A method and system for self-excitation adjustment of radio frequency automatic matching device power amplifier

Abstract

The present invention belongs to the technical field of radio frequency power amplifiers, and discloses a radio frequency automatic matching device power amplifier self-excitation adjustment method and system, including: placing the radio frequency automatic matching device in a running state, and performing self-excitation detection on the device; if self-excitation is detected, controlling a motor to adjust a vacuum capacitor. The present invention adds a judgment on whether the radio frequency power amplifier is self-excited during the matching process of the automatic matching device, and performs special processing on the impedance matching algorithm, so as to avoid the consequences of incorrect matching adjustment caused by an erroneous detection result during self-excitation, which results in the inability to correctly match or the extension of the matching time.

Description

Technical Field

[0001] The present invention relates to the technical field of radio frequency power amplifiers, and in particular to a method and system for self-excitation regulation of a radio frequency automatic matching device power amplifier. Background Art

[0002] The RF power supply can excite the gas to obtain plasma, and then use the ion beam sputtering deposition principle to perform vacuum coating, etching and other work. Since the impedance value of the load in the ion chamber will change linearly with time and the change of the environmental parameters in the chamber, if the RF power supply is directly connected to the load, it will inevitably lead to impedance mismatch and high-power reflection, resulting in insufficient load capacity and overheating of the RF power supply. Therefore, it is necessary to connect an automatically adjusted matcher in series between the RF power supply and the load. The matching network of the matcher can convert the impedance of the load into a standard 50 ohm to ensure that the RF power supply works efficiently and normally. The matching speed and effect of the matcher are also crucial to production efficiency. In the case of impedance mismatch, the power amplifier of the RF power supply will generate a strong reflection signal and superimpose it with the output signal. Due to the limited isolation of the power amplifier module, it is easy to form self-excitation at certain load impedances. At this time, the parameters measured by the matcher will be incorrect, thereby affecting the adjustment effect or adjustment speed of the matcher. The present invention mainly judges whether the power amplifier has self-excitation to make special treatment to the matching algorithm of the matcher to avoid the problem of incorrect matching or long matching time due to self-excitation.

[0003] The existing automatic matching algorithm basically does not make any special processing for the situation where the power amplifier has self-excitation. The load impedance value detected during self-excitation will be abnormal and erroneous. The matcher will adjust the matcher according to the detected erroneous impedance value, which often leads to erroneous adjustments such as motor reversal, back and forth oscillation adjustment, etc. It is possible to fall into an infinite loop and fail to match normally. It is also possible that the power amplifier will return to normal after a certain period of time and continue to adjust normally, but the overall matching time will be too long due to self-excitation, resulting in a longer high-power reflection time, thereby affecting the production efficiency and effect of the load and causing unnecessary losses. Summary of the invention

[0004] In view of this, the present invention provides a method and system for self-excitation adjustment of a radio frequency automatic matching power amplifier to solve the above problems.

[0005] In order to solve the above technical problems, the present invention provides a method for adjusting the self-excitation of a radio frequency automatic matching power amplifier, comprising:

[0006] Put the radio frequency automatic matching device into operation state and perform self-excitation detection on it;

[0007] If self-excitation is detected, the control motor will adjust the vacuum capacitor.

[0008] As an optional method, self-excitation detection includes:

[0009] The analog signal coupled from the coupler is obtained, and the analog signal is sampled through the preset FPGA control high-speed AD and converted into a digital signal; the sampled digital signal is low-pass filtered to remove noise, and it is determined whether the processed signal is self-excited.

[0010] As an optional method, the method for determining whether the processed signal has self-excitation is as follows:

[0011] Perform FFT transformation on the processed signal to analyze the amplitude of the main frequency signal and other frequency component signals. If the ratio of the amplitude of other frequency component signals to the amplitude of the main frequency signal is higher than the set threshold, it is determined that self-excitation occurs.

[0012] As an optional method, if self-excitation is detected, the motor is controlled by FPGA to maintain the last rotation direction of the vacuum capacitor and reduce the motor speed to the minimum speed;

[0013] If no self-excitation is detected or self-excitation occurs but has returned to normal, calculate the reflection coefficient value and determine whether the reflection coefficient value is higher than a preset threshold;

[0014] When the reflection coefficient value is higher than the preset threshold, it is determined that it has not reached the matching state and is tuned.

[0015] As an optional method, when adjusting the vacuum capacitor, the tuning capacitor and the load capacitor are adjusted respectively by two motors, so as to adjust the capacitance of the tuning capacitor and the load capacitor.

[0016] As an option, tuning includes:

[0017] The motor directions of the two motors used to control the capacitance of the tuning capacitor and the load capacitor, and the motor speed obtained according to the reflection coefficient value are calculated; based on the direction and speed, the tuning capacitor and the load capacitor are matched and tuned according to a preset strategy.

[0018] As an optional method, if the reflection coefficient is less than or equal to a preset threshold, it is determined that a matching state has been achieved, and the motor is controlled to stop rotating.

