阅读说明：本技术 微波功率源、微波等离子体系统、点火方法及自调谐方法 (Microwave power source, microwave plasma system, ignition method and self-tuning method ) 是由 林默原 章莹 姚利峰 于 2020-12-29 设计创作，主要内容包括：本发明公开了一种微波功率源、微波等离子体系统、点火方法及自调谐方法,微波功率源包括微波信号发生器,用于产生微波信号；信号调节单元,用于对微波信号的幅度、相位进行调节,并用于加载不同频率与占空比的脉冲信号；半导体放大单元；信号传输与负载检测单元,用于将半导体放大单元放大的微波信号发送至负载,并对发送的微波信号以及由负载产生的微波反射信号进行检测,得到检测采样信号；控制单元,用于接收并分析检测采样信号,以根据分析结果来控制微波信号发生器的信号发射频率和/或控制信号调节单元调节方式。本发明实现自动点火频率搜索、自动点火流程以及自调谐流程,解决了目前传统微波等离子设备较难自动点火,难以稳定工作的问题。(The invention discloses a microwave power source, a microwave plasma system, an ignition method and a self-tuning method, wherein the microwave power source comprises a microwave signal generator for generating a microwave signal; the signal adjusting unit is used for adjusting the amplitude and the phase of the microwave signal and loading pulse signals with different frequencies and duty ratios; a semiconductor amplification unit; the signal transmission and load detection unit is used for transmitting the microwave signal amplified by the semiconductor amplification unit to a load and detecting the transmitted microwave signal and a microwave reflection signal generated by the load to obtain a detection sampling signal; and the control unit is used for receiving and analyzing the detection sampling signal so as to control the signal emission frequency of the microwave signal generator and/or control the adjustment mode of the signal adjustment unit according to the analysis result. The invention realizes the automatic ignition frequency search, the automatic ignition process and the self-tuning process, and solves the problems that the traditional microwave plasma equipment is difficult to automatically ignite and stably work at present.)

1. A microwave power source, comprising:

the microwave signal generator is used for generating microwave signals of corresponding transmitting frequencies according to the instructions;

the signal adjusting unit is used for adjusting the amplitude and the phase of the microwave signal generated by the microwave signal generator and loading pulse signals with different frequencies and duty ratios;

the semiconductor amplifying unit is used for amplifying the microwave signal regulated by the signal regulating unit;

the signal transmission and load detection unit is used for sending the microwave signal amplified by the semiconductor amplification unit to a load, and detecting the microwave signal sent to the load and a microwave reflection signal generated by load mismatch to obtain a detection sampling signal;

and the control unit is used for receiving and analyzing the detection sampling signal of the signal transmission and load detection unit so as to generate a first control instruction and/or a second control instruction according to an analysis result, wherein the first control instruction is used for controlling the signal emission frequency of the microwave signal generator, and the second control instruction is used for controlling the signal regulation unit to regulate the amplitude, the phase and/or the pulse modulation mode of the microwave signal.

2. The microwave power source of claim 1, wherein the signal conditioning unit comprises a controllable attenuator, a controllable phase shifter, and a controllable high-speed radio frequency switch, wherein the controllable attenuator is configured to receive a control command from the control unit and attenuate the microwave signal according to the control command; the controllable phase shifter is used for receiving a control instruction of the control unit and adjusting the phase of the microwave signal according to the control instruction; the controllable high-speed radio frequency switch is used for receiving the control instruction of the control unit and carrying out pulse modulation on the microwave signal according to the control instruction.

3. The microwave power source of claim 1, wherein the signal transmission and load detection unit comprises a transmission directional coupler, a circulator, a reflection directional coupler, a transmission power detection module and a reflection power detection module, wherein the transmission directional coupler, the circulator and the reflection directional coupler are configured to transmit the amplified microwave signal to a load, the transmission power detection module is configured to perform coupling sampling detection on the microwave signal transmitted to the load and send a first detection voltage signal to the control unit, and the reflection power detection module is configured to perform coupling sampling detection on a microwave reflection signal generated by load mismatch and send a second detection voltage signal to the control unit.

4. A microwave power source according to claim 1, wherein the microwave signal generator comprises a voltage controlled oscillator and a phase locked loop arranged separately or integrally to enable the generated microwave signal to be tunable over a frequency range of 25-3000 MHz.

5. A microwave power source according to any one of claims 1 to 4 wherein the load is a plasma generating device.

6. A microwave plasma system, comprising a plasma generating device and a microwave power source as claimed in any one of claims 1 to 5, wherein the plasma generating device receives the microwave signal transmitted by the signal transmission and load detection unit of the microwave power source to generate an electric field capable of breaking down gas to generate plasma at a nozzle of the plasma generating device.

7. An auto-ignition method of a microwave plasma system, comprising: presetting a transmitting frequency range of a microwave signal generator, scanning in the transmitting frequency range, searching for the minimum return loss, and taking the transmitting frequency corresponding to the minimum return loss as an ignition frequency point.

