A method and apparatus for measuring the amplitude and phase response of a radio frequency cavity

Abstract

The present application relates to a kind of methods for measuring the amplitude-frequency and phase-frequency response of radio frequency cavity, comprising: the digital radio frequency low level system generates sawtooth wave pulse frequency signal, and generates frequency control word;The digital radio frequency low level system generates sine data sequence and cosine data sequence according to the frequency control word, and the sine data sequence and the cosine data sequence are quadrature modulated, the output of the quadrature modulation is converted to digital-analog after output to the power source, and then the power amplifier is carried out power amplification and the directional coupler coupling after generation radio frequency signal input to the radio frequency cavity;The digital radio frequency low level system obtains the cavity pressure signal of the radio frequency cavity, and the forward voltage signal and reverse voltage signal of the directional coupler;The digital radio frequency low level system carries out real-time signal processing according to the cavity pressure signal, the forward voltage signal and the reverse voltage signal, and obtains the amplitude-frequency and phase-frequency response curve of the radio frequency cavity.

Description

Technical Field

[0001] This invention relates to the field of particle accelerator technology, and in particular to a method and apparatus for measuring the amplitude and phase frequency response of a radio frequency cavity. Background Technology

[0002] Radio frequency (RF) cavities are an important component of accelerator devices. There are many types of RF cavities, including RF superconducting cavities.

[0003] Radio frequency superconducting cavities (RF superconducting cavities for short), as the core component of superconducting accelerators, possess advantages such as low loss and high gradient, making them ideal for accelerating high-average-current particle beams in continuous wave (CW) or long-pulse modes. Therefore, RF superconducting cavities are currently the preferred solution for accelerators under construction, in the planning stages, and in the future, both domestically and internationally.

[0004] The measurement of the amplitude-frequency and phase-frequency response curves and their characteristic parameters of a superconducting cavity is of great significance for monitoring the performance of the superconducting cavity and measuring whether the superconducting cavity is operating stably.

[0005] However, the inventors of this application discovered in their research that existing technologies for measuring the amplitude and phase frequency responses of superconducting cavities involve connecting a network analyzer to the superconducting cavity. This connection requires complex cabling, necessitating extensive pre-preparation for measurement, and the network analyzer can only measure one superconducting cavity at a time, resulting in low efficiency. Furthermore, the network analyzer cannot measure the superconducting cavity during operation, nor can it monitor changes in characteristic parameters during the cavity's reheating and cooling processes, thus limiting the correlation analysis between the characteristic parameters of the superconducting cavity and its operational stability. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a method and apparatus for measuring the amplitude and phase frequency response of a radio frequency cavity. Compared with existing network analyzer measurement methods, this method can improve measurement efficiency and can be applied during the operation of the radio frequency cavity, thus aiding in the analysis of the operational stability of the radio frequency cavity.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, this application provides a method for measuring the amplitude-frequency and phase-frequency response of a radio frequency cavity, applied to a superconducting accelerator, the superconducting accelerator comprising a digital radio frequency low-level system, a power source, a directional coupler, and a radio frequency cavity connected in sequence, the method comprising:

[0009] The digital radio frequency low-level system generates a sawtooth pulse frequency signal and generates a frequency control word based on the sawtooth pulse frequency signal.

[0010] The digital radio frequency low-level system generates a sine data sequence and a cosine data sequence according to the frequency control word, and performs quadrature modulation on the sine data sequence and the cosine data sequence. The output of the quadrature modulation is converted from digital to analog and then output as a radio frequency signal to the power source. After being amplified by the power source and coupled by the directional coupler, it is input into the radio frequency cavity.

[0011] The digital radio frequency low-level system acquires the cavity pressure signal of the radio frequency cavity, as well as the forward voltage signal and reverse voltage signal of the directional coupler;

[0012] The digital radio frequency low-level system performs real-time signal processing based on the cavity pressure signal, the forward voltage signal, and the reverse voltage signal to obtain the amplitude frequency and phase frequency response curves of the radio frequency cavity.

[0013] In one implementation of this application, the digital radio frequency low-level system generates a sawtooth pulse frequency signal, including:

[0014] The digital radio frequency low-level system generates a sawtooth pulse frequency signal through an internal FPGA chip.

