Power amplifier automatic level control method based on dynamic adjustment attenuation value

Abstract

The invention provides a power amplifier automatic level control method based on dynamic adjustment of an attenuation value. Through setting of a protection attenuation value based on input excitation and a rated output power range, it is ensured that power overshoot does not occur, and due to the fact that manual setting factors are eliminated in calculation, stability and applicability are enhanced; besides, through automatic updating of the attenuation value, calibration of next attenuation is realized so that accuracy is guaranteed and labor cost of initial accurate calibration is saved. Meanwhile, after the output radio frequency power is adjusted to a rated range, a hysteresis comparison method is adopted to trigger power adjustment, so that the problem of power reduction caused by long-time use of the radio frequency amplifier can be solved, and the problem of output power jitter caused by detection errors can also be solved.

Description

Technical Field

[0001] The invention relates to the field of wireless communications, and in particular to a power amplifier automatic level control method based on dynamically adjusting attenuation values. Background Art

[0002] Automatic level control (ALC) means that when the input level fluctuates, the output level remains unchanged (or fluctuates within a very small range). For RF amplifiers, when the RF excitation signal power is very unstable or has large changes, the output RF signal power is stable (or fluctuates very little) after ALC loop control.

[0003] In the field of military communications, various communication radio stations generally have three transmission power levels, namely high power 47dBm, medium power 37dBm, and low power 27dBm. In traditional radio design, the frequency source and high-power amplifier are integrated into one device, so the power gain and channel insertion loss of each frequency point can be tested during the debugging process, and the stable power output of each frequency point can be achieved by using a table lookup method. With the development of software radio technology, each module in traditional radio stations has gradually become independent, and a board design method is used. When changing the communication frequency band, only the corresponding board needs to be replaced. At this time, due to the particularity of the RF circuit, there are certain differences between each board, and it is difficult to achieve stable output after interchange.

[0004] Reference [1] (Invention patent: Method for fast control of power of high-power transmitter with large dynamic range 201310341360.3) adopts large-step digital controlled attenuator and high-precision analog electric adjustable attenuator to form dual-loop power control, which can achieve large-range high-precision output power control. Reference [2] (Invention patent: Fast digital AGC control method with large dynamic range 202111443468.4) adopts AGC loop in RF circuit and intermediate frequency circuit respectively to achieve large dynamic range gain control. Reference [3] (Liu Jilin. Implementation method of automatic level control of frequency hopping transmitter. Telecommunication Technology 2012.52(5)709-711) proposes frequency hopping clock prohibition method, which successfully solves the power overshoot problem of frequency hopping transmitter in ALC loop control process.

[0005] The power control methods in the above literatures have their own advantages and disadvantages: Literature [1] and literature [2] both use dual-loop two-stage attenuators for adjustment to ensure a large dynamic range and high-precision control, but in the early stage of the ALC loop, the power amplifier output has the risk of overshoot. Literature [3] adds an auxiliary circuit that uses a frequency-hopping clock to control the power-on process of the operational amplifier, achieving a voltage increase from low to high, solving the problem of overshoot of the RF output of the high-power amplifier, but has no advantages in the dynamic range and control time of the ALC loop adjustment. Therefore, a power amplifier with a simple structure and high efficiency for dynamic adjustment of attenuation is needed. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a method for automatic level control of a power amplifier based on dynamically adjusting attenuation value, which mainly solves the technical problem in the prior art of lacking a power amplifier with simple structure and high efficiency for dynamically adjusting attenuation.

[0007] The objective of the present invention is achieved through the following solutions:

[0008] According to an embodiment of the present invention, a method for automatic level control of a power amplifier based on dynamically adjusting an attenuation value is provided, comprising the following steps: S1, calculating a protection attenuation value of a digitally controlled attenuator according to an input excitation and a rated output power range, and setting an initial value of an attenuation table of the digitally controlled attenuator based on the protection attenuation value; S2, querying an attenuation value corresponding to the frequency information from the attenuation table according to the frequency information of the input excitation; S3, attenuating the power amplifier based on a current attenuation value, measuring the current output power of the power amplifier by a detector, and comparing it with the rated output power range; S4, when the current output power is outside the rated output power range, adjusting the current attenuation value accordingly, and repeating steps S3-S4; S5, when the current output power is within the rated output power range, writing the current attenuation value into the attenuation table; S6, before the input excitation frequency is updated, when the output power is within the rated output power range, using a hysteresis comparison method to trigger power adjustment, the trigger threshold is twice the accuracy of the digitally controlled attenuator, and repeating steps S2-S6 after the frequency is updated.

[0009] According to an embodiment of the present invention, measuring the current output power of the power amplifier by the detector is to measure the root mean square voltage of the power amplifier by the detector, and calculate the output power based on the root mean square voltage.

