Level control system and method for radio frequency signal output power

Abstract

The invention relates to a level control system and method for radio frequency signal output power, belongs to the technical field of signal processing, and solves the problem that an existing power compensation algorithm is complex and unstable. In the system, a radio frequency amplifier is used for performing power amplification on a radio frequency signal input according to set power; the electric control attenuator is used for adjusting the power of the input radio frequency signal according to the control voltage output by the feedback circuit; the directional coupler is used for outputting a radio frequency signal after power regulation through the straight-through port, and inputting the radio frequency signal to the first microwave detector to obtain output power; coupling the radio frequency signal after power regulation to a feedback circuit through a coupling port; a digital PID control module in the feedback circuit is used for acquiring an analog control voltage according to a radio frequency signal, and a feed-forward control module is used for acquiring a feed-forward control voltage according to power pre-amplitude-stabilizing data corresponding to set power; and the analog control voltage and the feed-forward control voltage are added to obtain a control voltage output by the feedback circuit. And the output power can be quickly and stably adjusted.

Description

Technical Field

[0001] The present invention relates to the technical field of signal processing, and in particular, to a level control system and method for the output power of a radio frequency signal. Background Art

[0002] In a signal source, due to the interference of the external environment and the instability of electronic components themselves, the output power of the signal source will have certain fluctuations and it is difficult to remain stable. At this time, the Automatic Level Control (ALC) system plays a key role. It can detect the output power value of the circuit through a detection circuit, compare it with the expected value, and then adjust the gain of the device in real time, so that the output of the signal source remains stable. At the same time, it can also provide any power value within a certain range for the subsequent system.

[0003] As a system that can automatically adjust the output level of the system and keep it stable, the ALC system is the key to adjusting the output power of a microwave signal source, which directly determines the performance of the microwave signal source such as power accuracy, range, flatness, etc. Therefore, it is of great significance to study the ALC system.

[0004] Pulse power level control is a difficult point in realizing the accurate output of the signal source power. As the most important application scenario of the ALC system, an automatic level control system is required in all signal sources to adjust the power of the output signal. At present, most microwave signal sources use the method of temperature open-loop power compensation to adjust the influence of temperature on the output signal power, which has the problems of complex compensation algorithms and unstable power compensation. Summary of the Invention

[0005] In view of the above analysis, embodiments of the present invention aim to provide a level control system and method for the output power of a radio frequency signal to solve the problems of complex and unstable existing power compensation algorithms.

[0006] On the one hand, embodiments of the present invention provide a level control system for the output power of a radio frequency signal, including: a radio frequency amplifier, an electronic control attenuator, a directional coupler, a first microwave detector, and a feedback circuit;

[0007] The radio frequency amplifier is used to amplify the radio frequency signal input according to the set power and input it to the electronic control attenuator;

[0008] The electronic control attenuator is used to adjust the power of the input radio frequency signal according to the control voltage output by the feedback circuit and then input it to the directional coupler;

[0009] The directional coupler is used to output the radio frequency signal with adjusted power through the through port and input it to the first microwave detector; at the same time, couple the radio frequency signal with adjusted power to the feedback circuit through the coupling port;

[0010] The first microwave detector is used to obtain the output power from the power-adjusted RF signal;

[0011] The feedback circuit includes a digital PID control module and a feedforward control module. The digital PID control module is used to obtain an analog control voltage according to the RF signal, and the feedforward control module is used to obtain a feedforward control voltage according to the power pre-stabilized amplitude data corresponding to the set power; the analog control voltage and the feedforward control voltage are added to obtain the control voltage output by the feedback circuit.

