Accelerator beam parameter calculation method and device

Abstract

The embodiment of the invention relates to an accelerator beam parameter calculation method and device, and the method and device have the beneficial effects that after a BPM digital signal is obtained, the BPM digital signal is demodulated through an NON-IQ algorithm, compared with a common digital IQ demodulation algorithm, a DC offset component and a clock jitter error can be effectively suppressed, and the measurement resolution and the anti-interference capability are remarkably improved. Meanwhile, after the I signal and the Q signal are obtained, the target position and the target phase of the accelerator beam can be accurately obtained through calculation of a CORDIC algorithm. In addition, the Non-IQ algorithm formula is simple, digital, simple and practical, the program flow and codes are easy to develop and implement in FPGA hardware, and the measurement result can be observed in real time and at a high speed through the algorithm implementation in the FPGA.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of particle accelerators, and in particular to a method and device for calculating accelerator beam parameters. Background Art

[0002] Particle accelerators can generate and accelerate charged particles to obtain the required energy and speed for various experiments or applications. Among them, linear accelerators can be used in basic physics research, and can also be used as injectors for synchrotrons, storage rings, free electron lasers and colliders. In addition, linear accelerators are also widely used in the medical industry, and their beams can be used clinically to treat cancer. In order to ensure the stable and reliable operation of the accelerator, real-time measurement and diagnosis of various beam parameters are very necessary, especially the position and phase of the beam.

[0003] Accelerator beamlines or linear accelerators mainly use non-intercepting beam position monitors (BPMs) to measure beam position and phase. The signal sampled by the ADC can be processed and calculated to obtain the position and phase information of the beam. Phase measurement methods mainly include oscilloscope measurement, zero-crossing detection, IQ quadrature demodulation, quadrature sampling, etc.

[0004] During the project execution, IQ quadrature demodulation and quadrature sampling are usually used to process BPM-induced signals. Among them, quadrature sampling requires analog down-conversion of the signal to an intermediate frequency, and then sampling at four times the intermediate frequency to obtain an orthogonal IQ signal sequence. This method has low performance requirements for ADC and FPGA, and has the advantages of simple implementation, short delay, and fast response. However, during orthogonal IQ sampling, the ADC sampling value is fixed at the four phase values ​​of the intermediate frequency. In addition, due to the influence of the inherent jitter of the ADC clock, the IQ sequence obtained by sampling is likely to have more glitches and more noise. Summary of the invention

[0005] In view of the above problems, an example of the present invention provides an accelerator beam parameter calculation method and device, which is used to solve the problem that the ADC sampling value in the prior art is fixed at the four phase values ​​of the intermediate frequency, and the IQ sequence obtained by sampling is likely to have many glitches and large noise due to the influence of the inherent jitter of the ADC clock.

[0006] According to one aspect of an example of the present invention, a method for calculating accelerator beam parameters is provided, the method comprising:

[0007] Acquire a BPM sensing signal, and perform ADC sampling on the BPM sensing signal to generate a BPM digital signal;

[0008] Demodulate the BPM digital signal by using a NON-IQ algorithm to obtain an I signal and a Q signal;

[0009] The I signal and Q signal are processed by the CORDIC algorithm to obtain the target position and target phase of the accelerator beam.

[0010] In some optional embodiments, the BPM digital signal expression is as follows:

[0011]

[0012] Among them, A s is the amplitude, ω s is the angular frequency, For phase.

[0013] In some optional embodiments, demodulating the BPM digital signal by a NON-IQ algorithm to obtain an I signal and a Q signal specifically includes:

[0014] Generate an oscillation signal according to the BPM digital signal through a digitally controlled oscillator, and multiply the oscillation signal and the BPM digital signal in the time domain to obtain a mixed signal, wherein the oscillation signal is a pair of orthogonal sine signals and cosine signals with the same frequency as the BPM digital signal;

[0015] Performing low-pass filtering on the mixed signal to generate an intermediate frequency signal, and demodulating the intermediate frequency signal to form an I component and a Q component;

[0016] The intermediate frequency signal is optimized by smooth sliding average to generate I signal and Q signal.

