Radio frequency power amplifier circuit and method of regulating the same

Abstract

The application provides a radio frequency power amplification circuit and a regulation method thereof.The radio frequency power amplification circuit comprises a picture transmission module, a first radio frequency switch, a radio frequency power amplification module, a radio frequency low noise amplifier, a second radio frequency switch and an antenna module; the radio frequency power amplification module comprises a GaN radio frequency power amplifier; the picture transmission module is connected with the RFC of the first radio frequency switch; the GaN radio frequency power amplifier is connected between the first radio frequency switch and the RF1 channel of the second radio frequency switch; the radio frequency low noise amplifier is connected between the first radio frequency switch and the RF2 channel of the second radio frequency switch; and the antenna module is connected with the RFC of the second radio frequency switch. The two radio frequency switches are configured to: in a radio frequency transmission state, control the radio frequency signal transmitted by the picture transmission module to flow to the GaN radio frequency power amplifier, and send the amplified radio frequency signal to the antenna module; and in a radio frequency receiving state, control the radio frequency signal received by the antenna module to flow to the radio frequency low noise amplifier, and send the amplified radio frequency signal to the picture transmission module. The application can realize super-long distance picture transmission of an unmanned device.

Description

Technical Field

[0001] This application relates to the field of power amplifier technology, specifically to an radio frequency power amplifier circuit and its adjustment method. Background Technology

[0002] With the widespread application of drones, remote robots, and other equipment in fields such as industrial inspection, emergency rescue, and professional aerial photography, severe challenges have been posed to their beyond-line-of-sight and highly reliable image link systems.

[0003] Existing image transmission link systems typically employ radio frequency (RF) power amplifiers to amplify RF signals, enabling image transmission over longer distances. However, traditional RF power amplifiers based on gallium arsenide and silicon are gradually approaching their physical limits in terms of transmit power gain, efficiency, and bandwidth, making it difficult to meet the ultra-long-distance image transmission requirements of unmanned equipment.

[0004] In view of this, there is an urgent need to provide a broadband radio frequency power amplifier circuit with high transmit power gain and high receive sensitivity, as well as its adjustment method, to meet the ultra-long-distance image transmission requirements of unmanned equipment. Summary of the Invention

[0005] To address the aforementioned technical problems, this application provides a radio frequency power amplifier circuit and its adjustment method. By using independent radio frequency transmitting amplification modules and radio frequency receiving amplification modules, the transmitting power gain and receiving sensitivity are improved, thereby enabling ultra-long-distance image transmission for unmanned equipment.

[0006] According to a first aspect of this application, a radio frequency power amplifier circuit is proposed, which is applied to an image transmission link system. The radio frequency power amplifier circuit includes: an image transmission module, a first radio frequency switch, a radio frequency power amplifier module, a radio frequency low noise amplifier, a second radio frequency switch, and an antenna module. The radio frequency power amplifier module includes a GaN radio frequency power amplifier. The image transmission module is electrically connected to the common terminal RFC of the first radio frequency switch. The GaN radio frequency power amplifier is electrically connected between the RF1 channel of the first radio frequency switch and the second radio frequency switch. The radio frequency low noise amplifier is electrically connected between the RF2 channel of the first radio frequency switch and the second radio frequency switch. The antenna module is electrically connected to the common terminal RFC of the second radio frequency switch. The first radio frequency switch and the second radio frequency switch are configured as follows: In the radio frequency transmission state, the radio frequency signal transmitted by the image transmission module is directed to the GaN radio frequency power amplifier, and after being amplified by the GaN radio frequency power amplifier, it is sent to the antenna module. In the radio frequency receiving state, the radio frequency signal received by the antenna module is controlled to flow to the radio frequency low noise amplifier, and after being amplified by the radio frequency low noise amplifier, it is sent to the image transmission module.

[0007] Preferably, the first RF switch and the second RF switch are open on the RF2 channel by default. In the RF transmission state, the image transmission module transmits RF signals and control signals simultaneously. The control signals are used to control the first RF switch and the second RF switch to switch from the RF2 channel to the RF1 channel.

[0008] Preferably, the radio frequency power amplification module further includes a power supply unit and a negative voltage regulation unit; The negative voltage regulation unit is electrically connected between the output terminal of the power supply unit and the gate input terminal of the GaN RF power amplifier; The negative voltage regulation unit is used to convert the output voltage of the power supply unit into a gate bias voltage that enables the GaN RF power amplifier to turn on.

[0009] Preferably, the power supply unit is an MCU, and the input terminal of the negative voltage regulation unit is electrically connected to the DAC port of the MCU; The radio frequency power amplifier module further includes a sampling unit, which includes a current detection chip and a sampling resistor. The drain output terminal of the GaN RF power amplifier is electrically connected to one end of the sampling resistor, the input terminal of the current detection chip is electrically connected to both ends of the sampling resistor, and the output terminal of the current detection chip is electrically connected to the ADC1 port of the MCU. The MCU is configured as follows: Based on the voltage conversion result of the ADC1 port, the output voltage of the DAC port is adjusted in steps to regulate the gate bias voltage of the GaN RF power amplifier.

