetic resonance signal obtained, obtain accurate information.
Beneficial effect: magnetic resonance three-component noise-eliminating method disclosed by the invention is applicable to the search coverage that neighbourhood noise is complicated and changeable and neighbourhood noise is uneven in space distribution, coil-induced x and the y component signal utilizing same detection place to lay and the correlativity of z component signal, after eliminating z component noise, filtering process obtains reliable magnetic resonance signal, not only significantly save wiring space but also result is accurate flexibly, especially, when the spike noise that amplitude is larger exists, de-noising effect is fine.Present invention eliminates the impact of strong electromagnetic suffered by near cities and village and water-deficient area, solve nuclear magnetic resonance underground water detection method and apply a limited difficult problem.
Accompanying drawing illustrates:
Fig. 1 is magnetic resonance three component seismic data acquisition system structured flowchart
Fig. 2 is that spatial relation figure laid by coil
Fig. 3 is magnetic resonance three-component direction schematic diagram
1 host computer, 2 control system, 3 radiating circuits, 4 power supplys, 5 join humorous electric capacity, 6 transmitting coils, 7 receiving coils, 8 reference coils, 9 reference coils, 10 modulate circuits, 11 amplifying circuits, 12A/D acquisition module.
Embodiment:
Be described in further detail below in conjunction with drawings and Examples:
As shown in Figure 1, this system is the exchange current of local Larmor frequency to underground transmission frequency by transmitting coil 6, produces alternating magnetic field.Under the exciting of the alternating magnetic field formed in ground, make Hydrogen Proton in underground water produce energy level transition, a large amount of Hydrogen Proton transits on high level.When removing supply current, these high level Hydrogen Proton just get back to low-lying level state gradually, discharge a large amount of quantum of energys with Larmor frequency, in receiving coil 7, reference coil 8 and reference coil 9, induce MRS signal.
As shown in Figure 2, due to the particular orientation that receiving coil 7, reference coil 8 and reference coil 9 are laid, can optionally be received the x, y, z component signal of MRS signal, utilize the correlativity of x and y component signal and z component signal, after using the time-domain filtering algorithm reference in magnetic resonance three-component noise-eliminating method to eliminate z component noise, filtering process can obtain reliable magnetic resonance signal.
Time-domain filtering algorithm in magnetic resonance three-component noise-eliminating method is calculated:
Set up h
x(t)=[h
x(t) * X (t)]+discrete data models of [hy (t) * Y (t)]:
Wherein, h
x, h
y, h
z, the subscript of X and Y refers to time samples, and n is the number of samples of impulse response, and m exports h
znumber of samples.
Variable in this model is contained over and sampling number in the future, is realized by Computer Simulation.
Calculate result by model to need to estimate shock response non trivial solution X
0, X
2x
n-2and Y
0, Y
2y
n-1, filter coefficient depends on stratal configuration instead of x and y component.Remainder error r
icomputing formula:
Wherein, p is estimated value; The computing formula of the average error σ between measured value and estimated value:
Wherein, m is data amount check, and n is filter width; Z component noise standard deviation computing formula:
Wherein,
z component noise mean value.
Snr computation formula:
Calculate Analysis signal-to-noise ratio (SNR) with reference to the signal quality after de-noising.
Magnetic resonance three-component noise-eliminating method, comprises following order and step:
A, as shown in Figure 1, connect instrument, host computer 1 is connected with control system 2, control system 2 is connected with radiating circuit 3, radiating circuit 3 is connected with transmitting coil 6 by joining humorous electric capacity 5, and radiating circuit 3 is connected with power supply 4, and control system 2 and A/D gather 12 and be connected, three passages that A/D gathers 12 by amplifying circuit 11 and modulate circuit 10 respectively with receiving coil 7, reference coil 8 is connected with reference coil 9;
B, survey district in select detection place, lay transmitting coil 6;
C, is as shown in Figure 2 that normal vector lays receiving coil 7 with vertical direction, is that normal vector lays reference coil 8 with North and South direction, is that normal vector lays reference coil 9 with east-west direction.Receiving coil 7, the orthogonal laying on locus centered by O point of reference coil 8 and reference coil 9, and transmitting coil 6 and receiving coil 7, reference coil 8 and reference coil 9 must be arranged and be laid on same place;
D, first a measurement noise, open magnetic resonance three component seismic data acquisition system, host computer 1 sends control word to control system 2, comprises the information exciting duration and stimulating frequency.Control system 2 produces control signal and controls radiating circuit 3, and radiating circuit 3 does not produce transmitter current to transmitting coil 6, and this is emitted as pseudo-transmitting.