[0015] In one implementation of this application, generating a frequency control word based on the sawtooth pulse frequency signal includes:

[0016] Based on the parameters of the sawtooth wave pulse frequency signal, the frequency control word M is solved using the following formula:

[0017]

[0018] f = f0 + ∑f step ;

[0019]

[0020] Among them, f clock The operating clock frequency of the FPGA chip is n, and the bit width of the phase accumulator in the FPGA chip is n;

[0021] f0 is the starting frequency of the sawtooth wave pulse frequency signal. c The cutoff frequency of the sawtooth wave pulse frequency signal is T, where T is the sweep duration of the sawtooth wave pulse frequency signal, and f0 and f are... c The value of T is set by the host computer.

[0022] In one implementation of this application, the digital radio frequency low-level system generates a sine data sequence and a cosine data sequence according to the frequency control word, and performs quadrature modulation on the sine data sequence and the cosine data sequence, including:

[0023] In the FPGA chip, the frequency control word is input to a numerically controlled oscillator to generate a sine data sequence sinα and a cosine data sequence cosα.

[0024] Based on the amplitude A and phase θ of the low-level control signal set by the host computer, the CORDIC algorithm is used to convert it into an I sequence and a Q sequence.

[0025] Using the modulation conversion formula I / Q output =Q*sinα+I*cosα, calculate the output of the quadrature modulation.

[0026] In one implementation of this application, the amplitude A of the low-level control signal set by the host computer is used to prevent the cavity pressure signal from generating Lorentz force detuning.

[0027] In one implementation of this application, the sweep width between the start frequency and the cutoff frequency is 1 kHz, and the sweep duration is 1 second;

[0028] The operating clock frequency is 100MHz; the amplitude of the low-level control signal is 0.2mV and the phase is 0 degrees.

[0029] In one implementation of this application, the digital radio frequency low-level system performs real-time signal processing based on the cavity pressure signal, the forward voltage signal, and the reverse voltage signal to obtain the amplitude-frequency and phase-frequency response curves of the radio frequency cavity, including:

[0030] The digital radio frequency low-level system solves for the amplitude-frequency response curve;

[0031] The solution to the amplitude-frequency response curve includes:

[0032] The FPGA chip performs IQ demodulation and CORDIC rotation on the acquired cavity pressure signal, forward voltage, and backward voltage signal to obtain the corresponding amplitude values.

[0033] The amplitude-frequency response curve is obtained by plotting the amplitude value on the vertical axis and the corresponding sweep frequency f on the horizontal axis.

[0034] In one implementation of this application, the digital radio frequency low-level system performs real-time signal processing based on the cavity pressure signal, the forward voltage signal, and the reverse voltage signal to obtain the amplitude-frequency and phase-frequency response curves of the radio frequency cavity, and further includes:

[0035] The digital radio frequency low-level system solves for the phase frequency response curve;

[0036] The solution to the amplitude-frequency response curve includes:

[0037] The FPGA chip performs IQ demodulation and CORDIC rotation on the acquired cavity pressure signal, forward voltage, and backward voltage signal to obtain the corresponding first phase value.

[0038] The FPGA chip performs CORDIC rotation on the output of the quadrature modulation to obtain the second phase value of the output signal of the quadrature modulation;

[0039] The phase frequency response curve is obtained by plotting the difference between the first phase value and the second phase value on the vertical axis and the corresponding sweep frequency f on the horizontal axis.

[0040] In one implementation of this application, the method further includes a process for evaluating measurement accuracy;

[0041] The measurement accuracy assessment includes:

[0042] Based on the measured amplitude-frequency response curve of the radio frequency cavity obtained from the digital radio frequency low-level system, the half bandwidth corresponding to the radio frequency cavity is calculated.

[0043] Connectivity measurements are performed using a network analyzer and the radio frequency cavity, and the corresponding half bandwidth is calculated based on the amplitude-frequency response curve of the connectivity measurements.

[0044] The accuracy of the measurement is evaluated based on whether the half-bandwidth of the two measurements mentioned above is within the set error range.