8. The auto-ignition method of a microwave plasma system according to claim 7, wherein the microwave plasma system is the microwave plasma system according to claim 6, and the ignition frequency point is determined in advance by the following steps:

s101, a microwave signal generator of a microwave power source generates a microwave signal according to an initial transmitting frequency instruction;

s102, the signal transmission and load detection unit of the microwave power source transmits the amplified microwave signal to the plasma generation device, performs coupling sampling detection on the microwave signal transmitted to the plasma generation device to obtain a first detection voltage signal, and performs coupling sampling detection on a microwave reflection signal generated by mismatch of the plasma generation device to obtain a second detection voltage signal;

s103, performing voltage sampling on the current first detection voltage signal and the current second detection voltage signal, and calculating a return loss value corresponding to the microwave power source;

s104, adjusting a transmitting frequency instruction sent to the microwave signal generator, and repeatedly executing S01 and S103 until the transmitting frequency range of the microwave signal generator is scanned;

s105, searching the minimum return loss from the return loss values in the scanning process, determining the transmitting frequency corresponding to the minimum return loss, and taking the transmitting frequency as an ignition frequency point.

9. The auto-ignition method of a microwave plasma system according to claim 8, wherein the method of calculating the return loss value corresponding to the microwave power source in step S103 is as follows:

according to the first detection voltage signal and the emission signal sampling voltage, a control unit of the microwave power source calculates to obtain forward power; according to the second detection voltage signal and the reflected signal sampling voltage, the control unit calculates to obtain reverse power; the return loss value is calculated by the following formula:

RL — P _ f, where RL is return loss, P _ r is reverse power, and P _ f is forward power.

10. A method of self-tuning a microwave plasma system, characterized by tuning to a stable operating state after ignition of the microwave plasma system by:

s201, calculating an initial return loss value of a microwave power source corresponding to an initial transmitting frequency of a microwave signal generator of the microwave power source;

s202, respectively reducing and increasing the transmitting frequency of the microwave signal generator, and respectively calculating a first return loss value in a state of reducing the transmitting frequency and a second return loss value in a state of increasing the transmitting frequency;

s203, comparing the initial return loss value, the first return loss value and the second return loss value to judge a frequency convergence trend, if the frequency convergence trend is a frequency downward convergence trend, executing S204, and if the frequency convergence trend is a frequency upward convergence trend, executing S205;

s204, gradually reducing the transmitting frequency of the microwave signal generator until the minimum return loss value is found, and taking the corresponding transmitting frequency as the tuning frequency of the microwave signal generator;

s205, gradually increasing the transmitting frequency of the microwave signal generator until the minimum return loss value is found, and taking the corresponding transmitting frequency as the tuning frequency of the microwave signal generator.

11. A self-tuning method of a microwave plasma system according to claim 10, wherein step S203 comprises:

if the first return loss value is smaller than the initial return loss value and smaller than the second return loss value, judging that the frequency convergence trend is a downward frequency convergence trend;

if the second return loss value is smaller than the initial return loss value and smaller than the first return loss value, judging that the frequency convergence trend is a frequency upward convergence trend;

if the initial return loss value is smaller than the first return loss value and smaller than the second return loss value, the adjustment amplitude of the transmission frequency in step S202 is reduced, and the steps S202 and S203 are executed.

12. A method of self-tuning a microwave plasma system, characterized by tuning to a stable operating state after ignition of the microwave plasma system by:

s301, calculating an initial return loss value of a microwave power source corresponding to the initial transmitting frequency of a microwave signal generator of the microwave power source;

s302, adjusting the transmitting frequency of the microwave signal generator to a first direction, and calculating a first return loss value after the transmitting frequency is adjusted;

s303, comparing the initial return loss value with the first return loss value, if the first return loss value is smaller than the initial return loss value, executing S304, otherwise executing S305-S306;

s304, continuously adjusting the transmitting frequency of the microwave signal generator along the first direction until the minimum value of the return loss is found, and taking the transmitting frequency corresponding to the minimum value as the tuning frequency of the microwave signal generator;

s305, adjusting the transmitting frequency of the microwave signal generator along a second direction opposite to the first direction, and calculating a second return loss value after the transmitting frequency is adjusted;

s306, comparing the initial return loss value with a second return loss value, if the second return loss value is smaller than the initial return loss value, executing S307, otherwise executing S308;

s307, continuing to adjust the transmitting frequency of the microwave signal generator along the second direction until the minimum return loss value is found, and taking the transmitting frequency corresponding to the minimum return loss value as the tuning frequency of the microwave signal generator;

s308, reducing the adjusting amplitude of the transmitting frequency, and returning to execute S302-S306.

13. A method of self-tuning a microwave plasma system according to claim 10 or 12, wherein the microwave plasma system is the microwave plasma system according to claim 6, and the method of obtaining the return loss value of the corresponding microwave power source according to the transmitting frequency is as follows:

a microwave signal generator of the microwave power source generates a microwave signal according to the initial transmitting frequency instruction;

the signal transmission and load detection unit of the microwave power source transmits the amplified microwave signal to the plasma generation device, performs coupling sampling detection on the microwave signal transmitted to the plasma generation device to obtain a first detection voltage signal, and performs coupling sampling detection on a microwave reflection signal generated by mismatch of the plasma generation device to obtain a second detection voltage signal;

performing voltage sampling on the current first detection voltage signal and the current second detection voltage signal, and calculating by a control unit of the microwave power source to obtain forward power according to the first detection voltage signal and the transmission signal sampling voltage; according to the second detection voltage signal and the reflected signal sampling voltage, the control unit calculates to obtain reverse power; the return loss value is calculated by the following formula:

RL — P _ f, where RL is return loss, P _ r is reverse power, and P _ f is forward power.