[0017] In some optional embodiments, generating a beam signal according to the BPM digital signal by a digitally controlled oscillator, and multiplying the beam signal and the BPM digital signal in the time domain to obtain a mixed signal specifically includes:

[0018] Assume that the oscillation signal amplitude A1, angular frequency ω1, and phase Then the sinusoidal signal of the oscillation signal is The cosine signal is

[0019] Multiply the oscillation signal by the BPM digital signal, then

[0020] By applying trigonometric function to formulas (5) and (6), we can obtain:

[0021]

[0022] In some optional embodiments, the step of performing low-pass filtering on the mixed signal to generate an intermediate frequency signal specifically includes:

[0023] The mixed signals shown in equations (6) and (7) are low-pass filtered, and

[0024]

[0025] Let the angular frequency ω1 of the oscillation signal be equal to the angular frequency ω of the BPM digital signal s Same, then remember

[0026] In some optional embodiments, the step of optimizing the intermediate frequency signal by smooth sliding average to generate the I signal and the Q signal specifically includes:

[0027] Take the sliding average at N points in M ​​cycles, set θ = 2πM / N, and discretize it through ADC to obtain I signal and Q signal. The formula is as follows:

[0028] In some optional embodiments, the I signal and the Q signal are processed by the CORDIC algorithm to obtain the target phase of the BPM digital signal, and the calculation formula is as follows:

[0029]

[0030] Among them, δ b is the absolute phase of the BPM induced signal, δ ref is the absolute phase of the reference signal, Q b and I b are the I and Q signals after demodulation of the BPM sensing signal, Q ref and I ref are the I and Q values ​​of the demodulated reference signal;

[0031] By subtracting formulas (13) and (14), the phase difference between the BPM sensing signal and the reference signal is obtained: def (t) = δ b (t)-δ ref (t)#(15); and correct the phase difference through the phase difference correction method to obtain the target phase.

[0032] In some optional embodiments, the phase difference correction method specifically includes:

[0033] If δ def (t)>π, then δ real (t) = δ def (t)-2π#(16), if δdef (t)<-π, then δ real (t) = δ def (t)+2π#(17).

[0034] In some optional embodiments, the I signal and the Q signal are processed by a CORDIC algorithm to obtain the target position of the accelerator beam, specifically including:

[0035] By formula: Get the amplitude of the BPM sensing signal;

[0036] The target position of the beam (P) is calculated by calculating the amplitude of the BPM sensing signal of the four channels, normalizing it by the difference ratio and the sum, and subtracting the position offset. x ,P y ), the specific formula is:

[0037]

[0038] According to another aspect of an embodiment of the present invention, there is provided an accelerator beam parameter calculation device, the device comprising:

[0039] A beam signal acquisition module is used to acquire a BPM sensing signal and perform ADC sampling on the BPM sensing signal to generate a BPM digital signal;

[0040] An I / Q signal calculation module, used to demodulate the BPM digital signal through a NON-IQ algorithm to obtain an I signal and a Q signal;

[0041] The parameter acquisition module is used to process the I signal and Q signal through the CORDIC algorithm to obtain the target position and target phase of the accelerator beam.

[0042] The present invention provides a method and device for calculating accelerator beam parameters, and the beneficial effects are as follows: after acquiring the BPM digital signal, the present invention demodulates the BPM digital signal through the NON-IQ algorithm, which can effectively suppress the DC offset component and the clock jitter error compared to the common digital IQ demodulation algorithm, and significantly improve the measurement resolution and anti-interference ability. At the same time, after acquiring the I signal and the Q signal, the target position and the target phase of the accelerator beam can be accurately obtained through the CORDIC algorithm calculation. In addition, the Non-IQ algorithm formula of the present invention is concise and digital, simple and practical, the program flow and code are easy to implement in FPGA hardware development, and the algorithm implementation in the FPGA can observe the measurement results in real time and at high speed.

