CN108020799B - Nuclear magnetic resonance signal receiver and nuclear magnetic resonance equipment - Google Patents
Nuclear magnetic resonance signal receiver and nuclear magnetic resonance equipment Download PDFInfo
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- CN108020799B CN108020799B CN201610970983.0A CN201610970983A CN108020799B CN 108020799 B CN108020799 B CN 108020799B CN 201610970983 A CN201610970983 A CN 201610970983A CN 108020799 B CN108020799 B CN 108020799B
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- G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
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- G01R33/44—Arrangements or instruments for measuring magnetic variables involving magnetic resonance using nuclear magnetic resonance [NMR]
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Abstract
The invention provides a nuclear magnetic resonance signal receiver and nuclear magnetic resonance equipment, comprising: the analog anti-aliasing filter filters the received nuclear magnetic resonance signal and sends the filtered signal to the analog-to-digital converter; the analog-to-digital converter converts the filtered signals into digital signals; the analog anti-aliasing filter compensation module compensates the analog anti-aliasing filter, and the frequency response characteristic of the analog anti-aliasing filter compensation module is the reciprocal of the frequency response characteristic of the analog anti-aliasing filter; the quadrature detector converts a real number signal output by the analog anti-aliasing filter compensation module into orthogonal real part data and imaginary part data; the configurable double-architecture digital down-conversion processor performs data extraction and filtering on orthogonal real part data and imaginary part data, sends the extracted and filtered data to a control unit of the nuclear magnetic resonance scanning equipment, and the filtering corresponds to at least two groups of frequency response characteristics. The noise in-band and out-of-band is suppressed, and the dynamic range of the received nuclear magnetic resonance signal is increased.
Description
Technical Field
The invention relates to the technical field of medical equipment, in particular to a nuclear magnetic resonance signal receiver and nuclear magnetic resonance equipment.
Background
The magnetic resonance imaging signal is derived from a narrow-band radio frequency signal which is acquired by a receiver and modulated on a Larmor precession frequency, the radio frequency signal acquired by the receiver is processed by the receiver and is filled into a digital dot matrix, K space for short is magnetic resonance original digital data filling space with space positioning coding information, and the K space data is closely related to the magnetic resonance signal in space positioning. The magnetic resonance signal is stronger in the center of the K space and weaker in the periphery, and the signal amplitude dynamic range is large. Furthermore, the difference between the amplitudes of the signals in different sequences is also large, which requires a large dynamic range of the nmr signal receiver (hereinafter referred to as receiver). The dynamic range of a receiver refers to the ratio of the received signal peak strength to the total noise of the receiver.
Therefore, in order to improve the dynamic range of the nuclear magnetic resonance signal received by the receiver, there are two main approaches: increasing the strength of the amplitude of the received small signal or reducing the overall noise level of the receiver. Wherein, the small signal refers to the nuclear magnetic resonance signal with smaller amplitude.
However, the strength of the amplitude of the received small signal is mainly increased by amplifying the nuclear magnetic resonance signal with a small amplitude acquired by the receiver, but when the small signal is subjected to a large gain, although the quantization range of the analog-to-digital converter is fully utilized, the intermodulation component is also raised by a gain more than 2 times the signal gain, and the dynamic range of the actual signal is increased to a very limited extent.
Disclosure of Invention
In order to solve the technical problems in the prior art, the invention provides a nuclear magnetic resonance signal receiver and nuclear magnetic resonance equipment, which can effectively improve the dynamic range of nuclear magnetic resonance signals received by the receiver.
An embodiment of the present invention provides a nuclear magnetic resonance signal receiver, including: the system comprises an analog anti-aliasing filter, an analog-to-digital converter, an analog anti-aliasing filter compensation module, an orthogonal detector and a configurable double-architecture digital down-conversion processor;
the analog anti-aliasing filter is used for filtering the received nuclear magnetic resonance signal and sending the filtered signal to the analog-to-digital converter;
the analog-to-digital converter is used for converting the filtered signals into digital signals;
the analog anti-aliasing filter compensation module is used for compensating the analog anti-aliasing filter, and the frequency response characteristic of the analog anti-aliasing filter compensation module is the reciprocal of the frequency response characteristic of the analog anti-aliasing filter;
the quadrature detector is used for converting the real number signal output by the analog anti-aliasing filter compensation module into orthogonal real part data and imaginary part data;
the configurable double-architecture digital down-conversion processor is used for extracting and filtering orthogonal real part data and imaginary part data, and sending the extracted and filtered data to a control unit of the nuclear magnetic resonance scanning equipment, wherein the filtering corresponds to at least two groups of frequency response characteristics.