[0010] According to an embodiment of the present invention, the root mean square voltage is:

[0011]

[0012] Among them, V in is the detector input voltage, T is the detection period, t1 and t2 are the starting point and end point of the detection period respectively.

[0013] According to an embodiment of the present invention, the output power is:

[0014]

[0015] Among them, V rms is the root mean square voltage.

[0016] According to an embodiment of the present invention, the current output power of the power amplifier is measured by the detector using a sampling and averaging algorithm, wherein the sampling and averaging algorithm is that the detector measures the detection voltage of the input detector multiple times within a specific time period, calculates the average value of the detection voltage, and calculates the current output power based on the average value of the detection voltage.

[0017] According to an embodiment of the present invention, the average value of the detection voltage is:

[0018]

[0019] Among them, a i is the detection voltage each time, and N is the number of detections.

[0020] According to an embodiment of the present invention, when the fluctuation of the sampled plurality of detection voltages is greater than a preset fluctuation value, the current sampling is discarded.

[0021] According to an embodiment of the present invention, when the root mean square voltage is less than the threshold voltage, the output power calculation is not performed.

[0022] According to an embodiment of the present invention, the current attenuation value is adjusted accordingly by using a sampling average algorithm to perform attenuation adjustment twice in succession.

[0023] Compared with the prior art, the present invention has the following beneficial effects: by setting the protection attenuation value based on the input excitation and the rated output power range, it is ensured that power overshoot does not occur, and because the calculation excludes the human setting factor, the stability and applicability are enhanced; in addition, by automatically updating the attenuation value, the calibration of the next attenuation is realized, thereby ensuring the accuracy and omitting the labor cost of the initial precise calibration; at the same time, when the output RF power is adjusted to the rated range, the hysteresis comparison method is used to trigger the power adjustment, which can solve the problem of power drop caused by long-term use of the RF amplifier and the problem of output power jitter caused by detection error. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The embodiments of the present invention are further described below with reference to the accompanying drawings:

[0025] Figure 1 A schematic diagram of a flow chart of a method for automatic level control of a power amplifier according to an embodiment of the present invention;

[0026] Figure 2 is a schematic diagram of a radio frequency signal change according to an embodiment of the present invention;

[0027] Figure 3 FIG. 4 is a schematic diagram of a hysteresis comparison method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] Before proceeding to the following detailed description, it may be advantageous to set forth the definitions of certain words and phrases used throughout this patent document. The terms "coupling", "connection" and their derivatives refer to any direct or indirect communication or connection between two or more elements, regardless of whether those elements are in physical contact with each other. The terms "transmission", "reception" and "communication" and their derivatives cover direct and indirect communication. The terms "include" and "comprising" and their derivatives refer to including but not limited to. The term "or" is inclusive, meaning and / or. The phrase "associated with..." and its derivatives refer to including, including within, interconnecting, containing, contained within, connecting or connecting with, coupling or coupling with, communicating with, cooperating, interweaving, parallel, close to, binding or binding with, having, having attributes, having a relationship or having a relationship with, etc. The term "controller" refers to any device, system or part thereof that controls at least one operation. Such a controller can be implemented with hardware, or a combination of hardware and software and / or firmware. The functions associated with any particular controller can be centralized or distributed, whether local or remote. The phrase "at least one of", when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one of the items in the list may be required. For example, "at least one of A, B, C" includes any of the following combinations: A, B, C, A and B, A and C, B and C, A and B and C.

[0029] Definitions for other specific words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior and future uses of such defined words and phrases.

[0030] In this patent document, the application combination of modules and the division level of sub-modules are only used for illustration, and the application combination of modules and the division level of sub-modules may have different forms without departing from the scope of the present disclosure.

