High-power radio frequency antenna impedance measuring equipment

Abstract

The utility model discloses a high-power radio frequency antenna impedance measuring device. The measuring device comprises a radio frequency source, a matcher, a Rogowski coil and a processor. The radio frequency source is used for generating a radio frequency source signal and inputting the radio frequency source signal into the matcher through a transmission line; the matcher is connected with the antenna and is used for measuring the voltage of the input end of the antenna through the voltage measuring circuit based on the transmitted radio frequency source signal; the Rogowski coil is arranged on a connecting wire between the matcher and the antenna and is used for measuring the current from the matcher to the input end of the antenna; and the processor is used for obtaining the antenna impedance based on the voltage and the current. According to the utility model, the technical problem of real-time measurement of the antenna impedance in the operation process of the high-power radio frequency antenna is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of antenna impedance measurement, in particular to a high-power radio frequency antenna impedance measurement device. Background Art

[0002] High-power RF sources (power ranging from kilowatts to megawatts) are widely used in nuclear fusion and low-temperature plasma devices. Microwaves with frequencies of MHz to GHz are coupled into the plasma through antennas. Power coupling performance is usually characterized by antenna impedance, which changes with changes in plasma performance. When the antenna impedance and the transmission line impedance are mismatched, the reflected power will increase and the coupled power will be reduced. Therefore, real-time measurement of antenna impedance is very important to ensure RF power coupling. Because the plasma environment is significantly different from a vacuum, the antenna impedance usually measured by a network analyzer when not working is difficult to use to characterize the antenna impedance in a plasma environment. Secondly, most of the probe-type voltage-current probes currently available on the market can only measure antenna impedance at low voltages (around 1000V), while the voltage of high-power RF antennas is usually several thousand to tens of kilovolts, and the current is tens to hundreds of amperes. These commercial voltage-current probes are difficult to use directly. Utility Model Content

[0003] The technical problem to be solved by the present invention is that most of the currently available probe-type voltage-current probes can only measure antenna impedance at low voltages, and cannot measure the antenna impedance of high-power radio frequency antennas during operation. The purpose of the present invention is to provide a high-power radio frequency antenna impedance measurement device, which uses two adjustable and high-voltage vacuum capacitors C3 and C4 connected in series and then in parallel in a matching circuit for voltage division; and the capacitance values ​​of capacitors C3 and C4 are controlled by a servo motor; in addition, a new type of PCB Rogowski coil is installed between the matching box and the antenna to detect the current from the matching circuit to the antenna input terminal, thereby obtaining the antenna impedance. The present invention solves the technical problem of real-time measurement of the antenna impedance of a high-power radio frequency antenna during operation.

[0004] The utility model is achieved through the following technical solutions:

[0005] A high-power radio frequency antenna impedance measurement device, comprising a radio frequency source, a matching device, a Rogowski coil, and a processor;

[0006] The radio frequency source is used to generate a radio frequency source signal and input the radio frequency source signal into the matching device through a transmission line;

[0007] The matching device is connected to the antenna and is used to measure the voltage at the antenna input terminal through the voltage measurement circuit based on the transmitted radio frequency source signal;

[0008] The Rogowski coil is provided on the connecting wire between the matching device and the antenna, and is used to measure the current from the matching device to the antenna input terminal;

[0009] The processor is configured to obtain antenna impedance based on the voltage and current.

[0010] Furthermore, the matcher includes a matching network and a voltage measurement circuit, and the matching network is connected to the voltage measurement circuit;

[0011] The matching network includes an inductor L1, a capacitor C1 and a capacitor C2, wherein the capacitor C2 is connected to both ends of the RF source, one end of the inductor L1 is connected to the capacitor C2 and the other end is connected to the capacitor C1, and the capacitor C1 is connected in parallel to both ends of the capacitor C2;

[0012] The voltage measurement circuit includes a capacitor C3 and a capacitor C4, which are connected in series and then in parallel to the two ends of the capacitor C1; the connection point between the capacitor C3 and the capacitor C4 serves as a voltage probe insertion point for measuring voltage;

[0013] The voltage measurement circuit further includes two motors, each motor being connected to the rotating shaft of the corresponding capacitor via a coupling, so as to adjust the ratio of capacitor C3 to capacitor C4 by changing the size of the capacitor, thereby realizing voltage measurement.