[0012] Based on the further improvement of the above system, the digital PID control module includes a second microwave detector, a logarithmic amplifier, an ADC analog-to-digital converter, a first DAC digital-to-analog converter, an FPGA module and an amplifier;

[0013] The second microwave detector is used to convert the power level of the RF signal into a DC signal;

[0014] The logarithmic amplifier is used to amplify and logarithmically operate on the DC signal;

[0015] The ADC analog-to-digital converter is used to convert the amplified DC signal into a digital signal;

[0016] The FPGA module is used to calculate the signal error between the digital signal and the stored digital quantity of the power reference voltage, and output a digitalized control voltage using the digital PID control algorithm;

[0017] The first DAC digital-to-analog converter and the amplifier are used to perform digital-to-analog conversion and amplification on the digitalized control voltage to obtain an analog control voltage.

[0018] Based on the further improvement of the above system, the FPGA module also uses the Kalman filter algorithm to perform noise reduction processing on the DC signal input to the ADC analog-to-digital converter.

[0019] Based on the further improvement of the above system, both the first microwave detector and the second microwave detector adopt diode detectors; the logarithmic amplifier adopts a dual-slope logarithmic amplifier.

[0020] Based on the further improvement of the above system, the feedforward control module includes a pre-stabilized amplitude data acquisition module and a second DAC digital-to-analog converter; the pre-stabilized amplitude data acquisition module is used to take out the power pre-stabilized amplitude data corresponding to the integer value of the current set power based on the mapping relationship table between the preset power pre-stabilized amplitude data and the set power; the second DAC digital-to-analog converter is used to output a feedforward control voltage according to the power pre-stabilized amplitude data taken out by the pre-stabilized amplitude data acquisition module.

[0021] Based on further improvements to the above system, the mapping relationship table between the preset power pre-stabilization data and the set power in the pre-stabilized amplitude data acquisition module is obtained by setting all the parameters of the digital PID control algorithm in the digital PID control module to 0, setting different first powers for the input radio frequency signal, obtaining the calibration voltage through the voltage calibration algorithm, and adjusting the power by the electronic control attenuator until the error between the second power output from the through port of the directional coupler and the first power is less than the threshold. At this time, the current electronic control voltage is used as the power pre-stabilization data, and the first power and the corresponding power pre-stabilization data are recorded in the mapping relationship table.

[0022] Based on further improvements to the above system, the voltage calibration algorithm obtains the calibration voltage by traversing and extracting values from the range [0, 65535] and then passing them into the third DAC digital-to-analog converter.

[0023] Based on further improvements to the above system, the first power is set to an integer-type power value.

[0024] On the other hand, an embodiment of the present invention provides a method for controlling the level of the output power of a radio frequency signal, including the following steps:

[0025] Input a radio frequency signal according to the set power. After amplifying the radio frequency signal, obtain the control voltage output from the negative feedback path, adjust the power of the radio frequency signal according to the control voltage, divide the radio frequency signal after power adjustment into two paths. One path directly outputs the radio frequency signal after power adjustment and detects the output power; the other path couples out the radio frequency signal after power adjustment and updates the control voltage in real time through the negative feedback path.

[0026] The negative feedback path obtains the analog control voltage according to the coupled radio frequency signal after power adjustment, and at the same time obtains the feedforward control voltage according to the power pre-stabilization data corresponding to the set power, and adds the analog control voltage and the feedforward control voltage to obtain a new control voltage.

[0027] Based on further improvements to the above method, obtaining the analog control voltage according to the coupled radio frequency signal after power adjustment includes:

[0028] Convert the coupled radio frequency signal after power adjustment into a DC signal, use the Kalman filter algorithm to denoise the DC signal and then convert it into a digital signal;

[0029] Calculate the signal error between the digital signal and the digital quantity of the set power reference voltage, use the digital PID control algorithm to output a digital control voltage, convert it into an analog signal and then amplify it to obtain the analog control voltage.

[0030] Compared with the prior art, the present invention can at least achieve one of the following beneficial effects:

[0031] 1. Use a Kalman filter to improve the accuracy of the detected voltage and reduce the influence of noise; achieve pre-stabilization amplitude control through feedforward control to improve the rapidity of level control; compensate the internal feedback loop through digital PID control, and adjust the output signal level in real time according to the level error to ensure good stability performance and small error of the output power.