Preferably, the configurable dual-architecture digital down-conversion processor comprises: the system comprises an integrating comb filter, a dynamic configuration module, a group delay controller and at least two compensation filters: a first compensation filter and a second compensation filter;
the integral comb filter is used for carrying out data extraction on the orthogonal real part data and imaginary part data;
the dynamic configuration module is used for receiving a parameter configuration instruction of an upper computer and performing parameter configuration on the first compensation filter and the second compensation filter according to the parameter configuration instruction;
the first compensation filter corresponds to a first set of coefficient tables, and the first set of coefficient tables corresponds to a first set of frequency response characteristics;
the second compensation filter corresponds to a second set of coefficient tables, and the second set of coefficient tables corresponds to a second set of frequency response characteristics;
the group delay controller is used for compensating the delay caused by the first group coefficient table and the second group coefficient table.
Preferably, the configurable dual-architecture digital down-conversion processor comprises: the system comprises an integrating comb filter, a dynamic configuration module, a group delay controller and a compensation filter;
the integral comb filter is used for carrying out data extraction on the orthogonal real part data and imaginary part data;
the compensation filter corresponds to at least two groups of coefficient tables, different groups of coefficient tables correspond to different frequency response characteristics, and the bandwidth of the compensation filter corresponding to each frequency response characteristic is different;
the dynamic configuration module is used for receiving a parameter configuration instruction of an upper computer and selecting a corresponding coefficient table for the compensation filter according to the parameter configuration instruction;
and the group delay controller is used for compensating the delay caused by different coefficient tables.
Preferably, the method further comprises the following steps: a clock module;
the clock module is used for providing a reference clock for the analog-to-digital converter;
the clock module comprises a first phase-locked loop and a second phase-locked loop;
the first phase-locked loop is used for carrying out first-stage phase-locked jitter removal on a synchronous clock signal sent by nuclear magnetic resonance control equipment;
and the second phase-locked loop is used for carrying out second-stage phase-locked debouncing on the clock signal output by the first phase-locked loop and providing the debouncing clock signal to the analog-to-digital converter.
Preferably, the method further comprises the following steps: a programmable gain adjuster;
the programmable gain adjuster is used for amplifying or reducing the filtered signal output by the analog anti-aliasing filter to accord with the measuring range of the analog-to-digital converter.
Preferably, the configurable dual-architecture digital down-conversion processor further comprises: a logic switch unit;
the logic switch unit is configured to switch on the integrating comb filter and the first compensation filter or switch on the integrating comb filter and the second compensation filter.
Preferably, the method further comprises the following steps: an analog-to-digital converter driver;
the analog-to-digital converter driver is used for converting the signal input into the analog-to-digital converter from a single-ended signal to a differential signal.
Preferably, the method further comprises the following steps: and the optical fiber transmission module or the Li-Fi transmission module is used for transmitting the signals output by the configurable double-framework digital down-conversion processor to a control unit of nuclear magnetic resonance scanning equipment.
An embodiment of the present invention further provides a nuclear magnetic resonance scanning apparatus, including the nuclear magnetic resonance signal receiver, further including: a local coil and a control unit;
the local coil includes: at least one RF coil, each RF coil comprising RF coil elements, each RF coil element corresponding to a preamplifier;
and the control unit is used for controlling the receiver to receive the signal transmitted by the RF coil and receiving the signal processed by the receiver for imaging.