[0043] The above description is only an overview of the technical solution of the example of the present invention. In order to more clearly understand the technical means of the embodiment of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the example of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The accompanying drawings are only used to illustrate the embodiments and are not to be considered as limiting the present invention. In addition, the same reference symbols are used to represent the same components throughout the accompanying drawings. In the accompanying drawings:

[0045] Figure 1 A schematic diagram showing a flow chart of an accelerator beam parameter calculation method according to Embodiment 1 of the present invention is provided;

[0046] Figure 2 The present invention provides a schematic diagram of a process of demodulating the BPM digital signal by using a NON-IQ algorithm according to Embodiment 2;

[0047] Figure 3 The present invention provides a schematic structural diagram of an accelerator beam parameter calculation device according to Embodiment 3;

[0048] Figure 4 The module diagram of the Non-IQ-based beam position and phase calculation algorithm provided in Example 2 of the present invention is shown;

[0049] Figure 5 A schematic diagram of laboratory algorithm test signal connection provided by the present invention is shown. DETAILED DESCRIPTION

[0050] Exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0051] The present invention uses NON-IQ algorithm to perform demodulation calculations in the beam line and straight line BPM beam position and phase calculations of the beam position detector. The I signal and Q signal in IQ demodulation have the meanings of in-phase and orthogonal. If a continuous signal is mapped to a two-dimensional rectangular coordinate system, an in-phase and orthogonal IQ signal can be obtained. The IQ signal obtained after mapping contains parameters such as the instantaneous amplitude and instantaneous phase of the demodulated signal. IQ demodulation is often used in signal modulation / demodulation of communication systems, and this type of BPM electronics system is similar to a receiver of a communication system, and the required parameters can be calculated through IQ demodulation.

[0052] The beam measurement technology based on digital IQ demodulation obtains the real and imaginary parts of the beam complex baseband signal through digital down-conversion, obtains the phase information of the signal by inverse tangent calculation, and calculates the amplitude information of the beam signal by square root modulus method, thereby outputting the position, phase and other parameters of the beam. For details, please refer to the following embodiments.

[0053] Embodiment 1:

[0054] Figure 1 An embodiment of a method for calculating accelerator beam parameters of the present invention is shown, the method comprising:

[0055] 110, obtain the BPM sensing signal, and perform ADC sampling on the BPM sensing signal to generate a BPM digital signal; in step 110, the BPM sensing signal is collected and obtained by the BPM probe, and can be initially adjusted by the RF front-end signal conditioning. Then the BPM sensing signal is sampled by ADC sampling to generate a BPM digital signal. Among them, ADC sampling can be sampled at a 250MHz sampling rate and a 16bit conversion accuracy. The BPM digital signal expression is as follows: Among them, A s is the amplitude, ω s is the angular frequency, For phase.

[0056] 120, demodulating the BPM digital signal through the NON-IQ algorithm to obtain the I signal and the Q signal; in step 120, the BPM digital signal is demodulated through the NON-IQ algorithm to obtain the I signal and the Q signal, specifically including: generating an oscillation signal according to the BPM digital signal through a numerically controlled oscillator, and multiplying the oscillation signal and the BPM digital signal in the time domain to obtain a mixed signal, wherein the oscillation signal is a pair of orthogonal sine signals and cosine signals with the same frequency as the BPM digital signal; performing low-pass filtering on the mixed signal to generate an intermediate frequency signal, and demodulating the intermediate frequency signal to form an I component and a Q component; optimizing the intermediate frequency signal through a smooth sliding average to generate the I signal and the Q signal.