14. A method of operating a microwave plasma system, comprising the steps of:

s401, starting a microwave power source of a microwave plasma system;

s402, starting an ignition frequency optimizing program, finding out the emission frequency of the microwave generator corresponding to the minimum return loss, and taking the emission frequency as an ignition frequency point;

s403, starting a plasma ignition process, which comprises adjusting the transmitting power of the microwave generator at an ignition frequency point until a return loss change value reaches a preset return loss mutation threshold value, and judging that ignition is successful;

s404, starting a self-tuning process, and scanning and searching the tuning frequency of the microwave generator;

s405, carrying out mismatch monitoring on the microwave plasma system, and if the real-time return loss value of the microwave power source is monitored to be larger than a preset alarm loss threshold value, sending out prompt information and/or returning to execute the steps S402-S405.

Technical Field

The invention relates to the technical field of plasma physics, in particular to a microwave power source, a microwave plasma system, an ignition method and a self-tuning method.

Background

Compared with other methods for exciting the plasma, the microwave plasma has the following advantages: 1. the ionization and decomposition degree is high, 2, the electron temperature is high, so that the plasma temperature is low, 3, no electrode is arranged, pollution caused by electrode loss is avoided, 4, the working air pressure range is wide, and the device can be applied to various gases; therefore, the microwave plasma technology is widely applied to a plurality of industrial fields of material synthesis, material analysis, surface treatment, medical cosmetology, semiconductor material preparation and the like, and obtains good application effect.

However, conventional microwave plasma torches suffer from at least the following disadvantages:

1) it is difficult to achieve auto-ignition: according to the principle of the microwave plasma torch, the output frequency of a microwave power source must be in the optimal excitation response frequency band of the torch tube, and the traditional microwave plasma torch adopts a magnetron as the microwave power source, so that the frequency of the magnetron is unstable and cannot be controlled, and the torch tube is difficult to excite for automatic ignition;

2) the unification of auto-ignition and auto-maintenance states cannot be achieved: before plasma is generated and after the plasma is successfully excited, the difference of the load matching state of the plasma torch tube is large, once the plasma is successfully ignited, the microwave power source needs to be capable of quickly tracking and adapting to the change of the load, the microwave power source of the traditional plasma torch cannot be automatically optimized and matched, and after the plasma is ignited, the microwave energy coupling efficiency is low and transmission matching needs to be manually adjusted;

3) time-varying adjustability is poor: in the whole working process of the microwave plasma torch, along with the change of temperature, airflow and gas, the transmission matching from the microwave power source to the torch tube needs to be adjusted in real time to achieve a better energy coupling effect.

The defects are also the root cause that the traditional microwave plasma torch is difficult to realize large-scale industrialization in practical application.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a microwave power source, a microwave plasma system, an ignition method and a self-tuning method, which can realize automatic ignition, automatic tracking of the torch load state and real-time optimization of load matching, and can be suitable for brand-new semiconductor microwave power sources and corresponding plasma torches applied to various types. The technical scheme is as follows:

in one aspect, the present invention provides a microwave power source comprising:

the microwave signal generator is used for generating microwave signals of corresponding transmitting frequencies according to the instructions;

the signal adjusting unit is used for adjusting the amplitude and the phase of the microwave signal generated by the microwave signal generator and loading pulse signals with different frequencies and duty ratios;

the semiconductor amplifying unit is used for amplifying the microwave signal regulated by the signal regulating unit;

the signal transmission and load detection unit is used for sending the microwave signal amplified by the semiconductor amplification unit to a load, and detecting the microwave signal sent to the load and a microwave reflection signal generated by load mismatch to obtain a detection sampling signal;

and the control unit is used for receiving and analyzing the detection sampling signal of the signal transmission and load detection unit so as to generate a first control instruction and/or a second control instruction according to an analysis result, wherein the first control instruction is used for controlling the signal emission frequency of the microwave signal generator, and the second control instruction is used for controlling the signal regulation unit to regulate the amplitude, the phase and/or the pulse modulation mode of the microwave signal.

Further, the signal conditioning unit comprises a controllable attenuator, a controllable phase shifter and a controllable high-speed radio frequency switch, wherein the controllable attenuator is used for receiving a control instruction of the control unit and attenuating the microwave signal according to the control instruction; the controllable phase shifter is used for receiving a control instruction of the control unit and adjusting the phase of the microwave signal according to the control instruction; the controllable high-speed radio frequency switch is used for receiving the control instruction of the control unit and carrying out pulse modulation on the microwave signal according to the control instruction.

