A microwave reflectometer and a measurement method based thereon

Abstract

The present application relates to the field of plasma measurement technology, and discloses a microwave reflectometer and a measurement method based thereon, wherein the microwave reflectometer comprises: a signal source unit for outputting a target crystal oscillator signal, a transmission signal and a reference signal; a transmission unit for obtaining an amplified detection signal; a transmission unit for extracting the amplified detection signal and sending it to the plasma; and transmitting the reflection signal to obtain a target reflection signal; a reference unit for frequency-multiplying the reference signal to obtain a target reference signal; a mixing unit for performing a first mixing modulation on the target reflection signal and the target reference signal to obtain an intermediate frequency signal, and performing a second mixing modulation on the intermediate frequency signal and the target crystal oscillator signal to obtain a baseband signal; and a signal processing unit for filtering and amplifying the baseband signal to obtain a target acquisition signal. The technical solution provided by the present application can effectively improve the plasma measurement range and accuracy.

Description

Technical Field

[0001] The present application relates to the field of plasma measurement technology, and in particular to a microwave reflectometer and a measurement method based thereon. Background Art

[0002] Microwave reflectometry technology is widely used in laboratory plasma density measurement. It obtains electron density profiles by scanning microwave frequencies, and provides important data, especially in the study of boundary plasma turbulence. However, existing technologies face problems such as single measurement area, multi-peak signals of frequency-doubler amplifiers, and leakage power of directional couplers, which affect the measurement accuracy and range, especially in complex plasma environments. Summary of the invention

[0003] The present application provides a microwave reflectometer and a measurement method based thereon, which achieves the technical effect of effectively improving the plasma measurement range and accuracy.

[0004] In order to achieve the above objectives, the main technical solutions adopted in this application include:

[0005] In a first aspect, an embodiment of the present application provides a microwave reflectometer, comprising:

[0006] A signal source unit, used to output a target crystal oscillator signal, a transmission signal and a reference signal;

[0007] A transmitting unit, used for performing frequency doubling conversion on the transmitting signal to obtain an amplified detection signal;

[0008] A transmission unit, configured to extract the amplified detection signal and send the extracted target detection signal to the plasma; and transmit the reflected signal reflected by the plasma after receiving the target detection signal to obtain a target reflected signal;

[0009] A reference unit, used for performing frequency multiplication conversion on the reference signal to obtain a target reference signal;

[0010] A mixing unit, used for performing a first mixing modulation on the target reflected signal and the target reference signal to obtain an intermediate frequency signal, and performing a second mixing modulation on the intermediate frequency signal and the target crystal oscillator signal to obtain a baseband signal;

[0011] The signal processing unit is used to filter and amplify the baseband signal to obtain a target acquisition signal, wherein the target acquisition signal represents an original signal that only carries plasma electron density information.

[0012] A microwave reflectometer provided in this embodiment realizes the whole process from signal generation, transmission to signal processing through the collaborative work of multiple units. First, the signal source unit provides a stable target crystal oscillator signal, a transmission signal and a reference signal, laying the foundation for frequency control and signal modulation. The transmitting unit performs frequency doubling conversion on the signal to enhance the frequency characteristics of the detection signal to ensure that it can effectively penetrate the plasma. The transmission unit is responsible for sending the detection signal to the plasma and receiving the reflected signal. The reference unit provides a reference signal with the same frequency characteristics as the target detection signal to ensure accurate comparison of the signal. The mixing unit converts the reflected signal into an intermediate frequency and a baseband signal through two mixing modulations for subsequent processing. Finally, the signal processing unit filters and amplifies the baseband signal, removes noise, strengthens the effective components in the signal, and finally obtains accurate electron density information. It effectively realizes the high-quality generation, transmission, reception and processing of the signal, providing reliable data support for subsequent analysis.

[0013] In one embodiment, the signal source unit comprises:

[0014] A crystal oscillator module, used for outputting the crystal oscillator signal, and dividing the crystal oscillator signal into two paths, one of which is output to the reference unit, and the other is output to the mixing unit after frequency multiplication;

[0015] The synthesis source module is used to output the transmission signal and the reference signal.

[0016] This embodiment provides a high-precision and stable frequency reference through a crystal oscillator module, and distributes the signal to the reference unit and the mixing unit to achieve efficient signal processing. After the crystal oscillator signal is multiplied, the frequency is increased to meet the needs of different frequency bands, while maintaining low noise and high stability to ensure accuracy when working at high frequencies. The synthetic source module outputs the reference signal and the transmission signal, ensuring the precise synchronization of each signal processing unit and improving the overall stability and measurement accuracy. Through the optimized signal distribution and multiplication design, the signal transmission efficiency is improved while ensuring the signal quality.

[0017] In one embodiment, the crystal oscillator module includes:

[0018] A crystal oscillator, used to output the crystal oscillator signal;

[0019] A coaxial power divider, used for dividing the crystal oscillator signal into two paths, one crystal oscillator signal is output to the first frequency multiplier, and the other crystal oscillator signal is output to the reference unit;

[0020] The first frequency multiplier is used for multiplying the output crystal oscillator signal to the V / E band to obtain a target crystal oscillator signal, and outputting the target crystal oscillator signal to the frequency mixing unit.

[0021] This embodiment realizes high-precision and stable signal generation and processing through the coordinated work of a crystal oscillator, a coaxial power divider, a first frequency multiplier and a mixing unit. The crystal oscillator provides a high-precision and stable reference signal, which lays a solid foundation for subsequent frequency multiplication and signal processing. The coaxial power divider evenly distributes the signal to multiple paths, ensuring low-loss transmission of the signal and improving reliability. The first frequency multiplier multiplies the input low-frequency signal to the V band or E band, expanding the frequency range and improving the measurement capability and accuracy in high-frequency applications. Finally, the mixing unit further improves the signal processing capability through frequency conversion and signal modulation, making it possible to process complex signals and high-frequency band applications.

[0022] In one embodiment, the synthesis source module includes:

[0023] A USB synthesis source, used for outputting a microwave signal, wherein the microwave signal has at least two operating frequency bands;

[0024] A coaxial isolator, used for unidirectionally transmitting the microwave signal;

[0025] The coaxial coupler is used to evenly divide the microwave signal output by the coaxial coupler into two signals, one of which is the transmission signal output to the transmission unit, and the other is the reference signal output to the reference unit.

[0026] This embodiment provides efficient and stable microwave signal processing capabilities through the coordinated work of the USB synthetic source, the coaxial isolator and the coaxial coupler. The USB synthetic source can output multi-band microwave signals to meet the needs of different applications while ensuring the stability of the signal. The coaxial isolator effectively prevents reverse signal interference, protects against the influence of signal reflection, and ensures the normal operation of the signal source and other components. The coaxial coupler divides the signal into two paths, one for signal transmission and the other for the output of the reference signal for real-time optimization. Therefore, this embodiment is not only flexible and can adjust the frequency as needed, but also maintains the stability and integrity of the signal, improves the overall performance, and ensures efficient and reliable signal transmission and processing.