[0057] 130, the I signal and the Q signal are processed by the CORDIC algorithm to obtain the target position and target phase of the accelerator beam. In step 130, the I signal and the Q signal are processed by the CORDIC algorithm to obtain the target phase of the BPM digital signal. The calculation formula is as follows: Among them, δ b is the absolute phase of the BPM induced signal, δ ref is the absolute phase of the reference signal, Q b and I b are the I and Q signals after demodulation of the BPM sensing signal, Qref and I ref are the I and Q values ​​of the reference signal after demodulation; by taking the difference between formulas (13) and (14), the phase difference between the BPM sensing signal and the reference signal is obtained: δ def (t) = δ b (t)-δ ref (t)#(15); and correct the phase difference by the phase difference correction method to obtain the target phase. The I signal and Q signal are processed by the CORDIC algorithm to obtain the target position of the accelerator beam, specifically including: by the formula: Obtain the amplitude of the BPM sensing signal; calculate the target position of the beam (P by calculating the amplitude of the BPM sensing signal of the four channels, normalizing it by the difference ratio and the sum, and subtracting the position offset offset. x ,P y ), the specific formula is:

[0058] After acquiring the BPM digital signal, the present invention demodulates the BPM digital signal through the NON-IQ algorithm. Compared with the common digital IQ demodulation algorithm, the DC offset component and the clock jitter error can be effectively suppressed, and the measurement resolution and anti-interference ability are significantly improved. At the same time, after acquiring the I signal and the Q signal, the target position and the target phase of the accelerator beam can be accurately obtained through the CORDIC algorithm calculation. In addition, the Non-IQ algorithm formula of the present invention is concise and digital, simple and practical, and the program flow and code are easy to implement in FPGA hardware development, and the algorithm implementation in FPGA can observe the measurement results in real time and at high speed.

[0059] Embodiment 2:

[0060] This embodiment describes the embodiment 1 in detail, wherein a method for calculating accelerator beam parameters includes steps 110-130 of the embodiment 1, see Figure 4 The sampled BPM sensing signal is demodulated by the NON-IQ algorithm and the calculation is performed in the I / Q signal calculation module. The I / Q signal calculation module of the method may include a direct digital frequency synthesizer DDS, a mixer or a fixed-point multiplier, a CIC comb filter, a FIR low-pass filter, and a sliding average filter.

[0061] Among them, the function of the direct digital frequency synthesizer DDS is to directly output a high-precision, high-stability signal using a digital circuit. Its basic principle is to achieve the generation of a sine wave and the control of the frequency through a phase accumulator and a lookup table. In DDS, the core of the phase accumulator is a counter, which counts and accumulates a phase increment in each clock cycle. The count value output of this phase accumulator is used as the memory mapping address of the lookup table, which stores a single-cycle sine signal in advance. When the lookup table is addressed and output, the output signal of the DDS is generated. When the phase accumulator counts once from small to large, the output amplitude is exactly a complete cycle of the sine wave. In the present invention, the DDS IP core is used to implement this function. The CIC comb filter is used to reduce the sampling rate in digital signal processing. In the present invention, the CIC comb filter is used to extract and filter the signal. The CIC comb filter consists of a cascaded integrator and a combiner, and the output sampling rate can be changed by adjusting the order of the integrator and the combiner. The integrator integrates the input signal and has a low-pass property, while the combiner performs a differential operation on the integrated signal and has a high-pass property. By cascading multiple integrators and combiners, a higher-order filter can be realized. After the input signal passes through the integrator, a broadband signal is obtained, and then the unnecessary frequency components are filtered out by the combiner to achieve the purpose of downsampling. The output of the FIR low-pass filter is only related to the current and past inputs, and does not involve future inputs. It is characterized by a linear phase characteristic and can achieve arbitrary frequency response. The working principle of the FIR low-pass filter is to multiply the input signal with a set of adjustable filter coefficients, and then add the products to obtain the output signal. The filter coefficients determine the characteristics of the filter, including passband gain, cutoff frequency, stopband attenuation, etc., which can be designed and optimized as needed.

