CN1603856B - Signal detection method for nuclear magnetic resonance - Google Patents
Signal detection method for nuclear magnetic resonance Download PDFInfo
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- CN1603856B CN1603856B CN 200410068160 CN200410068160A CN1603856B CN 1603856 B CN1603856 B CN 1603856B CN 200410068160 CN200410068160 CN 200410068160 CN 200410068160 A CN200410068160 A CN 200410068160A CN 1603856 B CN1603856 B CN 1603856B
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- 238000005481 NMR spectroscopy Methods 0.000 title claims abstract description 13
- 238000001514 detection method Methods 0.000 title abstract description 34
- 238000005070 sampling Methods 0.000 claims description 56
- 230000000630 rising effect Effects 0.000 claims description 7
- 230000007274 generation of a signal involved in cell-cell signaling Effects 0.000 claims description 4
- 230000008676 import Effects 0.000 claims description 3
- 238000000034 method Methods 0.000 abstract description 4
- 238000004088 simulation Methods 0.000 description 10
- 238000010586 diagram Methods 0.000 description 7
- 238000011896 sensitive detection Methods 0.000 description 6
- 230000015654 memory Effects 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 4
- 230000000875 corresponding effect Effects 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 230000007812 deficiency Effects 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
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Abstract
This invention relates to nuclear magnetic resonance technique, which in detail relates to a signal detection means of the nuclear magnetic resonance. It comprises signal amplifier, a cymoscope, one AD sample chip and a generator of reference signal. The signal amplifier and reference signal generator are separately connected with cymoscope, wherein; the cymoscope is connected with AD sample chipthrough amplifier. It is characterized by the following: the said reference signal generator uses digit frequency source; it connects an one from two switch between the DDS and cymoscope.
Description
Technical field
The present invention relates to nuclear magnetic resonance (NMR) technology, relate to a kind of signal supervisory instrument that is used for nuclear magnetic resonance concretely.
Background technology
In nuclear magnetic resonance, main signal detecting mode has three kinds.First kind is the single channel phase sensitive detection technology of seldom using, and its theory diagram as shown in Figure 1.Single channel phase sensitive detection technical pattern is simple, nor can occur because mirror image peak and the zero-frequency peak that the two-way imbalance causes.But in order to distinguish positive negative frequency, require radio-frequency drive frequency and reference frequency (receive frequency) all to place the outside of spectrum width, this has just wasted radio-frequency power greatly.Second kind is the two-way simulation orthogonal detection technology of comparatively generally using, as shown in Figure 2.The NMR signal is after amplifier Amplifier amplifies, by splitter Splitter device one-channel signal is divided into the two-way signal, the two-way phase differential that produces with phase shifter respectively is that 90 degree reference signals are done detection then, and the later signal of detection is gathered into computing machine by two AD cards respectively.Adopt simulation orthogonal detection technology can distinguish positive negative frequency, and radio-frequency drive frequency and reference frequency all place the center of spectrum.Compare the single channel phase sensitive detection, the requirement to radio-frequency power when using the simulation orthogonal detection is reduced to 1/4 of former power.But the orthogonal detection method is very strict to the intensity and the phase place requirement of two paths of signals, and promptly two-way phase wave detector (being made up of multiplier and low-pass filter) is identical, and phase differential also wants strictness to differ 90 °, not so can produce zero-frequency peak and mirror image peak.Be difficult to accomplish that two paths of signals intensity is identical in the realistic simulation hardware circuit, and analog phase shifter is not accomplished the phase place strict orthogonal of two-way reference signal yet, this will certainly produce mirror image peak and zero-frequency peak, need to eliminate by the software approach of " phase loop ", this can prolong experimental period, is not too suitable to some quick scanning sequences.The third is exactly the digital quadrature detection technology that occurs recently, and digital quadrature detection technology has hardware implementation mode, and software realization mode is also arranged.Digital quadrature detection technology has adopted single channel detection technology, method by numeral realizes quadrature detection, therefore digital quadrature detection technology can have been eliminated the not strict text of phase place of the uneven and two-way reference signal of two-way and the mirror image peak and the zero-frequency peak that cause, and can not increase radio-frequency power yet, but digital quadrature detection technology also has some shortcomings, such as the sampling spectrum width can not be set continuously, when doing digital operation, can cause certain round-off error to cause zero-frequency peak etc. inadequately owing to precision.
Summary of the invention
The objective of the invention is at above-mentioned the deficiencies in the prior art part, a kind of signal supervisory instrument that is used for nuclear magnetic resonance is provided, this device is specifically related to a kind of single channel timesharing orthogonal detection technology, and this technology can realize quadrature detection when adopting the single channel detecting circuit.