Compared with the prior art, the invention has at least the following advantages:
the analog anti-aliasing filter compensation module is arranged in the digital domain, so that the frequency response characteristic of the analog anti-aliasing filter in the analog domain can be compensated, and the compensated frequency response characteristic curve becomes flat. Additionally, a configurable dual-architecture DDC is provided that can configure multiple bandwidths. Therefore, different bandwidths are selected according to different application scenes to meet the requirements of nuclear magnetic resonance imaging. The analog anti-aliasing filter provided by the invention can effectively inhibit out-of-band noise, and the analog anti-aliasing filter compensation module can effectively inhibit in-band noise. Therefore, the receiver provided by the embodiment restrains the noise in-band and out-of-band, and increases the dynamic range of the received nuclear magnetic resonance signal.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments described in the present application, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a diagram of an embodiment of a nuclear magnetic resonance signal receiver according to the present invention;
FIG. 2 is a graph of the frequency response of the passband portion of the analog anti-aliasing filter provided by the present invention;
FIG. 3 is a graph of the frequency response of the pass band portion of the analog anti-aliasing filter compensation module provided by the present invention;
FIG. 4 is a schematic diagram of one embodiment of a configurable dual architecture digital down conversion processor provided in the present invention;
FIG. 5 is a schematic diagram of yet another embodiment of a configurable dual architecture digital down conversion processor provided in the present invention;
FIG. 6 is a schematic diagram of a clock module provided in the present invention;
fig. 7 is a schematic diagram of a nuclear magnetic resonance signal receiver according to a second embodiment of the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, a schematic diagram of an embodiment of a nuclear magnetic resonance signal receiver according to the present invention is shown.
The nuclear magnetic resonance signal receiver provided by the embodiment includes: an analog anti-aliasing filter 101, an analog-to-digital converter 102, an analog anti-aliasing filter compensation module 103, a quadrature detector 104 and a configurable dual-architecture digital down-conversion processor 105;
the overall noise figure of the receiver receive chain is controlled to be less than 0.55 db. The first stage of the receiving chain is a receiving coil, a preamplifier in the receiving chain plays a dominant role in the noise coefficient of the whole receiving chain, and the preamplifier in the receiving chain is designed to be a low-noise amplifier. Thus, the noise figure is lower than 0.5db, the gain is 27db, and the input impedance is less than 2 ohms. The preamplifier is not shown in fig. 1.
The analog anti-aliasing filter 101 is configured to filter a received nuclear magnetic resonance signal, and send the filtered signal to the analog-to-digital converter 102;
the analog-to-digital converter 102 is configured to convert the filtered signal into a digital signal;
in order to reduce the full bias value of the analog-to-digital converter, the quantization range of the analog-to-digital converter is increased. An analog-to-digital converter with a full bias amplitude of 1.5Vpp may be preferred, with an effective number of conversion bits above 14 bits, which is capable of recognizing signals above 91.5 microvolts. The data conversion rate of the analog-to-digital converter is more than 80MHz, and the oversampling of bandwidth signals is realized for the radio frequency signals of the magnetic resonance.
The analog anti-aliasing filter compensation module 103 is configured to compensate the analog anti-aliasing filter, and a frequency response characteristic of the analog anti-aliasing filter compensation module is an inverse of a frequency response characteristic of the analog anti-aliasing filter;
the passband index of the analog anti-aliasing filter 101 is designed to be 1MHz, and in order to increase the dynamic range of the analog signal, it is necessary to suppress the out-of-band noise by 80db or more. However, while the suppression of out-of-band noise of 80db or more is realized, the amplitude-frequency characteristic in the 1MHz passband fluctuates by more than 1db, and such in-band fluctuation causes severe nonlinearity in the band, which causes distortion of the receiver signal, and the flatness in the passband is not ideal. Therefore, according to the amplitude-frequency characteristic curve of the analog anti-aliasing filter 101 at 1MHz in the band, in the present embodiment, an analog anti-aliasing filter compensation module 103 is further added at the first stage of the digital domain. To achieve a higher flatness in the band. Higher flatness in-band can suppress noise in-band and increase dynamic range in-band. The analog-to-digital converter 102 in fig. 1 is preceded by the analog-to-digital converter 102 and followed by the digital-to-analog converter 102.
For the analog anti-aliasing filter compensation module 103, the main implementation is a compensation filter whose frequency response is the inverse of the frequency response of the analog anti-aliasing filter being compensated, as shown in fig. 3. By compensating fig. 2 with fig. 3, the compensated curve can be made flatter.