[0062] The core steps of the present invention are to calculate the I and Q orthogonal DC signals based on the NON-IQ demodulation algorithm, and to calculate the real-time position of the beam, the real-time single-channel phase, the phase difference and other measurement parameters through the position and phase algorithm in combination with the CORDIC algorithm; referring to FIG. X, the BPM sensing signal enters the Non-IQ module through the input channel and the ADC sampling to obtain the I and Q signals; the specific steps are as follows:

[0063] The BPM sensing signal is sampled by the ADC to generate a BPM digital signal, which is expressed as formula (1), including the amplitude A s , angular frequency ω s With phase Information, see The BPM digital signal is demodulated by the NON-IQ algorithm to obtain the I signal and the Q signal, and the following steps are specifically performed:

[0064] 210, generate an oscillation signal according to the BPM digital signal through a digitally controlled oscillator, and multiply the oscillation signal and the BPM digital signal in the time domain to obtain a mixed signal, wherein the oscillation signal is a pair of orthogonal sine signals and cosine signals with the same frequency as the BPM digital signal; in step 210, assume that the oscillation signal generated by the digitally controlled oscillator has an amplitude A1, an angular frequency ω1, and a phase Then the sinusoidal signal of the oscillation signal is The cosine signal is

[0065] Multiply the oscillation signal by the BPM digital signal, then

[0066] By applying trigonometric function to formulas (5) and (6), we can obtain:

[0067]

[0068] 220, performing low-pass filtering on the mixed signal to generate an intermediate frequency signal, and demodulating the intermediate frequency signal to form an I component and a Q component; In step 220, performing low-pass filtering on the mixed signal to generate an intermediate frequency signal specifically includes:

[0069] The mixed signals shown in equations (6) and (7) are low-pass filtered, and

[0070]

[0071] Let the angular frequency ω1 of the oscillation signal be equal to the angular frequency ω of the BPM digital signal s Same, then remember in, and is a pair of orthogonal vector bases, forming a two-dimensional vector space, I M and Q M They are generally referred to as the I and Q components of the intermediate frequency signal, which is the origin of IQ demodulation.

[0072] Furthermore, by the definition of I and Q, the amplitude and phase of the signal can be expressed as:

[0073]

[0074] From the above Amp and Phase formulas, we can see that the process of calculating the position and phase of the beam is transformed into the process of solving the I and Q components of the signal. The value directly obtained from the ADC is a series of mixed signal values. According to the knowledge of communication principles, by setting the sampling rate ADC sampling rate to f s =4f IFWhen a point is sampled every π / 2 on the intermediate frequency signal, the obtained sampling sequence y IF ,I,-Q,-I,Q.

[0075] In the Non-IQ demodulation algorithm, unlike IQ quadrature demodulation, the sampling rate is no longer fixed to the demodulated signal at 4 times the rate of the signal to be demodulated. Suppose the ADC sampling rate is f s , the frequency of the signal to be demodulated is f IF , the signal angular frequency is ω IF =2πf IF , the signal period is T IF , in Non-IQ sampling mode, Among them, M is 1 and N is 4, which corresponds to IQ sampling. Unlike orthogonal IQ, the sampling phase of Non-IQ is distributed on the entire IQ circle, with an equal interval of 2π / N. Therefore, during Non-IQ demodulation, the errors caused by ADC nonlinearity and clock jitter are smoothed within N cycles, thereby suppressing noise and improving the signal-to-noise ratio.

[0076] 230, optimizing the intermediate frequency signal by smooth sliding average to generate an I signal and a Q signal. In step 230, optimizing the intermediate frequency signal by smooth sliding average to generate an I signal and a Q signal specifically includes:

[0077] Take the sliding average at N points in M ​​cycles, set θ = 2πM / N, and discretize it through ADC to obtain I signal and Q signal. The formula is as follows: The NON-IQ demodulation algorithm of the present invention further optimizes the I and Q signals through sliding average, suppresses errors caused by direct current offset components and clock jitter, and reduces noise.

