A microwave wireless transmission transmitting system and a high power amplifier

Abstract

This invention belongs to the field of radio frequency communication technology and discloses a microwave wireless transmission system and a high-power amplifier. The high-power amplifier includes: a transistor; an output matching network, the input of which is connected to the output of the transistor; the output matching network includes: a coupling line, which is composed of a coupled first transmission line and a coupled second transmission line; the two ends of the first transmission line are a first port and a second port, respectively, and the two ends of the second transmission line are a third port and a fourth port, respectively; wherein, the first port is connected to the input, and the third port is open-circuited; an open-circuit stub is connected to the second port; a short-circuit stub is connected to the fourth port; and an output load is connected to the fourth port.

Description

Technical Field

[0001] This invention belongs to the field of radio frequency communication technology, and specifically relates to a microwave wireless transmission system and a high-power amplifier. Background Technology

[0002] Microwave wireless power transfer (MPT) technology aims to achieve contactless energy transfer via microwave beams, making it particularly suitable for scenarios such as micro-mobile robots where it is difficult to carry large-capacity batteries or where continuous power supply is required. Existing MPT transmitting systems typically consist of three main parts: a microwave signal source, a power amplification link, and a transmitting antenna. The signal source often employs a phase-locked loop (PLL) frequency synthesizer to ensure frequency stability and spectral purity, but its output power is relatively low, requiring multiple stages of amplification to reach the power level required for transmission. The power amplification link generally includes a linear amplifier, a driver amplifier, and a final-stage high-power amplifier. The final-stage power amplifier is the core module determining the system's output capability and efficiency, responsible for ultimately amplifying the microwave signal to several watts to tens of watts before feeding it to the antenna for radiation.

[0003] In the design of high-power amplifiers, early designs primarily employed silicon bipolar transistors (SiPs) or GaAs MESFETs. However, due to material limitations, their power density and efficiency were difficult to further improve. In recent years, wide-bandgap semiconductors such as GaN HEMTs have been increasingly used, becoming the preferred devices for high-power microwave amplifiers due to their potential for high breakdown voltage, high power density, and high efficiency. The design of matching networks has evolved from L-type, π-type, or T-type networks composed of discrete inductors and capacitors to distributed matching networks based on microstrip lines and striplines. However, their primary goal remains fundamental impedance matching to maximize power transfer, while their ability to control harmonic impedance is relatively weak. Additional filters are often needed to suppress out-of-band interference, which increases system size and insertion loss, and also limits the balance between broadband and high efficiency.

[0004] In terms of control and monitoring, traditional MPT transmitter systems mostly adopt an open-loop architecture, meaning the signal source output is fixed and the amplifier link gain is fixed. This makes the output power susceptible to drift due to factors such as temperature changes and component aging. Some high-end systems use directional couplers with diode detectors for power monitoring, adjusting manually or through simple circuits. However, the nonlinearity and narrow dynamic range of diode detection limit monitoring accuracy and adjustment range, making it difficult to achieve precise and stable output power control over a large dynamic range, thus failing to meet the stringent requirements of applications demanding stable power supply.

[0005] The main defects of the existing MPT transmission system include: (1) It is difficult to balance power amplifier efficiency and bandwidth: In order to achieve high efficiency (such as drain efficiency higher than 70%), traditional high power amplifier designs usually adopt harmonic tuning technology, but this often results in a narrow operating bandwidth. In order to achieve wide bandwidth operation, efficiency needs to be sacrificed to a certain extent. In the 3.2-3.8 GHz ISM band, it is difficult to achieve 10W output power and high efficiency (>58%) in a wide bandwidth at the same time.

[0006] (2) The output matching network has a single function: Traditional matching networks only focus on impedance transformation and lack the ability to suppress out-of-band harmonics. They may require additional filtering circuits, which increases the system size and insertion loss, affecting the overall efficiency and linearity.

[0007] (3) Unstable output power: Due to factors such as temperature changes and power fluctuations, the output power of the open-loop control transmission system is prone to drift, which cannot provide stable and reliable microwave energy for the micro robot, affecting the efficiency and stability of wireless power transmission.

[0008] (4) Low control accuracy and small dynamic range: The power monitoring scheme using diode detection has a nonlinear relationship between its output voltage and input power, and its dynamic range is limited, which cannot meet the requirement of accurately adjusting the output power in a large dynamic range. Summary of the Invention

[0009] One of the objectives of this invention is to provide a high-power amplifier that can achieve fundamental frequency broadband matching while effectively controlling harmonic impedance, thereby achieving broadband, high-efficiency, and high-power output of the core power amplifier.