Since the frequency response expression of the analog anti-aliasing filter cannot be known, a fitting method needs to be used to find an approximate "optimal expression", for example, the fitting method may use a least square method, a fitting curve is selected according to the principle of least square sum of deviation, and polynomial fitting may be used to represent the in-band frequency response characteristic curve of the analog anti-aliasing filter, where the polynomial fitting may use a binomial form, as shown in fig. 3.
In designing the analog anti-aliasing filter, the design of the subsequent analog anti-aliasing filter compensation module 103 is considered, so that the frequency response characteristic curve is designed into a circular arc shape, and thus, the design of the analog anti-aliasing filter compensation module 103 can be realized by using a smaller order.
Fig. 2 is a frequency response curve graph of a passband portion of the analog anti-aliasing filter, and a polynomial fitting can be performed by extracting a plurality of points of the frequency response curve in fig. 2 to obtain a fitting function. The frequency response characteristic of the analog anti-aliasing filter compensation module 103 can be obtained by taking the reciprocal of the fitting function, and the coefficient of the filter can be further obtained by utilizing the frequency response characteristic of the analog anti-aliasing filter compensation module 103, namely, the compensation filtering processing can be completed by utilizing a digital signal processing chip.
The quadrature detector 104 is configured to convert the real signal output by the analog anti-aliasing filter compensation module into orthogonal real data and imaginary data;
the quadrature detector 104 is arranged in the digital domain in this embodiment. The analog quadrature detector has two problems:
firstly, the problem of unbalance of real part data and imaginary part data can cause the image to generate orthogonal artifacts;
secondly, the local oscillator leaks. The local oscillator leaks to the radio frequency coil, so that a serious cross modulation problem is caused, an extra frequency component is generated, and the frequency spectrum of a normal signal is interfered, so that the dynamic range of a magnetic resonance receiving signal is reduced.
While the quadrature detector 104 in this embodiment is placed after the second stage of the digital domain, the analog anti-aliasing filter compensation module. The digital domain quadrature detector avoids the problems of the analog quadrature detector described above.
The configurable double-architecture Digital Down Converter (DDC) 105 is configured to perform data extraction and filtering on orthogonal real part data and imaginary part data, and send the extracted and filtered data to a control unit of the nuclear magnetic resonance scanning apparatus, where the filtering corresponds to at least two sets of frequency response characteristics.
It is to be appreciated that the configurable dual-architecture DDC has a suppression effect on out-of-band noise.
The configurable dual-architecture DDC105 provided in this embodiment configures multiple bandwidths, and in practical applications, a corresponding bandwidth may be selected according to different needs, instead of only one bandwidth. For example, some have wider bandwidths and some have narrower bandwidths. For example, when the bandwidth is greater than 27.5kHz, the bandwidth is relatively wide; when the bandwidth is less than 27.5kHz, the bandwidth is narrow.
In the nuclear magnetic resonance signal receiver provided in this embodiment, the analog anti-aliasing filter compensation module 103 is provided in the digital domain, and can compensate the frequency response of the analog anti-aliasing filter in the analog domain, so that the compensated frequency response curve becomes flat. Additionally, a configurable dual-architecture DDC105 is also provided, where the configurable dual-architecture DDC105 can configure multiple bandwidths. Therefore, different bandwidths are selected according to different application scenes to meet the requirements of nuclear magnetic resonance imaging. The analog anti-aliasing filter provided by the invention can effectively inhibit out-of-band noise, and the analog anti-aliasing filter compensation module can effectively inhibit in-band noise. Therefore, the receiver provided by the embodiment restrains the noise in-band and out-of-band, and increases the dynamic range of the received nuclear magnetic resonance signal.
Referring to fig. 4, a schematic diagram of an embodiment of a configurable dual-architecture digital down-conversion processor provided in the present invention is shown.