[0045] Secondly, this application provides an apparatus for measuring the amplitude and phase frequency response of a radio frequency cavity, comprising a digital radio frequency low-level system, a power source, a directional coupler, and a radio frequency cavity connected in sequence;

[0046] The digital radio frequency low-level system is used to generate a sawtooth pulse frequency signal and generate a frequency control word based on the sawtooth pulse frequency signal.

[0047] The digital radio frequency low-level system is also used to generate a sine data sequence and a cosine data sequence according to the frequency control word, and to perform quadrature modulation on the sine data sequence and the cosine data sequence. The output of the quadrature modulation is converted from digital to analog and then output as a radio frequency signal to the power source. After being amplified by the power source and coupled by the directional coupler, it is input to the radio frequency cavity.

[0048] The digital radio frequency low-level system is also used to acquire the cavity pressure signal of the radio frequency cavity, as well as the forward voltage signal and reverse voltage signal of the directional coupler;

[0049] The digital radio frequency low-level system is also used to perform real-time signal processing based on the cavity pressure signal, the forward voltage signal, and the reverse voltage signal to obtain the amplitude frequency and phase frequency response curves of the radio frequency cavity.

[0050] The present invention has the following advantages due to the adoption of the above technical solutions: In the present invention, the digital radio frequency low-level system generates a sawtooth pulse frequency signal and generates a frequency control word. Then, according to the frequency control word, a sine data sequence and a cosine data sequence are generated, and the sine data sequence and the cosine data sequence are orthogonally modulated. The output of the orthogonal modulation is converted from digital to analog and output as a radio frequency signal to a power source. After being amplified by the power source and coupled by a directional coupler, it is input to the radio frequency cavity. The digital radio frequency low-level system then acquires the cavity pressure signal of the superconducting cavity, as well as the forward voltage signal and the reverse voltage signal of the directional coupler, and performs real-time signal processing to obtain the amplitude frequency and phase frequency response curves of the radio frequency cavity. Compared with the prior art, this improves the measurement efficiency and helps to analyze the operational stability of the radio frequency cavity. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the connection structure of a device for measuring the amplitude and phase frequency response of a radio frequency cavity, as provided in an embodiment of this application.

[0052] Figure 2 This is a schematic flowchart of an algorithm for measuring the amplitude and phase frequency response of a radio frequency cavity, provided in an embodiment of this application.

[0053] Figure 3 This is a schematic diagram of the quadrature modulation principle in the embodiments of this application;

[0054] Figure 4 This is a schematic diagram of the amplitude and phase frequency response curves drawn in the embodiments of this application;

[0055] Figure 5 This is a schematic diagram showing the connection between a network analyzer and an RF cavity used for measurement accuracy assessment. Detailed Implementation

[0056] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention are within the scope of protection of the present invention.

[0057] To address the problems of complex connections and low measurement efficiency in existing technologies for measuring the amplitude-frequency and phase-frequency response curves of superconducting cavities using network analyzers, this application provides a method and apparatus for measuring the amplitude-frequency and phase-frequency response of a radio frequency (RF) cavity. The method includes: a digital radio frequency (RF) low-level system generating a sawtooth pulse frequency signal and generating a frequency control word based on the sawtooth pulse frequency signal; the RF low-level system generating a sine data sequence and a cosine data sequence based on the frequency control word, orthogonally modulating the sine and cosine data sequences, and outputting the output of the orthogonal modulation as an RF signal after digital-to-analog conversion to a power source, which then amplifies the signal and couples it to the RF cavity via a directional coupler; the RF low-level system acquiring the cavity pressure signal of the RF cavity, as well as the forward and reverse voltage signals of the directional coupler; and the RF low-level system performing real-time signal processing based on the cavity pressure signal, the forward voltage signal, and the reverse voltage signal to obtain the amplitude-frequency and phase-frequency response curves of the RF cavity. This technical solution improves measurement efficiency.

[0058] See Figure 1 In one aspect of the embodiments of this application, an apparatus for measuring the amplitude and phase frequency response of a radio frequency cavity is provided.

[0059] In the embodiments of this application, the radio frequency cavity may include a room-temperature cavity and a superconducting cavity. In subsequent embodiments, a superconducting cavity will be used as an example to illustrate the method and apparatus for measuring the amplitude and phase frequency response curves of a radio frequency cavity. It is understood that it is also feasible to replace the superconducting cavity with other types of cavities, and the superconducting cavity in the subsequent embodiments should not be regarded as a limitation of this application.