[0010] Preferably, the MCU is further configured to: The operating mode of the GaN RF power amplifier is determined based on the strength of the RF signal transmitted by the image transmission module. Adjust the output voltage of the DAC port according to the gate bias voltage of the GaN RF power amplifier corresponding to the operating mode until the GaN RF power amplifier operates in the operating mode.

[0011] Preferably, the GaN RF power amplifier operates in two modes: a first operating mode and a second operating mode. In the first operating mode, the gate bias voltage of the GaN RF power amplifier reaches the static operating point voltage; In the second operating mode, the gate bias voltage amplitude of the GaN RF power amplifier is less than the static operating point voltage amplitude; The MCU is also configured to: When the strength of the radio frequency signal transmitted by the image transmission module is less than a preset threshold, the GaN radio frequency power amplifier is controlled to operate in the first operating mode; When the strength of the radio frequency signal transmitted by the image transmission module is greater than a preset threshold, the GaN radio frequency power amplifier is controlled to operate in the second operating mode.

[0012] Preferably, the MCU stores a data table containing the gate bias voltage of the GaN RF power amplifier corresponding to different RF signal strengths emitted by the image transmission module. The MCU is further configured to: In the second operating mode, based on the strength of the radio frequency signal transmitted by the image transmission module, the output voltage of the DAC port is adjusted by querying the data table to provide the corresponding gate bias voltage for the GaN radio frequency power amplifier.

[0013] Preferably, it also includes a detector; The input terminal of the detector is electrically connected to the RF1 channel of the first radio frequency switch, and the output terminal of the detector is electrically connected to the ADC2 port of the MCU. The MCU is also configured to: The strength of the radio frequency signal transmitted by the image transmission module is determined based on the voltage conversion result of the ADC2 port.

[0014] Preferably, the radio frequency power amplifier module further includes a power switch unit; The input terminal of the power switch unit is electrically connected to the GPIO port of the MCU, and the output terminal of the power switch unit is electrically connected to the input terminal of the negative voltage regulation unit. The MCU is also configured to: Based on the RF transmit / receive status, the power switch unit is controlled to turn off / on to adjust the gate bias voltage of the GaN RF power amplifier, thereby controlling the GaN RF power amplifier to turn on / off.

[0015] Preferably, the RF power amplifier module further includes diodes D1 and D2; The two ends of diode D1 are electrically connected to the output terminal of the power switch unit and the input terminal of the negative voltage regulation unit, respectively. The two ends of diode D2 are electrically connected to the DAC port of the MCU and the output terminal of the power switch unit, respectively.

[0016] According to a second aspect of this application, a method for adjusting a radio frequency power amplifier circuit is proposed, applied to the radio frequency power amplifier circuit of the first aspect described above, the method comprising: In the radio frequency transmission state, the control image transmission module transmits radio frequency signal s10 and control signal s11. The first radio frequency switch and the second radio frequency switch receive the control signal s11 and switch from RF2 channel to RF1 channel. The radio frequency signal s10 flows to the loop where the GaN radio frequency power amplifier is located. After being amplified by the GaN radio frequency power amplifier, it is sent to the antenna module. In RF receiving mode, the control antenna module emits the received RF signal s12. The first and second RF switches switch back to the RF2 channel by default. The RF signal s12 flows to the loop where the RF low noise amplifier is located. After being amplified by the RF low noise amplifier, it is sent to the image transmission module.

[0017] Compared with the prior art, the beneficial results of this application are as follows: (1) The conduction of the transmitting and receiving links is controlled by an RF switch. In the transmitting state, the RF signal transmitted by the image transmission module is amplified by an RF power amplifier and then sent to the antenna module. In the receiving state, the RF signal received by the antenna module is amplified by an independent RF low-noise amplifier and then sent to the image transmission module. This application effectively improves the stability of signal transmission through a bidirectional power amplifier design and uses a GaN RF power amplifier, which has a higher transmit power gain and can realize ultra-long-distance image transmission.

[0018] (2) The current is sampled in real time by the sampling unit, and the output voltage of the DAC port of the MCU is adjusted stepwise by timing control, thereby adjusting the gate bias voltage of the RF power amplifier. When the current flowing through the sampling resistor reaches the preset static operating point of the RF power amplifier, the current DAC voltage output value is locked to complete the automatic calibration. In addition, in the RF transmission state, the RF signal strength is detected in real time by the detector, and the operating mode of the RF power amplifier is determined according to the RF signal strength. The gate bias voltage of the RF power amplifier is adjusted accordingly, thereby reducing the power consumption of the RF power amplifier while ensuring the signal transmission quality.