[0078] In some optional embodiments, the I signal and the Q signal are processed by a CORDIC algorithm to obtain the target phase of the BPM digital signal. The calculation formula is as follows:

[0079]

[0080] Among them, δ b is the absolute phase of the BPM induced signal, δ ref is the absolute phase of the reference signal, Q b and I b are the I and Q signals after demodulation of the BPM sensing signal, Q ref and I ref are the I and Q values ​​of the demodulated reference signal;

[0081] By subtracting formulas (13) and (14), the phase difference between the BPM sensing signal and the reference signal is obtained: def (t) = δ b (t)-δref (t)#(15); and correct the phase difference through the phase difference correction method to obtain the target phase.

[0082] In one implementation of the above embodiment, the phase difference correction method specifically includes:

[0083] If δ def (t)>π, then δ real (t) = δ def (t)-2π#(16), if δ def (t)<-π, then δ real (t) = δ def (t)+2π#(17).

[0084] In some optional embodiments, the I signal and the Q signal are processed by a CORDIC algorithm to obtain the target position of the accelerator beam, specifically including:

[0085] By formula: Get the amplitude of the BPM sensing signal;

[0086] Since the original beam signal contains the intensity and position information, after the BPM measures the induced beam signal, the beam needs to be normalized to remove the intensity information and extract the beam position information. The scheme adopts the general difference ratio method (Δ / Σ). By calculating the amplitude of the BPM induced signal of the four channels, normalizing it by the difference ratio, and subtracting the position offset, the target position (P x ,P y ), the specific formula is:

[0087]

[0088] See also Figure 5 The beam signal, i.e., the BPM sensing signal, can be obtained through the following signal transmission method. The signal generated by the R&SSMB100A waveform generator outputs a detection signal and a reference signal through a one-to-two power splitter. The detection signal passes through the pulse generator and the adjustable attenuator in turn, and then forms a beam signal through a one-to-four power splitter and is transmitted to the back-end module.

[0089] In orthogonal IQ sampling, the ADC sampling value is fixed at the four phase values ​​of the intermediate frequency, which makes the errors caused by the ADC's nonlinearity and clock jitter directly affect the final IQ sequence. Adding a low-pass filter to the post-stage of IQ sampling demodulation can suppress the impact of the above errors on the final phase measurement accuracy, but it also adds additional system delays. In addition, the problem of high-order harmonic aliasing in orthogonal IQ sampling mentioned above will also directly lead to a decrease in measurement accuracy. In Non-IQ sampling mode, choosing appropriate M and N values ​​can effectively solve the shortcomings of IQ sampling.

[0090] Embodiment 3:

[0091] Figure 3 An embodiment of an accelerator beam parameter calculation device of the present invention is shown. This embodiment is based on embodiment 1 or 2, and the device specifically includes:

[0092] The beam signal acquisition module 310 is used to execute step 110 of Example 1; specifically, the BPM sensing signal is acquired by the BPM probe, and can be initially adjusted by the RF front-end signal conditioning. Then the BPM sensing signal is sampled by ADC sampling to generate a BPM digital signal. Among them, the ADC sampling can be sampled at a sampling rate of 250MHz and a conversion accuracy of 16bit. The BPM digital signal expression is as follows: Among them, A s is the amplitude, ω s is the angular frequency, For phase.

[0093] The I / Q signal calculation module 320 is used to execute step 120 of Example 1; specifically including: demodulating the BPM digital signal through the NON-IQ algorithm to obtain the I signal and the Q signal, specifically including: generating an oscillation signal according to the BPM digital signal through a digitally controlled oscillator, and multiplying the oscillation signal and the BPM digital signal in the time domain to obtain a mixed signal, wherein the oscillation signal is a pair of orthogonal sine signals and cosine signals with the same frequency as the BPM digital signal; performing low-pass filtering on the mixed signal to generate an intermediate frequency signal, and demodulating the intermediate frequency signal to form an I component and a Q component; optimizing the intermediate frequency signal by smooth sliding average to generate the I signal and the Q signal.

