CN109714004B - Modulation method and modulation system of excitation pulse signal - Google Patents
Modulation method and modulation system of excitation pulse signal Download PDFInfo
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Abstract
The invention relates to a modulation method and a modulation system of an excitation pulse signal, wherein the method comprises the following steps: transmitting the first communication data; receiving first communication data, converting the first communication data to obtain second communication data and a PWM signal, and asynchronously sending the second communication data and the PWM signal; and asynchronously receiving the second communication data and the PWM signal, and modulating the excitation pulse signal according to the PWM signal and the second communication data. According to the modulation method and the modulation system of the excitation pulse signal, the first communication data, the second communication data and the PWM signal are asynchronously transmitted, the first communication data is used for controlling the second communication data and the PWM signal, the PWM signal and the second communication data are used for jointly controlling the excitation pulse signal, the precise control of the excitation pulse signal is realized, an effective excitation source is provided for the magnetic resonance signal, and the signal intensity and the signal to noise ratio of the magnetic resonance signal are improved.
Description
Technical Field
The invention relates to the technical field of nuclear magnetic resonance detection, in particular to a modulation method and a modulation system of an excitation pulse signal.
Background
Nuclear Quadrupole Resonance (NQR) is a Magnetic Resonance phenomenon related to Nuclear Magnetic Resonance (NMR) and Magnetic Resonance Imaging (MRI), and since it only detects substance molecules of an object to be detected, and is not affected by other factors such as metal materials, shells, shapes, etc., it is a more essential substance identification means, and is widely used in the fields of detection mines, petroleum resource exploration, geological petroleum logging, drug detection, pharmaceutical preparation, mineral detection, etc.
The method for detecting the NQR to the object to be detected can be realized by generating an excitation pulse signal used as an excitation source in a mode of adjustable pulse carrier modulation, exciting the object to be detected by using the excitation pulse signal to generate the NQR signal, but the form of the excitation pulse signal directly influences the NQR signal, for example: if the initial phases of the excitation pulse signals are not consistent, the NQR signals may also have different initial phases, and a phase detection (PSD) module is generally required to be added to make the phases of the NQR signals consistent, so as to improve the signal-to-noise ratio of the NQR signals.
However, the above method is limited to controlling the NQR signals, lacks phase control of the excitation pulse signals, and fails to provide an effective excitation source for the NQR signals, which is not conducive to subsequent processing of the NQR signals.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a modulation method and a modulation system of an excitation pulse signal, aiming at the defects that the excitation pulse signal is used as an excitation source for detecting an object to be detected by magnetic resonance, the excitation pulse signal lacks phase control, and an effective excitation source cannot be provided for the magnetic resonance signal in the prior art.
The technical scheme for solving the technical problems is as follows:
according to a first aspect of the present invention, there is provided a method for modulating an excitation pulse signal, comprising the following steps:
and step 130, asynchronously receiving the second communication data and the PWM signal, and modulating an excitation pulse signal according to the PWM signal and the second communication data.
The first aspect of the invention has the beneficial effects that: different first communication data can be converted into different second communication data and different PWM signals through asynchronous transmission of the first communication data, the second communication data and the PWM signals, asynchronous control of the second communication data and the PWM signals is achieved, the excitation pulse signals are controlled through the second communication data and the PWM signals together, accurate control of the excitation pulse signals is achieved, and the signal intensity and the signal to noise ratio of magnetic resonance signals generated when the excitation pulse signals serve as excitation sources can be improved.
Further, the step 110 is specifically implemented as:
step 111, setting pulse signal parameters on a user interface, wherein the pulse signal parameters comprise: pulse width, pulse interval, pulse number, pulse amplitude, resonance frequency and carrier frequency initial phase;
step 112, packing the pulse signal parameters according to a serial port communication protocol to obtain the first communication data;
and 113, sending the first communication data through a first communication interface.
The beneficial effects of the further scheme are as follows: through human-computer interaction on a user interface, a user can conveniently and visually set pulse signal parameters to realize accurate control of the pulse signal parameters, and communication data frames are sent through a serial port communication protocol and serial port communication, so that the sending mode of the pulse signal parameters is simplified, and the real-time control of the pulse signal parameters is realized.
Further, the step 120 is specifically implemented as:
step 121, receiving the first communication data through the first communication interface, and analyzing the first communication data according to the serial port communication protocol to obtain the pulse width, the pulse interval, the number of pulses, the pulse amplitude, the resonance frequency, and the carrier frequency initial phase;
step 122, digitally encoding the analog signal level according to the pulse width, the pulse interval and the number of pulses to obtain the PWM signal;
step 123, performing digital conversion on the pulse amplitude to obtain an amplitude control word, performing digital conversion on the resonance frequency to obtain a frequency control word, and performing digital conversion on the carrier frequency initial phase to obtain a phase control word;
step 124, packing the amplitude control word, the frequency control word and the phase control word according to the serial port communication protocol to obtain the second communication data;
and step 125, after the second communication data is sent through the second communication interface, sending the PWM signal through the second communication interface.