Main technical schemes of the present invention is as follows:
A kind of signal supervisory instrument that is used for nuclear magnetic resonance, comprise signal amplifier, a wave detector, an AD sampling A, and the generation device of reference signal, wherein signal amplifier and reference signal generation device are distinguished tie geophone, wave detector connects the AD sampling A by amplifier, that it is characterized in that described reference signal generation device use is digitization frequencies source DDS, is connected with the alternative change-over switch between DDS and wave detector.
The sampling clock of described AD sampling A is to be produced by programmable logic device (PLD) chip FPGA according to the sample frequency that the user imports, behind the sampling clock of AD sampling A, be connected to two divided-frequency rate circuit, this circuit produces the two divided-frequency rate signal of a sampling clock when producing sampled clock signal, this signal is connected to the selection port of controlling the alternative change-over switch as the selection signal of reference signal, selects signal to set up in advance than the rising edge or the negative edge of sampling clock.
Described two divided-frequency rate circuit also can be arranged on FPGA inside.
What detection technique of the present invention related to is a kind of single channel timesharing orthogonal detection technology, and its know-why block diagram as shown in Figure 3.The technology of the present invention basic thought mainly contains 3 points: 1, will eliminate the imbalance of two paths of signals in the two-way simulation orthogonal detection and the mirror image peak and the zero-frequency peak that cause, detecting circuit can only adopt the form of single channel so, promptly has only a wave detector and an AD sampling A ADC; 2, adopt the single channel detecting circuit still to realize quadrature detection again, at this problem, the present invention proposes the technology of " timesharing orthogonal detection ", specific practice is to produce the completely orthogonal reference signal of two-way in hardware circuit, the completely orthogonal reference signal of this two-way is connected on the wave detector by the alternative change-over switch of a high speed, being input as 0 at the Select end of at a high speed alternative change-over switch, just to select phase place be the reference signal of 0 degree, and being input as 1, just to select phase place be the reference signals of 90 degree.The sampling mechanism of AD sampling A is AD chip image data under the control of sampling clock, supposes the rising edge image data at sampling clock here, sampling clock rising edge of every generation, the AD sampling A data point of will sampling.Sampling mechanism according to the AD sampling A, behind AD sampling A sampling clock, connect a two divided-frequency rate circuit and just can produce a selection signal of selecting reference signal, the sequential of sampled clock signal and selection signal as shown in Figure 4, select this road signal to receive on the Select port of high speed alternative change-over switch then, so just can realize " timesharing orthogonal detection ", promptly in the odd number sampling clock cycle, the Select port input signal of high speed alternative change-over switch is 0, selecting phase place is that 0 signal of spending is as reference signal (being defined as real part), what the AD sampling A was adopted so is exactly a real part data point, in the even number of samples clock period, the Select port input signal of high speed alternative change-over switch is 1, selecting phase place is that 90 signals of spending are as reference signal (being defined as imaginary part), what the AD sampling A was adopted so is exactly an imaginary data point, and the AD sampling A has just realized the alternating sampling of real part data point and imaginary data point like this.Because real part data point and imaginary data point are that alternating sampling obtains, therefore imaginary data need proofread and correct by software algorithm with respect to sampling interval time of real part data delay, made it to become completely orthogonal real part data and imaginary data; 3, in traditional two-way simulation orthogonal detection technology, the reference signal of two-way quadrature produces by phase shifter, but analog phase shifter is difficult to produce the completely orthogonal reference signal of two-way, therefore used digitization frequencies source DDS device among the present invention, can export the completely orthogonal signal of two-way in the DDS chip (realizes owing to adopt digitizing technique, therefore two paths of signals is completely orthogonal), therefore can utilize the completely orthogonal signal of the two-way that produces in the DDS chip as the two-way orthogonal reference signal, directly receive on the high speed alternative change-over switch.
The present invention combines the advantage of single channel phase sensitive detection and two-way simulation orthogonal detection, and its major advantage is as follows:
1, uses the single channel pickup mode, simplified the detecting circuit structure greatly, provide cost savings;
2, adopt the single channel pickup mode, it is incomplete same and the unequal problem of two paths of signals intensity that causes can be avoided the zero-frequency peak effectively to have solved two-way wave detector in the two-way simulation orthogonal detection technology;
3, adopt an AD chip time sharing sampling solid part signal and imaginary signals, solved in the two-way simulation orthogonal detection technology the incomplete same and unequal problem of two paths of signals intensity that causes of two AD chips effectively;
4, adopt " timesharing orthogonal detection " mechanism, solved the problem of irrealizable quadrature detection in the single channel phase sensitive detection technology, saved radio-frequency power, reduced the sampling spectrum width, improved the signal to noise ratio (S/N ratio) of received signal;
5, adopt digitization frequencies source DDS as the reference signal, solved analog phase shifter effectively and can not strictness produce the problem of the completely orthogonal reference signal of two-way, thereby can avoid the existence at mirror image peak.