[0014] Furthermore, the capacitor C3 and the capacitor C4 are both adjustable ceramic vacuum capacitors, and the shapes, lengths, and weights of the rotating shafts of the capacitors C3 and C4 are different.

[0015] Furthermore, the rotating shaft of the capacitor C3 is plum blossom-shaped, has a length of 152 mm, and a maximum weight of 0.8 kg;

[0016] The rotating shaft of the capacitor C4 is a round rod with a hole in the middle, a length of 208 mm, and a maximum weight of 1.7 kg.

[0017] Furthermore, the adjustable range of the capacitor C3 is 0-100 pF, and the adjustable range of the capacitor C4 is 0-1300 pF.

[0018] Furthermore, the Rogowski coil serves as an insertion point for a current probe, which is used to measure the current from the matching device to the antenna input terminal.

[0019] Furthermore, the motor is a servo motor. This is because both stepper motors and servo motors are commonly used control components in industry, but there are certain differences between the two. Stepper motors use open-loop control to convert pulse signals into angles. The pulse signals correspond to the angles, and they have disadvantages such as low-frequency vibration, high-speed step loss, and a response time of approximately 200ms. They are used in applications where precision is not a priority. Servo motors, on the other hand, can compensate for the shortcomings of stepper motors and also provide closed-loop control. Therefore, the present invention adopts a servo motor to meet these requirements.

[0020] Further, the Rogowski coil adopts a PCB Rogowski coil;

[0021] The PCB Rogowski coil adopts a digital processing technology to uniformly arrange printed conductors on a printed circuit, and can ensure that the number of turns and the cross-sectional area of the coil are equal in the process;

[0022] This is because the ordinary Rogowski coil is uniformly wound on a ring-shaped non-magnetic skeleton by hand or a winding machine, and it is difficult to uniformly wind the coil and equalize the area of each turn, resulting in low accuracy during measurement and easy wire breakage. Therefore, the above-mentioned novel PCB Rogowski coil is designed to overcome the shortcomings of the ordinary Rogowski coil.

[0023] Further, the PCB Rogowski coil comprises a Rogowski coil and supports arranged on the left and right sides of the Rogowski coil, the supports are designed with ear hooks for fixing the Rogowski coil; and the Rogowski coil is a Rogowski coil composed of a printed circuit board;

[0024] The Rogowski coil is provided with a via hole in the middle for the measured current to pass through;

[0025] The Rogowski coil is provided with an outgoing end at the lower part for outputting the induced voltage signal of the Rogowski coil, and the outgoing end is externally connected to an oscilloscope for reading the induced voltage;

[0026] The printed circuit board is provided with a plurality of small holes on the inner side and the outer side, and the small holes on the inner side and the outer side are connected by copper paving.

[0027] Further, the PCB Rogowski coil adopts polytetrafluoroethylene as the PCB material, and has a temperature resistance range of -200 to 260 DEG C, and can be continuously used in a high-temperature environment.

[0028] Compared with the prior art, the utility model has the following advantages and beneficial effects:

[0029] 1. The high-power radio frequency antenna impedance measuring device adopts two adjustable and high-voltage-resistant vacuum capacitors C3 and C4 connected in series and then connected in parallel in the matching circuit, is used for voltage division, measures small voltage through voltage division, and obtains the voltage of the antenna; the capacitance values of the capacitors C3 and C4 are controlled through a servo motor; in addition, a novel PCB Rogowski coil is also installed between the matching box and the antenna, is used for detecting the current from the matching circuit to the input end of the antenna, and thus the antenna impedance is obtained. The utility model solves the technical problem of real-time measurement of the antenna impedance of the high-power radio frequency antenna during operation.