[0019] (3) By controlling the power switch unit through the MCU, in the RF transmission state, the power switch unit is controlled to turn off the output, and the MCU's DAC port provides the normal gate bias voltage to the RF power amplifier, so that the RF power amplifier is turned on. In the RF reception state, the power switch unit is controlled to turn on the output, and the negative voltage regulation unit switches to be powered by the power switch unit, forcing the output of the negative voltage regulation unit to be pulled down to below the pinch-off voltage of the RF power amplifier, so that the channel of the RF power amplifier is turned off and the RF power amplifier stops working. Thus, the RF power amplifier can be prevented from being in the on state for a long time during the reception period when it is not working, which would result in invalid power consumption and heat accumulation, and prevent the power amplifier performance from being degraded or damaged due to continuous heat generation, thereby improving the system reliability. Attached Figure Description

[0020] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and, together with the description, serve to explain the principles of this application. Other embodiments and many anticipated advantages of these embodiments will be readily recognized as they become better understood through reference to the following detailed description. Elements in the drawings are not necessarily to scale. The same reference numerals refer to corresponding similar parts.

[0021] Figure 1 This is a schematic block diagram of a radio frequency power amplifier circuit according to an embodiment of this application; Figure 2 This is a schematic diagram of a radio frequency power amplifier circuit according to an embodiment of this application.

[0022] The meanings of the numbers in the diagram are as follows: 10, image transmission module; 20, first RF switch; 30, RF power amplifier module; 31, GaN RF power amplifier; 32, power supply unit; 33, negative voltage regulation unit; 34, current detection chip; 35, power switch unit; 40, RF low noise amplifier; 50, second RF switch; 60, antenna module; 70, detector. Detailed Implementation

[0023] In the following detailed description, reference is made to the accompanying drawings, which form part of the detailed description and illustrate illustrative specific embodiments in which the present application may be practiced. In this regard, directional terms such as “top,” “bottom,” “left,” “right,” “up,” “down,” etc., are used with reference to the orientation of the described figures. Because components of the embodiments can be positioned in several different orientations, directional terms are used for illustrative purposes and are by no means limiting. It should be understood that other embodiments may be utilized or logical changes may be made without departing from the scope of the present application. Therefore, the following detailed description should not be taken in a limiting sense, and the scope of the present application is defined by the appended claims.

[0024] Furthermore, it should be understood that in the following description, "circuit" refers to a conductive loop consisting of at least one element or sub-circuit connected by electrical or electromagnetic connections. When an element or circuit is said to be "connected" to another element or "connected" between two nodes, it can be directly coupled or connected to another element, or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected" to another element, it means that there are no intermediate elements between them.

[0025] According to the first aspect of this application, a radio frequency power amplifier circuit is proposed for use in an image transmission link system. Figure 1 A schematic block diagram of a radio frequency power amplifier circuit according to an embodiment of this application is shown. Figure 2 A schematic diagram of a radio frequency power amplifier circuit according to an embodiment of this application is shown, such as... Figure 1 , Figure 2 As shown, the radio frequency power amplifier circuit includes a video transmission module 10, a first radio frequency switch 20, a radio frequency power amplifier module 30, a radio frequency low noise amplifier 40, a second radio frequency switch 50, and an antenna module 60.

[0026] The radio frequency power amplifier module 30 includes a GaN radio frequency power amplifier 31. The image transmission module 10 is electrically connected to the common terminal RFC of the first radio frequency switch 20. The GaN radio frequency power amplifier 31 is electrically connected between the RF1 channel of the first radio frequency switch 20 and the second radio frequency switch 50. The radio frequency low noise amplifier 40 is electrically connected between the RF2 channel of the first radio frequency switch 20 and the second radio frequency switch 50. The antenna module 60 is electrically connected to the common terminal RFC of the second radio frequency switch 50.

[0027] In some embodiments, the first RF switch 20 and the second RF switch 50 may be, for example, single-pole double-throw switches.

[0028] In some embodiments, the GaN RF power amplifier 31 can be selected from different PA models according to different operating frequency bands, such as NV5312 (1-2.5GHz), DF2G0060-08N (5-6GHz), etc.

[0029] In some embodiments, the RF low noise amplifier 40 may also select different models of LNAs according to different operating frequency bands, such as NV9092 (1-2.5GHz), NV9096 (5-6GHz), etc.

[0030] In some embodiments, the first radio frequency switch 20 and the second radio frequency switch 50 are configured to: The first RF switch 20 and the second RF switch 50 are open by default on the RF2 channel. In the RF transmission state, the image transmission module 10 simultaneously transmits the RF signal s10 and the control signal s11. The control signal s11 is used to control the first RF switch 20 and the second RF switch 50 to switch from the RF2 channel to the RF1 channel.