E, receiving coil 7, reference coil 8 and reference coil 9 are gathered by A/D acquisition module 12 after receiving signal after puppet being launched after three-channel modulate circuit 10 carries out signal condition and three-channel amplifying circuit 11 amplifies;
F, as shown in Figure 3, acquiescence North and South direction is x-axis direction, and the signal that reference coil 8 receives is x component noise; East-west direction is y-axis direction, and the signal that reference coil 9 receives is y component noise; Vertical direction is z-axis direction, and the signal that receiving coil 7 receives is z component noise;
G, measurement magnetic resonance signal, now host computer 1 sends control word to control system 2 again, comprises the information exciting duration and stimulating frequency.Control system 2 produces control signal and controls radiating circuit 3, and radiating circuit 3 produces by joining humorous electric capacity 5 exchange current that frequency is local Larmor frequency in transmitting coil 6;
H, receiving coil 7, gathered by A/D acquisition module 12 after three-channel modulate circuit 10 carries out signal condition and three-channel amplifying circuit 11 amplifies after reference coil 8 and reference coil 9 sense signal, the signal now received is respectively magnetic resonance x component signal, magnetic resonance y component signal and magnetic resonance z component signal;
I, with the handling object of the clock signal of record three components simultaneously, time-domain filtering algorithm is proposed:
h
z(t)=[h
x(t)*X(t)]+[h
y(t)*Y(t)]
Wherein h
x, h
yand h
zfor x, y and z component noise, X and Y is x and y component signal, and * is convolution algorithm;
J, obtain z component noise according to above-mentioned time-domain filtering algorithm, that from z component signal, removes that z component noise obtains is reliable magnetic resonance signal;
K, change transmitter current size, obtaining different pulses apart from detecting different depth of stratums, repeating d-j process, obtaining second group of magnetic resonance signal after process;
L, above-mentioned k process can be repeated, repeatedly detect, contrasting repeatedly processing the magnetic resonance signal obtained, obtain accurate information.
Embodiment 1
Magnetic resonance three-component noise-eliminating method a kind ofly measures magnetic resonance three component signal and utilize the noise-eliminating method of time-domain filtering algorithm stress release treatment, and this system is the exchange current of local Larmor frequency to underground transmission frequency by transmitting coil 6, produces alternating magnetic field.Under the exciting of the alternating magnetic field formed in ground, make Hydrogen Proton in underground water produce energy level transition, a large amount of Hydrogen Proton transits on high level.When removing supply current, these high level Hydrogen Proton just get back to low-lying level state gradually, discharge a large amount of quantum of energys with Larmor frequency, in receiving coil 7, reference coil 8 and reference coil 9, induce MRS signal.Acquiescence North and South direction is x-axis direction, east-west direction is y-axis direction, vertical direction is z-axis direction, due to the particular orientation that receiving coil 7, reference coil 8 and reference coil 9 are laid, can optionally be received the x, y, z component signal of MRS signal, utilize the correlativity of x and y component signal and z component signal, after using the time-domain filtering algorithm reference in magnetic resonance three-component noise-eliminating method to eliminate z component noise, filtering process can obtain reliable magnetic resonance signal.
Host computer 1 is connected with control system 2, control system 2 is connected with radiating circuit 3, radiating circuit 3 is connected with transmitting coil 6 by joining humorous electric capacity 5, radiating circuit 3 is connected with power supply 4, control system 2 and A/D gather 12 and are connected, A/D gathers 12 and is connected with amplifying circuit 11, and amplifying circuit 11 is connected with modulate circuit 10, and modulate circuit 10 is connected with receiving coil 7, reference coil 8 and reference coil 9.
Magnetic resonance three-component noise-eliminating method, comprises following order and step:
A, survey district in select detection place, lay transmitting coil 6;
B, be that normal vector lays receiving coil 7 with vertical direction, being that normal vector lays reference coil 8 with North and South direction, is that normal vector lays reference coil 9 with east-west direction.Receiving coil 7, the orthogonal laying on locus centered by O point of reference coil 8 and reference coil 9, and transmitting coil 6 and receiving coil 7, reference coil 8 and reference coil 9 must be arranged and be laid on same place;
C, first a measurement noise, open magnetic resonance three component seismic data acquisition system, host computer 1 sends control word to control system 2, comprises the information exciting duration and stimulating frequency.Control system 2 produces control signal and controls radiating circuit 3, and radiating circuit 3 does not produce transmitter current to transmitting coil 6, and this is emitted as pseudo-transmitting.