[0060] In this embodiment, a digital radio frequency (RF) low-level system, a power source, a directional coupler, and a superconducting cavity are connected in sequence. The RF low-level system is used to generate a sawtooth pulse frequency signal and generate a frequency control word based on the sawtooth pulse frequency signal. The RF low-level system is also used to generate a sine data sequence and a cosine data sequence based on the frequency control word, and to perform quadrature modulation on the sine data sequence and the cosine data sequence. The output of the quadrature modulation is converted from digital to analog and then output as an RF signal to the power source. After power amplification by the power source and coupling with the directional coupler, the signal is input to the superconducting cavity. The RF low-level system is also used to acquire the cavity pressure signal of the superconducting cavity, as well as the forward voltage signal and the reverse voltage signal of the directional coupler. The RF low-level system is also used to perform real-time signal processing based on the cavity pressure signal, the forward voltage signal, and the reverse voltage signal to obtain the amplitude-frequency and phase-frequency response curves of the superconducting cavity.

[0061] The core components of the digital low-level radio frequency (LLRF) system can be implemented, but are not limited to, by an FPGA (Field Programmable Gate Array), such as the ZYNQ7100 FPGA chip. The power source is a solid-state power source, each containing 24 inserts (model: KFPA-162-1-1), with a saturated output power of approximately 1.4kW per insert. The superconducting cavity is a half-wavelength superconducting cavity with a relativistic velocity of 0.1.

[0062] The apparatus provided in the above-described embodiments of this application generates a sawtooth pulse frequency signal through a digital radio frequency low-level system and generates a frequency control word. Based on the frequency control word, it generates a sine data sequence and a cosine data sequence, and performs quadrature modulation on the sine and cosine data sequences. The output of the quadrature modulation is converted from digital to analog and output as a radio frequency signal to a power source. After power amplification and coupling by a directional coupler, the signal is input to the superconducting cavity. The digital radio frequency low-level system then acquires the cavity pressure signal of the superconducting cavity, as well as the forward and reverse voltage signals of the directional coupler, and performs real-time signal processing to obtain the amplitude-frequency and phase-frequency response curves of the superconducting cavity. Compared with the prior art, this improves measurement efficiency and helps to analyze the operational stability of the superconducting cavity.

[0063] The following is combined Figure 1 and Figure 2 In another aspect of the embodiments of this application, a method for measuring the amplitude-frequency and phase-frequency response of a superconducting cavity provided by the embodiments of this application is described. The method is applicable to... Figure 1 The device in the middle.

[0064] The method for measuring the amplitude and phase frequency response of a superconducting cavity in this application embodiment includes:

[0065] S1, the digital radio frequency low-level system generates a sawtooth pulse frequency signal and generates a frequency control word based on the sawtooth pulse frequency signal;

[0066] Specifically, the digital radio frequency low-level system generates a sawtooth pulse frequency signal through an internal FPGA chip.

[0067] Step 1: The FPGA chip encodes and outputs a sawtooth wave pulse signal according to the start frequency, cutoff frequency, and measurement duration set by the host computer. In this embodiment, the center frequency of the superconducting cavity is, for example, 162.5MHz, and the sweep width between the start and cutoff frequencies is 1kHz. Therefore, the start frequency f0 can be set to 162.4995MHz, and the cutoff frequency f... c Set to 162.5005MHz, with a sweep duration (T) of 1 second.

[0068] Step 2: The FPGA chip further calculates the frequency control word M based on the parameters of the sawtooth wave pulse frequency signal using the following formula:

[0069] f step This is the sweep step size;

[0070] f = f0 + ∑f step ;

[0071]

[0072] Among them, f clock The clock frequency of the FPGA chip is n, and the bit width of the phase accumulator in the FPGA chip is n (e.g., 32 bits).

[0073] S2, the digital radio frequency low-level system generates a sine data sequence and a cosine data sequence according to the frequency control word, and performs quadrature modulation on the sine data sequence and the cosine data sequence. The output of the quadrature modulation is converted from digital to analog and then output as a radio frequency signal to the power source. After being amplified by the power source and coupled by the directional coupler, it is input to the superconducting cavity.