The configurable dual-architecture digital down-conversion processor provided by the embodiment comprises: an integrating comb filter 105a, a dynamic configuration module 105b, a group delay controller 105c, and at least two compensation filters: a first compensation filter 105d and a second compensation filter 105 e;
it should be noted that, according to different requirements of image bandwidth, the configurable dual-architecture DDC provided by this embodiment configures multiple bandwidths to meet the requirements of images for different bandwidths. The configurable dual-architecture DDC provided by this embodiment implements multiple bandwidths by providing a plurality of compensation filters, each compensation filter corresponding to one bandwidth. It is understood that the configurable dual-architecture DDC may be implemented by a programmable logic control gate array FPGA.
The integrator comb filter 105a is configured to perform data extraction on the orthogonal real part data and imaginary part data;
the dynamic configuration module 105b is configured to receive a parameter configuration instruction of an upper computer, and perform parameter configuration on the first compensation filter 105d and the second compensation filter 105e according to the parameter configuration instruction;
it is understood that the parameter configuration instruction sent by the upper computer is used to configure the frequency response characteristics, i.e., select the bandwidth, for the first compensation filter 105d and the second compensation filter 105 e.
The first compensation filter 105d corresponds to a first set of coefficient tables corresponding to a first set of frequency response characteristics;
the second compensation filter 105e corresponds to a second set of coefficient tables, which corresponds to a second set of frequency response characteristics;
it will be appreciated that the first set of frequency response characteristics corresponds to at least two frequency response characteristics and the second set of frequency response characteristics corresponds to at least two frequency response characteristics.
It should be noted that the two compensation filters are arranged in this embodiment because in most application occasions, two common decimation rate ranges are generally needed, and therefore the two common decimation rate ranges are respectively corresponding to the two compensation filters, so that in practical application, the first compensation filter or the second compensation filter can be directly selected without being configured by an upper computer, thereby saving configuration time, improving scanning speed and shortening imaging time. Because of the high imaging time requirements in some applications.
In addition, in some scanning situations, it is found that the image quality is poor, and in this embodiment, the upper computer may configure the coefficient table of the compensation filter, and change the frequency response characteristic of the compensation filter, that is, increase the order and change the stop-band rejection ratio, so as to enhance the filtering effect, improve the signal-to-noise ratio, increase the dynamic range of the receiver receiving signals, and make the image quality better. Specifically, a plurality of parameters (including the extraction rate, the order, and even the overall coefficient of the compensation filter) can be dynamically configured through the dynamic configuration module, so that the frequency response characteristics of the filter can be arbitrarily changed (stop band rejection ratio, pass band ripple, width of pass band bandwidth, and the like). Therefore, the adjustment configuration of the configurable double-architecture DDC provided by the invention is more flexible than that of the DDC with a single architecture in the prior art, and the imaging effect is good and the speed is high.
In the coefficient table, parameters of the compensation filter are stored, and these parameters determine the bandwidth corresponding to the compensation filter.
The bandwidth of the first compensation filter 105d is narrower than the bandwidth of the second compensation filter 105 e;
the group delay controller 105c is configured to compensate for a delay caused by the first and second sets of coefficient tables.
The group delays corresponding to different orders in the coefficient table of the compensation filter are different, and for example, some delays are long and some delays are short, and the short delays can be compensated for each long delay with the long delays as a reference. That is, the group delay controller 105c is used to compensate the delay differences caused by different orders of the compensation filter dynamically configured for the same scanning sequence under the premise of a certain extraction rate. For example, the number of parameters of the compensation filter is small, and the corresponding group delay value is small. On the contrary, the number of parameters of the compensation filter is large, and the corresponding group delay value is large. Some fast scanning sequence imaging has high requirements on imaging speed, large bandwidth and small group delay of a receiver, does not cause group delay difference of the receiver without dynamically adjusting the order of a compensation filter, and can bypass the group delay controller 105 c.
It is understood that the embodiment is described by taking two compensation filters as an example, and may include more compensation filters, for example, three or four compensation filters, so as to correspond to more bandwidths. The following describes that different bandwidths may correspond to different image requirements by combining formulas.
In addition, one or two dynamic configuration modules 105b may be provided, and when one is provided, the dynamic configuration module 105b configures the parameter table for the first compensation filter 105d and the parameter table for the second compensation filter 105 e. When two dynamically configurable modules 105b are provided, one dynamically configurable module for each compensation filter.