[0031] Therefore, in the RF transmission state, the RF signal s10 transmitted by the image transmission module 10 flows to the circuit where the GaN RF power amplifier 31 is located, and after being amplified by the GaN RF power amplifier 31, it is sent to the antenna module 60; in the RF reception state, the RF signal s12 received by the antenna module 60 flows to the circuit where the RF low noise amplifier 40 is located, and after being amplified by the RF low noise amplifier 40, it is sent to the image transmission module 10.

[0032] By using a bidirectional power amplifier design, the stability of signal transmission can be effectively improved. Furthermore, the PA in this application adopts a GaN RF power amplifier 31, which has a higher transmit power gain and can achieve ultra-long-distance image transmission.

[0033] It should be noted that, in some embodiments, the control signal s11 may be provided directly or through appropriate conversion (e.g., conversion into a digital switch signal) as a signal for controlling the first RF switch 20 and the second RF switch 50.

[0034] In some embodiments, the RF power amplifier module 30 further includes a power supply unit 32 and a negative voltage regulation unit 33. The negative voltage regulation unit 33 is electrically connected between the output terminal of the power supply unit 32 and the gate input terminal of the GaN RF power amplifier 31, and is used to convert the output voltage of the power supply unit 32 into a gate bias voltage VGS that enables the GaN RF power amplifier 31 to turn on.

[0035] In some embodiments, the power supply unit 32 is an MCU, such as the N32G4FRKCQ7 32-bit microcontroller. The input terminal of the negative voltage regulation unit 33 is electrically connected to the DAC port of the MCU, and the MCU is powered by the output voltage of the DAC port.

[0036] In some embodiments, since the GaN RF power amplifier 31 is a depletion-mode power amplifier, the output voltage of the MCU's DAC port needs to be converted to a negative voltage first. The negative voltage adjustment unit 33 can, for example, be an inverting amplifier constructed from an operational amplifier of model SL8052A, powered by a dual positive and negative power supply, such as +5V and -5V. The negative voltage adjustment unit 33 can convert the output voltage of the MCU's DAC port to a negative voltage and amplify it by approximately 3 times.

[0037] In some embodiments, the RF power amplifier module 30 further includes a sampling unit, which includes a current detection chip 34 and a sampling resistor R1. The drain output of the GaN RF power amplifier 31 is electrically connected to one end of the sampling resistor R1, the input of the current detection chip 34 is electrically connected to both ends of the sampling resistor R1, and the output of the current detection chip 34 is electrically connected to the ADC1 port of the MCU.

[0038] In some embodiments, the MCU is configured to: Based on the voltage conversion result of the ADC1 port, the output voltage of the DAC port is adjusted in steps to adjust the gate bias voltage of the GaN RF power amplifier 31, thereby achieving automatic calibration of the GaN RF power amplifier 31.

[0039] The quiescent current of the GaN RF power amplifier 31 can be determined using the formula Ids=Vout / (Gain*Rsense), where Ids is the quiescent current of the GaN RF power amplifier 31, Vout is the output voltage of the current sensing chip 34, Gain is the gain of the current sensing chip 34, and Rsense is the resistance value of the sampling resistor R1.

[0040] In some embodiments, the current detection chip 34 can be an INA186A3IDCKR chip. Its input terminal is connected to both ends of the sampling resistor R1, which can be used to detect the drain current of the GaN RF power amplifier 31. The output voltage is proportional to the voltage drop of the sampling resistor R1, thereby obtaining the output voltage of the current detection chip 34. The analog signal is converted into a digital signal through the ADC1 (analog-to-digital converter) port in the MCU, and the output voltage of the current detection chip 34 is acquired.

[0041] During the calibration process, the digital signal is converted into an analog signal through the DAC (digital-to-analog converter) port of the MCU. Since there is a positive correlation between the quiescent current and the gate voltage, the MCU can adjust the output voltage of the DAC port stepwise through timing control, thereby adjusting the output voltage of the negative voltage adjustment unit 33, and then adjusting the gate bias voltage of the GaN RF power amplifier 31 to reach the quiescent operating point voltage, thereby realizing the automatic calibration of the quiescent current of the GaN RF power amplifier 31.

[0042] In this embodiment, the output voltage range of the DAC port of the MCU is 0-3.3V, the amplification factor of the negative voltage adjustment unit 33 is about 3 times, the gate bias voltage of the GaN RF power amplifier 31 is off by default when it is -5V, and the gate bias voltage of the GaN RF power amplifier 31 reaches the static operating point when it is -2.5V.

[0043] Therefore, upon initial power-on, the output voltage of the MCU's DAC port can be set to approximately 1.7V. During calibration, the MCU gradually decreases the output voltage of the DAC port through timing control, for example, from approximately 1.7V, causing the output of the negative voltage regulation unit 33 to increase from -5V, for example, -5V, -4.95V, -4.9V, -4.85V... The MCU monitors the output voltage of the current detection chip 34 in real time, which reflects the current flowing through the sampling resistor R1. When the current reaches the quiescent current of the GaN RF power amplifier 31, the MCU locks the current output voltage of the DAC port (approximately 0.8V), completing the automatic calibration.