The beneficial effects of the above further scheme are: the pulse width and the duty ratio of the PWM signals can be controlled, the pulse amplitude, the resonance frequency and the carrier frequency initial phase are respectively and accurately converted into corresponding control words, different excitation pulse signal sequences can be modulated, and the amplitude, the frequency and the phase of the excitation pulse signals can be accurately controlled and generated.
Further, in step 121, receiving the first communication data through the first communication interface, specifically implemented as:
periodically inquiring data identification bits in the first communication data;
and judging whether the data identification bit is true, if so, indicating that the first communication data is synchronously received through the first communication interface, and if not, continuously inquiring the data identification bit.
The beneficial effects of the further scheme are as follows: the first communication data is received through the inquiry method, the integrity and the correctness of the first communication data are guaranteed, and compared with the method of receiving the communication data through an interruption method, the difficulty of receiving the first communication data is reduced.
Further, the step 130 is specifically implemented as:
step 131, receiving the second communication data through the second communication interface, analyzing the second communication data according to the serial port communication protocol to obtain the amplitude control word, the frequency control word and the phase control word, and storing the amplitude control word, the frequency control word and the phase control word in a register;
step 132, receiving the PWM signal through the second communication interface, and reading the amplitude control word, the frequency control word, and the phase control word in the register according to the PWM signal;
step 133, performing direct digital frequency synthesis on the read amplitude control word, frequency control word and phase control word to obtain a carrier frequency signal;
and step 134, performing envelope control on the carrier frequency signal according to a pulse signal envelope control window in the PWM signal to obtain the excitation pulse signal, where each sine wave sequence in the excitation pulse signal corresponds to a high level in each pulse signal envelope control window.
The beneficial effects of the further scheme are as follows: carrying out direct digital frequency synthesis on the amplitude control word, the frequency control word and the phase control word to obtain a carrier frequency signal and realize waveform control of the carrier frequency signal; the PWM signal is used as an envelope signal to accurately control the excitation time of the carrier frequency signal, so that the accurate control of the excitation pulse signal is realized, and the continuity and stability of the excitation pulse signal in time are improved.
According to a second aspect of the invention, a modulation system of an excitation pulse signal is provided, which comprises an upper computer, a lower computer and an excitation pulse signal generator, wherein the upper computer, the lower computer and the excitation pulse signal generator are sequentially connected through a communication interface;
the upper computer is used for sending first communication data;
the lower computer is used for receiving the first communication data, converting the first communication data to obtain second communication data and a PWM signal, and asynchronously sending the second communication data and the PWM signal;
the excitation pulse signal generator is used for asynchronously receiving the second communication data and the PWM signal and modulating the excitation pulse signal according to the PWM signal and the second communication data.
The second aspect of the invention has the advantages that: the lower computer receives the first communication data sent by the upper computer and asynchronously sends the second communication data and the PWM signal to realize asynchronous control of the first communication data, the second communication data and the PWM signal, the excitation pulse signal generator modulates the excitation pulse signal together according to the second communication data and the PWM signal to realize accurate control of the excitation pulse signal, an effective excitation source is provided for the magnetic resonance signal (such as an NQR signal), and the signal intensity and the signal-to-noise ratio of the magnetic resonance signal are improved.
Further, the host computer includes first communication interface, the host computer pass through first communication interface with the next computer is connected, the host computer specifically is used for:
set up the pulse signal parameter on the user interface of host computer, the pulse signal parameter includes: pulse width, pulse interval, pulse number, pulse amplitude, resonance frequency and carrier frequency initial phase;
packaging the pulse signal parameters according to a serial port communication protocol to obtain first communication data;
and sending the first communication data through the first communication interface.
The beneficial effects of the further scheme are as follows: the upper computer provides a human-computer interaction user interface for a user, the user can conveniently and accurately set pulse signal parameters, the user can control the pulse signal parameters in real time, the pulse signal parameters are transmitted through serial port communication between the upper computer and the lower computer, and the pulse signal control system has the advantages of low cost, visualization, human-computer real-time interaction and the like.