[0019] On the other hand, the present invention also provides a radio frequency automatic matching device power amplifier self-excitation adjustment system, which uses the above radio frequency automatic matching device power amplifier self-excitation adjustment method for tuning, including:

[0020] A radio frequency automatic matcher and a terminal load; the terminal load is connected to the output end of the radio frequency automatic matcher;

[0021] The radio frequency automatic matcher comprises an input end, an output end, a matching inductor, a tuning capacitor and a load capacitor; the matching inductor is connected in series with the tuning capacitor and connected in parallel with the load capacitor.

[0022] The beneficial effects of the present invention are:

[0023] The present invention adds a judgment on whether the radio frequency power amplifier is self-excited during the matching process of the automatic matcher, and performs special processing on the impedance matching algorithm, so as to avoid the wrong detection result during self-excitation leading to wrong matching adjustment, resulting in the consequence of incorrect matching or prolonged matching time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of a matching device self-excitation adjustment process according to an embodiment of the present invention;

[0025] Figure 2 A schematic diagram of the radio frequency power supply network structure provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with specific implementation methods.

[0027] See also Figure 1 and Figure 2 The present invention provides a method for adjusting the power amplifier self-excitation of a radio frequency automatic matching device, comprising: placing the radio frequency automatic matching device in a running state and performing a self-excitation detection on the radio frequency automatic matching device; if self-excitation is detected, controlling a motor to adjust a vacuum capacitor.

[0028] In the prior art, there is no special treatment for the self-excitation of the power amplifier. The load impedance value detected during self-excitation will be abnormally erroneous. The matcher will adjust the matcher according to the detected erroneous impedance value, which will often lead to erroneous adjustments such as motor reversal, back-and-forth oscillation adjustment, etc., and it is possible to fall into an endless loop and fail to match normally. It is also possible that the power amplifier will return to normal after a certain period of time and continue to adjust normally, but the overall matching time will be too long due to self-excitation, resulting in a longer high-power reflection time, thereby affecting the production efficiency and effect of the load and causing unnecessary losses.

[0029] Therefore, the matching device of this embodiment uses a high-speed AD to sample the coupled RF signal, and the sampled signal is basically consistent with the waveform of the RF signal. By performing FFT transformation on the sampled signal, the amplitude of the main frequency signal and other frequency component signals are analyzed. When the ratio of the amplitude of other frequency signals to the amplitude of the main frequency signal is higher than the set threshold, such as higher than -30dB, it is determined that the power amplifier has self-excitation, otherwise it is determined that the power amplifier is working normally. During normal operation, there are only high-order harmonics of the main frequency signal, and the harmonics of the RF signal after passing through the filter need to be lower than -45dB.

[0030] The matching process of the matcher takes advantage of the high-speed parallel operation of FPGA, controlling the rotation of the motor while judging the current matching state. The load can be adjusted to the matching state by adjusting the adjustable vacuum tuning capacitor CT and the adjustable vacuum load capacitor CL respectively. CT and CL are adjusted by two motors respectively, and the motor rotation direction corresponds to the capacitor size adjustment direction, and the motor speed is proportional to the reflection coefficient. Before calculating the reflection coefficient, the matcher first determines whether the power amplifier has self-excitation. If self-excitation occurs, the motor speed is reduced to the minimum speed, but the motor direction remains unchanged until the power amplifier is normal. If there is no self-excitation or it recovers from self-excitation, the reflection coefficient is calculated, and it is determined whether the reflection coefficient is higher than the threshold. When the reflection coefficient is higher than the set threshold, the motor speed and direction are controlled normally for matching and tuning. If it is lower than or equal to the threshold, it has been adjusted to the matching state and the adjustment is completed.

[0031] Through experiments, the above-mentioned means of this embodiment can avoid the problems such as motor reversal and back-and-forth oscillation adjustment caused by the self-excitation of the power amplifier, which leads to a long overall matching time. Because the motor cannot stop immediately when it is in high-speed motion, it needs a buffer period, and the motor also needs a certain amount of time to accelerate from stopping to rotating, so this adjustment method can obviously reduce the matching time.

[0032] For implementation in this embodiment, please refer to Figure 1 Because the waveforms of the analog signal and the RF signal during operation are basically the same, this embodiment first obtains the analog signal coupled by the coupler, and uses FPGA to control the high-speed AD to sample the coupled signal to obtain a quantized digital signal. The digital signal processing technology is used to perform FIR low-pass filtering on the sampled signal to filter out noise.

[0033] Afterwards, determine whether the current signal has self-excitation. Specifically, use Fast Fourier Transform (FFT) to analyze the amplitude of the main frequency signal and other frequency component signals. When the ratio of the amplitude of other frequency signals to the amplitude of the main frequency signal is higher than the set threshold, which is -30dB, self-excitation is considered to have occurred.