[0027] In one embodiment, the transmitting unit comprises:

[0028] A second frequency multiplier, used for multiplying the transmission signal to a V / E band to obtain an initial detection signal;

[0029] A first waveguide isolator, used for unidirectionally transmitting the initial detection signal;

[0030] A power amplifier is used to amplify the power of the initial detection signal output by the first waveguide isolator to obtain the amplified detection signal.

[0031] This embodiment significantly improves the performance of plasma detection through the synergistic effect of the second frequency multiplier, the first waveguide isolator and the power amplifier. First, the second frequency multiplier multiplies the transmitted signal to the V / E band, enhances the resolution and accuracy of the signal, adapts to high-frequency detection requirements, and improves the detection capability. Secondly, the first waveguide isolator ensures stability and efficient operation by ensuring unidirectional transmission of the signal, preventing reverse signal interference and damage to other components. Finally, the power amplifier enhances the signal power to ensure that the detection signal has sufficient strength and can be transmitted over a longer distance, thereby expanding the detection range and sensitivity. Overall, the combination of these three not only improves the signal quality and stability, but also enhances the detection capability and reliability of the reflectometer, ensuring efficient and stable operation in complex environments.

[0032] In one embodiment, the transmission unit comprises:

[0033] A directional coupler, used for directionally coupling the amplified detection signal;

[0034] A bandpass filter, used for filtering the amplified detection signal after directional coupling;

[0035] A vacuum window is used to transmit the filtered amplified detection signal to a vacuum environment to obtain a target detection signal;

[0036] a horn antenna for transmitting the target detection signal into the plasma; or

[0037] A horn antenna, used for transmitting a reflected signal reflected by the plasma after receiving the target detection signal to the vacuum window;

[0038] A vacuum window, used for transmitting the reflected signal to the bandpass filter;

[0039] A bandpass filter, used for filtering the reflected signal;

[0040] The directional coupler is used to perform direction coupling on the filtered reflected signal to obtain the target reflected signal, and transmit the target reflected signal to the mixing unit.

[0041] This embodiment achieves efficient signal reception and processing through the coordinated work of components such as a horn antenna, a vacuum window, a bandpass filter and a directional coupler. The horn antenna receives the reflected signal reflected by the plasma and transmits it to the vacuum window. The vacuum window ensures that the signal is smoothly transmitted between the vacuum environment and the atmospheric environment and maintains the integrity of the signal. Then, the bandpass filter selects the frequency band required by the signal, filters out stray signals and noise, and improves the signal quality. The directional coupler transmits the filtered signal in a direction to the mixing unit to ensure that the signal enters the subsequent processing stage without loss. Through the synergy of these components, the target reflection signal can be accurately and efficiently acquired and analyzed, and the accuracy, reliability and efficiency of plasma detection can be improved.

[0042] In one embodiment, the reference unit comprises:

[0043] A single sideband modulator, used for performing single sideband modulation on the reference signal;

[0044] A third frequency multiplier is used to multiply the reference signal after single-sideband modulation to the V / E band to obtain a target reference signal;

[0045] The second waveguide isolator is used to transmit the target reference signal unidirectionally.

[0046] This embodiment realizes efficient and stable signal transmission through the coordinated work of the single-sideband modulator, the third frequency multiplier and the second waveguide isolator. The single-sideband modulator improves the spectrum efficiency and signal-to-noise ratio by reducing the bandwidth requirement and suppressing one sideband and the carrier, thereby improving the signal quality and adapting to the requirements of long-distance and high-quality communication. The third frequency multiplier multiplies the modulated signal to the V / E band, avoiding low-frequency interference, and improving the signal's penetration ability and resolution, enhancing target identification and positioning accuracy. The second waveguide isolator ensures unidirectional transmission of the signal, prevents the reverse signal from interfering with the third frequency multiplier, and ensures stability and anti-interference ability. Through the combined effect of these three, the reflectometer can provide high-quality, stable and reliable signal transmission, which is particularly suitable for the field of plasma detection with high requirements for signal accuracy and stability.

[0047] In one embodiment, the frequency mixing unit comprises:

[0048] A first mixer, used for performing a first mixing of the target reflected signal and the target reference signal to obtain an intermediate frequency signal;

[0049] The second mixer is used to perform a second mixing on the intermediate frequency signal and the target crystal oscillator signal to obtain a baseband signal.

[0050] In this embodiment, the target reflection signal is mixed with the target reference signal by the first mixer to obtain an intermediate frequency signal, which effectively reduces the signal frequency, makes subsequent processing easier, and improves the signal-to-noise ratio of the signal for further analysis. The intermediate frequency signal contains information such as the distance and speed of the plasma, has less noise, and is suitable for subsequent processing. The second mixer mixes the intermediate frequency signal with the target crystal oscillator signal again to obtain a baseband signal, which can provide complete signal amplitude and phase information. This process not only further reduces the frequency of the signal, which is convenient for digital signal processing, but also enhances the demodulation capability of the signal, helps to more accurately extract characteristics such as the electron density of the plasma, and improves the overall performance and accuracy.

[0051] In one embodiment, the signal processing unit includes:

[0052] A first filter, used for performing a first filtering on the in-phase signal in the baseband signal to obtain a first filtered signal;

[0053] A first signal amplifier, used for amplifying the first filtered signal to obtain a target acquisition signal including an in-phase signal;

[0054] A second filter, used for performing a second filtering on the orthogonal signal in the baseband signal to obtain a second filtered signal;

[0055] A second signal amplifier, used for amplifying the second filtered signal to obtain a target acquisition signal containing an orthogonal signal;

[0056] An acquisition card is used to acquire the target acquisition signal.

[0057] This embodiment effectively filters, amplifies and collects the in-phase signal and quadrature signal in the baseband signal through the collaborative work of multiple components. First, the first filter extracts the in-phase component from the baseband signal, removes noise, and ensures the clarity of the signal; then, the first signal amplifier amplifies the filtered signal to make it strong enough for subsequent processing. The second filter also extracts the quadrature signal from the baseband signal and filters out irrelevant frequency components to further improve the signal quality. The second signal amplifier amplifies the quadrature signal to ensure that there will be no errors due to signal attenuation during the acquisition process. Finally, the acquisition card converts the filtered and amplified target acquisition signal into a digital signal to ensure the acquisition accuracy and high fidelity of the data. Through this series of processing, the system significantly improves the stability, clarity and acquisition accuracy of the signal, providing reliable data support for subsequent signal analysis.