Further, the lower computer comprises a second communication interface, the lower computer is connected with the excitation pulse signal generator through the second communication interface, and the lower computer is specifically used for:
receiving the first communication data through the first communication interface, and analyzing the first communication data according to the serial port communication protocol to obtain the pulse width, the pulse interval, the number of pulses, the pulse amplitude, the resonance frequency and the carrier frequency initial phase;
carrying out digital coding on the analog signal level according to the pulse width, the pulse interval and the pulse number to obtain the PWM signal;
carrying out digital conversion on the pulse amplitude to obtain an amplitude control word, carrying out digital conversion on the resonance frequency to obtain a frequency control word, and carrying out digital conversion on the carrier frequency initial phase to obtain a phase control word;
packing the amplitude control word, the frequency control word and the phase control word according to the serial port communication protocol to obtain second communication data;
and after the second communication data is sent through the second communication interface, sending the PWM signal through the second communication interface.
The beneficial effects of the above further scheme are: the lower computer accurately modulates PWM signals according to pulse width, pulse interval and pulse number, and accurately modulates different excitation pulse signal sequences by utilizing pulse amplitude, resonance frequency and carrier frequency initial phase to realize accurate control on the amplitude, frequency and phase of the excitation pulse signals; in addition, the lower computer is based on a serial communication protocol and a serial communication protocol, communication data are asynchronously transmitted between the upper computer and excitation pulse signal parameters, excitation pulse signal control is achieved, and the method has the advantages of being low in cost, strong in flexibility, simple in design and the like.
Further, the lower computer is also specifically configured to:
periodically inquiring data identification bits in the first communication data;
and judging whether the data identification bit is true, if so, indicating that the first communication data is synchronously received through the first communication interface, and if not, continuously inquiring the data identification bit.
The beneficial effects of the further scheme are as follows: the lower computer checks the synchronism of the first communication data transmitted and received through the first communication interface in a mode of periodically inquiring the data identification bits in the first communication data, so that the integrity and the correctness of the first communication data are guaranteed, and the receiving difficulty of the first communication data is reduced.
Further, the excitation pulse signal generator includes a direct digital frequency synthesizer DDS and a register, the second communication interface is electrically connected to the register through the DDS, and the DDS is specifically configured to:
receiving the second communication data through the second communication interface, analyzing the second communication data according to the serial port communication protocol to obtain the amplitude control word, the frequency control word and the phase control word, and storing the amplitude control word, the frequency control word and the phase control word into the register;
receiving the PWM signal through the second communication interface, and reading the amplitude control word, the frequency control word and the phase control word in the register according to the PWM signal;
performing direct digital frequency synthesis on the read amplitude control word, the frequency control word and the phase control word to obtain a carrier frequency signal;
and according to a pulse signal envelope control window in the PWM signal, carrying out envelope control on the carrier frequency signal to obtain the excitation pulse signal, wherein each sine wave sequence in the excitation pulse signal corresponds to a high level in each pulse signal envelope control window.
The beneficial effects of the above further scheme are: the excitation pulse signal generator carries out direct digital frequency synthesis on the amplitude control word, the frequency control word and the phase control word to obtain a carrier frequency signal, and takes the PWM signal as an envelope signal to realize the waveform control of the carrier frequency signal and accurately control the excitation time of the carrier frequency signal to realize the accurate control of the excitation pulse signal and improve the continuity and the stability of the excitation pulse signal in time.
Drawings
Fig. 1 is a schematic flowchart of a modulation method of an excitation pulse signal according to an embodiment of the present invention;
fig. 2 is a schematic flow chart of serial port communication according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a test single excitation pulse signal sequence provided by an embodiment of the present invention;
FIG. 4 is a schematic diagram of a user interface provided by an embodiment of the present invention;
FIG. 5 is a schematic diagram of a test periodic excitation pulse signal sequence provided by an embodiment of the present invention;
fig. 6 is a schematic structural diagram of a modulation system of an excitation pulse signal according to an embodiment of the present invention;
FIG. 7 is a diagram illustrating a control window for an envelope of a test pulse signal according to an embodiment of the present invention;
fig. 8 is a schematic diagram of a test excitation pulse signal according to an embodiment of the present invention.
Detailed Description
The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.
Example one
As shown in fig. 1, a schematic flowchart 100 of a modulation method of an excitation pulse signal according to an embodiment of the present invention is described with a nuclear quadrupole resonance NQR signal as a magnetic resonance signal, and includes the following specific steps:
and step 130, asynchronously receiving the second communication data and the PWM signal, and modulating the excitation pulse signal according to the PWM signal and the second communication data.
In the present embodiment, as shown in fig. 2, the PC terminal transmits first communication data to the control device through the USB interface; the control device analyzes the first communication data after receiving the first communication data to obtain pulse signal parameters, converts the pulse signal parameters to obtain second communication data and PWM signals, and asynchronously sends the second communication data and the PWM signals to the excitation pulse signal generator; the excitation pulse signal generator asynchronously receives the second communication data and the PWM signal, direct digital frequency synthesis is carried out on the second communication data according to the PWN signal, and an excitation pulse signal is obtained and is a sine wave sequence which is used for exciting the object to be detected and then generating a nuclear quadrupole resonance NQR signal.