[0010] Another objective of this invention is to provide a microwave wireless transmission system that can achieve broadband, high-efficiency, high-precision, and stable output, and ensure long-term power stability and precise adjustability, thus providing a reliable wireless power supply solution for micro-robots.

[0011] The technical solution provided by this invention is as follows: A high-power amplifier, comprising: transistor; An output matching network, the input of which is connected to the output of the transistor; The output matching network includes: The coupling line consists of a coupled first transmission line and a coupled second transmission line; the two ends of the first transmission line are a first port and a second port, respectively, and the two ends of the second transmission line are a third port and a fourth port, respectively. Wherein, the first port is connected to the input terminal, and the third port is open circuit; An open-circuit short wire is connected to the second port; Short-circuit stub wire, which is connected to the fourth port; The output load is connected to the fourth port.

[0012] Preferably, the transistor is a GaN HEMT transistor.

[0013] Preferably, the electrical length of the coupling line at the center frequency is 90°.

[0014] Preferably, the electrical length of the short-circuit stub at the center frequency is 90°.

[0015] Preferably, the static operating point of the transistor is set to Vds = 28V and Vgs = -2.8V.

[0016] A microwave wireless transmission system using the aforementioned high-power amplifier, the microwave wireless transmission system comprising, from the signal input end to the transmitting end, a closed-loop power control module, a signal generation and conditioning module, a power amplification link, and a transmitting antenna connected in sequence; The closed-loop power control module includes: a digitally controlled attenuator, a logarithmic amplifier, and a processor; The signal generation and conditioning module includes: a phase-locked loop frequency synthesizer and a digitally controlled amplifier; The power amplification link includes a linear amplifier, a driver amplifier, and the high-power amplifier connected in sequence.

[0017] Preferably, the processor is an ARM7TDMI processor.

[0018] Preferably, the ARM7TDMI processor is connected to the host computer via an RS232 interface.

[0019] The beneficial effects of this invention are: The microwave wireless transmission system provided by this invention constructs a four-stage cascaded amplification architecture consisting of a digitally controlled amplifier, a linear amplifier, a driver amplifier, and a high-power amplifier. Through progressively increasing power, it achieves efficient power conversion from 16dBm (40mW) to 40dBm (10W), providing sufficient transmission power for microwave wireless power transmission. By setting up a high-power amplifier, it effectively controls harmonic impedance while achieving fundamental frequency broadband matching. It protects a closed-loop power control system based on a logarithmic amplifier and an ARM processor. This mechanism, combined with a digitally controlled attenuator, achieves high-precision, wide dynamic range, and stable control of the output power. The filtered final-stage power amplifier, the three-stage amplification link, and the closed-loop control mechanism together constitute a complete microwave wireless power transmission system, achieving a high-efficiency, stable output of 10W in the 3.2GHz-3.8GHz frequency band. Attached Figure Description

[0020] Figure 1This is a framework diagram of the microwave wireless transmission system described in this invention. Figure 2 This is a schematic diagram of the output matching network described in this invention; Figure 3 The image shows the fundamental impedance trajectory of the output matching network described in this invention, and the contour plot of the combined output power and efficiency corresponding to the fundamental impedance extracted by load traction simulation that meets the conditions of efficiency ≥70% and output power ≥41dBm. Figure 4 The diagram shows the second harmonic impedance trajectory of the output matching network proposed in this invention, and the optimal region of the second harmonic impedance extracted by load traction simulation. Figure 5 This is a layout dimension diagram of the high-power amplifier in the microwave transmitting system according to an embodiment of the present invention; Figure 6 The figure shows the simulation results of the drain efficiency DE, output power Pout, and gain Gain of the power amplifier in the embodiment of the present invention as a function of frequency. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to the accompanying drawings, so that those skilled in the art can implement it based on the description.

[0022] like Figure 1 As shown, the present invention provides a microwave wireless transmission system. The microwave wireless transmission system includes, from the signal input end to the transmitting end, a closed-loop power control module, a signal generation and conditioning module, a power amplification link, and a transmitting antenna connected in sequence.

[0023] The closed-loop power control module includes: a digitally controlled attenuator, a logarithmic amplifier, and a processor; the digitally controlled attenuator is sequentially connected to the logarithmic amplifier, the logarithmic amplifier and the processor, as well as the processor and the digitally controlled attenuator, to form a closed-loop structure.