[0030] 2. This utility model considers that conventional Rogowski coils, which are wound uniformly on a non-ferromagnetic ring by hand or by a winding machine, are difficult to achieve with uniform winding and equal area per turn, resulting in low measurement accuracy and a high risk of wire breakage. Therefore, this utility model designs a novel PCB Rogowski coil to overcome these shortcomings. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings described herein are used to provide a further understanding of the embodiments of the present invention, constitute a part of this application, and do not constitute a limitation of the embodiments of the present invention. In the accompanying drawings:

[0032] Figure 1 This is a schematic structural diagram of a high-power radio frequency antenna impedance measurement device according to the present utility model;

[0033] Figure 2 This is a modeling diagram of the voltage measurement circuit of the utility model;

[0034] Figure 3 This is a structural diagram of the PCB Rogowski coil of the utility model;

[0035] Figure 4 This is the test result comparing the self-made high voltage probe of this utility model with the imported commercial probe;

[0036] Figure 5 This is the current test result of the Rogowski coil on the PCB board of the utility model.

[0037] Reference numerals and corresponding component names:

[0038] 1-RF source, 2-Rogowski coil, 3-processor, 4-matching device, 5-bracket, 6-via, 7-connection terminal, 8-small hole, 9-copper plating. DETAILED DESCRIPTION

[0039] Hereinafter, the terms "include" or "may include" used in various embodiments of the present invention indicate the presence of the function, operation or element of the utility model, and do not limit the addition of one or more functions, operations or elements. In addition, as used in various embodiments of the present invention, the terms "include", "have" and their cognates are intended only to indicate specific features, numbers, steps, operations, elements, components or combinations of the foregoing items, and should not be understood as first excluding the presence of one or more other features, numbers, steps, operations, elements, components or combinations of the foregoing items or the possibility of adding one or more features, numbers, steps, operations, elements, components or combinations of the foregoing items.

[0040] In various embodiments of the present invention, the expression "or" or "at least one of A or / and B" includes any or all combinations of the words listed simultaneously. For example, the expression "A or B" or "at least one of A or / and B" may include A, may include B, or may include both A and B.

[0041] The expressions (such as "first", "second", etc.) used in the various embodiments of the present invention may modify the various components in the various embodiments, but may not limit the corresponding components. For example, the above expressions do not limit the order and / or importance of the elements. The above expressions are only used to distinguish one element from other elements. For example, the first user device and the second user device indicate different user devices, although both are user devices. For example, without departing from the scope of the various embodiments of the present invention, the first element may be referred to as the second element, and similarly, the second element may also be referred to as the first element.

[0042] It should be noted that when a component is described as being “connected” to another component, the first component may be directly connected to the second component, and a third component may be “connected” between the first and second components. Conversely, when a component is described as being “directly connected” to another component, it can be understood that there is no third component between the first and second components.

[0043] The terms used in the various embodiments of the present invention are only used to describe the purpose of specific embodiments and are not intended to limit the various embodiments of the present invention. As used herein, the singular form is intended to also include the plural form, unless the context clearly indicates otherwise. Unless otherwise specified, all terms used herein (including technical terms and scientific terms) have the same meaning as those generally understood by those skilled in the art of the various embodiments of the present invention. The terms (such as those defined in generally used dictionaries) will be interpreted as having the same meaning as the contextual meaning in the relevant technical field and will not be interpreted as having an idealized meaning or an overly formal meaning, unless clearly specified in the various embodiments of the present invention.