For example: as shown in fig. 3, the resonance time of the single sine wave sequence is equal to the duration of the high level of the PWM signal, and the center frequency of the single sine wave sequence is one of the pulse signal parameters.
Different first communication data can be converted into different second communication data and different PWM signals through asynchronous transmission of the first communication data, the second communication data and the PWM signals, asynchronous control of the second communication data and the PWM signals is achieved, the excitation pulse signals are controlled through the second communication data and the PWM signals together, accurate control of the excitation pulse signals is achieved, and the signal intensity and the signal to noise ratio of magnetic resonance signals generated when the excitation pulse signals serve as excitation sources can be improved.
Preferably, step 110 is implemented as:
step 111, setting pulse signal parameters on a user interface, wherein the pulse signal parameters comprise: pulse width, pulse interval, pulse number, pulse amplitude, resonance frequency and carrier frequency initial phase;
step 112, packing the pulse signal parameters according to a serial port communication protocol to obtain first communication data;
step 113, sending the first communication data through the first communication interface.
As shown in fig. 4, in the user interface on the PC terminal of the present embodiment, a user can input a pulse signal parameter on the user interface, and the user interface may be a user interface developed by using LabVIEW or VB language; then, the PC terminal converts the pulse signal parameters into 16-system character strings, encodes the character strings to obtain data blocks, and packages the data blocks according to a serial port communication protocol to obtain first communication data; the serial port communication protocol is shown in table 1.
TABLE 1 Serial port communication protocol
The PC terminal is provided with a Virtual serial port driver (for example, USB _ Virtual _ Com), and establishes serial port communication with the control device through a Virtual serial port, wherein the Virtual serial port can be a first communication interface.
Through human-computer interaction on a user interface, a user can conveniently and visually set pulse signal parameters to realize accurate control of the pulse signal parameters, and communication data frames are sent through a serial port communication protocol and serial port communication, so that the sending mode of the pulse signal parameters is simplified, and the real-time control of the pulse signal parameters is realized.
Preferably, step 120 is implemented as:
and step 121, receiving the first communication data through the first communication interface, and analyzing the first communication data according to a serial port communication protocol to obtain a pulse width, a pulse interval, a pulse number, a pulse amplitude, a resonance frequency and a carrier frequency initial phase.
And step 122, carrying out digital coding on the analog signal level according to the pulse width, the pulse interval and the number of pulses to obtain a PWM signal.
Step 123, performing digital conversion on the pulse amplitude to obtain an amplitude control word, performing digital conversion on the resonance frequency to obtain a frequency control word, and performing digital conversion on the initial phase of the carrier frequency to obtain a phase control word;
and step 124, packing the amplitude control word, the frequency control word and the phase control word according to a serial port communication protocol to obtain second communication data.
And step 125, after the second communication data is sent through the second communication interface, sending the PWM signal through the second communication interface.
For example: referring to fig. 5, the excitation pulse signal is 5 sine wave sequences, the pulse width of the first sine wave sequence is 5us, the pulse widths of the second to fifth sine wave sequences are 10us, the pulse interval is 1-3us, the resonance frequency is 4.6MHz, the pulse amplitude is full scale, and the initial phase of the carrier frequency is 90 degrees.
The amplitude control word is obtained by converting the pulse amplitude according to a first formula, wherein the first formula is as follows:
ASF＝2 14 ×A
where ASF stands for amplitude control word and a stands for pulse amplitude.
The frequency control word is obtained by converting the pulse frequency according to a second formula, wherein the second formula is as follows:
wherein FTW represents an amplitude control word, F OUT Representing the pulse frequency, F SYSCLK Represents the command response time, which represents the total time for the first and second communication interfaces to receive the return command.
The phase control word is obtained by converting the carrier frequency initial phase by a second formula, wherein the second formula is as follows:
wherein, POW represents the phase control word, and Δ θ represents the initial phase of the carrier frequency.
The PC terminal comprises a USB interface, the control device comprises a data sending pin TXD and an I/O port, the PC terminal sends first communication data to the control device through the USB interface, the control device sends second communication data to the excitation pulse signal generator through the data sending pin TXD, and the control device sends PWM signals to the excitation pulse signal generator through the I/O port; the USB is used as a first communication interface, and the sending data pin and the I/O port are used as a second communication interface.
The method has the advantages that the PWM signals are precisely controlled and generated according to the pulse width, the pulse interval and the pulse number, the pulse width and the duty ratio of the PWM signals can be controlled, the pulse amplitude, the resonance frequency and the carrier frequency initial phase are respectively and precisely converted into corresponding control words, different excitation pulse signal sequences can be modulated, and the amplitude, the frequency and the phase of the excitation pulse signals can be precisely controlled.