[0031] 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 through specific embodiments in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] As described in the background technology, the prior art lacks a power amplifier with simple structure and high efficiency for dynamically adjusting attenuation. Figure 1As shown, according to an embodiment of the present invention, a method for automatic level control of a power amplifier based on dynamically adjusting attenuation value is provided, comprising the following steps: S1, calculating the protection attenuation value of a digitally controlled attenuator according to input excitation and rated output power range, and setting the initial value of the attenuation table of the digitally controlled attenuator based on the protection attenuation value; S2, querying the attenuation value corresponding to the frequency information from the attenuation table according to the frequency information of the input excitation; S3, attenuating the power amplifier based on the current attenuation value, measuring the current output power of the power amplifier by a detector, and comparing it with the rated output power range; S4, when the current output power is outside the rated output power range, adjusting the current attenuation value accordingly, and repeating steps S3-S4; S5, when the current output power is within the rated output power range, writing the current attenuation value into the attenuation table; S6, before the input excitation frequency is updated, when the output power is within the rated output power range, using the hysteresis comparison method to trigger the power adjustment, the trigger threshold is twice the accuracy of the digitally controlled attenuator, and repeating steps S2-S6 after the frequency is updated. . By setting the protection attenuation value based on the input excitation and rated output power range, it is ensured that power overshoot will not occur, and because the calculation excludes the human setting factor, the stability is enhanced; in addition, the automatic update of the attenuation value realizes the calibration of the next attenuation, thus ensuring accuracy, omitting the labor cost of the initial precise calibration, and enhancing the applicability of circuits with different input and output conditions. At the same time, when the output RF power is adjusted to the rated range, the hysteresis comparison method is used to trigger the power adjustment, which can solve the problem of power drop caused by long-term use of the RF amplifier and the problem of output power jitter caused by detection error.

[0033] For example, the detection error of AD8361 is ±0.25dB, and the minimum accuracy of the selected digital controlled attenuator is 0.25dB. In practice, the digital controlled attenuator will still be repeatedly adjusted due to the error, causing output RF power jitter.

[0034] Hysteresis comparison principle Figure 2 As shown, the present invention uses 2 times the minimum precision of the digital controlled attenuator (i.e. 0.5 dB) as the switching moment of the digital controlled attenuator. Therefore, the digital controlled attenuator starts to work only when this variation is reached.

[0035] The hysteresis comparison algorithm can solve the problem of RF output power jitter caused by detection error, and can also solve the problem of RF output power reduction caused by long-term use. When the RF amplifier is in an extreme ambient temperature (such as -40℃ or 70℃), the efficiency of the RF amplifier will change significantly. After using hysteresis comparison, the environmental adaptability of the RF amplifier can be improved.

[0036] According to an embodiment of the present invention, the current output power of the power amplifier is measured by the detector by measuring the root mean square voltage of the power amplifier by the detector, and the output power is calculated based on the root mean square voltage. For example, a root mean square detection chip AD8361 is used, and the root mean square voltage is obtained by root mean square detection. In addition, the mean value detection method and the peak value detection method can also be used, and both can be set according to different application scenarios.

[0037] In the detector, according to an embodiment of the present invention, the root mean square voltage is:

[0038]

[0039] Among them, V in is the detector input voltage, T is the detection period, t1 and t2 are the starting point and end point of the detection period respectively.

[0040] Based on the root mean square voltage, according to an embodiment of the present invention, the output power is:

[0041]

[0042] Among them, V rms is the rms voltage. This equation is calculated based on a 50 ohm transmission line system.

[0043] As we all know, the RF signal will have a gradual rise or fall process, and it does not immediately rise to the maximum value or fall to the minimum value. Figure 2 When the RF signal is sampled during its rising process or gradually falling, and the digital controlled attenuator is adjusted, the RF output power will inevitably be too large or too small.

[0044] In view of the above problem, according to an embodiment of the present invention, the current output power of the power amplifier is measured by the detector by adopting a sampling average algorithm, wherein the sampling average algorithm is that the detector measures the detection voltage of the input detector multiple times within a specific time period, calculates the average value of the detection voltage, and calculates the current output power based on the average value of the detection voltage. According to an embodiment of the present invention, the average value of the detection voltage is:

[0045]

[0046] Among them, a i is the detection voltage each time, and N is the number of detections. When N is 10, 10 data are sampled each time. In addition, in order to avoid the influence of the head data and the tail data, the maximum value and the minimum value can be removed, and then the average value of the remaining 8 data is taken.

[0047] In addition, for certain detection chips, such as AD8361, multiple detections will still have certain errors. For example, when the detection signal dynamic is 14dB, the detection error is ±0.25dB; when the detection signal dynamic is 23dB, the detection error is ±1dB; when the detection signal dynamic is 30dB, the detection error is ±2dB. Considering the RF excitation signal fluctuation range of 7dBm to 13dBm, the detection error of AD8361 is ±0.25dB. Given that there is also a certain error in AD (analog-to-digital) sampling, the sampling data a i A certain error margin should be ensured.

[0048] Therefore, in order to ensure the accuracy of sampling, according to an embodiment of the present invention, when the fluctuation of the sampled multiple detection voltages is greater than the preset fluctuation value, the current sampling is discarded. For example, when the corresponding RF fluctuation exceeds ±0.5dB, it is considered that the RF signal is in a rising or falling state, and the current sampling is discarded. Only when the collected RF signal fluctuation is less than ±0.5dB, it is considered valid. Then remove the maximum and minimum values, and calculate the average value of the remaining 8 data. Then, based on the calculated average voltage, the RF power P (dBm) is calculated, and then the CNC attenuator is adjusted based on this RF power and the RF power range.