[0074] Specifically, the steps include: Step 1, in the FPGA chip, inputting the frequency control word sequence into the numerically controlled oscillator (NCO module, NCO, Numerically Controlled Oscillator), the NCO module will output sine and cosine data sequences (hereinafter referred to as sinα and cosα sequences).

[0075] Step 2: Based on the amplitude (A) and phase (θ) of the low-level control signal sent by the host computer, the signal is converted in real time into an I (In-phase) sequence and a Q (Quadrature phase) sequence (I = A·cosθ, Q = A·sinθ) using the CORDIC (Coordinate Rotation Digital Computer) algorithm. To avoid excessive cavity pressure causing Lorentz force detuning and thus inaccurate measurement results, the amplitude is set to 0.2mV and the phase to 0 degrees in this example.

[0076] Step 3: Perform in-phase / quadrature modulation (I / Q modulation) transformation on the above sinα and cosα data sequences and the transformed I and Q sequences (orthogonal modulation algorithm as follows). Figure 3 ), where the formula for I / Q modulation conversion is: I / Q output=Q*sinα+I*cosα=Acos(θ-α).

[0077] Step 4: The I / Q modulated signal is then driven by the solid-state power source through the DAC output, and the output signal of the solid-state power source scans the superconducting cavity.

[0078] S3, the digital radio frequency low-level system acquires the cavity pressure signal of the superconducting cavity, as well as the forward voltage signal and reverse voltage signal of the directional coupler;

[0079] Specifically, using a signal extraction coupler (antenna Q) e ~10 7 Online measurement of superconducting cavity sampling signal (P) t (signal); online measurement of cavity incident and reflected signals using a directional coupler (P) f and P r (Signal). Among them, P t P f and P r All are 162.5MHz radio frequency signals.

[0080] After sequentially down-converting and digitizing the above radio frequency signals, the original digitized baseband voltage signal, i.e., cavity voltage V, is obtained in the digital radio frequency low-level system. c Forward voltage V f and reverse voltage V r .

[0081] S4, the digital radio frequency low-level system performs real-time signal processing based on the cavity pressure signal, the forward voltage signal and the reverse voltage signal to obtain the amplitude frequency and phase frequency response curves of the superconducting cavity.

[0082] Specifically, real-time signal processing includes plotting amplitude-frequency response curves and phase-frequency response curves.

[0083] Step 1: First, in the low-level FPGA, process the read V... c V f V r The I and Q sequences of the signal are demodulated using I and Q methods, and then rotated using CORDIC to obtain the corresponding amplitude and phase signals.

[0084] Step 2: Obtain the I and Q sequence data of the DAC output, demodulate them, and rotate them using CORDIC to obtain the phase of the DAC output signal;

[0085] Step 3: The signal oscillation change in the phase of the DAC output causes a low-level read of V. c V f V r The phase signal also oscillates and changes, making V impossible to observe directly.c V f V r Phase information of the voltage signal. Therefore, V c V f V r The phase frequency response curve needs to be obtained by subtracting the phase of the DAC output signal from the phase obtained in step 1, thus obtaining the corresponding signal phase frequency response curve. The horizontal axis of the curve is the sweep frequency f corresponding to the phase signal, and the amplitude frequency response curve is the curve with the amplitude obtained in step 1 as the vertical axis and the corresponding sweep frequency f as the horizontal axis. One of the superconducting cavities V obtained using this method c The amplitude-frequency and phase-frequency response curves are as follows Figure 4 The meaning is as shown.

[0086] Furthermore, in this embodiment of the application, a process for evaluating measurement accuracy is also included.

[0087] Specifically, the amplitude-frequency response curve of a superconducting cavity is first measured using the method provided in the embodiments of this application, and the half bandwidth of the cavity is calculated based on the measurement.

[0088] In this embodiment of the application, a network analyzer is used to connect the components within the same superconducting cavity. A schematic diagram of the connection is shown below. Figure 5 Measure the amplitude-frequency response curve of the same cavity and calculate the half bandwidth of the cavity.

[0089] In this application example, comparative tests were conducted on three superconducting cavities, and the measurement results are shown in Table 1. The difference in half-bandwidth of the same superconducting cavity measured by the two methods is within ±5 Hz. Therefore, the accuracy of the measurement method in this application embodiment can be guaranteed.

