CN1489297A - Integrated magnetic resonance digital receiver - Google Patents
Integrated magnetic resonance digital receiver Download PDFInfo
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- CN1489297A CN1489297A CNA031504523A CN03150452A CN1489297A CN 1489297 A CN1489297 A CN 1489297A CN A031504523 A CNA031504523 A CN A031504523A CN 03150452 A CN03150452 A CN 03150452A CN 1489297 A CN1489297 A CN 1489297A
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Abstract
The invention relates to receiving device of nuclear magnetic resonance apparatus, and nuclear quadrupole resonance apparatus. The device comprises wideband low noise amplifier, mixer, high speed and high precision A/D converter as well as orthogonal digital frequency converter. First, input magnetic resonance signal enters to low noise preamplifier; next, entering to mixer, then passing through A/D converter; finally, entering to orthogonal digital frequency converter. Advantages of the invention are simple, flexible, integrative, low cost, precision output in continuous wide spectrum, high reliability and fast data transmission ability.
Description
Technical field
The present invention relates to the measurement mechanism or the instrument class of magnetic resonance, relate to the receiving system of a kind of nulcear magnetic resonance (NMR) and nuclear quadrupole resonance instrument concretely.
Background technology
In nulcear magnetic resonance (NMR) and nuclear quadrupole resonance spectrometer system, receiver plays a part to amplify and collecting magnetic resonance signal, its performance impact the signal to noise ratio of magnetic resonance spectrum.Usually, nuclear magnetic resonance spectrometer adopts traditional analog receiving system, because simulation quadrature detector reference signal wherein is difficult to accomplish complete quadrature, and measured signal is gathered respectively by the two-way amplifier and is amplified, their gain also is difficult to accomplish in full accord, thus can not eliminate the mirror image peak in the magnetic resonance spectrogram fully in actual applications, though, this mirror image peak available phases circulating technology overcomes, but has increased experimental period.The disclosed a kind of digital nuclear magnetic resonance receiver of application for a patent for invention prospectus in Chinese patent application number 00128169.0, this device has the following disadvantages: 1, digital receiver system is not sufficiently complete, only comprise Digital Down Convert and ADC unit, can not constitute complete broadband receiving system, realize the broadband signal measurement, also need beyond this system, to add complicated broadband frequency changer circuit; 2, the discrete IC module that function of use is single, cost height, volume are big; 3, adopted integer number filtering extraction technology, the spectrum width that can only obtain dispersing can not accurately be adjusted spectrum width according to the nuclear-magnetism experimental requirements; Above factor has determined these systems still can not satisfy the needs of modern mr techniques well.
Summary of the invention
The objective of the invention is to overcome above-mentioned the deficiencies in the prior art part, for modern magnetic resonance spectrum instrument system provides a kind of integrated, broadband, flexible, the convenient and practical magnetic resonance digital receiver of use.
The object of the invention realizes being finished by following technical scheme:
A kind of magnetic resonance digital receiver, mainly be by wideband low noise amplifier (Low NoiseAmplifier, LNA), frequency mixer (Local Oscillator, LO), high speed and high-precision analog to digital converter (ADC) and orthogonal digital low-converter (Digital Down Converter, DDC) constitute, wherein Shu Ru magnetic resonance signal at first arrives low-noise preamplifier, enters frequency mixer then, through analog to digital converter, enter the orthogonal digital low-converter at last again.
In the structure of above-mentioned receiver, can also include continuous Gain Adjustable amplifier (VariableGain Amplifier, VGA) and the folded filter of reflexed (Anti-alias Filter, AAF).
Adopt in local oscillation signal source in the frequency mixer be Direct Digital Frequency Synthesizers (Direct DigitalSynthesizer, DDS).
Described analog to digital converter refers to has 16 or above high-precision analog to digital converter.
Described digital down converter comprises the filter of digital multiplier, digital quadravalence comb filter, digital adjustable extraction yield.
Described analog to digital converter and digital down converter adopt Direct Digital Frequency Synthesizers (DDS) as sampling clock.
Above-mentioned receiver structure composition has adopted System on Chip/SoC System on Chip (SOC) technology, and being necessary parts are integrated on the chip piece.
Magnetic resonance signal is input to wideband low noise amplifier and amplifies, enter frequency mixer then and obtain intermediate-freuqncy signal, fold filter (AAF) after being mixed in the harmonic component filtering that might fold progressive die number converter (ADC) in the intermediate-freuqncy signal by reflexed then, the amplifier (VGA) of sending into continuous Gain Adjustable amplifies digital medium-frequency signal again, after amplifying conditioning, carry out direct intermediate frequency (IF) Sampling by analog to digital converter (ADC) again, finish detection by orthogonal digital low-converter (DDC) at last and obtain magnetic resonance signal.