The decimation rate R of the integrating comb filter 105a can be obtained by the following equation (1):
wherein R is the extraction rate, c is a predetermined constant, fsB is the sampling frequency and bandwidth.
The predetermined constant c may be set to 0.06875 at a large decimation rate (e.g., greater than 100) and to 0.1238 at a small decimation rate (e.g., less than 100).
The bandwidth B can be obtained by the following equation (2):
B＝γ×Gx×(FOV)x (2)
where γ is a gyromagnetic ratio defined as a ratio of an angular frequency to a magnetic induction intensity when an atom performs larmor precession in a magnetic field, and has a unit of rad/(sT).
GxIs the x-direction gradient strength.
The Field of View (FOV) of the imaging is the actual size of the image area in the frequency and phase encoding directions, the FOV being the acquisition array size x pixel size.
As can be seen from equation (2), when the imaging fields of view are different, the corresponding bandwidths are different, so that different bandwidths can be set to meet the imaging requirements. In the present embodiment, two compensation filters are provided, corresponding to two different bandwidths.
For a fast sequence working in a continuous sampling mode, the FOV requirement of the magnetic resonance system imaging is large, and as can be seen from formula 2, the sequence has a wide bandwidth requirement, generally more than 50KHz, and has not high requirements on stop band rejection ratio.
For a single scanning sequence, the extraction rate may be constant, but the pass-band bandwidth width of the filter and the stop-band rejection ratio of the frequency response characteristic need to be dynamically adjusted according to the image quality, and then the upper computer needs to obtain a dynamically updated coefficient table according to c and the coefficient table order in the formula (1), and in this case, a high image dynamic range is obtained by consuming a certain coefficient dynamic configuration time. In this case, the same sequence may be dynamically configured as a table of coefficients of different orders, and the group delay controller 105c is required to compensate for the different delays due to the differences in the group delay of the receivers.
As can be seen from equations (1) and (2), the conventional receiver providing a single DDC cannot be well adapted to the imaging requirements of different sequences, so that the configurable dual-architecture DDC provided by the present embodiment can provide two compensation filters according to different sequences. For sequences with narrow bandwidth requirements and high dynamic range requirements, a high-order compensation filter is used; for sequences with large bandwidth and not high dynamic range requirements, a low-order compensation filter can be used, which is beneficial to reducing the group delay of the system.
It is understood that the configurable dual-architecture digital down-conversion processor provided in fig. 4 meets the requirements of imaging for different bandwidths by setting at least two compensation filters for at least two bandwidths. In addition, a compensation filter is arranged, the compensation filter corresponds to a plurality of groups of coefficient tables, and each group of coefficient tables corresponds to one bandwidth, so that the requirements of imaging on different bandwidths can be met. Referring to fig. 5, a schematic diagram of a configurable dual-architecture digital down-conversion processor according to another embodiment of the present invention is shown.
The configurable dual architecture digital down conversion processor comprises: an integrating comb filter 105a, a dynamic configuration module 105b, a group delay controller 105c, and a compensation filter 105 f;
the integral comb filter is used for carrying out data extraction on the orthogonal real part data and imaginary part data;
the compensation filter corresponds to at least two groups of coefficient tables, different groups of coefficient tables correspond to different frequency response characteristics, and the bandwidth of the compensation filter corresponding to each frequency response characteristic is different;
the dynamic configuration module is used for receiving a parameter configuration instruction of an upper computer and selecting a corresponding coefficient table for the compensation filter according to the parameter configuration instruction;
and the group delay controller is used for compensating the delay caused by different coefficient tables.
It should be noted that both configurable dual-architecture digital down-conversion processors corresponding to multiple bandwidths can be implemented by an FPGA.
In addition, the present invention provides a two-stage phase-locked loop structure for reducing the overall jitter of the clock signal supplied to the analog-to-digital converter. The clock module is described in detail below with reference to the accompanying drawings.
Referring to fig. 6, a schematic diagram of a clock module provided by the present invention is shown.