Summary of drawings
Accompanying drawing 1 is a single channel phase sensitive detection know-why block diagram;
Accompanying drawing 2 is two-way simulation orthogonal detection know-why block diagram;
Accompanying drawing 3 single channel timesharing orthogonal detection know-why block diagrams;
Accompanying drawing 4 is sampling clock and the sequential chart of selecting signal;
Accompanying drawing 5 is the analog receiver theory diagram based on single channel timesharing orthogonal detection technology.
Concrete technical scheme
Feature of the present invention and other correlated characteristic are described in further detail by embodiment below in conjunction with accompanying drawing, so that technician's of the same trade understanding:
Present embodiment specifically is used for an analog receiver, and its hardware connects block diagram as shown in Figure 5.This analog receiver is made up of analog device and digital device.Analog device comprises signal amplification circuit and detecting circuit, and wherein digital device mainly comprises a PCI bridging chip (PCI 9052Bridge), a programmable logic device (PLD) chip (FPGA), a digitization frequencies source DDS chip (AD9854), a high-speed sampling chip (ADS804), a slice alternative change-over switch (AD8180), a digital signal processing chip (DSP) and two internal memories.PCI 9052 Bridge chips are interface chips, are used for transmitting data between internal memory and pci bus (PCI Bus).What digitization frequencies source DDS chip adopted is the AD9854 chip of Analog Devices company, provides two independently to export I and Q on the AD9854 chip, and I and Q are completely orthogonal, therefore can be used as the completely orthogonal reference signal of two-way.We select for use high speed alternative change-over switch is the AD8180 of Analog Devices company, and it has the switching time of 10ns.What the AD sampling A adopted is the ADS804 chip, and the highest sample rate can reach 10MHz, and sampling resolution is 12.Fpga chip mainly starts to control making usefulness, controls each parts co-ordination.A slice internal memory is used to deposit amplitude, frequency and the phase place of many group reference signals, and another sheet internal memory is used to deposit the data of AD sampling.Dsp chip is mainly used in proofreaies and correct real part and imaginary data.
Signal at first amplifies by amplifier, then with the wave detector detection after the input end input.The sampling clock of AD sampling A ADC is to be produced by FPGA according to the sample frequency that the user imports, at frequency-halving circuit of the inner interpolation of FPGA, when producing sampling clock, produce the two divided-frequency rate signal of a sampling clock, the reference signal that is used for alternate selection two-way quadrature, its sequential as shown in Figure 4.The completely orthogonal reference signal of two-way is provided by the I and the Q output of DDS (AD9854) chip, and I and Q output directly are connected on the alternative change-over switch AD8180.The ADS804 chip is in the rising edge sampled data points of sampling clock, the maximum sampling rate of ADS804 chip is 10MHz, the so minimum sampling clock cycle is 100ns (half sampling clock cycle is 50ns), and be 10ns the switching time of alternative change-over switch AD8180.As can be seen from Figure 4, select the rising edge in advance half sampling clock cycle foundation of signal, so the alternative change-over switch can be selected corresponding reference signal (0 degree or 90 degree reference signals) fully before the rising edge arrival of sampling clock than sampling clock.The reference signal of alternative change-over switch AD8180 alternate selection two-way quadrature under the control of the selection signal that FPGA produces, the ADS804 chip is image data point (real part and imaginary part are alternately gathered) under the control of the sampling clock that FPGA produces, and has so just realized " timesharing orthogonal detection " mechanism.
The real part data and the imaginary data that adopt the technology of the present invention to collect alternately collect, the real part of not corresponding point and imaginary part, therefore imaginary data need be proofreaied and correct by software algorithm with respect to the sampling interval time of real part data delay (supposing the collection earlier of real part data).The principle of proofreading and correct is to have utilized a characteristic of Fourier transform
Be that delay on the time domain is equivalent to makes a single order phase correction on frequency domain.Concrete correcting algorithm process is as follows: 1, real part data and imaginary data are made Fourier transform respectively; 2, according to formula
The later imaginary data of Fourier transform is made the single order phase correction; 3, the real part data on the frequency domain and imaginary data are added and subtracted be combined to form complex Fourier transform; 4, the real part data on the frequency domain and imaginary data are carried out plural inverse fourier transform and obtain time domain data.Whole correcting algorithm can be handled by DSP.