Further, signal transmission and load detection unit is including transmission directional coupler, circulator, reflection directional coupler, transmission power detection module and reflection power detection module, wherein, transmission directional coupler, circulator and reflection directional coupler be used for with the microwave signal transmission of amplifying is to the load, transmission power detection module is used for carrying out the coupling sample detection to the microwave signal of transmission to the load and sends the first detection voltage signal that obtains to the control unit, reflection power detection module is used for carrying out the coupling sample detection to the microwave reflection signal that produces by the load mismatch and sends the second detection voltage signal that obtains to the control unit.

Further, the microwave signal generator comprises a voltage-controlled oscillator and a phase-locked loop which are separately or integrally arranged, so that the generated microwave signal is adjustable in the frequency range of 25-3000 MHz.

Further, the load is a plasma generating device.

In another aspect, the present invention provides a microwave plasma system, including a plasma generating device and a microwave power source as described above, where the plasma generating device receives a microwave signal transmitted by a signal transmission and load detection unit of the microwave power source, so as to generate an electric field at a nozzle of the plasma generating device, where the electric field can break down gas to generate plasma.

In one aspect, the present invention provides an auto-ignition method of a microwave plasma system, including: presetting a transmitting frequency range of a microwave signal generator, scanning in the transmitting frequency range, searching for the minimum return loss, and taking the transmitting frequency corresponding to the minimum return loss as an ignition frequency point.

Further, the microwave plasma system is the above microwave plasma system, and the ignition frequency point is determined in advance by the following steps:

s101, a microwave signal generator of a microwave power source generates a microwave signal according to an initial transmitting frequency instruction;

s102, the signal transmission and load detection unit of the microwave power source transmits the amplified microwave signal to the plasma generation device, performs coupling sampling detection on the microwave signal transmitted to the plasma generation device to obtain a first detection voltage signal, and performs coupling sampling detection on a microwave reflection signal generated by mismatch of the plasma generation device to obtain a second detection voltage signal;

s103, performing voltage sampling on the current first detection voltage signal and the current second detection voltage signal, and calculating a return loss value corresponding to the microwave power source;

s104, adjusting a transmitting frequency instruction sent to the microwave signal generator, and repeatedly executing S01 and S103 until the transmitting frequency range of the microwave signal generator is scanned;

s105, searching the minimum return loss from the return loss values in the scanning process, determining the transmitting frequency corresponding to the minimum return loss, and taking the transmitting frequency as an ignition frequency point.

Further, the method for calculating the return loss value corresponding to the microwave power source in step S103 is as follows:

according to the first detection voltage signal and the emission signal sampling voltage, a control unit of the microwave power source calculates to obtain forward power; according to the second detection voltage signal and the reflected signal sampling voltage, the control unit calculates to obtain reverse power; the return loss value is calculated by the following formula:

RL — P _ f, where RL is return loss, P _ r is reverse power, and P _ f is forward power.

The invention also provides two self-tuning methods of the microwave plasma system, so that the microwave plasma system is tuned to a stable working state after being ignited, and the first self-tuning method comprises the following steps:

s201, calculating an initial return loss value of a microwave power source corresponding to an initial transmitting frequency of a microwave signal generator of the microwave power source;

s202, respectively reducing and increasing the transmitting frequency of the microwave signal generator, and respectively calculating a first return loss value in a state of reducing the transmitting frequency and a second return loss value in a state of increasing the transmitting frequency;

s203, comparing the initial return loss value, the first return loss value and the second return loss value to judge a frequency convergence trend, if the frequency convergence trend is a frequency downward convergence trend, executing S204, and if the frequency convergence trend is a frequency upward convergence trend, executing S205;

s204, gradually reducing the transmitting frequency of the microwave signal generator until the minimum return loss value is found, and taking the corresponding transmitting frequency as the tuning frequency of the microwave signal generator;

s205, gradually increasing the transmitting frequency of the microwave signal generator until the minimum return loss value is found, and taking the corresponding transmitting frequency as the tuning frequency of the microwave signal generator.

Further, step S203 includes:

if the first return loss value is smaller than the initial return loss value and smaller than the second return loss value, judging that the frequency convergence trend is a downward frequency convergence trend;

if the second return loss value is smaller than the initial return loss value and smaller than the first return loss value, judging that the frequency convergence trend is a frequency upward convergence trend;

if the initial return loss value is smaller than the first return loss value and smaller than the second return loss value, the adjustment amplitude of the transmission frequency in step S202 is reduced, and the steps S202 and S203 are executed.

A second self-tuning method comprises the steps of:

s301, calculating an initial return loss value of a microwave power source corresponding to the initial transmitting frequency of a microwave signal generator of the microwave power source;

s302, adjusting the transmitting frequency of the microwave signal generator to a first direction, and calculating a first return loss value after the transmitting frequency is adjusted;

s303, comparing the initial return loss value with the first return loss value, if the first return loss value is smaller than the initial return loss value, executing S304, otherwise executing S305-S306;

s304, continuously adjusting the transmitting frequency of the microwave signal generator along the first direction until the minimum value of the return loss is found, and taking the transmitting frequency corresponding to the minimum value as the tuning frequency of the microwave signal generator;

s305, adjusting the transmitting frequency of the microwave signal generator along a second direction opposite to the first direction, and calculating a second return loss value after the transmitting frequency is adjusted;

s306, comparing the initial return loss value with a second return loss value, if the second return loss value is smaller than the initial return loss value, executing S307, otherwise executing S308;

s307, continuing to adjust the transmitting frequency of the microwave signal generator along the second direction until the minimum return loss value is found, and taking the transmitting frequency corresponding to the minimum return loss value as the tuning frequency of the microwave signal generator;

s308, reducing the adjusting amplitude of the transmitting frequency, and returning to execute S302-S306.