[0044] In some embodiments, the RF power amplification current also includes a detector 70. The input of the detector 70 is electrically connected to the RF1 channel of the first RF switch 20, and the output of the detector 70 is electrically connected to the ADC2 port of the MCU.

[0045] In the radio frequency transmission state, the radio frequency signal s10 transmitted by the image transmission module 10 passes through the detector 70. The detector 70 can linearly convert the radio frequency signal s10 into a DC output voltage. The MCU reads the voltage value through the ADC2 port and can calculate the original power value (i.e., radio frequency signal strength) of the radio frequency signal s10 based on the voltage conversion result.

[0046] In some embodiments, detector 70 may be, for example, a logarithmic detector (such as AD8318) or an RMS detector (such as LT5581, ADL5904).

[0047] In some embodiments, the MCU is further configured to: Based on the strength of the radio frequency signal transmitted by the image transmission module 10, the operating mode of the GaN radio frequency power amplifier 31 is determined; based on the gate bias voltage of the GaN radio frequency power amplifier 31 corresponding to the operating mode, the output voltage of the DAC port is adjusted until the GaN radio frequency power amplifier operates in the operating mode.

[0048] In some embodiments, the GaN RF power amplifier 31 operates in two modes: a first operating mode and a second operating mode. In the first operating mode, the gate bias voltage of the GaN RF power amplifier 31 reaches the quiescent operating point voltage, which is approximately 0.8V at the output voltage of the MCU's DAC port, and approximately -2.5V at the gate bias voltage of the GaN RF power amplifier 31. In the second operating mode, the gate bias voltage amplitude of the GaN RF power amplifier 31 is less than the quiescent operating point voltage amplitude, which is less than 0.8V at the output voltage of the MCU's DAC port, and greater than -2.5V (e.g., -2.4V, -2.3V, -2.2V...).

[0049] In some embodiments, the MCU is further configured to: When the strength of the radio frequency signal transmitted by the image transmission module 10 is less than a preset threshold, the GaN radio frequency power amplifier 31 is controlled to operate in the first operating mode; when the strength of the radio frequency signal transmitted by the image transmission module 10 is greater than the preset threshold, the GaN radio frequency power amplifier 31 is controlled to operate in the second operating mode.

[0050] In this embodiment, the preset threshold corresponding to the radio frequency signal strength can be an empirical value or a signal strength value set according to the actual application scenario, and there is no limitation here.

[0051] In some embodiments, the MCU is further configured to: The MCU stores a data table containing the gate bias voltage of the GaN RF power amplifier 31 corresponding to different RF signal strengths transmitted by the image transmission module 10. In the second operating mode, based on the RF signal strength transmitted by the image transmission module 10, the output voltage of the DAC port is adjusted by querying the data table to provide the corresponding gate bias voltage for the GaN RF power amplifier 31.

[0052] In practical applications, when the RF signal s10 transmitted by the image transmission module 10 is weak, the MCU can control the GaN RF power amplifier 31 to operate in the first operating mode, i.e., the static operating point. At this time, the performance of the GaN RF power amplifier 31 is optimal, ensuring that the RF signal s10 reaches a relatively ideal signal strength after amplification. However, the power consumption of the GaN RF power amplifier 31 will also increase. When the RF signal s10 transmitted by the image transmission module 10 is strong, the MCU can control the GaN RF power amplifier 31 to operate in the second operating mode. By looking up a table, the MCU finds the corresponding gate bias voltage value for that signal strength and adjusts the output voltage of the DAC port. Although the performance of the GaN RF power amplifier 31 is not optimal at this time, the RF signal s10 can still reach a relatively ideal signal strength after amplification, and the power consumption of the GaN RF power amplifier 31 will be reduced.

[0053] Therefore, by detecting the strength of the radio frequency signal 10 through the detector 70, the MCU dynamically adjusts the operating mode of the GaN radio frequency power amplifier 31 and dynamically adjusts the transmit power gain of the GaN radio frequency power amplifier 31. Under the premise of ensuring signal transmission quality, the power consumption of the GaN radio frequency power amplifier 31 can be reduced, preventing the power amplifier performance from degrading or being damaged due to continuous heat generation, thereby improving system reliability.

[0054] In some embodiments, the RF power amplifier module 30 further includes a power switch unit 35. The input terminal of the power switch unit 35 is electrically connected to the GPIO port of the MCU, and the output terminal of the power switch unit 35 is connected to the input terminal of the negative voltage regulation unit 33.

[0055] In this embodiment, the power switch unit 35 outputs a voltage of 1.8V when it is turned on.