[0044] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The schematic implementation methods of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0045] Most of the existing probe-type voltage-current probes can only measure the antenna impedance at low voltages, and cannot measure the antenna impedance of high-power radio frequency antennas during operation. The purpose of this utility model is to provide a high-power radio frequency antenna impedance measurement device. Due to the high antenna voltage, two adjustable and high-voltage vacuum capacitors C3 and C4 are connected in series and then in parallel in the matching circuit for voltage division. The overall structure is as follows: Figure 2 As shown in the figure, larger series capacitors reduce the voltage divider. Therefore, capacitors C3 and C4 are 100pF and 1300pF, adjustable vacuum capacitors, respectively. The antenna voltage (point B) can be inferred by measuring the voltage across the larger capacitor, C4 (point D). Taking the voltage divider ratio into account, actual measurements typically measure capacitor C3 at tens of picofarads and capacitor C4 at hundreds of picofarads, which has minimal impact on the original circuit. The capacitances of capacitors C3 and C4 are controlled by a servo motor using closed-loop control, ensuring very high angular accuracy in the capacitor rotation.

[0046] In addition, a new PCB Rogowski coil is installed between the matching box and the antenna to detect the current flowing from the matching circuit to the antenna input, thereby determining the antenna impedance. The antenna impedance can be calculated based on the measured voltage after voltage division and the current flowing through the PCB Rogowski coil. Calculating impedance from voltage and current is a well-known method and will not be elaborated on here.

[0047] The utility model solves the technical problem of real-time measurement of antenna impedance of a high-power radio frequency antenna during operation.

[0048] Example 1

[0049] like Figure 1 As shown, the utility model is a high-power radio frequency antenna impedance measurement device, which includes a radio frequency source 1, a matcher 4, a Rogowski coil 2 and a processor 3;

[0050] The RF source 1 is used to generate a RF source signal and input the RF source signal into the matching device 4 through a transmission line;

[0051] The matcher 4 is connected to the antenna and is used to measure the voltage at the antenna input terminal through the voltage measurement circuit based on the transmitted radio frequency source signal;

[0052] The Rogowski coil 2 is provided on the connecting wire between the matching device 4 and the antenna, and is used to measure the current from the matching device 4 to the antenna input terminal;

[0053] The processor 3 is configured to obtain antenna impedance based on the voltage and current.

[0054] In this embodiment, the matcher 4 includes a matching network and a voltage measurement circuit, and the matching network is connected to the voltage measurement circuit;

[0055] The matching network includes an inductor L1, a capacitor C1 and a capacitor C2, wherein the capacitor C2 is connected to both ends of the RF source 1, one end of the inductor L1 is connected to the capacitor C2 and the other end is connected to the capacitor C1, and the capacitor C1 is connected in parallel to both ends of the capacitor C2;

[0056] The voltage measurement circuit includes capacitors C3 and C4, which are connected in series and then in parallel with capacitor C1. Capacitors C3 and C4 are arranged side by side to avoid inductive capacitance between them. The connection between capacitors C3 and C4 serves as the insertion point for a voltage probe for measuring voltage.

[0057] The voltage measurement circuit further includes two motors, each motor being connected to the rotating shaft of the corresponding capacitor via a coupling, so as to adjust the ratio of capacitor C3 to capacitor C4 by changing the size of the capacitor, thereby realizing voltage measurement.

[0058] like Figure 2 As shown, Figure 2 The figure below shows a three-dimensional model of the voltage measurement circuit. Theoretically, the capacitance of a capacitor differs when an RF signal is present and when it is absent. To determine the actual ratio between points B and D, the voltage measurement circuit must be calibrated. Parameters are input on the motor control system's display to control motor rotation, thereby changing the capacitance. In the absence of a signal input, the capacitance can be measured using a bridge circuit and compared to the theoretical value. The signal source is input at point B, and the oscilloscope probe is connected to the voltage measurement circuit. Manually changing the signal source's output voltage amplitude allows the oscilloscope to obtain real-time voltage data at the voltage measurement terminal. The signal source output voltage and the voltage at the voltage measurement circuit terminal are recorded.