Further, the microwave plasma system is the above microwave plasma system, and the method of obtaining the return loss value of the corresponding microwave power source according to the emission frequency is as follows:

a microwave signal generator of the microwave power source generates a microwave signal according to the initial transmitting frequency instruction;

the signal transmission and load detection unit of the microwave power source transmits the amplified microwave signal to the plasma generation device, performs coupling sampling detection on the microwave signal transmitted to the plasma generation device to obtain a first detection voltage signal, and performs coupling sampling detection on a microwave reflection signal generated by mismatch of the plasma generation device to obtain a second detection voltage signal;

performing voltage sampling on the current first detection voltage signal and the current second detection voltage signal, and calculating by a control unit of the microwave power source to obtain forward power according to the first detection voltage signal and the transmission signal sampling voltage; according to the second detection voltage signal and the reflected signal sampling voltage, the control unit calculates to obtain reverse power; the return loss value is calculated by the following formula:

RL — P _ f, where RL is return loss, P _ r is reverse power, and P _ f is forward power.

In addition, the invention also provides a working method of the microwave plasma system, which comprises the following steps:

s401, starting a microwave power source of a microwave plasma system;

s402, starting an ignition frequency optimizing program, finding out the emission frequency of the microwave generator corresponding to the minimum return loss, and taking the emission frequency as an ignition frequency point;

s403, starting a plasma ignition process, which comprises adjusting the transmitting power of the microwave generator at an ignition frequency point until a return loss change value reaches a preset return loss mutation threshold value, and judging that ignition is successful;

s404, starting a self-tuning process, and scanning and searching the tuning frequency of the microwave generator;

s405, carrying out mismatch monitoring on the microwave plasma system, and if the real-time return loss value of the microwave power source is monitored to be larger than a preset alarm loss threshold value, sending out prompt information and/or returning to execute the steps S402-S405.

The invention has the following technical effects:

a. before the plasma torch is ignited, finding out an optimal ignition frequency point through load detection;

b. the optimal coupling state of the plasma torch for maintaining the microwave power is realized by utilizing a load tracking algorithm, so that the work of a plasma torch tube is always kept stable;

c. the full semiconductor technology can accurately control the frequency, power and phase of microwave signals;

d. the stable work of high reliability reduces frequent ignition operation, increase of service life.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a schematic structural diagram of a microwave plasma system according to an embodiment of the present invention;

FIG. 2 is a schematic structural diagram of a signal conditioning unit according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of a signal transmission and load detection unit according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a work flow of a microwave plasma system according to an embodiment of the present invention;

FIG. 5 is a schematic flow chart of an ignition frequency optimization routine provided by an embodiment of the present invention;

FIG. 6 is a schematic diagram of a plasma ignition process provided by an embodiment of the present invention;

FIG. 7 is a diagram illustrating a first self-coordination process according to an embodiment of the present invention;

fig. 8 is a schematic diagram of a second self-coordination procedure provided in the embodiment of the present invention.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that the terms "first," "second," and the like in the description and claims of the present invention and in the drawings described above are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used is interchangeable under appropriate circumstances such that the embodiments of the invention described herein are capable of operation in sequences other than those illustrated or described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, apparatus, article, or device that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or device.

In one embodiment of the present invention, there is provided a microwave power source, see fig. 1, comprising:

the microwave signal generator is used for generating microwave signals of corresponding transmitting frequencies according to the instructions;

the signal adjusting unit is used for adjusting the amplitude and the phase of the microwave signal generated by the microwave signal generator and loading pulse signals with different frequencies and duty ratios;

the semiconductor amplifying unit is used for amplifying the microwave signal regulated by the signal regulating unit;

a signal transmission and load detection unit, configured to send the microwave signal amplified by the semiconductor amplification unit to a load, and detect the microwave signal sent to the load and a microwave reflection signal generated by load mismatch to obtain a detection sampling signal, where the load is specifically a plasma generation device (hereinafter referred to as a plasma torch);

and the control unit is used for receiving and analyzing the detection sampling signal of the signal transmission and load detection unit so as to generate a first control instruction and/or a second control instruction according to an analysis result, wherein the first control instruction is used for controlling the signal emission frequency of the microwave signal generator, and the second control instruction is used for controlling the signal regulation unit to regulate the amplitude, the phase and/or the pulse modulation mode of the microwave signal.