The nuclear magnetic resonance signal receiver provided in this embodiment further includes: a clock module 106;
the clock module is used for providing a reference clock for the analog-to-digital converter;
the clock module includes a first phase-locked loop 106a and a second phase-locked loop 106 b;
the first phase-locked loop 106a is configured to perform first-stage phase-locked debouncing on a synchronous clock signal sent by the nuclear magnetic resonance control device;
the second phase-locked loop 106b is configured to perform second-stage phase-locked debounce on the clock signal output by the first phase-locked loop, and provide the debounced clock signal to the analog-to-digital converter.
The total jitter of a voltage-controlled oscillator externally arranged on a phase-locked loop is controlled within 120 femtoseconds. The clock output by the clock module to the analog-to-digital converter is lower than 180 femtoseconds, so that the signal-to-noise ratio of the analog-to-digital converter is over 78db, and the dynamic range reaches 156 db/Hz.
Referring to fig. 7, a schematic diagram of a second embodiment of a nuclear magnetic resonance signal receiver according to the present invention is shown.
The nuclear magnetic resonance signal receiver provided in this embodiment further includes: a programmable gain adjuster 107;
the programmable gain adjuster is used for amplifying or reducing the filtered signal output by the analog anti-aliasing filter to accord with the measuring range of the analog-to-digital converter.
In addition, the nuclear magnetic resonance signal receiver further includes: an analog-to-digital converter driver 108;
the analog-to-digital converter driver 108 is configured to convert the signal input to the analog-to-digital converter from a single-ended signal to a differential signal. And the analog-to-digital converter driver 108 may also perform impedance matching of the front and rear stages.
The nuclear magnetic resonance signal receiver further includes: and the optical fiber transmission module or the Li-Fi transmission module 109 is configured to transmit the signal output by the configurable dual-architecture digital down-conversion processor to a control unit of the nuclear magnetic resonance scanning device.
It is understood that the fiber optic transmission module is a wired transmission medium, while Li-Fi is a wireless transmission medium.
In addition, in this embodiment, the configurable dual-architecture digital down-conversion processor further includes: a logic switch unit;
the logic switch unit is configured to switch on the integrating comb filter and the first compensation filter or switch on the integrating comb filter and the second compensation filter.
That is, the logic switch unit is a multi-way switch, and when two compensation filters are included, the logic switch unit is just two switches. When the first compensation filter is selected to work, the integrating comb filter is switched on with the first compensation filter. When the second compensation filter is selected to work, the integrating comb filter is switched on with the second compensation filter. The corresponding compensation filter is directly selected to work through the logic switch unit, so that the corresponding required bandwidth is selected, parameter configuration can be carried out through an upper computer, two bandwidths can be available, the speed is high, and the configuration time is saved.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the invention in any manner. Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make numerous possible variations and modifications to the present teachings, or modify equivalent embodiments to equivalent variations, without departing from the scope of the present teachings, using the methods and techniques disclosed above. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention are still within the scope of the protection of the technical solution of the present invention, unless the contents of the technical solution of the present invention are departed.
Claims (9)
1. A nuclear magnetic resonance signal receiver, comprising: the system comprises an analog anti-aliasing filter, an analog-to-digital converter, an analog anti-aliasing filter compensation module, an orthogonal detector and a configurable double-architecture digital down-conversion processor;
the analog anti-aliasing filter is used for filtering the received nuclear magnetic resonance signal and sending the filtered signal to the analog-to-digital converter;
the analog-to-digital converter is used for converting the filtered signals into digital signals;
the analog anti-aliasing filter compensation module is used for compensating the analog anti-aliasing filter, and the frequency response characteristic of the analog anti-aliasing filter compensation module is the reciprocal of the frequency response characteristic of the analog anti-aliasing filter;
the quadrature detector is used for converting the real number signal output by the analog anti-aliasing filter compensation module into orthogonal real part data and imaginary part data;
the configurable dual-architecture digital down-conversion processor is used for extracting and filtering orthogonal real part data and imaginary part data, and sending the extracted and filtered data to a control unit of nuclear magnetic resonance scanning equipment, wherein the filtering of the configurable dual-architecture digital down-conversion processor corresponds to at least two groups of frequency response characteristics.