Preferably, in step 121, receiving the first communication data through the first communication interface, specifically implemented as: periodically inquiring a data identification bit in the first communication data; and judging whether the data identification bit is true, if so, indicating that the first communication data is synchronously received through the first communication interface, and if not, continuously inquiring the data identification bit.
And judging the initial identification bit and the end identification bit in the first communication data according to the receiving period of the first communication data, if the initial identification bit and the end identification bit are true, indicating that the first communication data is synchronously and completely received through the first communication interface, otherwise, indicating that the first communication data is not synchronously received through the first communication interface, and continuously inquiring the initial identification bit and the end identification bit in the next first communication data.
The first communication data are received through the inquiry method, the integrity and the correctness of the first communication data are guaranteed, and compared with the method of receiving data frames through an interruption method, the receiving difficulty of the first communication data is reduced.
Preferably, step 130 is implemented as:
and 131, receiving second communication data through the second communication interface, analyzing the second communication data according to a serial port communication protocol to obtain an amplitude control word, a frequency control word and a phase control word, and storing the amplitude control word, the frequency control word and the phase control word into a register.
Step 132, receiving the PWM signal through the second communication interface, and reading the amplitude control word, the frequency control word, and the phase control word in the register according to the PWM signal.
And step 133, performing direct digital frequency synthesis on the read amplitude control word, frequency control word and phase control word to obtain a carrier frequency signal.
And step 134, carrying out envelope control on the carrier frequency signal according to the pulse signal envelope control window in the PWM signal to obtain an excitation pulse signal, wherein each sine wave sequence in the excitation pulse signal corresponds to the high level in each pulse signal envelope control window.
As shown in fig. 5, each sequence of sine waves in the high level envelope excitation pulse signal in the pulse signal envelope control window is spaced apart from each sequence of sine waves in the low level envelope excitation pulse signal in the pulse signal envelope control window.
The excitation pulse signal generator carries out direct digital frequency synthesis on the amplitude control word, the frequency control word and the phase control word to obtain a carrier frequency signal, waveform control of the carrier frequency signal is achieved, the PWM signal is used as an envelope signal, resonance time of the carrier frequency signal is accurately controlled, accurate control of the excitation pulse signal is achieved, and continuity and stability of the excitation pulse signal in time are improved.
Example two
In this embodiment, as shown in fig. 6, a schematic structural diagram of a modulation system of an excitation pulse signal according to an embodiment of the present invention includes an upper computer, a lower computer, and an excitation pulse signal generator, where the upper computer, the lower computer, and the excitation pulse signal generator are sequentially connected through a communication interface.
The upper computer is used for sending first communication data; the lower computer is used for receiving the first communication data, converting the first communication data to obtain second communication data and a PWM signal, and asynchronously sending the second communication data and the PWM signal; the excitation pulse signal generator is used for asynchronously receiving the second communication data and the PWM signal and modulating the excitation pulse signal according to the PWM signal and the second communication data.
The upper computer comprises a first communication interface which can be a USB interface, the upper computer is in serial port communication with the lower computer through the USB interface, the USB interface transmits pulse signal parameters to the lower computer from the upper computer, and the lower computer packages the pulse signal parameters according to a serial port communication protocol to obtain first communication data; the lower computer can be further connected with a keyboard, the keyboard is used for inputting pulse signal parameters to the lower computer, the pulse signal parameters are finely adjusted through the keyboard, and the lower computer updates the first communication data to the pulse signal parameter packets according to serial port communication analysis.
The lower computer can adopt STM32F103 series chips, the core working frequency in the STM32F103 series chips can reach 72MHz at most, a built-in high-speed memory (512 KB Flash and 64KB SRAM) is provided with abundant I/O ports and a large number of peripherals connected to two internal APB buses, and 2 12-bit analog-to-digital converters (AD)C,2 universal 16-bit timer, 2 IC bus I 2 C,2 serial peripheral interfaces SPI,3 universal synchronous asynchronous transceivers USART,1 universal serial bus USB and 1 controller area network CAN, etc.
The excitation pulse signal generator can adopt AD9910, the AD9910 is integrated with a direct digital frequency synthesis chip and a register, the internal clock speed can reach 1GSPS, a carrier frequency signal with specified frequency can be output, and the carrier frequency signal has the advantages of high precision, good stability and continuous phase.
An I/O port (for example: a PC0 port) and a sending data pin TXD on the lower computer are used as a second communication interface, a timer TIM2 arranged in the lower computer overturns the I/O interface in the second communication interface, the pulse width of the PWM signal is controlled through the I/O interface in the second communication interface, and if the I/O interface outputs the specified pulse number, the timer TIM2 is closed. And the square wave is output by software I/O simulation, so that the frequency, the duty ratio and the pulse number of the PWM signal are adjustable.