[0058] In a second aspect, an embodiment of the present application provides a measurement method of the microwave reflectometer according to the above-mentioned method, the method comprising:

[0059] The signal source unit outputs a target crystal oscillator signal, a transmission signal and a reference signal;

[0060] The transmitting unit performs frequency doubling conversion on the transmitting signal to obtain an amplified detection signal;

[0061] The transmission unit extracts the amplified detection signal and sends the extracted target detection signal to the plasma; and transmits the reflected signal reflected by the plasma after receiving the target detection signal to obtain a target reflected signal;

[0062] The reference unit performs frequency multiplication conversion on the reference signal to obtain a target reference signal;

[0063] The mixing unit performs a first mixing modulation on the target reflected signal and the target reference signal to obtain an intermediate frequency signal, and performs a second mixing modulation on the intermediate frequency signal and the target crystal oscillator signal to obtain a baseband signal;

[0064] The signal processing unit filters and amplifies the baseband signal to obtain a target acquisition signal, wherein the target acquisition signal represents an original signal that only carries plasma electron density information. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0066] Figure 1 A schematic diagram of a microwave reflectometer for a specific scenario example;

[0067] Figure 2 A block diagram of a microwave reflectometer provided in an embodiment of the present application;

[0068] Figure 3 A block diagram of a signal source unit provided in an embodiment of the present application;

[0069] Figure 4 A block diagram of a crystal oscillator module provided in an embodiment of the present application;

[0070] Figure 5 A block diagram of a synthesis source module provided in an embodiment of the present application;

[0071] Figure 6 A block diagram of a transmitting unit provided in an embodiment of the present application;

[0072] Figure 7A block diagram of a transmission unit provided in an embodiment of the present application;

[0073] Figure 8 A block diagram of a reference unit provided in an embodiment of the present application;

[0074] Fig. 9 A block diagram of a frequency mixing unit provided in an embodiment of the present application;

[0075] Fig.10 A block diagram of a signal processing unit provided in an embodiment of the present application;

[0076] Fig.11 A flow chart of a microwave reflectometer measurement method provided in an embodiment of the present application. DETAILED DESCRIPTION

[0077] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0078] Microwave reflectometry technology has been widely used in the measurement of laboratory plasma density. It relies on the propagation characteristics of microwave signals in plasma, and the reflected microwave signals provide information about the plasma density. Usually, the reflectometer scans the electron density profile of the plasma by adjusting the microwave frequency, thereby effectively observing the distribution of the plasma. Especially in the study of boundary plasma turbulence, microwave reflectometry can provide important density data. However, the existing microwave reflectometry technology still faces some challenges in measurement accuracy and range, which directly affects its application effect in complex plasma environments.

[0079] First, the existing reflectometer technology has the problem of a single measurement area. Usually, the reflectometer uses a fixed frequency for measurement, which limits its coverage and cannot fully reflect the changes in the plasma. In the study of turbulence in boundary plasmas, the limitations of the frequency range may lead to incomplete measurement results and make it difficult to capture the complex dynamics of boundary plasmas.

[0080] Secondly, the multi-peak problem of frequency multipliers is also a major challenge in current technology. When using frequency multipliers (such as quadruplers or sextuples) for signal amplification, it may cause unnecessary multi-peak signal phenomena, which will affect the clarity and accuracy of the signal. In the measurement, the signal enhancement effect of the frequency multiplier sometimes cannot effectively suppress these additional signals, which ultimately leads to an increase in measurement errors.

[0081] In addition, the leakage power problem of the directional coupler will also affect the measurement accuracy of the reflectometer. The directional coupler is used for the transmission and coupling of microwave signals, but its energy transfer may lead to the generation of leakage power, especially under high-power signals. The leakage power may interfere with the reception and processing of the signal, resulting in deviations in the measurement results.

[0082] In summary, although microwave reflectometry technology has achieved certain application results in plasma density measurement and turbulence research, in order to further improve its performance, especially in the observation of boundary plasma turbulence, many challenges in existing technologies still need to be solved.

[0083] Based on this, in order to solve the above technical problems, please refer to Figure 1 In a specific scenario example, it includes: a signal source unit for outputting a target crystal oscillator signal, a transmission signal and a reference signal. The signal source unit includes: a crystal oscillator module for outputting a crystal oscillator signal and dividing the crystal oscillator signal into two paths, one crystal oscillator signal is output to the reference unit, and the other crystal oscillator signal is output to the mixing unit after frequency doubling; a synthesis source module for outputting a transmission signal and a reference signal. Among them, the crystal oscillator module includes: a crystal oscillator for outputting a crystal oscillator signal; a coaxial power divider for dividing the crystal oscillator signal into two paths, one crystal oscillator signal is output to the first frequency multiplier, and the other crystal oscillator signal is output to the reference unit; the first frequency multiplier is used to multiply the output crystal oscillator signal to the V / E band to obtain a target crystal oscillator signal, and output the target crystal oscillator signal to the mixing unit. The synthesis source module includes: a USB synthesis source, which is used to output microwave signals, wherein the working frequency bands of the microwave signals include at least two; a coaxial isolator, which is used to transmit the microwave signals unidirectionally; and a coaxial coupler, which is used to divide the microwave signals output by the coaxial coupler into two signals, one of which is a transmission signal output to a transmission unit, and the other is a reference signal output to a reference unit.

[0084] The transmitting unit is used to perform frequency multiplication conversion on the transmitting signal to obtain an amplified detection signal. The transmitting unit includes: a second frequency multiplier, used to multiply the frequency of the transmitting signal to the V / E band to obtain an initial detection signal; a first waveguide isolator, used to perform unidirectional transmission of the initial detection signal; and a power amplifier, used to amplify the power of the initial detection signal output by the first waveguide isolator to obtain an amplified detection signal.

[0085] The transmission unit is used to extract the amplified detection signal and send the extracted target detection signal to the plasma; and transmit the reflected signal reflected by the plasma after receiving the target detection signal to obtain the target reflected signal. The transmission unit includes: a directional coupler, used to directionally couple the amplified detection signal; a bandpass filter, used to filter the amplified detection signal after directionally coupling; a vacuum window, used to conduct the filtered amplified detection signal to a vacuum environment to obtain the target detection signal; a horn antenna, used to send the target detection signal to the plasma; or a horn antenna, used to transmit the reflected signal reflected by the plasma after receiving the target detection signal to the vacuum window; a vacuum window, used to transmit the reflected signal to the bandpass filter; the bandpass filter is used to filter the reflected signal; a directional coupler, used to directionally couple the filtered reflected signal to obtain the target reflected signal, and transmit the target reflected signal to the mixing unit.

[0086] The reference unit is used to perform frequency multiplication conversion on the reference signal to obtain the target reference signal. The reference unit includes: a single sideband modulator, used to perform single sideband modulation on the reference signal; a third frequency multiplier, used to multiply the frequency of the reference signal after single sideband modulation to the V / E band to obtain the target reference signal; and a second waveguide isolator, used to perform unidirectional transmission of the target reference signal.

[0087] The mixing unit is used to perform a first mixing modulation on the target reflected signal and the target reference signal to obtain an intermediate frequency signal, and perform a second mixing modulation on the intermediate frequency signal and the target crystal oscillator signal to obtain a baseband signal. The mixing unit includes: a first mixer, used to perform a first mixing on the target reflected signal and the target reference signal to obtain an intermediate frequency signal; and a second mixer, used to perform a second mixing on the intermediate frequency signal and the target crystal oscillator signal to obtain a baseband signal.