[0094] The parameter acquisition module 330 is used to execute step 130 of embodiment 1; specifically, it includes: processing the I signal and the Q signal by the CORDIC algorithm to obtain the target phase of the BPM digital signal, and the calculation formula is as follows: Among them, δ b is the absolute phase of the BPM induced signal, δ ref is the absolute phase of the reference signal, Q b and Ib are the I and Q signals after demodulation of the BPM sensing signal, Q ref and I ref are the I and Q values ​​of the reference signal after demodulation; by taking the difference between formulas (13) and (14), the phase difference between the BPM sensing signal and the reference signal is obtained: δ def (t) = δ b (t)-δ ref (t)#(15); and correct the phase difference by the phase difference correction method to obtain the target phase. The I signal and Q signal are processed by the CORDIC algorithm to obtain the target position of the accelerator beam, specifically including: by the formula: Obtain the amplitude of the BPM sensing signal; calculate the target position of the beam (P by calculating the amplitude of the BPM sensing signal of the four channels, normalizing it by the difference ratio and the sum, and subtracting the position offset offset. x ,P y ), the specific formula is:

[0095] The present invention introduces a NON-IQ demodulation algorithm for the BPM position and phase calculation of an accelerator beam line and a linear accelerator. Compared with a common digital IQ demodulation algorithm, it can effectively suppress the DC offset component and clock jitter error, and significantly improve the measurement resolution and anti-interference ability. The position and phase calculation algorithm of the present invention adopts a digital demodulation algorithm in the implementation process. Since fewer analog processing modules are required for implementation, the performance is higher than that of analog IQ demodulation and intermediate frequency orthogonal sampling, and the beam position and phase measurement of the fundamental frequency and second harmonic signal based on BPM induction can be realized simultaneously. The Non-IQ algorithm formula of the present invention is concise and digital, simple and practical, and the program flow and code are easy to implement in FPGA hardware development, and the algorithm implementation in FPGA can observe the measurement results in real time and at high speed. Based on the programmable characteristics of FPGA, the future upgrade iteration of the algorithm and data transmission in the system is very convenient and flexible, and can be quickly transplanted to other accelerator beam lines or linear accelerator beam position and phase measurement projects. The key modules of the algorithm implementation are all independently developed and have lower costs, which have accumulated experience for the localization of BPM; it has high use value.

[0096] The algorithms or displays provided herein are not inherently related to any particular computer, virtual system or other device. In addition, the embodiments of the present invention are not directed to any particular programming language.

[0097] In the description provided herein, a large number of specific details are described. However, it is understood that embodiments of the present invention can be practiced without these specific details. Similarly, in order to simplify the present invention and help understand one or more of the various inventive aspects, in the above description of exemplary embodiments of the present invention, the various features of the embodiments of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. Wherein, the claims that follow the specific embodiment are hereby expressly incorporated into the specific embodiment, wherein each claim itself is a separate embodiment of the present invention.

[0098] Those skilled in the art will appreciate that the modules in the devices in the embodiments may be adaptively changed and arranged in one or more devices different from the embodiments. The modules or units or components in the embodiments may be combined into one module or unit or component, and further may be divided into a plurality of submodules or subunits or subcomponents. Except that at least some of such features and / or processes or units are mutually exclusive.

[0099] It should be noted that the above embodiments illustrate the present invention rather than limit it, and that those skilled in the art may devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference symbol between brackets shall not be construed as a limitation on the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "one" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present invention may be implemented by means of hardware comprising a number of different elements and by means of a suitably programmed computer. In a unit claim enumerating a number of devices, several of these devices may be embodied by the same hardware item. The use of the words first, second, and third, etc. does not indicate any order. These words may be interpreted as names. The steps in the above embodiments, unless otherwise specified, should not be understood as limitations on the order of execution.

Claims

1. A method for calculating accelerator beam parameters, characterized in that: The method comprises: Acquire a BPM sensing signal, and perform ADC sampling on the BPM sensing signal to generate a BPM digital signal; Demodulate the BPM digital signal by using a NON-IQ algorithm to obtain an I signal and a Q signal; The I signal and Q signal are processed by the CORDIC algorithm to obtain the target position and target phase of the accelerator beam.