Fig. 1 also provides a microwave plasma system, which includes a plasma generating device (plasma torch) and a microwave power source as described above, wherein the microwave power source is responsible for generating and transmitting a microwave signal with proper frequency and power to the plasma torch, so as to excite the plasma generation and maintain the stable operation of the plasma; the plasma generating device receives the microwave signal transmitted by the signal transmission and load detection unit of the microwave power source so as to generate an electric field capable of breaking down gas to generate plasma at a pipe orifice of the plasma generating device.

In summary, the microwave signal generator generates a microwave signal with a set frequency f according to the instruction of the control unit and transmits the microwave signal to the signal control unit, and the signal adjusting unit can adjust the amplitude and the phase of the signal and load pulse signals with different frequencies and duty ratios; the microwave signal regulated by the signal control unit is transmitted to the semiconductor amplification unit for amplification and is transmitted to the signal transmission and load detection unit, the signal transmission and load detection unit sends the amplified microwave signal to the plasma torch tube, simultaneously, the microwave emission signal and a microwave reflection signal generated by load mismatch of the torch tube can be detected, the detection sampling signal is transmitted to the control unit, the control unit calculates and analyzes the emission signal sampling voltage and the reflection signal sampling voltage, controls the signal emission frequency of the microwave signal emission unit according to the analysis result, and simultaneously controls the signal control unit to control the amplitude, the phase and the pulse modulation mode of the signal, so that the self-ignition, the self-maintenance and the automatic optimization aiming at different ionized gases of the microwave plasma torch tube are realized. The following detailed description is made for each unit:

the microwave signal generator is a controllable frequency generator, which can generate microwave signals requiring level setting according to the setting of a system control unit, the microwave signal generator can be realized by a discrete voltage-controlled oscillator and a phase-locked loop, and can also be designed by an integrated IC (integrated Circuit). in the embodiment, the microwave signal generator is designed by an integrated chip HMC832, the voltage-controlled oscillator and the phase-locked loop are integrated by the chip, the frequency range of 25MHz to 3000MHz can be covered, the frequency band required by plasma excitation can be realized, and in the working process of the system, the microwave signal generator can adjust the signal frequency in real time according to the instruction of the system control unit.

Referring to fig. 2, the signal adjusting unit is composed of a controllable attenuator, a controllable phase shifter and a controllable high-speed radio frequency switch, wherein the controllable attenuator can receive a setting instruction of the system control unit to attenuate the microwave signal generated by the microwave signal generator, and the controllable phase shifter can receive the setting instruction of the system control unit to adjust the phase of the microwave signal generated by the microwave signal generator by 0-360 degrees; the controllable high-speed radio frequency switch can receive a set instruction of the system control unit and carry out pulse modulation on the microwave signal generated by the microwave signal generator; in general, the signal conditioning unit may perform amplitude, phase, and pulse modulation conditioning on the microwave signal generated by the microwave signal generator by an instruction of the system control unit, and transmit the conditioned microwave signal to the semiconductor amplifying unit.

The semiconductor amplifying unit is composed of a multistage semiconductor amplifier and can amplify and output the microwave signal subjected to signal conditioning.

Referring to fig. 3, the signal transmission and load detection unit is composed of a transmission directional coupler, a circulator, a reflection directional coupler, a transmission power detection module, and a reflection power detection module, wherein the transmission directional coupler, the circulator, and the reflection directional coupler can transmit the amplified microwave signal to the transmitting end, and simultaneously can perform coupling sampling detection on the transmitted microwave signal and a reflection signal generated by output load mismatch, and transmit the detection voltage to the system control unit for analysis and calculation. Wherein the power coupled from the forward power coupler is detected by a power detector to obtain a forward power detection voltage V_DFThe reverse power coupled by the circulator is detected by the power detector to obtain a reverse power detection voltage V_DR，V_DFAnd V_DRThe forward power P _ f and the reverse power P _ r can be obtained after voltage sampling and calculation, the unit is dBm, the output return loss RL in the working state of the power amplifier can be calculated as P _ r-P _ f, the unit is dB, the smaller RL is, the smaller the microwave energy reflection output by the power amplifier is, the higher the load absorption energy is, the higher the RL is, the larger the reflected microwave energy is, and the lower the load absorption energy is.

The system control unit is realized by a microprocessor, can control the microwave signal generator, the signal adjusting unit, the semiconductor power amplifying unit and the microwave transmission and load detecting unit, and can adjust the frequency and the power of the output microwave signal; extracting various parameters, including monitoring module temperature, extracting forward power and extracting reverse power; calculating return loss and establishing an alarm mechanism, wherein the alarm mechanism comprises over-temperature alarm, forward power alarm, reverse power alarm, load standing wave ratio alarm and the like.

When the microwave power source transmits microwave energy to the plasma torch tube, an electric field with certain field intensity is generated at the opening of the torch tube, and gas sprayed out of the inner tube of the torch tube can be broken down to generate plasma. Before the plasma torch tube is successfully ignited and after the ignition is successful, the frequency response of the input end of the plasma torch tube has a large difference, which is a pain point which is difficult to excite the torch tube to automatically ignite and to automatically adjust transmission matching, so that the plasma torch tube always has an interruption phenomenon in the working process.