[0059] In this embodiment, the voltage measurement circuit and matching network are often integrated in practical applications, so the choice of motor is crucial. Considering that both stepper motors and servo motors are commonly used control components in industry, there are certain differences between the two. Stepper motors are open-loop control that converts pulse signals into angles. The pulse signals correspond to the angles, and they have disadvantages such as low-frequency vibration, high-speed step loss, and a response time of approximately 200ms. They are used in places where precision requirements are not high. Servo motors can compensate for the shortcomings of stepper motors and also provide closed-loop control. Therefore, the present invention adopts servo motors to meet these requirements.

[0060] In this embodiment, considering that capacitance is also key to voltage measurement, capacitor performance is determined by various parameters such as frequency response, withstand voltage, and maximum current. High-power RF devices have relatively high discharge voltages, making conventional capacitors less suitable. Therefore, this utility model utilizes adjustable ceramic vacuum capacitors. Both capacitors C3 and C4 utilize adjustable ceramic vacuum capacitors, and the shafts of capacitors C3 and C4 differ in shape, length, and weight.

[0061] Specifically, the rotating shaft of the capacitor C3 is plum blossom-shaped, has a length of 152 mm, and a maximum weight of 0.8 kg;

[0062] The rotating shaft of the capacitor C4 is a round rod with a hole in the middle, a length of 208 mm, and a maximum weight of 1.7 kg;

[0063] From the perspective of key parameters, the maximum capacity, high-frequency peak voltage, and number of rotations of capacitors C3 and C4 are different. In the present invention, the adjustable range of capacitor C3 is 0-100pF, and the adjustable range of capacitor C4 is 0-1300pF.

[0064] In this embodiment, the Rogowski coil 2 serves as an insertion point of a current probe for measuring the current from the matching device 4 to the antenna input terminal.

[0065] In this embodiment, considering that the ultimate goal of the present invention is to measure impedance, in addition to voltage, current must also be determined to obtain impedance. Antenna current is primarily measured using a Rogowski coil, which operates on the principle of electromagnetic induction. The varying current in the conductor being measured generates an induced voltage in the Rogowski coil. Based on the proportional relationship between the current and the induced voltage, the current in the conductor can be measured. Therefore, a Rogowski coil is an electrical device used to measure alternating current (AC), such as high-speed transients, pulsed currents, or industrial frequency sinusoidal currents. Currently, Rogowski coils are widely used to measure various alternating currents. As current sensing units, they offer a wide measurement range, lack of magnetic saturation, and lack of an iron core. However, conventional Rogowski coils are wound uniformly on a toroidal non-ferromagnetic frame, either manually or by a winding machine. This makes it difficult to achieve uniform winding and equal area per turn, resulting in low measurement accuracy and a high risk of wire breakage. Therefore, the present invention designs a novel PCB Rogowski coil to overcome the shortcomings of conventional Rogowski coils.

[0066] The PCB board Rogowski coil uses digital processing technology to evenly arrange the printed conductors on the printed circuit, which can ensure that the number of coil turns and cross-sectional area are equal.

[0067] like Figure 3 As shown, the PCB board Rogowski coil includes a Rogowski coil and brackets 5 provided on the left and right sides of the Rogowski coil. The brackets 5 adopt a hanging ear design for fixing the Rogowski coil for easy installation. The Rogowski coil is a Rogowski coil composed of a printed circuit board.

[0068] A via hole 6 is provided in the middle of the Rogowski coil for the measured current to pass through, and is also suitable for measuring the measured current in a narrow space; the aperture of the via hole 6 is 20 mm;

[0069] The lower part of the Rogowski coil is provided with an outlet end 7 for outputting the induced voltage signal of the Rogowski coil, and the outlet end 7 is connected with an oscilloscope for reading the induced voltage.