[0032] 2. By combining the feedforward control and digital PID control compensation methods, the influence of the change of the set power of the RF input signal and external disturbances on the output signal power is suppressed, so that the output signal power is stabilized at the set value, with strong robustness, high accuracy and control rapidity, and can be applied to fields such as signal sources and radars.

[0033] In the present invention, the above technical solutions can also be combined with each other to realize more preferred combination schemes. Other features and advantages of the present invention will be described in the subsequent specification, and some advantages can be made obvious from the specification or understood by implementing the present invention. The purpose and other advantages of the present invention can be realized and obtained from the content specifically pointed out in the specification and the drawings. Description of the Drawings

[0034] The drawings are only for the purpose of showing specific embodiments and are not considered as a limitation of the present invention. Throughout the drawings, the same reference signs represent the same components.

[0035] Figure 1 It is a block diagram of a level control system for the output power of a radio frequency signal in Embodiment 1 of the present invention;

[0036] Figure 2 It is a schematic diagram of the level control of the output power of a radio frequency signal in Embodiment 1 of the present invention. Detailed Embodiments

[0037] The following will specifically describe the preferred embodiments of the present invention in conjunction with the drawings, wherein the drawings form a part of this application and are used together with the embodiments of the present invention to explain the principle of the present invention, and are not used to limit the scope of the present invention.

[0038] Embodiment 1

[0039] A specific embodiment of the present invention discloses a level control system for the output power of a radio frequency signal, as Figure 1 shown, including: a radio frequency amplifier, an electronic control attenuator, a directional coupler, a first microwave detector and a feedback circuit;

[0040] The radio frequency amplifier is used to amplify the radio frequency signal input according to the set power and input it to the electronic control attenuator;

[0041] The electronic attenuator is used to adjust the power of the input radio frequency signal according to the control voltage output by the feedback circuit and then input it to the directional coupler;

[0042] The directional coupler is used to output the radio frequency signal with adjusted power through the through port and input it to the first microwave detector; at the same time, the radio frequency signal with adjusted power is coupled to the feedback circuit through the coupling port;

[0043] The first microwave detector is used to obtain the output power from the radio frequency signal with adjusted power;

[0044] The feedback circuit includes a digital PID control module and a feedforward control module. The digital PID control module is used to obtain an analog control voltage according to the radio frequency signal, and the feedforward control module is used to obtain a feedforward control voltage according to the power pre-stabilized amplitude data corresponding to the set power; the analog control voltage and the feedforward control voltage are added to obtain the control voltage output by the feedback circuit.

[0045] During implementation, the feedback circuit is used to achieve level dynamic amplitude stabilization control of the radio frequency signal output power. Among them, the feedforward control module is used to improve the rapidity of control, but there is still an error between the system output power and the input set signal power, and the error will be relatively large when the external temperature changes; while the digital PID control module is used to achieve the error compensation function.

[0046] It should be noted that as Figure 2 shown, the digital PID control module includes a second microwave detector, a logarithmic amplifier, an ADC analog-to-digital converter, a first DAC digital-to-analog converter, an FPGA module, and an amplifier.

[0047] Among them, the second microwave detector is used to convert the power level of the radio frequency signal into a direct current signal. Preferably, both the first microwave detector and the second microwave detector use diode detectors; the logarithmic amplifier is used to amplify and perform logarithmic operations on the direct current signal. Preferably, a dual-slope logarithmic amplifier is used.

[0048] The ADC analog-to-digital converter is used to convert the amplified direct current signal into a digital signal to obtain voltage data that has a linear relationship with the power reference voltage data stored in the FPGA module; the FPGA module is used to calculate the signal error between the digital signal and the stored power reference voltage digital quantity and output a digitalized control voltage using the digital PID control algorithm; the first DAC digital-to-analog converter and the amplifier are used to perform digital-to-analog conversion and amplification on the digitalized control voltage to obtain an analog control voltage.