[0049] In addition, when there is no RF signal, or the RF signal is very weak (below the detection range of the detector chip), the controller will still collect a static voltage V fer (The static voltage of AD8361 is 0.1V). At this time, the detection judgment is necessarily inaccurate and meaningless. Therefore, in order to ensure the effectiveness of the method, according to an embodiment of the present invention, when the root mean square voltage is less than the threshold voltage, the output power calculation is not performed. The threshold voltage is a static voltage and varies according to the detection chip.

[0050] In order to avoid the situation that the RF amplifier is sampled when the power is saturated, and the RF output power cannot be accurately adjusted by adjusting the digital attenuator once, according to an embodiment of the present invention, the current attenuation value is adjusted accordingly to use a sampling average algorithm to perform attenuation adjustment twice in a row. During the detection process, the digital attenuator is adjusted by sampling the average value algorithm twice in a row. Assuming that the RF amplifier is initially operating in a saturated state, it will inevitably operate in the linear region after being adjusted by the digital attenuator once. Then, the RF output power can be accurately adjusted by adjusting the digital attenuator once. After two digital attenuator adjustments, the RF output power meets the RF requirements.

[0051] The present invention may be a system, a method and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present invention.

[0052] Computer readable storage medium can be a tangible device that holds and stores instructions used by an instruction execution device. Computer readable storage medium can include, for example, but is not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination thereof. More specific examples (non-exhaustive list) of computer readable storage medium include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disk read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, for example, a punch card or a protruding structure in a groove on which instructions are stored, and any suitable combination thereof.

[0053] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for automatic level control of a power amplifier based on dynamically adjusting attenuation value, characterized in that: The following steps are involved: S1. Calculate the protection attenuation value of the digital controlled attenuator according to the input excitation and the rated output power range, and set the initial value of the attenuation table of the digital controlled attenuator based on the protection attenuation value; S2. according to the frequency information of the input excitation, querying the attenuation value corresponding to the frequency information from the attenuation table; S3, attenuating the power amplifier based on the current attenuation value, measuring the current output power of the power amplifier by a detector, and comparing it with the rated output power range; S4, when the current output power is outside the rated output power range, adjusting the current attenuation value accordingly, and repeating steps S3-S4; S5. When the current output power is within the rated output power range, write the current attenuation value into the attenuation table. S6. Before the input excitation frequency is updated, when the output power is within the rated output power range, a hysteresis comparison method is used to trigger power adjustment, and the trigger threshold is twice the accuracy of the digital controlled attenuator. After the frequency is updated, steps S2-S6 are repeated.

2. A method for automatic level control of a power amplifier based on dynamically adjusting attenuation value as claimed in claim 1, characterized in that: Measuring the current output power of the power amplifier by the detector is measuring the root mean square voltage of the power amplifier by the detector, and calculating the output power based on the root mean square voltage.

3. A method for automatic level control of a power amplifier based on dynamically adjusting attenuation value as claimed in claim 2, characterized in that: The rms voltage is: Among them, V in is the detector input voltage, T is the detection period, t1 and t2 are the starting point and end point of the detection period respectively.

4. A method for automatic level control of a power amplifier based on dynamically adjusting attenuation value as claimed in claim 3, characterized in that: The output power is: Among them, V rms is the root mean square voltage.

5. A method for automatic level control of a power amplifier based on dynamically adjusting attenuation value as claimed in claim 1, characterized in that: The current output power of the power amplifier is measured by the detector using a sampling and averaging algorithm, wherein the sampling and averaging algorithm is that the detector measures the detection voltage of the input detector multiple times within a specific time period, calculates the average value of the detection voltage, and calculates the current output power based on the average value of the detection voltage.

6. A method for automatic level control of a power amplifier based on dynamically adjusting attenuation value as claimed in claim 5, characterized in that: The average value of the detection voltage is: Among them, a i is the detection voltage each time, and N is the number of detections.

7. A method for automatic level control of a power amplifier based on dynamically adjusting attenuation value as claimed in claim 6, characterized in that: When the fluctuation of the sampled multiple detection voltages is greater than the preset fluctuation value, the current sampling is discarded.

8. A method for automatic level control of a power amplifier based on dynamically adjusting attenuation value as claimed in claim 2, characterized in that: When the root mean square voltage is less than the threshold voltage, the output power calculation is not performed.

9. A method for automatic level control of a power amplifier based on dynamically adjusting attenuation value as claimed in claim 5, characterized in that: The current attenuation value is adjusted accordingly by using a sampling average algorithm to perform attenuation adjustment twice in succession.

Images