[0034] Please refer again Figure 2 , Figure 2 This is the internal matching network structure of the automatic matcher of this embodiment. The matching inductor, adjustable vacuum capacitor CL and CT constitute the matcher. By adjusting the capacitance of CL and CT through the forward and reverse rotation of the motor, dynamic matching between the power supply and the load can be achieved.

[0035] Therefore, in this embodiment, if self-excitation is detected, the FPGA controls the motor to maintain the rotation direction of the last adjustment of the capacitors CT and CL, but reduces the motor speed to the minimum speed (the minimum speed can be configured through the software interface according to actual needs).

[0036] If no self-excitation is detected or recovery from self-excitation is detected, the reflection coefficient value is calculated and it is determined whether the reflection coefficient value is higher than a threshold value (the threshold value can be configured through the software interface according to actual needs).

[0037] When the reflection coefficient value is higher than the set threshold, the matching state is not reached. The normal algorithm is used to calculate the two motor directions of the control capacitors CT and CL, and the motor speed is controlled according to the reflection coefficient value (the motor speed is proportional to the reflection coefficient), and the capacitors CT and CL are adjusted for matching tuning.

[0038] If it is lower than or equal to the threshold, it has been adjusted to a matching state, the motor is controlled to stop rotating, and the adjustment is completed.

[0039] In this way, this embodiment adds a judgment on whether the RF power amplifier is self-excited during the matching process of the automatic matcher, and performs special processing on the impedance matching algorithm, so as to avoid incorrect detection results during self-excitation leading to incorrect matching adjustments, resulting in the consequences of incorrect matching or prolonged matching time.

[0040] On the other hand, this embodiment further provides a radio frequency automatic matching device power amplifier self-excitation adjustment system, which uses the above radio frequency automatic matching device power amplifier self-excitation adjustment method for tuning, including:

[0041] A radio frequency automatic matcher and a terminal load; the terminal load is connected to the output end of the radio frequency automatic matcher; the radio frequency automatic matcher includes an input end, an output end, a matching inductor, a tuning capacitor and a load capacitor; the matching inductor is connected in series with the tuning capacitor and connected in parallel with the load capacitor.

[0042] Through the above settings, the matcher is composed of a matching inductor, an adjustable vacuum tuning capacitor CT and an adjustable vacuum load capacitor CL. The capacitance values ​​of the tuning capacitor CT and the load capacitor CL are adjusted by an algorithm to achieve dynamic impedance matching between the power supply and the load.

[0043] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for self-excitation adjustment of a radio frequency automatic matching device power amplifier, characterized in that: include: Put the radio frequency automatic matching device into operation state and perform self-excitation detection on it; If self-excitation is detected, the motor is controlled by FPGA to maintain the last rotation direction of the vacuum capacitor and reduce the motor speed to the minimum speed; If no self-excitation is detected or self-excitation occurs but has returned to normal, calculate the reflection coefficient value and determine whether the reflection coefficient value is higher than a preset threshold; If the reflection coefficient value is higher than a preset threshold, it is determined that the matching state has not been reached and the matching state is tuned; the tuning includes: Calculating the motor direction of two motors used to control the size of the tuning capacitor and the load capacitor, and the motor speed obtained according to the reflection coefficient value; based on the direction and speed, matching and tuning the tuning capacitor and the load capacitor according to a preset strategy; Wherein, when the vacuum capacitor is adjusted, the tuning capacitor and the load capacitor are adjusted respectively by two motors; the adjustment is to adjust the capacitance of the tuning capacitor and the load capacitor.

2. The method for self-excitation adjustment of a radio frequency automatic matching device power amplifier according to claim 1, characterized in that: The self-excitation detection comprises: The analog signal coupled from the coupler is obtained, and the analog signal is sampled by the preset FPGA to control the high-speed AD and converted into a digital signal; the sampled digital signal is low-pass filtered to remove noise, and it is determined whether the processed signal is self-excited.

3. The method for self-excitation adjustment of a radio frequency automatic matching device power amplifier according to claim 2, characterized in that: The method to determine whether the processed signal has self-excitation is: Perform FFT transformation on the processed signal to analyze the amplitude of the main frequency signal and other frequency component signals. If the ratio of the amplitude of other frequency component signals to the amplitude of the main frequency signal is higher than the set threshold, it is determined that self-excitation occurs.

4. The method for self-excitation adjustment of a radio frequency automatic matching device power amplifier according to claim 1, characterized in that: If the reflection coefficient is less than or equal to a preset threshold, it is determined that a matching state has been achieved, and the motor is controlled to stop rotating.

5. A radio frequency automatic matching device power amplifier self-excitation adjustment system, which is tuned by the radio frequency automatic matching device power amplifier self-excitation adjustment method described in any one of claims 1 to 4, characterized in that: include: A radio frequency automatic matcher and a terminal load; the terminal load is connected to the output end of the radio frequency automatic matcher; The radio frequency automatic matcher comprises an input end, an output end, a matching inductor, a tuning capacitor and a load capacitor; the matching inductor is connected in series with the tuning capacitor and connected in parallel with the load capacitor.

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