2. The nuclear magnetic resonance signal receiver of claim 1, wherein the configurable dual-architecture digital down-conversion processor comprises: the system comprises an integrating comb filter, a dynamic configuration module, a group delay controller and at least two compensation filters: a first compensation filter and a second compensation filter;
the integral comb filter is used for carrying out data extraction on the orthogonal real part data and imaginary part data;
the dynamic configuration module is used for receiving a parameter configuration instruction of an upper computer and performing parameter configuration on the first compensation filter and the second compensation filter according to the parameter configuration instruction;
the first compensation filter corresponds to a first set of coefficient tables, and the first set of coefficient tables corresponds to a first set of frequency response characteristics;
the second compensation filter corresponds to a second set of coefficient tables, and the second set of coefficient tables corresponds to a second set of frequency response characteristics;
the group delay controller is used for compensating the delay caused by the first group coefficient table and the second group coefficient table.
3. The nuclear magnetic resonance signal receiver of claim 1, wherein the configurable dual-architecture digital down-conversion processor comprises: the system comprises an integrating comb filter, a dynamic configuration module, a group delay controller and a compensation filter;
the integral comb filter is used for carrying out data extraction on the orthogonal real part data and imaginary part data;
the compensation filter corresponds to at least two groups of coefficient tables, different groups of coefficient tables correspond to different frequency response characteristics, and the bandwidth of the compensation filter corresponding to each frequency response characteristic is different;
the dynamic configuration module is used for receiving a parameter configuration instruction of an upper computer and selecting a corresponding coefficient table for the compensation filter according to the parameter configuration instruction;
and the group delay controller is used for compensating the delay caused by different coefficient tables.
4. The nuclear magnetic resonance signal receiver of any one of claims 1-3, further comprising: a clock module;
the clock module is used for providing a reference clock for the analog-to-digital converter;
the clock module comprises a first phase-locked loop and a second phase-locked loop;
the first phase-locked loop is used for carrying out first-stage phase-locked jitter removal on a synchronous clock signal sent by nuclear magnetic resonance control equipment;
and the second phase-locked loop is used for carrying out second-stage phase-locked debouncing on the clock signal output by the first phase-locked loop and providing the debouncing clock signal to the analog-to-digital converter.
5. The nuclear magnetic resonance signal receiver of claim 1, further comprising: a programmable gain adjuster;
the programmable gain adjuster is used for amplifying or reducing the filtered signal output by the analog anti-aliasing filter to accord with the measuring range of the analog-to-digital converter.
6. The nuclear magnetic resonance signal receiver of claim 2, wherein the configurable dual architecture digital down-conversion processor further comprises: a logic switch unit;
the logic switch unit is configured to switch on the integrating comb filter and the first compensation filter or switch on the integrating comb filter and the second compensation filter.
7. The nuclear magnetic resonance signal receiver of any one of claims 1-3, further comprising: an analog-to-digital converter driver;
the analog-to-digital converter driver is used for converting the signal input into the analog-to-digital converter from a single-ended signal to a differential signal.
8. The nuclear magnetic resonance signal receiver according to claim 2 or 3, further comprising: and the optical fiber transmission module or the Li-Fi transmission module is used for transmitting the signals output by the configurable double-framework digital down-conversion processor to a control unit of nuclear magnetic resonance scanning equipment.
9. A nuclear magnetic resonance scanning apparatus comprising the nuclear magnetic resonance signal receiver according to any one of claims 1 to 8, further comprising: a local coil and a control unit;
the local coil includes: at least one RF coil, each RF coil comprising RF coil elements, each RF coil element corresponding to a preamplifier;
and the control unit is used for controlling the receiver to receive the signal transmitted by the RF coil and receiving the signal processed by the receiver for imaging.
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| CN112462308A (en) * | 2020-10-21 | 2021-03-09 | 上海东软医疗科技有限公司 | Magnetic resonance signal receiving device and magnetic resonance equipment |
| CN112763956B (en) * | 2020-12-29 | 2022-02-15 | 电子科技大学 | Method for increasing dynamic range of magnetic resonance signal by scrambling technique |
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| JP4920478B2 (en) * | 2007-04-05 | 2012-04-18 | 株式会社東芝 | MRI equipment |
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