[0088] The signal processing unit is used to filter and amplify the baseband signal to obtain a target acquisition signal, wherein the target acquisition signal represents the original signal that only carries the plasma electron density information. The signal processing unit includes: a first filter, used to perform a first filtering of the in-phase signal in the baseband signal to obtain a first filtered signal; a first signal amplifier, used to amplify the first filtered signal to obtain a target acquisition signal containing the in-phase signal; a second filter, used to perform a second filtering of the orthogonal signal in the baseband signal to obtain a second filtered signal; a second signal amplifier, used to amplify the second filtered signal to obtain a target acquisition signal containing the orthogonal signal; and an acquisition card, used to acquire the target acquisition signal.

[0089] This embodiment can more intuitively observe the changes in plasma turbulence in the magnetic link area of ​​the ion cyclotron antenna, solving the problem of multiple co-frequency caused by the frequency multiplier and the problem of low leakage power and directivity of the directional coupler. The reflectometer effectively improves the measurement accuracy and range by expanding the measurement range to cover the V band (50-75GHz) and the E band (60-90GHz). After integration with the ion cyclotron heating resonance system, the microwave reflectometer can directly diagnose the changes in the plasma near the ion cyclotron resonance antenna, help to deeply understand the impact of the ion cyclotron antenna on the boundary turbulence and its heating mechanism, and promote the physical understanding of the interaction between ion cyclotron resonance heating and plasma sheath layer. This technology is applied on the tokamak EAST to enrich the EAST boundary turbulence diagnostic database.

[0090] In this embodiment, a microwave reflectometer is provided. Figure 2 A block diagram of a microwave reflectometer provided in an embodiment of the present application, such as Figure 2 As shown, the microwave reflectometer comprises:

[0091] The signal source unit is used to output the target crystal oscillator signal, the transmission signal and the reference signal.

[0092] The transmitting unit is used to perform frequency doubling conversion on the transmitting signal to obtain an amplified detection signal.

[0093] The transmission unit is used to extract the amplified detection signal and send the extracted target detection signal to the plasma; and transmit the reflected signal reflected by the plasma after receiving the target detection signal to obtain the target reflected signal.

[0094] The reference unit is used to perform frequency multiplication conversion on the reference signal to obtain a target reference signal.

[0095] The mixing unit is used to perform a first mixing modulation on the target reflection signal and the target reference signal to obtain an intermediate frequency signal, and perform a second mixing modulation on the intermediate frequency signal and the target crystal oscillator signal to obtain a baseband signal.

[0096] The signal processing unit is used to filter and amplify the baseband signal to obtain a target acquisition signal, wherein the target acquisition signal represents the original signal that only carries the plasma electron density information.

[0097] Specifically, the signal source unit is used to output a target crystal oscillator signal, a transmission signal and a reference signal. The target crystal oscillator signal is generated by a high-stability crystal oscillator as a reference frequency signal of the reflectometer. The transmission signal is generated by a frequency synthesizer for subsequent frequency multiplication and amplification processing. The reference signal is used to mix with the reflection signal to extract plasma information. The transmission unit increases the frequency of the transmission signal to the required frequency band (such as V / E band) through a frequency multiplier to meet the high-frequency requirements of plasma detection. The transmission unit sends the amplified detection signal to the plasma; and transmits the reflection signal reflected by the plasma to the subsequent processing unit to obtain the target reflection signal. The reference unit performs frequency multiplication conversion on the reference signal and increases it to a frequency band matching the reflection signal for subsequent mixing operations. The mixing unit performs a first mixing modulation on the target reflection signal and the target reference signal to obtain an intermediate frequency signal; and performs a second mixing modulation on the intermediate frequency signal and the target crystal oscillator signal to obtain a baseband signal. The baseband signal contains the original information of the plasma. The signal processing unit filters and amplifies the baseband signal to obtain a target acquisition signal, which represents the plasma electron density information.

[0098] A microwave reflectometer provided in this embodiment realizes the whole process from signal generation, transmission to signal processing through the collaborative work of multiple units. First, the signal source unit provides a stable target crystal oscillator signal, a transmission signal and a reference signal, laying the foundation for frequency control and signal modulation. The transmitting unit performs frequency doubling conversion on the signal to enhance the frequency characteristics of the detection signal to ensure that it can effectively penetrate the plasma. The transmission unit is responsible for sending the detection signal to the plasma and receiving the reflected signal. The reference unit provides a reference signal with the same frequency characteristics as the target detection signal to ensure accurate comparison of the signal. The mixing unit converts the reflected signal into an intermediate frequency and a baseband signal through two mixing modulations for subsequent processing. Finally, the signal processing unit filters and amplifies the baseband signal, removes noise, strengthens the effective components in the signal, and finally obtains accurate electron density information. It effectively realizes the high-quality generation, transmission, reception and processing of the signal, providing reliable data support for subsequent analysis.

[0099] Figure 3 A block diagram of a signal source unit provided in an embodiment of the present application, the unit comprising:

[0100] The crystal oscillator module is used to output the crystal oscillator signal and divide the crystal oscillator signal into two paths, one of which is output to the reference unit, and the other is output to the mixing unit after frequency multiplication.

[0101] The synthesis source module is used to output a transmission signal and a reference signal.

[0102] Specifically, the main task of the crystal oscillator module is to generate a reference frequency signal and use it in the subsequent signal processing unit. In order to ensure the high stability and low phase noise of the signal source, the crystal oscillator module usually uses a high-quality crystal oscillator (Crystal Oscillator), such as a temperature-compensated crystal oscillator (TCXO) or a voltage-controlled crystal oscillator (VCXO). The crystal oscillator module divides the output signal into two paths, one is directly passed to the reference unit, and the other is output to the mixing unit after frequency multiplication. Frequency multiplication processing usually uses nonlinear elements or digital frequency synthesis technology, and the multiplied signal is used in the mixing process to generate the required working frequency band. The synthetic source module can output high-precision and high-stability microwave signals, and output the generated microwave signals to the transmitting unit for emission into the plasma, and also output a reference signal for signal processing in the mixing unit. Among them, the synthetic source module can output signals of multiple working frequency bands to meet the measurement requirements in different frequency bands.

[0103] This embodiment provides a high-precision and stable frequency reference through a crystal oscillator module, and distributes the signal to the reference unit and the mixing unit to achieve efficient signal processing. After the crystal oscillator signal is multiplied, the frequency is increased to meet the needs of different frequency bands, while maintaining low noise and high stability to ensure accuracy when working at high frequencies. The synthetic source module outputs the reference signal and the transmission signal, ensuring the precise synchronization of each signal processing unit and improving the overall stability and measurement accuracy. Through the optimized signal distribution and multiplication design, the signal transmission efficiency is improved while ensuring the signal quality.

[0104] Figure 4 A block diagram of a crystal oscillator module provided in an embodiment of the present application, the module includes:

[0105] Crystal oscillator, used to output crystal oscillator signal.

[0106] The coaxial power divider is used to divide the crystal oscillator signal into two paths, one crystal oscillator signal is output to the first frequency multiplier, and the other crystal oscillator signal is output to the reference unit.

[0107] The first frequency multiplier is used for multiplying the output crystal oscillator signal to the V / E band to obtain a target crystal oscillator signal, and outputting the target crystal oscillator signal to the frequency mixing unit.