D, receiving coil 7, reference coil 8 and reference coil 9 are gathered by A/D acquisition module 12 after receiving signal after puppet being launched after three-channel modulate circuit 10 carries out signal condition and three-channel amplifying circuit 11 amplifies;
E, acquiescence North and South direction are x-axis direction, and the signal that reference coil 8 receives is x component noise; East-west direction is y-axis direction, and the signal that reference coil 9 receives is y component noise; Vertical direction is z-axis direction, and the signal that receiving coil 7 receives is z component noise;
F, measurement magnetic resonance signal, now host computer 1 sends control word to control system 2 again, comprises the information exciting duration and stimulating frequency.Control system 2 produces control signal and controls radiating circuit 3, and radiating circuit 3 produces by joining humorous electric capacity 5 exchange current that frequency is local Larmor frequency in transmitting coil 6;
G, receiving coil 7, gathered by A/D acquisition module 12 after three-channel modulate circuit 10 carries out signal condition and three-channel amplifying circuit 11 amplifies after reference coil 8 and reference coil 9 sense signal, the signal now received is respectively magnetic resonance x component signal, magnetic resonance y component signal and magnetic resonance z component signal;
H, with the handling object of the clock signal of record three components simultaneously, time-domain filtering algorithm is proposed:
h
z(t)=[h
x(t)*X(t)]+[h
y(t)*Y(t)]
Wherein h
x, h
yand h
zfor x, y and z component noise, X and Y is x and y component signal, and * is convolution algorithm;
I, obtain z component noise according to above-mentioned time-domain filtering algorithm, that from z component signal, removes that z component noise obtains is reliable magnetic resonance signal;
J, change transmitter current size, obtaining different pulses apart from detecting different depth of stratums, repeating c-i process, obtaining second group of magnetic resonance signal after process;
K, repeat above-mentioned j process, carry out 16 detections, 16 groups of detection datas are processed.
Embodiment 2
Magnetic resonance three-component noise-eliminating method a kind ofly measures magnetic resonance three component signal and utilize the reference noise-eliminating method of time-domain filtering algorithm stress release treatment, this system is the exchange current of local Larmor frequency to underground transmission frequency by transmitting coil 6, produces alternating magnetic field.Under the exciting of the alternating magnetic field formed in ground, make Hydrogen Proton in underground water produce energy level transition, a large amount of Hydrogen Proton transits on high level.When removing supply current, these high level Hydrogen Proton just get back to low-lying level state gradually, discharge a large amount of quantum of energys with Larmor frequency, in receiving coil 7, reference coil 8 and reference coil 9, induce MRS signal.Acquiescence North and South direction is x-axis direction, east-west direction is y-axis direction, vertical direction is z-axis direction, due to the particular orientation that receiving coil 7, reference coil 8 and reference coil 9 are laid, can optionally be received the x, y, z component signal of MRS signal, utilize the correlativity of x and y component signal and z component signal, after using the time-domain filtering algorithm reference in magnetic resonance three-component noise-eliminating method to eliminate z component noise, filtering process can obtain reliable magnetic resonance signal.
Host computer 1 is connected with control system 2, control system 2 is connected with radiating circuit 3, radiating circuit 3 is connected with transmitting coil 6 by joining humorous electric capacity 5, radiating circuit 3 is connected with power supply 4, control system 2 and A/D gather 12 and are connected, A/D gathers 12 and is connected with amplifying circuit 11, and amplifying circuit 11 is connected with modulate circuit 10, and modulate circuit 10 is connected with receiving coil 7, reference coil 8 and reference coil 9.
Magnetic resonance three-component noise-eliminating method, comprises following order and step:
A, survey district in select detection place, lay transmitting coil 6;
B, be that normal vector lays receiving coil 7 with vertical direction, being that normal vector lays reference coil 8 with North and South direction, is that normal vector lays reference coil 9 with east-west direction.Receiving coil 7, the orthogonal laying on locus centered by O point of reference coil 8 and reference coil 9, and transmitting coil 6 and receiving coil 7, reference coil 8 and reference coil 9 must be arranged and be laid on same place;
C, first a measurement noise, open magnetic resonance three component seismic data acquisition system, host computer 1 sends control word to control system 2, comprises the information exciting duration and stimulating frequency.Control system 2 produces control signal and controls radiating circuit 3, and radiating circuit 3 does not produce transmitter current to transmitting coil 6, and this is emitted as pseudo-transmitting.