The invention can find the optimal ignition frequency point through load detection before the ignition of the plasma torch tube, emit microwave energy to generate plasma, and after the plasma is generated, the matching frequency of the torch tube is greatly changed, the matching frequency is automatically tracked, the microwave signal emission frequency is optimized, the optimal ignition maintaining effect is achieved, meanwhile, when the working condition of the torch tube is changed, the automatic optimization state is kept, the optimal coupling state of microwave power is maintained, the work of the plasma torch tube is always kept stable, and the specific implementation mode is as follows:

the working process of the microwave plasma system in the embodiment of the invention is as follows, and is shown in figure 4:

s401, starting a microwave power source of a microwave plasma system;

s402, starting an ignition frequency optimizing program, finding out the emission frequency of the microwave generator corresponding to the minimum return loss, and taking the emission frequency as an ignition frequency point;

s403, starting a plasma ignition process, which comprises adjusting the transmitting power of the microwave generator at an ignition frequency point until a return loss change value reaches a preset return loss mutation threshold value, and judging that ignition is successful;

s404, starting a self-tuning process, and scanning and searching the tuning frequency of the microwave generator;

s405, carrying out mismatch monitoring on the microwave plasma system, and if the real-time return loss value of the microwave power source is monitored to be larger than a preset alarm loss threshold value, sending out prompt information and/or returning to execute the steps S402-S405.

The ignition frequency optimization routine in step S402 is specifically shown in fig. 5: firstly, a scanning frequency range (the frequency range can be drawn up according to the input echo of a static torch tube) and a frequency stepping and scanning power are preset. The scanning frequency range can be scanned according to the frequency stepping full frequency band under the low power, the return loss RL of each frequency point is calculated and recorded as P _ r-P _ f, and the frequency point with the lowest RL is selected and recorded as the ignition frequency point. The method comprises the following specific steps:

s101, a microwave signal generator of a microwave power source generates a microwave signal according to an initial transmitting frequency instruction;

s102, the signal transmission and load detection unit of the microwave power source transmits the amplified microwave signal to the plasma generation device, performs coupling sampling detection on the microwave signal transmitted to the plasma generation device to obtain a first detection voltage signal, and performs coupling sampling detection on a microwave reflection signal generated by mismatch of the plasma generation device to obtain a second detection voltage signal;

s103, performing voltage sampling on the current first detection voltage signal and the current second detection voltage signal, and calculating a return loss value corresponding to the microwave power source;

s104, adjusting a transmitting frequency instruction sent to the microwave signal generator, and repeatedly executing S01 and S103 until the transmitting frequency range of the microwave signal generator is scanned;

s105, searching the minimum return loss from the return loss values in the scanning process, determining the transmitting frequency corresponding to the minimum return loss, and taking the transmitting frequency as an ignition frequency point.

Further, the method for calculating the return loss value corresponding to the microwave power source in step S103 is as follows:

according to the first detection voltage signal and the emission signal sampling voltage, a control unit of the microwave power source calculates to obtain forward power; according to the second detection voltage signal and the reflected signal sampling voltage, the control unit calculates to obtain reverse power; the return loss value is calculated by the following formula:

RL — P _ f, where RL is return loss, P _ r is reverse power, and P _ f is forward power.

The plasma ignition process in S403 is specifically shown in fig. 6: after the ignition frequency of the plasma torch is searched, the microwave power source emits signals, the plasma excitation needs enough electric field intensity excitation to generate plasma, after the electric field is enough to ionize gas to generate plasma, the plasma forms a load at the torch mouth, the output matching of the torch tube is changed, the plasma automatic ignition process is judged whether the ignition is successful or not by judging the instant change state, a power increasing step and a reflection loss mutation threshold can be set according to a plasma automatic ignition process shown in figure 6, the difference result of the reflection loss RL' after the power is increased each time and the reflection loss before the power is increased exceeds the threshold, and the reflection loss is judged to generate mutation, the ignition was successful. The method comprises the following specific steps:

s501, the microwave signal generator generates a microwave signal according to a current transmitting power instruction;

s502, the control unit calculates the return loss and the return loss change value of a microwave power source corresponding to the current transmitting power of the microwave signal generator;

s503, comparing the return loss change value with a preset return loss mutation threshold, if the return loss change value is smaller than the return loss mutation threshold, increasing a power value in a transmitting power instruction sent by the microwave signal generator, and repeatedly executing S501-S503, otherwise executing S504;

s504, judging that the ignition is successful, and recording the transmitting power of the current microwave signal generator as the ignition power.

After the ignition is successful, the output frequency of the microwave power source is not matched with the optimal power frequency point of the plasma torch in the working state, and self-tuning to the optimal frequency point is needed. The invention also provides two self-tuning methods of the microwave plasma system, so that the microwave plasma system is tuned to a stable working state after being ignited.