Claims (2)
1. signal supervisory instrument that is used for nuclear magnetic resonance, comprise signal amplifier, a wave detector, an AD sampling A, and the generation device of reference signal, wherein signal amplifier and reference signal generation device are distinguished tie geophone, wave detector connects the AD sampling A, that it is characterized in that described reference signal generation device use is digitization frequencies source DDS, between DDS and wave detector, be connected with the alternative change-over switch, the reference signal that produces is the completely orthogonal reference signal of two-way, the completely orthogonal reference signal of this two-way is connected on the wave detector by the alternative change-over switch, the sampling clock of described AD sampling A is to be produced by programmable logic device (PLD) chip FPGA according to the sample frequency that the user imports, behind the sampling clock of AD sampling A, be connected to two divided-frequency rate circuit, this circuit produces the two divided-frequency signal of a sampling clock when producing sampled clock signal, this signal connects the selection port of control alternative change-over switch as the selection signal of reference signal, be input as 0 at this selection port, just selecting phase place is the reference signal of 0 degree, just to select phase place be the reference signals of 90 degree selecting port to be input as 1, described two divided-frequency rate circuit is arranged on FPGA inside, and described alternative change-over switch is an alternative change-over switch at a high speed.
2. a kind of signal supervisory instrument that is used for nuclear magnetic resonance according to claim 1 is characterized in that described selection signal sets up in advance than the rising edge or the negative edge of sampling clock.
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| CN 200410068160 CN1603856B (en) | 2004-11-15 | 2004-11-15 | Signal detection method for nuclear magnetic resonance |
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| CN 200410068160 CN1603856B (en) | 2004-11-15 | 2004-11-15 | Signal detection method for nuclear magnetic resonance |
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Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103424725B (en) * | 2013-08-26 | 2015-09-16 | 东南大学 | Based on the nuclear magnetic resonance chip radio frequency transmission channel of micro-control unit |
| CN103995293B (en) * | 2014-06-09 | 2017-02-15 | 桂林电子科技大学 | Method for detecting magnetic resonance sounding signals |
| CN105806868A (en) * | 2014-12-29 | 2016-07-27 | 丹东东方测控技术股份有限公司 | Digital nuclear magnetic resonance console device |
| CN104931901B (en) * | 2015-06-12 | 2017-09-29 | 杭州永川科技有限公司 | A kind of signal excitation and data acquisition device and method for magnetic induction image |
| CN116520223B (en) * | 2023-07-03 | 2023-08-25 | 北京化工大学 | Radio frequency transceiver of high-field spectrometer |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5585720A (en) * | 1995-10-23 | 1996-12-17 | Western Atlas International, Inc. | Signal processing method for multiexponentially decaying signals and application to nuclear magnetic resonance well logging tools |
| US5691641A (en) * | 1995-01-09 | 1997-11-25 | "O.D.A.M." Office De Distribution D'appareils Medicaux (Societe Anonyme) | NMR pickup device delivering a signal representative of breathing of a patient |
| CN1291288A (en) * | 1998-12-23 | 2001-04-11 | 凡利安股份有限公司 | Digital filter pre-charging for transient spectroscopies |
| CN1310345A (en) * | 2000-01-18 | 2001-08-29 | 通用电器横河医疗系统株式会社 | Radio-frequency coil, magnetic resonance imaging apparatus and receiving method of nuclear magnetic resonance signal |
| CN1455265A (en) * | 2002-05-02 | 2003-11-12 | 西门子公司 | Transmission method for magnetic resonance signal and relevant receiving device and magnetic resonance apparatus |
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Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5691641A (en) * | 1995-01-09 | 1997-11-25 | "O.D.A.M." Office De Distribution D'appareils Medicaux (Societe Anonyme) | NMR pickup device delivering a signal representative of breathing of a patient |
| US5585720A (en) * | 1995-10-23 | 1996-12-17 | Western Atlas International, Inc. | Signal processing method for multiexponentially decaying signals and application to nuclear magnetic resonance well logging tools |
| CN1291288A (en) * | 1998-12-23 | 2001-04-11 | 凡利安股份有限公司 | Digital filter pre-charging for transient spectroscopies |
| CN1310345A (en) * | 2000-01-18 | 2001-08-29 | 通用电器横河医疗系统株式会社 | Radio-frequency coil, magnetic resonance imaging apparatus and receiving method of nuclear magnetic resonance signal |
| CN1455265A (en) * | 2002-05-02 | 2003-11-12 | 西门子公司 | Transmission method for magnetic resonance signal and relevant receiving device and magnetic resonance apparatus |
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