[0108] Specifically, the role of the crystal oscillator is to generate a stable reference signal. The stability of the crystal oscillator comes from the mechanical resonance characteristics of the crystal inside it. The crystal has a highly accurate frequency control capability and can generate a very stable output signal, namely the crystal oscillator signal. The crystal oscillator signal is divided into two paths by a coaxial power divider to ensure that the signal power of each output path is the same, and is output to the first frequency multiplier and the reference unit respectively. The first frequency multiplier doubles the frequency of the crystal oscillator signal through a nonlinear device (such as a diode or a transistor) to a higher frequency range, the V band (50-75GHz) or the E band (60-90GHz). These high-frequency signals can be used for many high-precision measurement applications, especially in the fields of plasma physics, communications, radar, etc. The increase in frequency can improve the resolution and accuracy of the measurement. In the measurement of plasma density, the switching and expansion of the frequency can cover multiple different frequency ranges, thereby measuring the density information of different regions. Signals of different frequencies can penetrate different levels of the plasma, and each frequency corresponds to different electromagnetic wave propagation characteristics, so the characteristics of the plasma can be deeply analyzed. Avoid signal attenuation or measurement blind spots that may be encountered when relying only on a single frequency band measurement.

[0109] This embodiment realizes high-precision and stable signal generation and processing through the coordinated work of a crystal oscillator, a coaxial power divider, a first frequency multiplier and a mixing unit. The crystal oscillator provides a high-precision and stable reference signal, which lays a solid foundation for subsequent frequency multiplication and signal processing. The coaxial power divider evenly distributes the signal to multiple paths, ensuring low-loss transmission of the signal and improving reliability. The first frequency multiplier multiplies the input low-frequency signal to the V band or E band, expanding the frequency range and improving the measurement capability and accuracy in high-frequency applications. Finally, the mixing unit further improves the signal processing capability through frequency conversion and signal modulation, making it possible to process complex signals and high-frequency band applications.

[0110] Figure 5 A block diagram of a synthesis source module provided in an embodiment of the present application, the module includes:

[0111] The USB synthesis source is used to output a microwave signal, wherein the working frequency bands of the microwave signal include at least two.

[0112] Coaxial isolator is used to transmit microwave signals in one direction.

[0113] The coaxial coupler is used to evenly divide the microwave signal output by the coaxial coupler into two signals, one is a transmission signal output to the transmission unit, and the other is a reference signal output to the reference unit.

[0114] Specifically, the USB synthetic source is a device for outputting microwave signals, and its main function is to generate high-precision, high-stability microwave signals, which are suitable for multiple frequency bands. The USB synthetic source of this embodiment can output microwave signals of at least two working frequency bands, such as 8-12.5GHz and 10-15GHz. That is, the USB synthetic source can output microwave signals of different frequencies to adapt to different application scenarios of plasma measurement. The coaxial isolator can ensure the unidirectional transmission of microwave signals and prevent the reverse signal from affecting the operation of the USB synthetic source or other components. This unidirectional transmission characteristic avoids signal reflection and interference. The microwave signal is output from the coaxial isolator and enters the coaxial coupler, which "couples" part of the input microwave signal to the output end through the transmission of the electromagnetic field without interfering with the transmission of the main signal. This way of distributing signals ensures the integrity of the signal and provides multiple signal outputs at the same time, which is suitable for scenarios where multiple signals need to be processed simultaneously. In this embodiment, the coaxial coupler outputs part of the microwave signal to the transmitting unit, and the other part of the signal is output to the reference unit. The reference signal is usually used for comparison with the transmitted signal, and the reference signal can be used for signal detection, frequency analysis and other performance tests.

[0115] This embodiment provides efficient and stable microwave signal processing capabilities through the coordinated work of the USB synthetic source, the coaxial isolator and the coaxial coupler. The USB synthetic source can output multi-band microwave signals to meet the needs of different applications while ensuring the stability of the signal. The coaxial isolator effectively prevents reverse signal interference, protects against the influence of signal reflection, and ensures the normal operation of the signal source and other components. The coaxial coupler divides the signal into two paths, one for signal transmission and the other for the output of the reference signal for real-time optimization. Therefore, this embodiment is not only flexible and can adjust the frequency as needed, but also maintains the stability and integrity of the signal, improves the overall performance, and ensures efficient and reliable signal transmission and processing.

[0116] Figure 6 A block diagram of a transmitting unit provided in an embodiment of the present application, the unit comprising:

[0117] The second frequency multiplier is used to multiply the transmission signal to the V / E band to obtain an initial detection signal.

[0118] The first waveguide isolator is used for unidirectionally transmitting the initial detection signal.

[0119] The power amplifier is used to amplify the power of the initial detection signal output by the first waveguide isolator to obtain an amplified detection signal.

[0120] Specifically, the main function of the second frequency multiplier is to increase the frequency of the input transmission signal to the V / E band to generate an initial detection signal. Specifically, the frequency of the transmission signal in this embodiment is increased to six times to generate a high-frequency V / E band signal. This high-frequency signal has a wide range of applications in fields such as plasma detection. High-frequency signals can provide higher resolution and accuracy, so they are particularly important in detection, especially in scenarios where detailed observation or smaller target detection is required. The key role of the first waveguide isolator is to ensure the unidirectional transmission of the initial detection signal and prevent the adverse effects of signal reflection. Signal reflection usually produces reflected waves, which may return to the transmission source or the second frequency multiplier, causing interference or damage. The first waveguide isolator ensures the smooth flow of the signal from the second frequency multiplier to the power amplifier by unidirectional transmission, while avoiding potential problems caused by reflection. The main function of the power amplifier is to power amplify the initial detection signal from the first waveguide isolator to generate an amplified detection signal. This signal needs to be amplified to a sufficient power level for effective detection. For high-frequency signals, the amplifier must have a high power amplification capability while ensuring that the quality of the output signal is not affected by over-amplification.

[0121] This embodiment significantly improves the performance of plasma detection through the synergistic effect of the second frequency multiplier, the first waveguide isolator and the power amplifier. First, the second frequency multiplier multiplies the transmitted signal to the V / E band, enhances the resolution and accuracy of the signal, adapts to high-frequency detection requirements, and improves the detection capability. Secondly, the first waveguide isolator ensures stability and efficient operation by ensuring unidirectional transmission of the signal, preventing reverse signal interference and damage to other components. Finally, the power amplifier enhances the signal power to ensure that the detection signal has sufficient strength and can be transmitted over a longer distance, thereby expanding the detection range and sensitivity. Overall, the combination of these three not only improves the signal quality and stability, but also enhances the detection capability and reliability of the reflectometer, ensuring efficient and stable operation in complex environments.

[0122] Figure 7 A block diagram of a transmission unit provided in an embodiment of the present application, the unit comprising:

[0123] The directional coupler is used for directionally coupling the amplified detection signal.

[0124] The bandpass filter is used to filter the amplified detection signal after directional coupling.

[0125] The vacuum window is used to transmit the filtered amplified detection signal into a vacuum environment to obtain a target detection signal.

[0126] A horn antenna is used to send the target detection signal into the plasma.