In order to make the more complete wide-band applications of being convenient to of the present invention, the shortcoming of digital receiver before overcoming, the present invention has adopted the wideband signal source of direct digital frequency synthesis technology (Direct Digital Synthesizer) as the digital receiver local oscillator.At present, commercial signal source is (as Programmed TestSources, PTS) because cost an arm and a leg bulky, can not effectively reduce the cost of nuclear magnetic resonance spectrometer, and phase-locked loop (Phase Lock Loop, PLL) technology is again because its narrow relatively bandwidth and long switching time can not satisfy the demand of broadband nuclear magnetic resonance receiving system, but be to use the DDS technology to address these problems well.
The DDS that the present invention uses can produce the high-resolution sinusoidal signal in broadband, and DDS has very fast switching time simultaneously.Adopt the DDS technology, reduce production costs except having, the advantage such as broadband, switch speed are fast, also eliminated the phase noise that uses PHASE-LOCKED LOOP PLL TECHNIQUE to introduce, simultaneously, used DDS as the local oscillation signal source, make this device realize complete integrated digital receiver system, only need add a synchronizing signal just can satisfy the requirement that NMR signal phase coherence adds up.
In nuclear magnetic resonance experiment, the spectrum width of nuclear magnetic signal will actual conditions per sample be adjusted, to satisfy the demand of experiment.Usually, because digital receiver adopts the method for integer decimation filtering to handle digital medium-frequency signal, so its spectrum width expression formula can be write as
SW＝f
s/N
de，
F wherein
sBe the sampling clock of ADC and decimation filter, N
DeExtracting multiple for decimation filter of digital.From following formula as can be known because N
DeCan only round numbers, f usually
sRemain unchanged, the nulcear magnetic resonance (NMR) spectrum width that obtains also can only disperse.In order to overcome this difficulty, we have used the sampling clock of a slice DDS as receiver ADC and digital filter.F like this
sCan change with little hertz of precision.Basic ideas of the present invention are to utilize N
DeCome coarse adjustment spectrum width SW, again by f
sCome fine tuning SW.Though still use the method for integer decimation filtering, can realize that high-precision spectrum width is regulated, output by the sampling clock that DDS finely tunes receiver ADC and digital filter, satisfy the demand of modern nuclear magnetic resonance experiment.
Advantage of the present invention is as complete a, digital receiver system independently, use very easy, flexible, adopted the integrated design thinking, production cost is low, has realized the accurate output of continuous spectrum width, has improved the reliability of whole system, has very fast data transmittability, can with the miscellaneous part of spectrometer system as collaborative works such as digitized signal source, pulse-series generators, can also be as phased-array receiver, multichannel is sampled simultaneously.
Summary of drawings
Accompanying drawing 1 is schematic diagram in kind for the present invention uses;
Accompanying drawing 2 is structural representation of the present invention;
Accompanying drawing 3 is application structure schematic diagram of the present invention;
Accompanying drawing 4 is FPGA internal logic block diagram of the present invention;
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 technical staff's of the same trade understanding:
Shown in Fig. 1-4, label 1-9 is: the local oscillator (2) of digital receiver core (1), receiver core, the sampling clock (3) of receiver core, D: static memory (7) (8), NMR signal input (9) on the PCI bridge (5) of external reference clock input (4), special use, FPGA (6), the plate.
Whole receiver system work is mainly by SOC receiver core and Direct Digital Frequency Synthesizers (DDS), field-programmable gate array (Field Programmable Gate Array, FPGA), the peripheral devices interconnection (Peripheral Component Interconnect, PCI), the combinations such as (SRAM) of static high-speed internal memory finishes.
The receiver core mainly comprises wideband low noise amplifier (LNA), frequency mixer (LO), high speed 16 precision analog to digital converters (ADC) and orthogonal digital low-converter (DDC), and wherein digital down converter comprises the filter of digital multiplier, digital quadravalence comb filter, digital adjustable extraction yield.The receiver core is integrated on the chip piece
For the receiver core, at first, can amplify in advance to improve detection sensitivity with the one-level low-noise preamplifier from the magnetic resonance signal of probe output, also can directly import this receiver chip, again after the LNA of chip internal amplifies, be input to frequency mixer, obtain the digital medium-frequency signal after the demodulation; Then, the folded filter (AAF) of three rank reflexeds is sent into VGA after the harmonic component filtering that might fold ADC in the intermediate-freuqncy signal digital medium-frequency signal is amplified again being mixed in, after by VGA intermediate-freuqncy signal being nursed one's health, 16 Precision A C sample with high speed, can reach the dynamic range of about 95dB like this; At last, use DDC that it is carried out filtering extraction and obtain the base band NMR signal.Since the necessary parts such as the LNA of above-mentioned all receivers, VGA, LO, high-speed ADC, digital down converter all are integrated on the chip piece, only need a small amount of peripheral passive device, thereby simplified design greatly, realized integrated design, and had sizable bandwidth range.
In order to realize the integrated and integrality of receiver, present embodiment has adopted the signal source of DDS as the local oscillator of whole receiving system, radiofrequency signal (0-135MHz) from DDS output, be directly inputted to the local oscillator of digital received machine chip, on the DDS output, also can add nonlinear circuit, signal to output is done frequency multiplication and frequency-selecting, so that realize higher frequency.