[0090]

[0091] Table 1

[0092] In summary, the technical solution of this application has the following advantages:

[0093] (1) This invention achieves the measurement of the amplitude-frequency and phase-frequency response curves of superconducting cavities by constructing a real-time signal processing algorithm inside the FPGA. The measurement process can be fully automated and can simultaneously measure multiple superconducting cavities, greatly improving the measurement efficiency of the amplitude-frequency and phase-frequency response curves of superconducting cavities. The measurement process can be completed quickly during the aging process of the superconducting cavity without occupying machine time.

[0094] (2) Since the new generation of particle accelerator systems generally adopts FPGA-based digital low-level technology, the discrimination algorithm of the present invention can be fully deployed inside the low-level system without adding additional hardware devices or changing the hardware device connections of the existing radio frequency system.

[0095] (3) This measurement scheme can also be used to monitor other characteristic parameters of the superconducting cavity, such as the superconducting cavity quality factor Q, in real time during the heating and cooling process. L These findings provide data support for further clarifying the coupling relationship between the characteristic parameters of the superconducting cavity and other physical quantities (such as cavity pressure and helium pressure).

[0096] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0097] In the embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of the units described above is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be an indirect coupling or communication connection between devices or units through some interfaces, and may be electrical, mechanical, or other forms.

[0098] The integrated units implemented as software functional units described above can be stored in a computer-readable storage medium. These software functional units, stored in a storage medium, include several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute some steps of the methods described in the various embodiments of the present invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0099] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for measuring the amplitude and phase frequency response of a radio frequency cavity, applied to an accelerator, said accelerator comprising a digital radio frequency low-level system, a power source, a directional coupler, and a radio frequency cavity connected in sequence, characterized in that, The method includes: The digital radio frequency low-level system generates a sawtooth pulse frequency signal and generates a frequency control word based on the sawtooth pulse frequency signal. The digital radio frequency low-level system generates a sine data sequence and a cosine data sequence according to the frequency control word, and performs quadrature modulation on the sine data sequence and the cosine data sequence. The output of the quadrature modulation is converted from digital to analog to generate a radio frequency signal, which is output to the power source. After being amplified by the power source and coupled by the directional coupler, it is input to the radio frequency cavity. The digital radio frequency low-level system acquires the cavity pressure signal of the radio frequency cavity, as well as the forward voltage signal and reverse voltage signal of the directional coupler; The digital radio frequency low-level system performs real-time signal processing based on the cavity pressure signal, the forward voltage signal, and the reverse voltage signal to obtain the amplitude frequency and phase frequency response curves of the radio frequency cavity.

2. The method for measuring the amplitude and phase frequency response of a radio frequency cavity according to claim 1, characterized in that, The digital radio frequency low-level system generates a sawtooth pulse frequency signal, including: The digital radio frequency low-level system generates a sawtooth pulse frequency signal through an internal FPGA chip.

3. The method for measuring the amplitude and phase frequency response of a radio frequency cavity according to claim 2, characterized in that, The step of generating a frequency control word based on the sawtooth wave pulse frequency signal includes: Based on the parameters of the sawtooth wave pulse frequency signal, the frequency control word M is solved using the following formula: f=f0+Σf step ; Among them, f clock The operating clock frequency of the FPGA chip is n, and the bit width of the phase accumulator in the FPGA chip is n; f0 is the starting frequency of the sawtooth wave pulse frequency signal. c The cutoff frequency of the sawtooth wave pulse frequency signal is T, where T is the sweep duration of the sawtooth wave pulse frequency signal, and f0 and f are... c The value of T is set by the host computer.

4. The method for measuring the amplitude and phase frequency response of a radio frequency cavity according to claim 3, characterized in that, The digital radio frequency low-level system generates a sine data sequence and a cosine data sequence according to the frequency control word, and performs quadrature modulation on the sine data sequence and the cosine data sequence, including: In the FPGA chip, the frequency control word is input to a numerically controlled oscillator to generate a sine data sequence sinα and a cosine data sequence cosα. Based on the amplitude A and phase θ of the low-level control signal set by the host computer, the CORDIC algorithm is used to convert it into an I sequence and a Q sequence. Using the modulation conversion formula I / Q output =Q*sinα+I*cosα, calculate the output of the quadrature modulation.