[0049] Preferably, considering that the digital signal processed by sampling is affected by the internal noise of the system and the accuracy problem of the components themselves, the FPGA module uses the Kalman filter algorithm to perform noise reduction processing on the direct current signal input to the ADC analog-to-digital converter to improve the voltage digitization accuracy.

[0050] The digital PID control algorithm utilizes the variability of system parameters K P 、K I 、K D to improve the optimality, flexibility, and robustness of the system. The mathematical formula of the digital PID control algorithm is as follows:

[0051] U z =e(z)(K p +K I / (1 - z -1 ) + K D (1 - z -1 )) Formula (1)

[0052] Wherein, U z represents the digital control voltage of the output, and e(z) represents the z-transform of the error signal e.

[0053] It should be noted that the impacts of the three parameters of PID on the entire level control system are as follows in three aspects:

[0054] (1) Proportional coefficient K P : Shorten the control response time. When there is a large numerical difference between the actual power and the set power, the role of the proportional coefficient dominates, making the power deviation decrease rapidly. The larger the proportional coefficient, the faster the actual power approaches the set power. However, if the role of the proportional coefficient is too strong, it will also make the stability of the automatic level control system very poor and increase the overshoot of the system.

[0055] (2) Integral time K I : Reduce or even eliminate the static deviation existing in the system. The actual power control curve will gradually reach a steady state over time. After reaching the steady state, the input and output of the system are in dynamic balance, and both the actual power and the given power are constant values. However, there is still a static error at this time, which will affect the control effect of the controller. The larger the integral time value, the smaller the effect, and vice versa. However, the size of the integral time value should be within a reasonable range because if the integral value is too small, the system will oscillate, and if the integral value is too large, the static deviation of the system cannot be eliminated.

[0056] (3) Derivative time K D : Make a prediction in advance according to the magnitude of the power deviation change rate and give a corresponding adjustment action in advance. The derivative time can improve the steady-state performance of the power control system. Enhancing the role of the derivative time can reduce the overshoot and overcome the shortcoming of too long integral time.

[0057] It should be noted that the feedforward control module includes a pre-stabilized amplitude data acquisition module and a second DAC digital-to-analog converter; the pre-stabilized amplitude data acquisition module is used to retrieve the power pre-stabilized amplitude data corresponding to the integer value of the current set power based on the mapping relationship table between the preset power pre-stabilized amplitude data and the set power; the second DAC digital-to-analog converter is used to output a feedforward control voltage according to the power pre-stabilized amplitude data retrieved by the pre-stabilized amplitude data acquisition module.

[0058] Specifically, the mapping relationship table between the preset power pre-stabilized amplitude data and the set power in the pre-stabilized amplitude data acquisition module is obtained by setting all the parameters of the digital PID control algorithm in the digital PID control module to 0, that is, the digital PID control module does not function in the feedback circuit. Then, different first powers are set for the input radio frequency signal, the calibration voltage is obtained through the voltage calibration algorithm, and the electronic control attenuator adjusts the power according to the calibration voltage until the error between the second power output from the through port of the directional coupler and the first power is less than the threshold value. At this time, the current electronic control voltage is used as the power pre-stabilized amplitude data, and the first power and the corresponding power pre-stabilized amplitude data are recorded in the mapping relationship table.

[0059] Considering the large workload in the operation process, the voltage calibration algorithm is adopted in this embodiment to obtain the calibration voltage, that is, the output obtained by traversing and retrieving values from the range [0, 65535] and then passing them into the third DAC digital-to-analog converter is used as the calibration voltage.

[0060] To improve efficiency, the first power is set as an integer type power value. In actual application, the corresponding power pre-stabilized amplitude data is also retrieved from the mapping relationship table according to the integer value of the set power.