[0056] In some embodiments, the RF power amplifier module 30 further includes diodes D1 and D2. Diode D1 is electrically connected to the output terminal of the power switch unit 35 and the input terminal of the negative voltage regulation unit 33, respectively, while diode D2 is electrically connected to the DAC port of the MCU and the output terminal of the power switch unit 35, respectively. Diodes D1 and D2 prevent reverse power supply and protect the circuit.

[0057] In this embodiment, the 1.8V output by the power switch unit 35 in the on state is approximately 1.7V after the diode voltage drop.

[0058] In some embodiments, the MCU is further configured to: Based on the RF transmit / receive status, the power switch unit 35 is controlled to turn off / on, thereby adjusting the gate bias voltage of the GaN RF power amplifier 31 and thus controlling the GaN RF power amplifier 31 to turn on / off.

[0059] Specifically, in the RF transmission state, the detector 70 detects the RF signal s10 and converts it into a DC output voltage. The ADC2 port of the MCU receives the voltage signal and controls the power switch unit 35 to turn off the output. The DAC port of the MCU provides the normal gate bias voltage to the GaN RF power amplifier 31, enabling it to operate. In the RF reception state, the detector 70 does not detect the RF signal s10, and the ADC2 port of the MCU also does not receive the voltage signal. The MCU controls the power switch unit 35 to turn on the output. Since the 1.7V output voltage of the power switch unit 35 is higher than the 0.8V output voltage of the DAC port of the MCU, the negative voltage regulation unit 33 switches to be powered by the power switch unit 35, forcing the output of the negative voltage regulation unit 33 to be pulled down to about -5.1V, which is lower than the pinch-off voltage of the GaN RF power amplifier 31, -5V, causing the channel of the GaN RF power amplifier 31 to turn off, and the GaN RF power amplifier 31 stops working.

[0060] Therefore, by controlling the working state of the power switch unit 35 through the MCU according to the RF transmit / receive status, the GaN RF power amplifier 31 can be prevented from being in the on state for a long time during the receiving period when it is not in operation, thus avoiding the generation of invalid power consumption and heat accumulation. This prevents the performance degradation or damage of the GaN RF power amplifier 31 due to continuous heat generation, thereby improving the system reliability.

[0061] In some embodiments, the RF power amplifier circuit further includes power filters F1 and F2. Power filter F1 is electrically connected to the output terminal of the negative voltage regulation unit 33 and the gate input terminal of the GaN RF power amplifier 31, respectively. Power filter F2 is electrically connected to the drain output terminal of the GaN RF power amplifier 31 and one end of the sampling resistor R1, respectively. The power filters provide a clean operating voltage for the GaN RF power amplifier 31.

[0062] In some embodiments, the RF power amplifier circuit further includes DC blocking capacitors C1, C2, C3, and C4. Specifically, the two ends of DC blocking capacitor C1 are electrically connected to the RF1 channel of the first RF switch 20 and the gate input terminal of the GaN RF power amplifier 31, respectively; the two ends of DC blocking capacitor C2 are electrically connected to the drain output terminal of the GaN RF power amplifier 31 and the RF1 channel of the second RF switch 50, respectively; the two ends of DC blocking capacitor C3 are electrically connected to the RF2 channel of the second RF switch 50 and the input terminal of the RF low-noise amplifier 40, respectively; and the two ends of DC blocking capacitor C4 are electrically connected to the output terminal of the RF low-noise amplifier 40 and the RF2 channel of the first RF switch 20, respectively. The DC blocking capacitors can eliminate the DC component in the RF signals s10 and s12.

[0063] According to a second aspect of this application, based on the above-described radio frequency power amplifier circuit, a method for adjusting the radio frequency power amplifier circuit is also provided, the method comprising: Step S100: Upon first power-on, the operating current of the GaN RF power amplifier is detected by the sampling unit. Based on the voltage conversion result of the ADC1 port, the MCU dynamically adjusts the output voltage of the DAC port to make the gate bias voltage of the GaN RF power amplifier reach the static operating point voltage, and records the current DAC output voltage value.

[0064] Step S200: After the first power-on: In the RF transmission state, the control image transmission module transmits RF signal s10 and control signal s11. The first RF switch and the second RF switch receive the control signal s11 and switch from RF2 channel to RF1 channel. RF signal s10 flows to the loop where the GaN RF power amplifier is located. After being amplified by the GaN RF power amplifier, it is sent to the antenna module. In the RF reception state, the control antenna module transmits the received RF signal s12. The first RF switch and the second RF switch switch back to RF2 channel by default. RF signal s12 flows to the loop where the RF low noise amplifier is located. After being amplified by the RF low noise amplifier, it is sent to the image transmission module.