5. The method for measuring the amplitude and phase frequency response of a radio frequency cavity according to claim 4, characterized in that, The amplitude A of the low-level control signal set by the host computer is used to prevent the cavity pressure signal from becoming detuned by Lorentz force.

6. The method for measuring the amplitude and phase frequency response of a radio frequency cavity according to claim 5, characterized in that, The sweep width between the start frequency and the cutoff frequency is 1 kHz, and the sweep duration is 1 second; The operating clock frequency is 100MHz; the amplitude of the low-level control signal is 0.2mV and the phase is 0 degrees.

7. The method for measuring the amplitude and phase frequency response of a radio frequency cavity according to claim 4, characterized in that, The digital radio frequency low-level system performs real-time signal processing based on the cavity pressure signal, the forward voltage signal, and the reverse voltage signal to obtain the amplitude-frequency and phase-frequency response curves of the radio frequency cavity, including: The digital radio frequency low-level system solves for the amplitude-frequency response curve; The solution to the amplitude-frequency response curve includes: The FPGA chip performs IQ demodulation and CORDIC rotation on the acquired cavity pressure signal, forward voltage, and reverse voltage signal to obtain the corresponding amplitude values. The amplitude-frequency response curve is obtained by plotting the amplitude value on the vertical axis and the corresponding sweep frequency f on the horizontal axis.

8. The method for measuring the amplitude and phase frequency response of a radio frequency cavity according to claim 4, characterized in that, The digital radio frequency low-level system performs real-time signal processing based on the cavity pressure signal, the forward voltage signal, and the reverse voltage signal to obtain the amplitude-frequency and phase-frequency response curves of the radio frequency cavity, and further includes: The digital radio frequency low-level system solves for the phase frequency response curve; The solution to the amplitude-frequency response curve includes: The FPGA chip performs IQ demodulation and CORDIC rotation on the acquired cavity pressure signal, forward voltage and reverse voltage signal to obtain the corresponding first phase value; The FPGA chip performs CORDIC rotation on the output of the quadrature modulation to obtain the second phase value of the output signal of the quadrature modulation; The phase frequency response curve is obtained by plotting the difference between the first phase value and the second phase value on the vertical axis and the corresponding sweep frequency f on the horizontal axis.

9. The method for measuring the amplitude and phase frequency response of a radio frequency cavity according to claim 1, characterized in that, The method also includes a process for assessing measurement accuracy; The measurement accuracy assessment includes: Based on the measured amplitude-frequency response curve of the radio frequency cavity obtained from the digital radio frequency low-level system, the half bandwidth corresponding to the radio frequency cavity is calculated. Connectivity measurements are performed using a network analyzer and the radio frequency cavity, and the corresponding half bandwidth is calculated based on the amplitude-frequency response curve of the connectivity measurements. The accuracy of the measurement is evaluated based on whether the half-bandwidth of the two measurements mentioned above is within the set error range.

10. An apparatus for measuring the amplitude and phase frequency response of a radio frequency cavity, characterized in that, It includes a digital radio frequency low-level system, a power source, a directional coupler, and a radio frequency cavity connected in sequence; The digital radio frequency low-level system is used to generate a sawtooth pulse frequency signal and generate a frequency control word based on the sawtooth pulse frequency signal. The digital radio frequency low-level system is further configured to generate a sine data sequence and a cosine data sequence according to the frequency control word, and to perform quadrature modulation on the sine data sequence and the cosine data sequence, and to generate a radio frequency signal output to the power source after the output of the quadrature modulation is converted from digital to analog, and the output of the power source is then coupled to the radio frequency cavity through the directional coupler. The digital radio frequency low-level system is also used to acquire the cavity pressure signal of the radio frequency cavity, as well as the forward voltage signal and reverse voltage signal of the directional coupler; The digital radio frequency low-level system is also used to perform real-time signal processing based on the cavity pressure signal, the forward voltage signal, and the reverse voltage signal to obtain the amplitude frequency and phase frequency response curves of the radio frequency cavity.

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