[0061] Compared with the prior art, a level control system for the output power of a radio frequency signal provided in this embodiment uses a Kalman filter to improve the detection voltage accuracy and reduce the influence of noise; through feedforward control, pre-stabilized amplitude control is achieved, improving the rapidity of level control; through the internal feedback loop compensated by digital PID control, the output signal level is adjusted in real time according to the level error, ensuring good stability performance and small error of the output power. By combining the feedforward control and the digital PID control compensation method, the influence of the change of the set power of the radio frequency input signal and external disturbances on the output signal power is suppressed, so that the output signal power is stabilized at the set value, with strong robustness, high precision and fast control, and can be applied to fields such as signal sources and radars.

[0062] Embodiment 2

[0063] Another embodiment of the present invention discloses a method for controlling the level of the output power of a radio frequency signal. The specific implementation manners of each step refer to the description of the corresponding components in Embodiment 1. The method includes the following steps:

[0064] Input a radio frequency signal according to the set power. After amplifying the radio frequency signal, obtain the control voltage output from the negative feedback path. Adjust the power of the radio frequency signal according to the control voltage. Divide the radio frequency signal with adjusted power into two paths. One path directly outputs the radio frequency signal with adjusted power and detects the output power. The other path couples out the radio frequency signal with adjusted power and updates the control voltage in real time through the negative feedback path.

[0065] The negative feedback path obtains an analog control voltage according to the coupled radio frequency signal with adjusted power. At the same time, it obtains a feedforward control voltage according to the power pre-stabilized amplitude data corresponding to the set power. Add the analog control voltage and the feedforward control voltage to get a new control voltage.

[0066] It should be noted that obtaining the analog control voltage according to the coupled radio frequency signal with adjusted power includes:

[0067] Convert the coupled radio frequency signal with adjusted power into a DC signal. Use the Kalman filter algorithm to denoise the DC signal and then convert it into a digital signal.

[0068] Calculate the signal error between the digital signal and the digital quantity of the set power reference voltage. Use the digital PID control algorithm to output a digitalized control voltage. After converting it into an analog signal and amplifying, obtain the analog control voltage.

[0069] Since the method for controlling the level of the output power of a radio frequency signal in this embodiment can be mutually referred to with the foregoing system for controlling the level of the output power of a radio frequency signal, and this is a repeated description here, it will not be elaborated further. Since the principle of this method embodiment is the same as that of the above system embodiment, this method embodiment also has the corresponding technical effects of the above system embodiment.

[0070] Those skilled in the art can understand that all or part of the processes for implementing the method in the above embodiments can be completed by instructing relevant hardware through a computer program. The program can be stored in a computer-readable storage medium. Among them, the computer-readable storage medium is a disk, an optical disc, a read-only memory, or a random access memory, etc.

[0071] The above is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A level control system for the output power of a radio frequency signal, characterized in that, Including: A radio frequency amplifier, an electronically controlled attenuator, a directional coupler, a first microwave detector, and a feedback circuit; The radio frequency amplifier is used to amplify the radio frequency signal input at a set power and input it to the electronically controlled attenuator; The electronically controlled attenuator is used to adjust the power of the input radio frequency signal according to the control voltage output by the feedback circuit and then input it to the directional coupler; The directional coupler is used to output the radio frequency signal with adjusted power through the through port and input it to the first microwave detector; At the same time, the radio frequency signal with adjusted power is coupled to the feedback circuit through the coupling port; The first microwave detector is used to obtain the output power from the radio frequency signal with adjusted power; The feedback circuit includes a digital PID control module and a feedforward control module. The digital PID control module is used to obtain an analog control voltage according to the radio frequency signal, and the feedforward control module is used to obtain a feedforward control voltage according to the power pre-stabilization amplitude data corresponding to the set power; the analog control voltage and the feedforward control voltage are added to obtain the control voltage output by the feedback circuit.