[0127] Specifically, the directional coupler is used to couple the amplified detection signal from the main transmission path to the bypass path while maintaining the directionality of signal transmission and avoiding energy loss. The main function of the bandpass filter is to retain the frequency band required by the target signal by filtering out unnecessary frequency components. This can improve the quality of the signal and reduce noise interference. The function of the vacuum window is to ensure that the signal strength is not affected when the signal is transmitted between the vacuum environment and the atmospheric environment, and to ensure that the signal effectively enters the vacuum environment for plasma detection. The horn antenna is an antenna shaped like a horn with a wide radiation angle. It can effectively radiate signals by concentrating and guiding electromagnetic waves to a designated area. Specifically, the antenna horn effectively radiates the detection signal from the transmission path into the plasma for target detection.

[0128] or

[0129] The horn antenna is used to transmit the reflected signal after the plasma receives the target detection signal to the vacuum window.

[0130] A vacuum window is used to transmit the reflected signal to a bandpass filter.

[0131] Bandpass filter, used to filter the reflected signal.

[0132] The directional coupler is used to perform direction coupling on the filtered reflected signal to obtain a target reflected signal, and transmit the target reflected signal to the mixing unit.

[0133] Specifically, the main function of the horn antenna is to receive the signal reflected from the plasma. The plasma will reflect the reflected signal carrying the target information due to the interaction with the target detection signal. The horn antenna captures these signals from free space and transmits them to the vacuum window through its wide bandwidth and high-efficiency receiving capability. The vacuum window transmits the signal from the vacuum environment to the bandpass filter while maintaining the signal quality. The bandpass filter is used to filter out the stray signals, noise and other unwanted frequency components in the reflected signal, retaining only the filtered reflected signal. The function of the directional coupler is to directionally couple the filtered signal to the subsequent mixing unit. The directional coupler can ensure the directionality of the signal.

[0134] This embodiment achieves efficient signal reception and processing through the coordinated work of components such as a horn antenna, a vacuum window, a bandpass filter and a directional coupler. The horn antenna receives the reflected signal reflected by the plasma and transmits it to the vacuum window. The vacuum window ensures that the signal is smoothly transmitted between the vacuum environment and the atmospheric environment and maintains the integrity of the signal. Then, the bandpass filter selects the frequency band required by the signal, filters out stray signals and noise, and improves the signal quality. The directional coupler transmits the filtered signal in a direction to the mixing unit to ensure that the signal enters the subsequent processing stage without loss. Through the synergy of these components, the target reflection signal can be accurately and efficiently acquired and analyzed, and the accuracy, reliability and efficiency of plasma detection can be improved.

[0135] Figure 8 A block diagram of a reference unit provided in an embodiment of the present application, the unit comprising:

[0136] The single sideband modulator is used for performing single sideband modulation on the reference signal.

[0137] The third frequency multiplier is used to multiply the reference signal after single-sideband modulation to the V / E band to obtain a target reference signal.

[0138] The second waveguide isolator is used for unidirectionally transmitting the target reference signal.

[0139] Specifically, single-sideband modulation improves the spectrum efficiency and signal-to-noise ratio by moving the spectrum of the reference signal from the baseband to a higher carrier frequency and suppressing a sideband and the carrier. After the reference signal is subjected to single-sideband modulation, the third frequency multiplier multiplies the single-sideband modulated reference signal by six times (i.e., the frequency of the signal is increased to six times the original frequency), thereby converting it to the V / E band to obtain the target reference signal. The frequency multiplication process can not only effectively increase the transmission frequency of the signal, but also shorten the wavelength of the signal, thereby obtaining higher resolution and more accurate positioning capabilities in plasma detection. The second waveguide isolator transmits the target reference signal unidirectionally to prevent the reflected signal from interfering with the transmitting source or the third frequency multiplier. The interference of the reflected signal may cause the performance of the reflectometer to deteriorate, generate unnecessary noise, and may even cause feedback effects, affecting the normal operation of the third frequency multiplier. By using a waveguide isolator, the signal can only be transmitted along a predetermined path, ensuring stability and signal purity.

[0140] This embodiment realizes efficient and stable signal transmission through the coordinated work of the single-sideband modulator, the third frequency multiplier and the second waveguide isolator. The single-sideband modulator improves the spectrum efficiency and signal-to-noise ratio by reducing the bandwidth requirement and suppressing one sideband and the carrier, thereby improving the signal quality and adapting to the requirements of long-distance and high-quality communication. The third frequency multiplier multiplies the modulated signal to the V / E band, avoiding low-frequency interference, and improving the signal's penetration ability and resolution, enhancing target identification and positioning accuracy. The second waveguide isolator ensures unidirectional transmission of the signal, prevents the reverse signal from interfering with the third frequency multiplier, and ensures stability and anti-interference ability. Through the combined effect of these three, the reflectometer can provide high-quality, stable and reliable signal transmission, which is particularly suitable for the field of plasma detection with high requirements for signal accuracy and stability.

[0141] Fig. 9 A block diagram of a frequency mixing unit provided in an embodiment of the present application, the unit comprising:

[0142] The first mixer is used to perform a first mixing on the target reflected signal and the target reference signal to obtain an intermediate frequency signal.

[0143] The second mixer is used to perform a second mixing on the intermediate frequency signal and the target crystal oscillator signal to obtain a baseband signal.

[0144] Specifically, the first mixer performs a first mixing of the target reflected signal and the target reference signal to generate an intermediate frequency signal. Specifically, this process includes multiplying the target reflected signal with the target reference signal, and obtaining a new signal after mixing, whose frequency is the difference frequency of the target reflected signal and the target reference signal. The second mixer performs a second mixing of the intermediate frequency signal and the target crystal oscillator signal to generate a baseband signal. In order to ensure efficient demodulation and accurate analysis of the signal, the second mixer usually uses an IQ mixer. The IQ mixer can generate two signals: an I signal and a Q signal. The I signal represents the real part of the original signal, and the Q signal represents the imaginary part. After the two are synthesized, the amplitude and phase of the signal can be accurately represented, which can provide a basis for clearer demodulation and analysis of target information.

[0145] In this embodiment, the target reflection signal is mixed with the target reference signal by the first mixer to obtain an intermediate frequency signal, which effectively reduces the signal frequency, makes subsequent processing easier, and improves the signal-to-noise ratio of the signal for further analysis. The intermediate frequency signal contains information such as the distance and speed of the plasma, has less noise, and is suitable for subsequent processing. The second mixer mixes the intermediate frequency signal with the target crystal oscillator signal again to obtain a baseband signal, which can provide complete signal amplitude and phase information. This process not only further reduces the frequency of the signal, which is convenient for digital signal processing, but also enhances the demodulation capability of the signal, helps to more accurately extract characteristics such as the electron density of the plasma, and improves the overall performance and accuracy.

[0146] Fig.10 A block diagram of a signal processing unit provided in an embodiment of the present application, the unit comprising:

[0147] The first filter is used to perform a first filtering on the in-phase signal in the baseband signal to obtain a first filtered signal.

[0148] The first signal amplifier is used to amplify the first filtered signal to obtain a target acquisition signal containing an in-phase signal.