[0065] In some embodiments, step S200 further includes: In RF transmission mode, the signal strength of RF signal s10 is detected by the detector. The MCU determines the signal strength of RF signal s10 based on the voltage conversion result of the ADC2 port, and determines the operating mode of GaN RF power amplifier. Then, the output voltage of DAC port is dynamically adjusted so that GaN RF power amplifier operates in this operating mode.

[0066] In some embodiments, step S200 further includes: The GaN RF power amplifier has two operating modes: a first operating mode and a second operating mode. In the first operating mode, the gate bias voltage of the GaN RF power amplifier reaches the static operating point voltage. In the second operating mode, the gate bias voltage amplitude of the GaN RF power amplifier is less than the static operating point voltage amplitude. In RF transmission mode, when the signal strength of RF signal s10 is determined to be less than a preset threshold, the MCU dynamically adjusts the output voltage of the DAC port, so that the GaN RF power amplifier operates in the first operating mode; when the signal strength of RF signal s10 is determined to be greater than the preset threshold, the MCU dynamically adjusts the output voltage of the DAC port, so that the GaN RF power amplifier operates in the second operating mode.

[0067] In some embodiments, step S200 further includes: The MCU stores a data table, which stores the gate bias voltage of the GaN RF power amplifier corresponding to different signal strengths of the RF signal s10. When the signal strength of the RF signal s10 is detected to be greater than the preset threshold, the MCU adjusts the output voltage of the DAC port by querying the data table, thereby providing the corresponding gate bias voltage for the GaN RF power amplifier.

[0068] In some embodiments, step S200 further includes: In RF transmission mode, the MCU controls the power switch unit to shut down the output, and the MCU's DAC port supplies power to provide the GaN RF power amplifier with normal gate bias voltage, enabling it to start working. In RF receiving mode, the MCU controls the power switch unit to turn on the output. Powered by the power switch unit, the gate bias voltage of the GaN RF power amplifier is pulled down to less than the pinch-off voltage, causing the channel of the GaN RF power amplifier to turn off and stop working.

[0069] It is obvious that those skilled in the art can make various modifications and alterations to the embodiments of this application without departing from the spirit and scope of this application. In this way, this application also aims to cover such modifications and alterations if they fall within the scope of the claims and their equivalents. The word "comprising" does not exclude the presence of other elements or steps not listed in the claims. The simple fact that certain measures are described in mutually different dependent claims does not indicate that a combination of these measures cannot be used for profit. Any reference numerals in the claims should not be considered limiting in scope.

Claims

1. A radio frequency power amplifier circuit, characterized in that, The radio frequency power amplifier circuit is applied to the image transmission link system. The radio frequency power amplifier circuit includes: an image transmission module, a first radio frequency switch, a radio frequency power amplifier module, a radio frequency low noise amplifier, a second radio frequency switch, and an antenna module. The RF power amplifier module includes a power supply unit, a negative voltage regulation unit, and a GaN RF power amplifier. The image transmission module is electrically connected to the common terminal RFC of the first RF switch. The negative voltage regulation unit is electrically connected between the output terminal of the power supply unit and the gate input terminal of the GaN RF power amplifier. The negative voltage regulation unit is used to convert the output voltage of the power supply unit into a gate bias voltage that enables the GaN RF power amplifier to turn on. The GaN RF power amplifier is electrically connected between the RF1 channel of the first RF switch and the second RF switch. The RF low noise amplifier is electrically connected between the RF2 channel of the first RF switch and the second RF switch. The antenna module is electrically connected to the common terminal RFC of the second RF switch. The first radio frequency switch and the second radio frequency switch are configured as follows: In the radio frequency transmission state, the radio frequency signal transmitted by the image transmission module is directed to the GaN radio frequency power amplifier, and after being amplified by the GaN radio frequency power amplifier, it is sent to the antenna module. In the radio frequency receiving state, the radio frequency signal received by the antenna module is controlled to flow to the radio frequency low noise amplifier, and after being amplified by the radio frequency low noise amplifier, it is sent to the image transmission module; The power supply unit is an MCU. The input terminal of the negative voltage regulation unit is electrically connected to the DAC port of the MCU. The RF power amplifier module also includes a sampling unit. The sampling unit includes a current detection chip and a sampling resistor. The drain output terminal of the GaN RF power amplifier is electrically connected to one end of the sampling resistor. The input terminal of the current detection chip is electrically connected to both ends of the sampling resistor. The output terminal of the current detection chip is electrically connected to the ADC1 port of the MCU. The MCU is configured as follows: Based on the voltage conversion result of the ADC1 port, the output voltage of the DAC port is adjusted in steps to adjust the gate bias voltage of the GaN RF power amplifier; The MCU is also configured to: Based on the strength of the radio frequency signal transmitted by the image transmission module, the operating mode of the GaN radio frequency power amplifier is determined. Based on the gate bias voltage of the GaN radio frequency power amplifier corresponding to the operating mode, the output voltage of the DAC port is adjusted until the GaN radio frequency power amplifier operates in the operating mode. The GaN RF power amplifier has two operating modes: a first operating mode and a second operating mode. In the first operating mode, the gate bias voltage of the GaN RF power amplifier reaches the static operating point voltage. In the second operating mode, the gate bias voltage amplitude of the GaN RF power amplifier is less than the static operating point voltage amplitude. The MCU is also configured to: When the strength of the radio frequency signal transmitted by the image transmission module is less than a preset threshold, the GaN radio frequency power amplifier is controlled to operate in the first operating mode; when the strength of the radio frequency signal transmitted by the image transmission module is greater than the preset threshold, the GaN radio frequency power amplifier is controlled to operate in the second operating mode.