2. The level control system for the radio frequency signal output power according to claim 1, wherein The digital PID control module includes a second microwave detector, a logarithmic amplifier, an ADC analog-to-digital converter, a first DAC digital-to-analog converter, an FPGA module, and an amplifier; The second microwave detector is used to convert the power level of the radio frequency signal into a direct current signal; The logarithmic amplifier is used to amplify and perform logarithmic operation on the direct current signal; The ADC analog-to-digital converter is used to convert the amplified direct current signal into a digital signal; The FPGA module is used to calculate the signal error between the digital signal and the stored digital quantity of the power reference voltage and output a digitalized control voltage using the digital PID control algorithm; The first DAC digital-to-analog converter and the amplifier are used to perform digital-to-analog conversion and amplification on the digitalized control voltage to obtain an analog control voltage.

3. The level control system for the output power of the radio frequency signal according to claim 2, characterized in that, The FPGA module also uses the Kalman filter algorithm to perform noise reduction processing on the direct current signal input to the ADC analog-to-digital converter.

4. The level control system for the radio frequency signal output power according to claim 2, characterized in that, Both the first microwave detector and the second microwave detector use diode detectors; the logarithmic amplifier uses a dual-slope logarithmic amplifier.

5. The level control system for the radio frequency signal output power according to claim 1, characterized in that, The feedforward control module includes a pre-stabilization amplitude data acquisition module and a second DAC digital-to-analog converter; The pre-stabilization amplitude data acquisition module is used to take out the power pre-stabilization amplitude data corresponding to the integer value of the current set power based on the mapping relationship table between the preset power pre-stabilization amplitude data and the set power; The second DAC digital-to-analog converter is used to output a feedforward control voltage according to the power pre-stabilization amplitude data taken out by the pre-stabilization amplitude data acquisition module.

6. The level control system for the output power level of a radio frequency signal according to claim 5, characterized in that The mapping relationship table between the preset power pre-stabilization data and the set power in the pre-stabilization data acquisition module is obtained by setting all the parameters of the digital PID control algorithm in the digital PID control module to 0, setting different first powers for the input radio frequency signal, obtaining the calibration voltage through the voltage calibration algorithm, and adjusting the power by the electronic control attenuator according to the calibration voltage until the error between the second power output from the through port of the directional coupler and the first power is less than the threshold. Then, the current electronic control voltage is used as the power pre-stabilization data, and the first power and the corresponding power pre-stabilization data are recorded in the mapping relationship table.

7. The level control system for the output power of the radio frequency signal according to claim 6, wherein The voltage calibration algorithm obtains the calibration voltage by traversing and taking out values from the range [0, 65535] and then inputting them into the third DAC digital-to-analog converter.

8. The level control system for the radio frequency signal output power according to claim 6, characterized in that, The first power is set as an integer-type power value.

9. A method for controlling the level of the output power of a radio frequency signal, characterized in that, It includes the following steps: Input the radio frequency signal according to the set power. After amplifying the radio frequency signal, obtain the control voltage output from the negative feedback path, adjust the power of the radio frequency signal according to the control voltage, divide the radio frequency signal after power adjustment into two paths. One path directly outputs the radio frequency signal after power adjustment and detects the output power; the other path couples out the radio frequency signal after power adjustment and updates the control voltage in real time through the negative feedback path. The negative feedback path obtains the analog control voltage according to the coupled radio frequency signal after power adjustment, and at the same time obtains the feedforward control voltage according to the power pre-stabilization data corresponding to the set power, and adds the analog control voltage and the feedforward control voltage to obtain a new control voltage.

10. The method for controlling the level of the radio frequency signal output power according to claim 9, characterized in that, The obtaining of the analog control voltage according to the coupled radio frequency signal after power adjustment includes: Convert the coupled radio frequency signal after power adjustment into a DC signal, use the Kalman filter algorithm to denoise the DC signal and then convert it into a digital signal. Calculate the signal error between the digital signal and the digital quantity of the set power reference voltage, use the digital PID control algorithm to output a digital control voltage, convert it into an analog signal and then amplify it to obtain the analog control voltage.

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