[0149] The second filter is used to perform a second filtering on the orthogonal signal in the baseband signal to obtain a second filtered signal.

[0150] The second signal amplifier is used to amplify the second filtered signal to obtain a target acquisition signal containing an orthogonal signal.

[0151] The acquisition card is used to acquire the target acquisition signal.

[0152] Specifically, the task of the first filter is to extract the in-phase signal (I signal) from the baseband signal and perform the first filtering on it. The purpose of the filtering process is to remove unnecessary frequency components, such as noise and interference signals, so as to ensure that the signal for subsequent processing is purer and easier to analyze. The I signal usually carries the real part information of the target signal and reflects the amplitude change of the signal. By filtering, high-frequency noise and irrelevant frequency components are removed, and the main information in the signal can be retained to ensure that it has a high signal-to-noise ratio during further processing. The first signal amplifier amplifies the first filtered signal in order to enhance the strength of the signal so that it is large enough for subsequent processing and analysis. After the first filtering, although the signal is relatively clean, its amplitude may be small, so it needs to be enhanced by the first signal amplifier to ensure that the amplitude of the signal is sufficient to be transmitted to the processing module of the next stage. At the same time, the first signal amplifier also helps to improve the quality of the signal and reduce the signal attenuation problem that may occur in subsequent processing.

[0153] The function of the second filter is similar to that of the first filter, but it mainly performs a second filtering on the orthogonal signal (Q signal) in the baseband signal. The Q signal usually carries the imaginary part of the signal and reflects the phase change of the signal. The filtering process is also to remove unnecessary frequency components to ensure that the Q signal can accurately reflect the real information of the target. The Q signal is used to describe the phase change of the signal and can provide information such as the speed and direction of the target. By filtering and removing unnecessary frequency components, the information in the Q signal can be ensured to be more accurate and the interference caused by turbulence, noise, etc. to subsequent analysis can be reduced. Similar to the first signal amplifier, the function of the second signal amplifier is to amplify the Q signal after the second filtering to ensure that the signal can maintain good strength and quality in subsequent processing. After amplification, the Q signal not only enhances the strength of the signal, but also improves the clarity of the signal to a certain extent, reducing the fuzzy analysis results caused by weak signals.

[0154] The acquisition card converts the analog waveforms of the I and Q signals into digital data through, for example, an analog-to-digital converter (ADC) to facilitate subsequent digital signal processing. In plasma, changes in electron density can cause changes in the frequency and phase of the reflected signal. The amplitude and phase information in the I and Q signals reflect this change. By analyzing the amplitude and phase of these signals, the density disturbance at the plasma boundary can be inferred. In addition, turbulence usually manifests itself as rapid phase and amplitude changes, which can produce short-term fluctuations in the I and Q signals. By analyzing the short-term changes in the I and Q signals, relevant information about the turbulence can be extracted, thereby further analyzing the dynamic characteristics of the plasma.

[0155] This embodiment effectively filters, amplifies and collects the in-phase signal and quadrature signal in the baseband signal through the collaborative work of multiple components. First, the first filter extracts the in-phase component from the baseband signal, removes noise, and ensures the clarity of the signal; then, the first signal amplifier amplifies the filtered signal to make it strong enough for subsequent processing. The second filter also extracts the quadrature signal from the baseband signal and filters out irrelevant frequency components to further improve the signal quality. The second signal amplifier amplifies the quadrature signal to ensure that there will be no errors due to signal attenuation during the acquisition process. Finally, the acquisition card converts the filtered and amplified target acquisition signal into a digital signal to ensure the acquisition accuracy and high fidelity of the data. Through this series of processing, the system significantly improves the stability, clarity and acquisition accuracy of the signal, providing reliable data support for subsequent signal analysis.

[0156] According to an embodiment of the present application, an embodiment of a measurement method of a microwave reflectometer is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0157] In this embodiment, a microwave reflectometer measurement method is provided. Fig.11 A flow chart of a microwave reflectometer measurement method provided in an embodiment of the present application, such as Fig.11 As shown, the process includes the following steps:

[0158] Step S1, the signal source unit outputs a target crystal oscillator signal, a transmission signal and a reference signal.

[0159] Step S3: the transmitting unit performs frequency doubling conversion on the transmitting signal to obtain an amplified detection signal.

[0160] In step S5, the transmission unit extracts the amplified detection signal and sends the extracted target detection signal to the plasma; and transmits the reflected signal reflected by the plasma after receiving the target detection signal to obtain the target reflected signal.

[0161] Step S7: The reference unit performs frequency multiplication conversion on the reference signal to obtain a target reference signal.

[0162] Step S9: The frequency mixing unit performs a first mixing modulation on the target reflected signal and the target reference signal to obtain an intermediate frequency signal, and performs a second mixing modulation on the intermediate frequency signal and the target crystal oscillator signal to obtain a baseband signal.

[0163] In step S11, the signal processing unit filters and amplifies the baseband signal to obtain a target acquisition signal, wherein the target acquisition signal represents an original signal that only carries plasma electron density information.

[0164] In some optional implementations, the signal source unit performs the following steps:

[0165] The crystal oscillator module outputs a crystal oscillator signal and divides the crystal oscillator signal into two paths, one of which is output to the reference unit, and the other is output to the mixing unit after frequency multiplication.

[0166] The synthesis source module outputs a transmission signal and a reference signal.

[0167] In some optional implementations, the crystal oscillator module performs the following steps:

[0168] The crystal oscillator outputs a crystal oscillator signal;

[0169] The coaxial power divider divides the crystal oscillator signal into two paths, one of which is output to the first frequency multiplier, and the other is output to the reference unit;

[0170] The first frequency multiplier multiplies the output crystal oscillator signal to the V / E band to obtain a target crystal oscillator signal, and outputs the target crystal oscillator signal to the frequency mixing unit.

[0171] In some optional implementations, the execution steps of the synthesis source module are as follows:

[0172] The USB synthesis source outputs a microwave signal, wherein the working frequency bands of the microwave signal include at least two;

[0173] The coaxial isolator transmits microwave signals in one direction;

[0174] The coaxial coupler evenly divides the microwave signal output by the coaxial coupler into two signals, one is a transmission signal output to the transmission unit, and the other is a reference signal output to the reference unit.

[0175] In some optional implementations, the transmitting unit performs the following steps:

[0176] The second frequency multiplier multiplies the transmission signal to the V / E band to obtain an initial detection signal;

[0177] The first waveguide isolator transmits the initial detection signal unidirectionally;

[0178] The power amplifier amplifies the power of the initial detection signal output by the first waveguide isolator to obtain an amplified detection signal.

[0179] In some optional implementations, the transmission unit performs the following steps:

[0180] The directional coupler couples the amplified detection signal in a directional manner;

[0181] The bandpass filter filters the amplified detection signal after directional coupling;

[0182] The vacuum window transmits the filtered amplified detection signal to the vacuum environment to obtain the target detection signal;

[0183] A horn antenna sends the target detection signal into the plasma; or

[0184] The horn antenna transmits the reflected signal reflected by the plasma after receiving the target detection signal to the vacuum window;

[0185] The vacuum window transmits the reflected signal to a bandpass filter;

[0186] The bandpass filter filters the reflected signal;

[0187] The directional coupler performs direction coupling on the filtered reflected signal to obtain a target reflected signal, and transmits the target reflected signal to the mixing unit.