2. The method for calculating accelerator beam parameters according to claim 1, characterized in that: The BPM digital signal expression is as follows: Among them, A s is the amplitude, ω s is the angular frequency, For phase.

3. The accelerator beam parameter calculation method according to claim 2, characterized in that: Demodulating the BPM digital signal by using a NON-IQ algorithm to obtain an I signal and a Q signal specifically includes: Generate an oscillation signal according to the BPM digital signal through a digitally controlled oscillator, and multiply the oscillation signal and the BPM digital signal in the time domain to obtain a mixed signal, wherein the oscillation signal is a pair of orthogonal sine signals and cosine signals with the same frequency as the BPM digital signal; Performing low-pass filtering on the mixed signal to generate an intermediate frequency signal, and demodulating the intermediate frequency signal to form an I component and a Q component; The intermediate frequency signal is optimized by smooth sliding average to generate I signal and Q signal.

4. The accelerator beam parameter calculation method according to claim 3, characterized in that: The step of generating a beam signal according to the BPM digital signal by a digitally controlled oscillator, and multiplying the beam signal and the BPM digital signal in the time domain to obtain a mixed signal specifically includes: Assume that the oscillation signal amplitude A1, angular frequency ω1, and phase Then the sinusoidal signal of the oscillation signal is The cosine signal is Multiply the oscillation signal by the BPM digital signal, then By applying trigonometric function to formulas (5) and (6), we can obtain:

5. The accelerator beam parameter calculation method according to claim 4, characterized in that: The low-pass filtering of the mixed signal to generate an intermediate frequency signal specifically includes: The mixed signals shown in equations (6) and (7) are low-pass filtered, and Let the angular frequency ω1 of the oscillation signal be equal to the angular frequency ω of the BPM digital signal s Same, then remember 6. The accelerator beam parameter calculation method according to claim 5, characterized in that: The step of optimizing the intermediate frequency signal by smooth sliding average to generate an I signal and a Q signal specifically includes: Take the sliding average at N points in M ​​cycles, set θ = 2πM / N, and discretize it through ADC to obtain I signal and Q signal. The formula is as follows:

7. The accelerator beam parameter calculation method according to claim 6, characterized in that: The I signal and the Q signal are processed by the CORDIC algorithm to obtain the target phase of the BPM digital signal. The calculation formula is as follows: Among them, δ b is the absolute phase of the BPM induced signal, δ ref is the absolute phase of the reference signal, Q b and I b are the I and Q signals after demodulation of the BPM sensing signal, Q ref and I ref are the I and Q values ​​of the demodulated reference signal; By subtracting formulas (13) and (14), the phase difference between the BPM sensing signal and the reference signal is obtained: def (t) = δ b (t)-δ ref (t)#(15); and correct the phase difference through the phase difference correction method to obtain the target phase.

8. The accelerator beam parameter calculation method according to claim 7, characterized in that: The phase difference correction method specifically includes: If δ def (t) > π, then δ real (t) = δ def (t) - 2π #(16), if δ def (t) < -π, then δ real (t) = δ def (t) + 2π #(17).

9. The accelerator beam parameter calculation method according to claim 7, characterized in that: The I signal and Q signal are processed by the CORDIC algorithm to obtain the target position of the accelerator beam, including: By formula: Get the amplitude of the BPM sensing signal; The target position of the beam (P) is calculated by calculating the amplitude of the BPM sensing signal of the four channels, normalizing it by the difference ratio and the sum, and subtracting the position offset. x ,P y ), the specific formula is:

10. An accelerator beam parameter calculation device, characterized in that: The device comprises: A beam signal acquisition module is used to acquire a BPM sensing signal and perform ADC sampling on the BPM sensing signal to generate a BPM digital signal; An I / Q signal calculation module, used to demodulate the BPM digital signal through a NON-IQ algorithm to obtain an I signal and a Q signal; The parameter acquisition module is used to process the I signal and Q signal through the CORDIC algorithm to obtain the target position and target phase of the accelerator beam.

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