[0070] The inner side and the outer side of the printed circuit board are provided with a plurality of small holes 8, and the small holes on the inner side and the outer side are connected by copper 9, which is equivalent to a wire connection. The Rogowski coil is wound in this way, and the small holes 8 are designed to have 85 holes.

[0071] In this embodiment, based on the measured voltage after voltage division and the current of the PCB Rogowski coil, the impedance of the antenna can be calculated by the processor 3. It is a well-known means to calculate the impedance according to the voltage and the current, and will not be described here. The processor 3 in the utility model can adopt RIGOL DS7014 oscilloscope. The oscilloscope has the functions of measuring the phase relationship between signals and filtering, and also has the function of mathematical calculation. The measured impedance can be calculated through the voltage signal, the current signal and the phase relationship between them.

[0072] In this embodiment, the input point B of the voltage measurement circuit is connected to the input end of the antenna through a coaxial line, so that the voltage at the input end of the antenna is equal to the voltage at point B of capacitor C3. The C point and the D point of the adjustable vacuum capacitor are connected together through a copper bar, which is externally plated with silver to prevent oxidation. The E point of the capacitor is grounded, forming a series circuit of capacitors C3 and C4. The actually measured voltage is the voltage of capacitor C4, and the voltage at the input end of the antenna can be obtained by proportional conversion of the capacitance values of capacitors C3 and C4. The shafts of capacitors C3 and C4 are connected to the motor through a coupling, thereby realizing the rotation of the capacitors. Bakelite has the advantages of good insulation and high strength, so the C end and the D end of capacitors C3 and C4 are fixed with bakelite, so that the C end and the D end are not in contact with the bottom of the box. This can not only avoid the generation of induced capacitance with the bottom surface of the box, but also reduce the error caused by motor vibration.

[0073] Figure 2 The left side of the model is provided with a motor, and the right side is provided with an adjustable vacuum capacitor. A rectangular with a length of 4cm and a width of 3cm is reserved on the upper and lower parts of the motor part for connecting the wires of the motor and the controller. A circular hole with a diameter of 2cm is reserved on the upper and lower parts of the capacitor part. The upper circular hole is connected with the radio frequency input wire, and the lower circular hole is connected with the voltage measurement circuit wire. The connection part of the wire and the capacitor is provided with a screw hole of M3 for easy disassembly. Handles are designed on the left and right sides of the model for easy movement of the box.

[0074] A servo motor primarily consists of three parts: a stator, a rotor, and an encoder. The stator, consisting of an iron core and coils, provides a rotating magnetic field. The rotor is a permanent magnet that rotates synchronously with the magnetic field generated by the stator. The encoder, mounted at the rear of the servo motor, provides feedback on the motor's speed and position. The servo motor system's power supply is divided into two parts: one that rectifies AC power into DC, which is then supplied to the servo motor via an inverter; and the other that directly supplies power to the control unit after rectification. A programmable logic controller (PLC) is used as the control unit. When the controller outputs PWM to control position, the servo motor's position loop, velocity loop, and current loop must work together. When controlling speed, the velocity loop and current loop must work together.

[0075] Because high-power RF devices have high discharge voltages, conventional capacitors are not suitable. Therefore, this utility model uses adjustable ceramic vacuum capacitors. Capacitor C3 in this utility model's voltage measurement circuit has a maximum capacity of 100pF, an error of ±5pF, a high-frequency peak voltage of 15kV, and a rotational speed of 21 revolutions. Capacitor C4 has a maximum capacity of 1300pF, an error of ±65pF, a high-frequency peak voltage of 3.5kV, and a rotational speed of 24 revolutions. At a frequency of 13.56MHz, the maximum RF current that capacitors C3 and C4 can withstand is 60A.