[0188] In some optional implementations, the reference unit performs the following steps:

[0189] The single sideband modulator performs single sideband modulation on the reference signal;

[0190] The third frequency multiplier multiplies the single-sideband modulated reference signal to the V / E band to obtain a target reference signal;

[0191] The second waveguide isolator transmits the target reference signal in one direction.

[0192] In some optional implementations, the frequency mixing unit performs the following steps:

[0193] The first mixer performs a first mixing on the target reflected signal and the target reference signal to obtain an intermediate frequency signal;

[0194] The second mixer performs a second mixing on the intermediate frequency signal and the target crystal oscillator signal to obtain a baseband signal.

[0195] In some optional implementations, the signal processing unit performs the following steps:

[0196] The first filter performs a first filtering on the in-phase signal in the baseband signal to obtain a first filtered signal;

[0197] The first signal amplifier amplifies the first filtered signal to obtain a target acquisition signal including an in-phase signal;

[0198] The second filter performs a second filtering on the orthogonal signal in the baseband signal to obtain a second filtered signal;

[0199] The second signal amplifier amplifies the second filtered signal to obtain a target acquisition signal including an orthogonal signal;

[0200] The acquisition card acquires the target acquisition signal.

[0201] The further functional description of each of the above modules and units is the same as that of the above corresponding embodiments and will not be repeated here.

[0202] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the process, method, commodity or device including the elements.

[0203] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0204] The above is only an embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.

[0205] Although the embodiments of the present application have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present application, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A microwave reflectometer, characterized in that: include: A signal source unit, used to output a target crystal oscillator signal, a transmission signal and a reference signal; The signal source unit comprises: A crystal oscillator module, used to output the crystal oscillator signal, and divide the crystal oscillator signal into two paths, one of which is output to the reference unit, and the other is output to the mixing unit after frequency multiplication; A synthesis source module, used for outputting the transmission signal and the reference signal; Wherein, the crystal oscillator module comprises: A crystal oscillator, used to output the crystal oscillator signal; A coaxial power divider, used for dividing the crystal oscillator signal into two paths, one crystal oscillator signal is output to the first frequency multiplier, and the other crystal oscillator signal is output to the reference unit; A first frequency multiplier, used for multiplying the output crystal oscillator signal to a V / E band to obtain a target crystal oscillator signal, and outputting the target crystal oscillator signal to the frequency mixing unit; The synthesis source module comprises: A USB synthesis source, used for outputting a microwave signal, wherein the microwave signal has at least two operating frequency bands; A coaxial isolator, used for unidirectionally transmitting the microwave signal; A coaxial coupler, used to equally divide the microwave signal output by the coaxial coupler into two signals, one of which is the transmission signal output to the transmission unit, and the other is the reference signal output to the reference unit; A transmitting unit, used for performing frequency doubling conversion on the transmitting signal to obtain an amplified detection signal; A transmission unit, configured to extract the amplified detection signal and send the extracted target detection signal to the plasma; and transmit the reflected signal reflected by the plasma after receiving the target detection signal to obtain a target reflected signal; A reference unit, used for performing frequency multiplication conversion on the reference signal to obtain a target reference signal; A mixing unit, used for performing a first mixing modulation on the target reflected signal and the target reference signal to obtain an intermediate frequency signal, and performing a second mixing modulation on the intermediate frequency signal and the target crystal oscillator signal to obtain a baseband signal; The signal processing unit is used to filter and amplify the baseband signal to obtain a target acquisition signal, wherein the target acquisition signal represents an original signal that only carries plasma electron density information.

2. The microwave reflectometer according to claim 1, characterized in that: The transmitting unit comprises: A second frequency multiplier, used for multiplying the transmission signal to a V / E band to obtain an initial detection signal; A first waveguide isolator, used for unidirectionally transmitting the initial detection signal; A power amplifier is used to amplify the power of the initial detection signal output by the first waveguide isolator to obtain the amplified detection signal.

3. The microwave reflectometer according to claim 1, characterized in that: The transmission unit comprises: A directional coupler, used for directionally coupling the amplified detection signal; A bandpass filter, used for filtering the amplified detection signal after directional coupling; A vacuum window is used to transmit the filtered amplified detection signal to a vacuum environment to obtain a target detection signal; a horn antenna for transmitting the target detection signal into the plasma; or A horn antenna, used for transmitting a reflected signal reflected by the plasma after receiving the target detection signal to the vacuum window; A vacuum window, used for transmitting the reflected signal to the bandpass filter; A bandpass filter, used for filtering the reflected signal; The directional coupler is used to perform direction coupling on the filtered reflected signal to obtain the target reflected signal, and transmit the target reflected signal to the mixing unit.

4. The microwave reflectometer according to claim 1, characterized in that: The reference unit comprises: A single sideband modulator, used for performing single sideband modulation on the reference signal; A third frequency multiplier is used to multiply the reference signal after single-sideband modulation to the V / E band to obtain a target reference signal; The second waveguide isolator is used to transmit the target reference signal unidirectionally.

5. The microwave reflectometer according to claim 1, characterized in that: The frequency mixing unit comprises: A first mixer, used for performing a first mixing of the target reflected signal and the target reference signal to obtain an intermediate frequency signal; The second mixer is used to perform a second mixing on the intermediate frequency signal and the target crystal oscillator signal to obtain a baseband signal.

6. The microwave reflectometer according to claim 1, characterized in that: The signal processing unit comprises: A first filter, used for performing a first filtering on the in-phase signal in the baseband signal to obtain a first filtered signal; A first signal amplifier, used for amplifying the first filtered signal to obtain a target acquisition signal including an in-phase signal; A second filter, used for performing a second filtering on the orthogonal signal in the baseband signal to obtain a second filtered signal; A second signal amplifier, used for amplifying the second filtered signal to obtain a target acquisition signal containing an orthogonal signal; An acquisition card is used to acquire the target acquisition signal.

7. A microwave reflectometer measurement method according to any one of claims 1 to 6, characterized in that: The method comprises: The signal source unit outputs a target crystal oscillator signal, a transmission signal and a reference signal; The transmitting unit performs frequency doubling conversion on the transmitting signal to obtain an amplified detection signal; The transmission unit extracts the amplified detection signal and sends the extracted target detection signal to the plasma; and transmits the reflected signal reflected by the plasma after receiving the target detection signal to obtain a target reflected signal; The reference unit performs frequency multiplication conversion on the reference signal to obtain a target reference signal; The mixing unit performs a first mixing modulation on the target reflected signal and the target reference signal to obtain an intermediate frequency signal, and performs a second mixing modulation on the intermediate frequency signal and the target crystal oscillator signal to obtain a baseband signal; The signal processing unit filters and amplifies the baseband signal to obtain a target acquisition signal, wherein the target acquisition signal represents an original signal that only carries plasma electron density information.

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