D, receiving coil 7, reference coil 8 and reference coil 9 are gathered by A/D acquisition module 12 after receiving signal after puppet being launched after three-channel modulate circuit 10 carries out signal condition and three-channel amplifying circuit 11 amplifies;
E, acquiescence North and South direction are x-axis direction, and the signal that reference coil 8 receives is x component noise; East-west direction is y-axis direction, and the signal that reference coil 9 receives is y component noise; Vertical direction is z-axis direction, and the signal that receiving coil 7 receives is z component noise;
F, measurement magnetic resonance signal, now host computer 1 sends control word to control system 2 again, comprises the information exciting duration and stimulating frequency.Control system 2 produces control signal and controls radiating circuit 3, and radiating circuit 3 produces by joining humorous electric capacity 5 exchange current that frequency is local Larmor frequency in transmitting coil 6;
G, receiving coil 7, gathered by A/D acquisition module 12 after three-channel modulate circuit 10 carries out signal condition and three-channel amplifying circuit 11 amplifies after reference coil 8 and reference coil 9 sense signal, the signal now received is respectively magnetic resonance x component signal, magnetic resonance y component signal and magnetic resonance z component signal;
H, with the handling object of the clock signal of record three components simultaneously, time-domain filtering algorithm is proposed:
h
z(t)=[h
x(t)*X(t)]+[h
y(t)*Y(t)]
Wherein h
x, h
yand h
zfor x, y and z component noise, X and Y is x and y component signal, and * is convolution algorithm;
I, obtain z component noise according to above-mentioned time-domain filtering algorithm, that from z component signal, removes that z component noise obtains is reliable magnetic resonance signal;
J, change transmitter current size, obtaining different pulses apart from detecting different depth of stratums, repeating c-i process, obtaining second group of magnetic resonance signal after process;
K, repeat above-mentioned j process, carry out 24 detections, 24 groups of detection datas are processed.
Claims (1)
1. a magnetic resonance three-component noise-eliminating method, realized by magnetic resonance three-component noise cancellation apparatus, this device is through control system (2), radiating circuit (3) with join humorous electric capacity (5) and be connected with transmitting coil (6) by host computer (1), radiating circuit (3) is connected with power supply (4), and control system (2) gathers (12), amplifying circuit (11) and modulate circuit (10) through A/D and connects and composes with receiving coil (7), reference coil a (8) and reference coil b (9) respectively;
Receiving coil (7), reference coil a (8) and reference coil b (9) centered by point of fixity O along X, Y, Z axis orthogonal laying reference coil a (8), reference coil b (9) and receiving coil (7);
It is characterized in that, comprise the following steps:
A, survey district in select detection place, lay transmitting coil (6);
B, be that normal vector lays receiving coil (7) with vertical direction, North and South direction is that normal vector lays reference coil a (8), is that normal vector lays reference coil b (9) with east-west direction; Receiving coil (7), reference coil a (8) and reference coil b (9) orthogonal laying on locus centered by O point, and transmitting coil (6) and receiving coil (7), reference coil a (8) and reference coil b (9) are laid on same place;
C, first a measurement noise, open magnetic resonance three component seismic data acquisition system, host computer (1) sends control word to control system (2), comprise the information exciting duration and stimulating frequency, control system (2) produces control signal and controls radiating circuit (3), radiating circuit (3) does not produce transmitter current to transmitting coil (6), and this is emitted as pseudo-transmitting;
The signal that d, receiving coil (7), reference coil a (8) and reference coil b (9) receive after puppet being launched is gathered by A/D acquisition module (12) after three-channel modulate circuit (10) carries out signal condition and three-channel amplifying circuit (11) amplifies;
E, acquiescence North and South direction are x-axis direction, and the signal that reference coil a (8) receives is x component noise; East-west direction is y-axis direction, and the signal that reference coil b (9) receives is y component noise; Vertical direction is z-axis direction, and the signal that receiving coil (7) receives is z component noise;
F, measurement magnetic resonance signal, now host computer (1) sends control word to control system (2) again, comprise the information exciting duration and stimulating frequency, control system (2) produces control signal and controls radiating circuit (3), and radiating circuit (3) produces by joining humorous electric capacity (5) exchange current that frequency is local Larmor frequency in transmitting coil (6);
Gathered by A/D acquisition module (12) after three-channel modulate circuit (10) carries out signal condition and three-channel amplifying circuit (11) amplifies after g, receiving coil (7), reference coil a (8) and reference coil b (9) sense signal, the signal now received is respectively magnetic resonance x component signal, magnetic resonance y component signal and magnetic resonance z component signal;
H, with the handling object of the clock signal of record three components simultaneously, time-domain filtering algorithm is proposed:
Wherein
,
with
for x, y and z component noise,
with
for x and y component signal,
for convolution algorithm;
I, obtain z component noise according to above-mentioned time-domain filtering algorithm, that from z component signal, removes that z component noise obtains is reliable magnetic resonance signal;
J, change transmitter current size, obtaining different pulses apart from detecting different depth of stratums, repeating c-i process, obtaining second group of magnetic resonance signal after process;
K, repeat above-mentioned j process, carry out multi collect, the data of multi collect are carried out process the magnetic resonance signal obtained and contrast, eliminate the false and retain the true, obtain accurate information.
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