[0076] In this measurement, a new type of PCB board Rogowski coil is used, such as Figure 3 As shown. The PCB Rogowski coil is computer-aided and uses digital processing technology to evenly arrange the printed conductors on the printed circuit. This ensures that the number of coil turns and cross-sectional area are equal, overcoming the shortcomings of traditional Rogowski coils. PCB Rogowski coils are widely used in high-alternating current applications due to their fast response speed, excellent linearity, and low cost. The dispersion of coil parameters is small during mass production, and the distributed parameters of mass-produced coils are essentially consistent. Furthermore, the PCB material used is polytetrafluoroethylene, which has a temperature resistance range of -200 to 260°C and can be used continuously in high-temperature environments. This design is relatively small, with an outer diameter of 78mm, which can meet the requirements for current measurement in a small space.

[0077] In specific implementation, after all modules of the voltage measurement circuit are completed, all components are integrated into a box and tested after calibration. The output signal of the RF source enters the matching box via a coaxial cable. The matching box is connected to the antenna, and the energy is finally coupled into the vacuum chamber by the antenna. The motor in the voltage measurement circuit is connected to the motor control system via a motor control line, which is used to adjust the ratio of capacitors C3 and C4. The Rogowski coil is used to measure the current at the antenna input. During discharge, the voltage measurement terminal can observe the voltage at the antenna input through an oscilloscope. The oscilloscope probe has a withstand voltage of 600V and a bandwidth of 0 to 300MHz.

[0078] The first set of discharge parameters is magnetic field B = 550G, the gas filled in the vacuum chamber is argon, the pressure is 1.03Pa, the output power of the emission source varies from 1500W to 5000W, motor A rotates 5 circles, motor B rotates 13 circles, and the voltage at the antenna input changes with the power. Figure 4 (a) is shown. Figure 4 As shown in Figure (a), when the power is between 1500W and 2500W, the voltage at the antenna input increases linearly with the power. When the power is between 2500W and 3500W, the voltage increases faster than it slows down. When the power is between 3500W and 5000W, the voltage and power increase linearly again, and the growth rate is the same as when the power is between 2500W and 3500W.

[0079] The second set of discharge parameters is as follows: the power of the emission source is P = 3000W, the gas filled in the vacuum chamber is argon, the pressure is 1.03Pa, the magnetic field B varies from 500G to 1000G, the motor A rotates 5 times, and the motor B rotates 13 times. The voltage at the antenna input terminal changes with the magnetic field. Figure 4 (b) is shown. Figure 4 (b) It can be seen that when the magnetic field changes from 500G to 900G, the voltage increases slightly, when the magnetic field is 900G to 950G, the voltage decreases slightly, and when the magnetic field is 950G to 1000G, the voltage increases the most.

[0080] After the design of the PCB board Rogowski coil is completed, the ratio of the induced voltage to the measured current is calibrated. The calibrated ratio value is K=V coil / I = 658.43 (mV / A). Current is then measured using a Rogowski coil on a PCB. The PCB Rogowski coil is mounted on the connecting wire between the matching device and the antenna, and the induced voltage on the Rogowski coil is observed using an oscilloscope.

[0081] Group 1 Figure 5 (a) The test conditions are a magnetic field of 500G, argon as the working gas, a controlled air flow of 0.4 SLM, a pressure of 0.87 Pa, and test power ranging from 500W to 1400W. The test results show that the antenna current increases with increasing discharge power.

[0082] Group 2 Figure 5 (b) The test conditions are a discharge power of 1400W, an air volume of 0.4SLM, an air pressure of 0.87Pa, and a magnetic field range of 500 to 1000G. The test results show that the antenna current changes little with changes in the magnetic field.

[0083] The above specific embodiments explain the purpose, technical scheme and beneficial effects of the present application in further detail, and it should be understood that the above description is only a specific embodiment of the present application and is not used to limit the protection scope of the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A high-power radio frequency antenna impedance measurement device, characterized in that: The measuring device comprises a radio frequency source (1), a matching device (4), a Rogowski coil (2) and a processor (3); The radio frequency source (1) is used to generate a radio frequency source signal and input the radio frequency source signal into the matching device (4) via a transmission line; The matcher (4) is connected to the antenna and is used to measure the voltage at the antenna input terminal through the voltage measurement circuit based on the transmitted radio frequency source signal; The Rogowski coil (2) is arranged on a connecting wire between the matching device (4) and the antenna, and is used to measure the current from the matching device (4) to the antenna input end; The processor (3) is used to obtain antenna impedance based on the voltage and current.