A first self-tuning method is shown in fig. 7, and includes the following steps:

s201, calculating an initial return loss value of a microwave power source corresponding to an initial transmitting frequency of a microwave signal generator of the microwave power source;

s202, respectively reducing and increasing the transmitting frequency of the microwave signal generator, and respectively calculating a first return loss value in a state of reducing the transmitting frequency and a second return loss value in a state of increasing the transmitting frequency;

s203, comparing the initial return loss value, the first return loss value and the second return loss value to judge a frequency convergence trend, if the frequency convergence trend is a frequency downward convergence trend, executing S204, and if the frequency convergence trend is a frequency upward convergence trend, executing S205;

s204, gradually reducing the transmitting frequency of the microwave signal generator until the minimum return loss value is found, and taking the corresponding transmitting frequency as the tuning frequency of the microwave signal generator;

s205, gradually increasing the transmitting frequency of the microwave signal generator until the minimum return loss value is found, and taking the corresponding transmitting frequency as the tuning frequency of the microwave signal generator.

Further, step S203 includes:

if the first return loss value is smaller than the initial return loss value and smaller than the second return loss value, judging that the frequency convergence trend is a downward frequency convergence trend;

if the second return loss value is smaller than the initial return loss value and smaller than the first return loss value, judging that the frequency convergence trend is a frequency upward convergence trend;

if the initial return loss value is smaller than the first return loss value and smaller than the second return loss value, the adjustment amplitude of the transmission frequency in step S202 is reduced, and the steps S202 and S203 are executed.

Referring to fig. 8, a second self-tuning method includes the following specific steps:

s301, calculating an initial return loss value of a microwave power source corresponding to the initial transmitting frequency of a microwave signal generator of the microwave power source;

s302, adjusting (for example, reducing) the transmitting frequency of the microwave signal generator in a first direction, and calculating a first return loss value after the transmitting frequency is adjusted;

s303, comparing the initial return loss value with the first return loss value, if the first return loss value is smaller than the initial return loss value, executing S304, otherwise executing S305-S306;

s304, continuously adjusting the transmitting frequency of the microwave signal generator along the first direction until the minimum value of the return loss is found, and taking the transmitting frequency corresponding to the minimum value as the tuning frequency of the microwave signal generator;

s305, adjusting (correspondingly increasing) the transmitting frequency of the microwave signal generator along a second direction opposite to the first direction, and calculating a second return loss value after the transmitting frequency is adjusted;

s306, comparing the initial return loss value with a second return loss value, if the second return loss value is smaller than the initial return loss value, executing S307, otherwise executing S308;

s307, continuing to adjust the transmitting frequency of the microwave signal generator along the second direction until the minimum return loss value is found, and taking the transmitting frequency corresponding to the minimum return loss value as the tuning frequency of the microwave signal generator;

s308, reducing the adjusting amplitude of the transmitting frequency, and returning to execute S302-S306.

It should be noted that, when S308 needs to be executed, it is indicated that the return loss values after the transmission frequency is adjusted in the first direction and the second direction are both greater than the initial return loss value, it is indicated that the convergence trend of the return loss cannot be determined, and at this time, the adjustment amplitude of the transmission frequency needs to be reduced (adjustment step). Obviously, the adjustment amplitude of the transmission frequency needs to set a minimum value, so as to avoid wireless circulation of the self-coordination process; and if the amplitude value is adjusted to reach the set minimum value after a plurality of cycles and the convergence trend of the return loss still cannot be judged, taking the initial return loss value as the tuning frequency of the microwave signal generator.

The idea of the above two self-tuning methods is the same, that is, the tuning frequency of the microwave signal generator when the return loss is minimum is probed left and right with the initial frequency as the reference. It should be noted that, in step S302, the first direction may be turned up first, and in step S305, the second direction is turned down correspondingly. The amplitude of each adjustment is called as an adjustment step, the adjustment step is minimum, the precision of finding the return loss minimum is higher, and the adjustment step can be manually set.

As described above, the method for obtaining the return loss value of the corresponding microwave power source according to the transmitting frequency is as follows:

a microwave signal generator of the microwave power source generates a microwave signal according to the initial transmitting frequency instruction;

the signal transmission and load detection unit of the microwave power source transmits the amplified microwave signal to the plasma generation device, and performs coupling sampling detection on the microwave signal transmitted to the plasma generation device to obtain a first detection voltage signal (namely a forward power detection voltage V)_DF) And performing coupled sampling detection on the microwave reflection signal generated by mismatch of the plasma generator to obtain a second detection voltage signal (i.e. reverse power detection voltage V)_DR)；

V_DFAnd V_DRThe microwave power source is transmitted to a system monitoring unit, the current first detection voltage signal and the current second detection voltage signal are subjected to voltage sampling, and the control unit of the microwave power source calculates forward power P _ f according to the first detection voltage signal and the emission signal sampling voltage; according to the second detection voltage signal and the reflected signal sampling voltage, the control unit calculates to obtain reverse power P _ r, and the forward power/reverse power is calculated according to the sampled amplitude voltage by a conventional method; the return loss value is calculated by the following formula:

RL — P _ f, where RL is return loss, P _ r is reverse power, and P _ f is forward power.

In addition, when the working state of the plasma torch changes, such as gas change, flow change and temperature change, the plasma torch may be interrupted to ignite, and at this time, the plasma torch will be in a mismatch state, that is, the output return loss of the microwave power source suddenly changes to a higher value.

The sequence of the above embodiments of the present invention is only for description, and does not represent the advantages and disadvantages of the embodiments.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.