An I/O port in the second communication interface is electrically connected with an OSK pin on the AD9910, and the lower computer sends a PWM signal to the OSK pin through the I/O port in the second communication interface; and a transmitting data pin TXD in the second communication interface is electrically connected with the I/0 _UPDATEport on the AD9910, and the lower computer transmits the second communication data to the I/0 _UPDATEport through the transmitting data pin TXD in the second communication interface.
The lower computer receives the first communication data sent by the upper computer and asynchronously sends the second communication data and the PWM signal to realize asynchronous control of the first communication data, the second communication data and the PWM signal, the excitation pulse signal generator jointly modulates the excitation pulse signal according to the second communication data and the PWM signal to realize precise control of the excitation pulse signal, an effective excitation source is provided for a magnetic resonance signal (such as an NQR signal), and the signal intensity and the signal-to-noise ratio of the magnetic resonance signal are improved.
Preferably, the host computer includes first communication interface, and the host computer passes through first communication interface to be connected with the next machine, and the host computer machine body is used for: set up the pulse signal parameter on the user interface of host computer, the pulse signal parameter includes: pulse width, pulse interval, pulse number, pulse amplitude, resonance frequency and carrier frequency initial phase; packaging the pulse signal parameters according to a serial port communication protocol to obtain first communication data; the first communication data is transmitted through the first communication interface.
The user interface can be a Labview based on a graphic language as a development tool, a program is written in a mode of replacing text with icons and connecting lines, serial port communication design of an upper computer is completed by using a serial port program to design a VISA library editing function, compared with other programming language tools, the development speed is 4-10 times faster, and the Labview based on the graphic language is easy to learn and use and does not relate to a complex bottom layer programming technology.
The upper computer provides a human-computer interaction user interface for a user, the user can conveniently and accurately set pulse signal parameters, the user can control the pulse signal parameters in real time, the pulse signal parameters are transmitted through serial port communication between the upper computer and the lower computer, and the pulse signal control system has the advantages of low cost, visualization, human-computer real-time interaction and the like.
Preferably, the lower computer comprises a second communication interface, the lower computer is connected with the excitation pulse signal generator through the second communication interface, and the lower computer is used for: receiving first communication data through a first communication interface, and analyzing the first communication data according to a serial port communication protocol to obtain pulse width, pulse interval, pulse number, pulse amplitude, resonance frequency and carrier frequency initial phase; carrying out digital coding on the analog signal level according to the pulse width, the pulse interval and the number of pulses to obtain a PWM signal; carrying out digital conversion on the pulse amplitude to obtain an amplitude control word, carrying out digital conversion on the resonance frequency to obtain a frequency control word, and carrying out digital conversion on the initial phase of the carrier frequency to obtain a phase control word; packing the amplitude control word, the frequency control word and the phase control word according to a serial port communication protocol to obtain second communication data; and after the second communication data is sent through the second communication interface, the PWM signal is sent through the second communication interface.
For example: the STM32 chip outputs a PWM signal based on the pulse width, pulse spacing, and number of pulses through a function, which is shown below,
int8_t Set_PWM_Out(uint32_t frequency,uint8_t Duty,uint32_t Number)
wherein, frequency represents the frequency of the PWM signal, duty represents the Duty ratio of the PWM signal, and Number represents the Number of pulses in the PWM signal.
The lower computer accurately controls the PWM signals according to the pulse width, the pulse interval and the number of pulses, so that the pulse period, the pulse width and the pulse interval in the PWM signals are controlled, and the flexibility of parameter setting and the controllability of the PWM signals are improved; the three control words are used for modulating different excitation pulse signal sequences to realize the precise control of the amplitude, the frequency and the phase of the excitation pulse signals; in addition, the lower computer is based on serial communication and serial communication protocols, communication data are asynchronously transmitted between the upper computer and excitation pulse signal parameters, control over excitation pulse signals is achieved, and the method has the advantages of being low in cost, high in flexibility, simple in design and the like.
Preferably, the lower machine tool is used for: periodically inquiring a data identification bit in the first communication data; and judging whether the data identification bit is true, if so, indicating that the first communication data is synchronously received through the first communication interface, and if not, continuously inquiring the data identification bit.
The lower computer periodically inquires the data identification bits in the first communication data, the data identification bits comprise a starting identification bit and an ending identification bit, under the condition that the starting identification bit and the ending identification bit are true, the first communication data are synchronously and completely received through the first communication interface, the synchronization of receiving and sending the first communication data through the first communication interface is guaranteed, the integrity and the correctness of the first communication data are guaranteed, and the receiving difficulty of the first communication data is reduced.