2. The radio frequency power amplifier circuit according to claim 1, characterized in that, The first and second RF switches are enabled by default on the RF2 channel. In the RF transmission state, the image transmission module transmits RF signals and control signals simultaneously. The control signals are used to control the first and second RF switches to switch from the RF2 channel to the RF1 channel.

3. The radio frequency power amplifier circuit according to claim 1, characterized in that, The MCU stores a data table containing the gate bias voltage of the GaN RF power amplifier corresponding to different RF signal strengths emitted by the image transmission module. The MCU is also configured to: In the second operating mode, based on the strength of the radio frequency signal transmitted by the image transmission module, the output voltage of the DAC port is adjusted by querying the data table to provide the corresponding gate bias voltage for the GaN radio frequency power amplifier.

4. The radio frequency power amplifier circuit according to claim 1, characterized in that, It also includes detectors; The input terminal of the detector is electrically connected to the RF1 channel of the first radio frequency switch, and the output terminal of the detector is electrically connected to the ADC2 port of the MCU. The MCU is also configured to: The strength of the radio frequency signal transmitted by the image transmission module is determined based on the voltage conversion result of the ADC2 port.

5. The radio frequency power amplifier circuit according to claim 4, characterized in that, The radio frequency power amplifier module also includes a power switch unit; The input terminal of the power switch unit is electrically connected to the GPIO port of the MCU, and the output terminal of the power switch unit is electrically connected to the input terminal of the negative voltage regulation unit. The MCU is also configured to: Based on the RF transmit / receive status, the power switch unit is controlled to turn off / on to adjust the gate bias voltage of the GaN RF power amplifier, thereby controlling the GaN RF power amplifier to turn on / off.

6. The radio frequency power amplifier circuit according to claim 5, characterized in that, The radio frequency power amplifier module also includes diodes D1 and D2; The two ends of diode D1 are electrically connected to the output terminal of the power switch unit and the input terminal of the negative voltage regulation unit, respectively. The two ends of diode D2 are electrically connected to the DAC port of the MCU and the output terminal of the power switch unit, respectively.

7. A method for adjusting a radio frequency power amplifier circuit, applied to the radio frequency power amplifier circuit as described in any one of claims 1-6, characterized in that, The method includes: Step S100: Upon first power-on, the operating current of the GaN RF power amplifier is detected by the sampling unit. Based on the voltage conversion result of the ADC1 port, the MCU dynamically adjusts the output voltage of the DAC port to make the gate bias voltage of the GaN RF power amplifier reach the static operating point voltage, and records the current DAC output voltage value. Step S200: After the first power-on: In RF transmission mode, the control image transmission module transmits RF signal s10 and control signal s11. The first RF switch and the second RF switch receive control signal s11 and switch from RF2 channel to RF1 channel. RF signal s10 flows to the loop where the GaN RF power amplifier is located. After being amplified by the GaN RF power amplifier, it is sent to the antenna module. In RF reception mode, the control antenna module transmits the received RF signal s12. The first RF switch and the second RF switch switch back to RF2 channel by default. RF signal s12 flows to the loop where the RF low noise amplifier is located. After being amplified by the RF low noise amplifier, it is sent to the image transmission module. Step S200 further includes: In the RF transmission state, the signal strength of RF signal s10 is detected, and the operating mode of GaN RF power amplifier is determined. Then, the output voltage of the MCU's DAC port is dynamically adjusted so that GaN RF power amplifier operates in that operating mode. The GaN RF power amplifier has two operating modes: a first operating mode and a second operating mode. In the first operating mode, the gate bias voltage of the GaN RF power amplifier reaches the static operating point voltage. In the second operating mode, the gate bias voltage amplitude of the GaN RF power amplifier is less than the static operating point voltage amplitude. In RF transmission mode, when the signal strength of RF signal s10 is less than a preset threshold, the MCU dynamically adjusts the output voltage of the DAC port, so that the GaN RF power amplifier operates in the first operating mode; when the signal strength of RF signal s10 is greater than the preset threshold, the MCU dynamically adjusts the output voltage of the DAC port, so that the GaN RF power amplifier operates in the second operating mode.

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