In whole receiver system, also adopted the sampling clock of another sheet DDS as ADC and digital filter, adopt the sampling clock of DDS technology fine setting digital receiver core, so just realized accurate adjusting for magnetic resonance spectrum figure spectrum width.
In order to make this digital receiver system more flexible, improve reliability, reduce production costs, present embodiment has used the controller of field-programmable gate array (FPGA) as receiving baseband signal, as the master control chip on the plate, its effect is the sampling of sampling number, log-on data can be set, sampled data is deposited static memory (SRAM) on the plate.When it receives the startup sampled signal, just start sampling, the magnetic resonance signal of one group of quadrature of every reception, counter just adds one, till the sampled point numerical value that the numerical value in counter equals to preset, produces the end signal notice main frame of sampling simultaneously.In addition, FPGA also is responsible for receiver management to bus when data sampling.Consider to be applied in the Magnetic resonance imaging phase array receiving system, so in FPGA, reserved the triggering line of multichannel phase array.
When beginning to sample, main frame is provided with other parameters of sampling number, spectrum width and receiver in advance by pci bus, start sampling then, and sampling finishes, FPGA uses and interrupts or flag bit notice main frame, and main frame reads the MR data that obtains by pci bus then.
In the nulcear magnetic resonance (NMR) fast imaging, give main frame in order to transmit NMR signal in real time, need bus very fast.In this example, we have used pci (peripheral component interconnect) bus (PCI bridge) as the express passway that data transmit, and have used special-purpose pci bridge chip here, finish this function.Pci bus is at present in a lot of industrial control computers and the general bus mode that extensively adopts of home computer, this digital receiver adopts pci bus can be in expanded application scope farthest, also reduced simultaneously the production cost of whole spectrometer, use pci bus can also with the miscellaneous part of nuclear magnetic resonance spectrometer as (digitization frequencies source, pulse-series generator, the multi-path digital receiver) concurrent working.
Claims (7)
1, a kind of magnetic resonance digital receiver, it is characterized in that this receiver mainly is to be made of wideband low noise amplifier, frequency mixer, high speed and high-precision analog to digital converter and orthogonal digital low-converter, wherein Shu Ru magnetic resonance signal at first arrives low-noise preamplifier, enter frequency mixer then, through analog to digital converter, enter the orthogonal digital low-converter at last again.
2, a kind of magnetic resonance digital receiver according to claim 1 is characterized in that also including the amplifier and the folded filter of reflexed of continuous Gain Adjustable in the structure of described receiver.
3, a kind of magnetic resonance digital receiver according to claim 1, what it is characterized in that local oscillation signal source in the described frequency mixer adopts is Direct Digital Frequency Synthesizers.
4, a kind of magnetic resonance digital receiver according to claim 1 is characterized in that described high speed and high-precision analog to digital converter refer to and have 16 or above high-precision analog to digital converter.
5, a kind of magnetic resonance digital receiver according to claim 1 is characterized in that described digital down converter comprises the filter and the digital filter of digital multiplier, quadravalence comb filter, adjustable extraction yield.
6,, it is characterized in that described analog to digital converter and digital down converter adopt Direct Digital Frequency Synthesizers as sampling clock according to claim 1,4 or 5 described a kind of integral nuclear magnetic resonance digital receivers.
7, according to claim 1,2,3,4 or 5 described a kind of magnetic resonance digital receivers, it is characterized in that the parts that are necessary of described receiver all are integrated on the chip piece.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNA031504523A CN1489297A (en) | 2003-08-20 | 2003-08-20 | Integrated magnetic resonance digital receiver |
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| CNA031504523A CN1489297A (en) | 2003-08-20 | 2003-08-20 | Integrated magnetic resonance digital receiver |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1831552B (en) * | 2006-04-20 | 2010-05-12 | 华东师范大学 | Integral nuclear magnetic resonance spectrometer control stage bused on USB bus |
| CN101403715B (en) * | 2008-11-14 | 2011-11-09 | 中国科学院电工研究所 | Nano-upgrading sample nuclear magnetic resonance detection digital receiver |
| CN103309265A (en) * | 2013-05-21 | 2013-09-18 | 北京大学 | Small-sized nuclear magnetic resonance equipment controller used for one-dimensional spectrum analysis |
-
2003
- 2003-08-20 CN CNA031504523A patent/CN1489297A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1831552B (en) * | 2006-04-20 | 2010-05-12 | 华东师范大学 | Integral nuclear magnetic resonance spectrometer control stage bused on USB bus |
| CN101403715B (en) * | 2008-11-14 | 2011-11-09 | 中国科学院电工研究所 | Nano-upgrading sample nuclear magnetic resonance detection digital receiver |
| CN103309265A (en) * | 2013-05-21 | 2013-09-18 | 北京大学 | Small-sized nuclear magnetic resonance equipment controller used for one-dimensional spectrum analysis |
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