Preferably, the excitation pulse signal generator includes a direct digital frequency synthesizer DDS and a register, the second communication interface is electrically connected to the register through the DDS, and the DDS is specifically configured to: receiving second communication data through a second communication interface, analyzing the second communication data according to a serial port communication protocol to obtain an amplitude control word, a frequency control word and a phase control word, and storing the amplitude control word, the frequency control word and the phase control word in a register; receiving the PWM signal through a second communication interface, and reading an amplitude control word, a frequency control word and a phase control word in a register according to the PWM signal; carrying out direct digital frequency synthesis on the read amplitude control word, frequency control word and phase control word to obtain a carrier frequency signal; and according to a pulse signal envelope control window in the PWM signal, carrying out envelope control on the carrier frequency signal to obtain an excitation pulse signal, wherein each sine wave sequence in the excitation pulse signal corresponds to the high level in each pulse signal envelope control window.
An OSK pin and an I/0 _UPDATEport on the AD9910 are respectively and electrically connected with a direct digital frequency synthesis chip DDS; in an instruction period, an I/0_UPDATE port receives a data instruction sent by a sending data pin TXD, the data instruction is second communication data, a direct digital frequency synthesis chip DDS writes an amplitude control word, a frequency control word and a phase control word into a register corresponding to the storage information according to the storage information in the data instruction, the register comprises three parameters, the three parameters are respectively written into the amplitude control word, the frequency control word and the phase control word, and when the I/0_UPDATE port has updating data, an AD9910 generates a rising edge pulse to enable the parameter updating function.
In a data period after the instruction period is finished, when the direct digital frequency synthesis chip DDS receives a PWM signal through an OSK pin, an amplitude control word, a frequency control word and a phase control word are read from a register so as to jointly modulate an excitation pulse signal by the PWM signal, the amplitude control word, the frequency control word and the phase control word.
The excitation pulse signal generator carries out direct digital frequency synthesis on the amplitude control word, the frequency control word and the phase control word to obtain a carrier frequency signal, waveform control of the carrier frequency signal is achieved, the PWM signal is used as an envelope signal, resonance time of the carrier frequency signal is accurately controlled, accurate control of the excitation pulse signal is achieved, and continuity and stability of the excitation pulse signal in time are improved.
Optionally, the modulation system of the excitation pulse signal may further include a signal conditioning circuit, which is electrically connected to the AD9910 and the STM32, respectively, for amplifying or attenuating the excitation pulse signal.
Fig. 7 is a schematic diagram of testing a pulse signal envelope control window according to the present embodiment, fig. 7a is a schematic diagram of testing a single pulse signal envelope control window, and fig. 7b is a schematic diagram of testing a plurality of pulse signal envelope control windows.
For example: in a single pulse signal envelope control window, the pulse width is 50us and the pulse interval T is gap ＝T d +T s +T p ＝20ms+2.3ms+10ms，T d Indicating the control time of the pulse, T, waiting for the ringing tail signal s Indicating NQR signal sampling control time, T p Representing the reserved time for processing the NQR signals by the system, and setting 10ms; in a plurality of pulse signal envelope control windows, the refocusing pulse width is 150us at a spin plate chamfer of 0 °.
Fig. 8 is a schematic diagram of the test excitation pulse signal of the present embodiment, in which the attenuation of the high-band pulse amplitude is severe, and although the theoretical minimum pulse width is 10us, in the actual test process, the pulse width is only about 20us, and compared with the pulse width being greater than 100us, the pulse width is unstable about 20 us.
It should be noted that the data transmission principle, the pulse signal parameter conversion principle, the user interface, and the serial port communication protocol in this embodiment are the same as those in the first embodiment, and are not described herein again.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (4)
1. A modulation method of an excitation pulse signal is characterized by comprising the following specific steps:
step 110, sending first communication data;
step 120, receiving the first communication data, converting the first communication data to obtain second communication data and a PWM signal, and asynchronously sending the second communication data and the PWM signal;
step 130, asynchronously receiving the second communication data and the PWM signal, and modulating an excitation pulse signal according to the PWM signal and the second communication data;
the step 110 is specifically implemented as:
step 111, setting pulse signal parameters on a user interface, wherein the pulse signal parameters comprise: pulse width, pulse interval, pulse number, pulse amplitude, resonance frequency and carrier frequency initial phase;
step 112, packing the pulse signal parameters according to a serial port communication protocol to obtain the first communication data;
step 113, sending the first communication data through a first communication interface;
the step 120 is specifically implemented as:
step 121, receiving the first communication data through the first communication interface, and analyzing the first communication data according to the serial port communication protocol to obtain the pulse width, the pulse interval, the number of pulses, the pulse amplitude, the resonance frequency, and the carrier frequency initial phase;
step 122, performing digital coding on the analog signal level according to the pulse width, the pulse interval and the number of pulses to obtain the PWM signal;
step 123, performing digital conversion on the pulse amplitude to obtain an amplitude control word, performing digital conversion on the resonance frequency to obtain a frequency control word, and performing digital conversion on the carrier frequency initial phase to obtain a phase control word;
step 124, packing the amplitude control word, the frequency control word and the phase control word according to the serial port communication protocol to obtain the second communication data;
step 125, after the second communication data is sent through the second communication interface, sending the PWM signal through the second communication interface;
the step 130 is specifically implemented as:
step 131, receiving the second communication data through the second communication interface, analyzing the second communication data according to the serial port communication protocol to obtain the amplitude control word, the frequency control word and the phase control word, and storing the amplitude control word, the frequency control word and the phase control word in a register;
step 132, receiving the PWM signal through the second communication interface, and reading the amplitude control word, the frequency control word, and the phase control word in the register according to the PWM signal;
step 133, performing direct digital frequency synthesis on the read amplitude control word, the read frequency control word, and the read phase control word to obtain a carrier frequency signal;
and step 134, performing envelope control on the carrier frequency signal according to a pulse signal envelope control window in the PWM signal to obtain the excitation pulse signal, where each sine wave sequence in the excitation pulse signal corresponds to a high level in each pulse signal envelope control window.