2. The high-power radio frequency antenna impedance measurement device according to claim 1, characterized in that: The matcher (4) comprises a matching network and a voltage measurement circuit, wherein the matching network is connected to the voltage measurement circuit; The matching network includes an inductor L1, a capacitor C1 and a capacitor C2, wherein the capacitor C2 is connected to both ends of the radio frequency source (1), one end of the inductor L1 is connected to the capacitor C2 and the other end is connected to the capacitor C1, and the capacitor C1 is connected in parallel to both ends of the capacitor C2; The voltage measurement circuit includes a capacitor C3 and a capacitor C4, which are connected in series and then in parallel to the two ends of the capacitor C1; the connection point between the capacitor C3 and the capacitor C4 serves as a voltage probe insertion point for measuring voltage; The voltage measurement circuit further includes two motors, each motor being connected to the rotating shaft of the corresponding capacitor via a coupling, so as to adjust the ratio of capacitor C3 to capacitor C4 by changing the size of the capacitor, thereby realizing voltage measurement.

3. The high-power radio frequency antenna impedance measurement device according to claim 2, characterized in that: The capacitor C3 and the capacitor C4 are both adjustable ceramic vacuum capacitors, and the shapes, lengths, and weights of the rotating shafts of the capacitors C3 and C4 are different.

4. The high-power radio frequency antenna impedance measurement device according to claim 3, characterized in that: The rotating shaft of the capacitor C3 is plum blossom-shaped, 152 mm long, and has a maximum weight of 0.8 kg; The rotating shaft of the capacitor C4 is a round rod with a hole in the middle, a length of 208 mm, and a maximum weight of 1.7 kg.

5. The high-power radio frequency antenna impedance measurement device according to claim 3, characterized in that: The adjustable range of the capacitor C3 is 0-100 pF, and the adjustable range of the capacitor C4 is 0-1300 pF.

6. The high-power radio frequency antenna impedance measurement device according to claim 1, characterized in that: The Rogowski coil (2) serves as a current probe insertion point for measuring the current from the matching device (4) to the antenna input end.

7. The high-power radio frequency antenna impedance measurement device according to claim 2, characterized in that: The motor is a servo motor.

8. The high-power radio frequency antenna impedance measurement device according to claim 1, characterized in that: The Rogowski coil (2) is a PCB board Rogowski coil; The PCB board Rogowski coil adopts digital processing technology to evenly arrange printed conductors on the printed circuit, which can ensure that the number of coil turns and the cross-sectional area are equal from a technical point of view.

9. The high-power radio frequency antenna impedance measurement device according to claim 8, characterized in that: The PCB board Rogowski coil comprises a Rogowski coil and brackets (5) arranged on the left and right sides of the Rogowski coil, wherein the brackets (5) adopt a hanging ear design and are used to fix the Rogowski coil; the Rogowski coil is a Rogowski coil composed of a printed circuit board; A via (6) is provided in the middle of the Rogowski coil for the measured current to pass through the via; The lower part of the Rogowski coil is provided with an output terminal (7) for outputting the induced voltage signal of the Rogowski coil, and the output terminal (7) is externally connected to an oscilloscope for reading the induced voltage; A plurality of small holes (8) are provided on the inner side and the outer side of the printed circuit board, and the small holes on the inner side and the outer side are connected by copper plating (9).

10. The high-power radio frequency antenna impedance measurement device according to claim 8, characterized in that: The PCB board material of the PCB board Rogowski coil is polytetrafluoroethylene.

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