2. The method according to claim 1, wherein in the step 121, the first communication data is received through the first communication interface, and is specifically implemented as:
periodically inquiring data identification bits in the first communication data;
and judging whether the data identification bit is true, if so, indicating that the first communication data is synchronously received through the first communication interface, and if not, continuously inquiring the data identification bit.
3. The system for modulating the excitation pulse signals is characterized by comprising an upper computer, a lower computer and an excitation pulse signal generator, wherein the upper computer, the lower computer and the excitation pulse signal generator are sequentially connected through a communication interface;
the upper computer is used for sending first communication data;
the lower computer is used for receiving the first communication data, converting the first communication data to obtain second communication data and a PWM signal, and asynchronously sending the second communication data and the PWM signal;
the excitation pulse signal generator is used for asynchronously receiving the second communication data and the PWM signal and modulating the excitation pulse signal according to the PWM signal and the second communication data;
the upper computer includes first communication interface, the upper computer pass through first communication interface with the lower computer is connected, the upper computer specifically is used for:
set up the pulse signal parameter on the user interface of host computer, the pulse signal parameter includes: pulse width, pulse interval, pulse number, pulse amplitude, resonance frequency and carrier frequency initial phase;
packaging the pulse signal parameters according to a serial port communication protocol to obtain first communication data;
transmitting the first communication data through the first communication interface;
the lower computer comprises a second communication interface, the lower computer is connected with the excitation pulse signal generator through the second communication interface, and the lower computer is specifically used for:
receiving the first communication data through the first communication interface, and analyzing the first communication data according to the serial port communication protocol to obtain the pulse width, the pulse interval, the number of pulses, the pulse amplitude, the resonance frequency and the carrier frequency initial phase;
carrying out digital coding on the analog signal level according to the pulse width, the pulse interval and the pulse number to obtain the PWM signal;
carrying out digital conversion on the pulse amplitude to obtain an amplitude control word, carrying out digital conversion on the resonance frequency to obtain a frequency control word, and carrying out digital conversion on the carrier frequency initial phase to obtain a phase control word;
packing the amplitude control word, the frequency control word and the phase control word according to the serial port communication protocol to obtain second communication data;
after the second communication data is sent through the second communication interface, the PWM signal is sent through the second communication interface;
the excitation pulse signal generator comprises a direct digital frequency synthesizer (DDS) and a register, the second communication interface is electrically connected with the register through the DDS, and the DDS is specifically used for:
receiving the second communication data through the second communication interface, analyzing the second communication data according to the serial port communication protocol to obtain the amplitude control word, the frequency control word and the phase control word, and storing the amplitude control word, the frequency control word and the phase control word into the register;
receiving the PWM signal through the second communication interface, and reading the amplitude control word, the frequency control word and the phase control word in the register according to the PWM signal;
performing direct digital frequency synthesis on the read amplitude control word, the frequency control word and the phase control word to obtain a carrier frequency signal;
and according to a pulse signal envelope control window in the PWM signal, carrying out envelope control on the carrier frequency signal to obtain the excitation pulse signal, wherein each sine wave sequence in the excitation pulse signal corresponds to a high level in each pulse signal envelope control window.
4. The system for modulating the excitation pulse signal according to claim 3, wherein the lower computer is further configured to:
periodically inquiring data identification bits in the first communication data;
and judging whether the data identification bit is true, if so, indicating that the first communication data is synchronously received through the first communication interface, and if not, continuously inquiring the data identification bit.
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