[0024] The numerically controlled attenuator receives the coupled signal and attenuates it according to the processor's instructions to extend the dynamic range of power detection.

[0025] A logarithmic amplifier precisely converts the attenuated RF signal power into a DC voltage signal that has a logarithmic linear relationship with it. This is the key to achieving high-precision feedback.

[0026] The processor is the control core of the system. It collects the voltage output of the logarithmic amplifier, determines the current output power through a built-in algorithm, and dynamically adjusts the gain of the digitally controlled amplifier and the attenuation of the digitally controlled attenuator to form a negative feedback closed loop, thereby stabilizing the output power at the set value.

[0027] In this embodiment, the processor is an ARM7TDMI processor. The ARM7TDMI processor is connected to a host computer (PC) via an RS232 interface to enable remote parameter setting, status monitoring, and data recording.

[0028] The signal generation and conditioning module includes a phase-locked loop (PLL) frequency synthesizer and a digitally controlled amplifier connected in sequence. The processor is connected to both the PLL frequency synthesizer and the digitally controlled amplifier.

[0029] Phase-locked loop frequency synthesizers (PLL frequency synthesizers) generate highly stable radio frequency signals in the range of 3.2 GHz to 3.8 GHz.

[0030] It receives signals from the phase-locked loop frequency synthesizer and performs preliminary adjustment of the signal amplitude according to the processor's instructions.

[0031] The power amplification link is a three-stage power amplification link, including a linear amplifier, a driver amplifier, and a high-power amplifier connected in sequence.

[0032] Linear amplifiers amplify signals linearly, minimizing distortion.

[0033] The driver amplifier further amplifies the signal power to 1W (30 dBm) to drive the final stage power amplifier.

[0034] A high-power amplifier amplifies the signal to over 10 W (40 dBm) to power the transmitting antenna.

[0035] To improve the performance of microwave wireless transmission systems, this invention also provides a high-power amplifier.

[0036] The high-power amplifier provided by this invention includes an input matching network, a transistor, and an output matching network. Preferably, the transistor is a Cree GaN HEMT transistor CGH40010F, which operates at a DC-6 GHz frequency, has an output power of 10W, and possesses high efficiency and high gain potential. The transistor's quiescent operating point is set to Vds = 28V and Vgs = -2.8V. The input matching network is designed using a step impedance matching method, matching the 50Ω system impedance to the transistor's input impedance to ensure efficient signal injection.

[0037] The input terminal of the output matching network is connected to the output terminal of the transistor. For example... Figure 2As shown, the output matching network includes: a coupling line, which consists of a coupled first transmission line 111 and a coupled second transmission line 112; the two ends of the first transmission line 111 are a first port and a second port, respectively, and the two ends of the second transmission line 112 are a third port and a fourth port, respectively. The first port and the third port are positioned close to the input end, and the first port is adjacent to the input end (…). The third port is open-circuited. One end of the open-circuit stub 120 is connected to the second port, and the other end is open-circuited; one end of the short-circuit stub 130 is connected to the fourth port, and the other end is grounded. Output load ( It is connected to the fourth port.

[0038] Coupled line (odd-even mode impedance) , Electrical length As a broadband impedance transformer, it utilizes the odd-even mode transmission characteristics to achieve a smooth transition between two impedance segments, and can also transmit electrical length. Control the frequency response while balancing fundamental frequency matching and harmonic suppression.

[0039] 120Ω open circuit stub (impedance) Electrical length Provides inductive susceptance to cancel the imaginary part in Zopt. This converts complex impedance into pure real impedance.

[0040] Short-circuit stub 130 (impedance) Electrical length It works in conjunction with the coupling line to further adjust the impedance trajectory, while introducing a high impedance point at the harmonic frequency to achieve harmonic suppression.

[0041] One characteristic of the coupled line segment as a matching element is its ability to match real loads. Complex matching can be achieved by connecting a short-circuit line to the straight-through end of the coupled line and applying the following formula. Furthermore, introducing a short-circuit stub line optimizes fundamental frequency matching, expands the high-frequency bandwidth, and achieves second harmonic suppression (when...). When the second harmonic electrical length is π, the short-circuited stub is an open circuit to the second harmonic, blocking the harmonic output); the overall input impedance formula of the circuit is as follows.

[0042] (1) Output-side parallel short-circuit stub (impedance) Electrical length ); The input impedance of the short-circuited stub is: ; in, The input impedance of the short-circuited stub line. It is the imaginary unit.

[0043] (2) Coupled-line two-port network (odd-even mode impedance) , Electrical length The coupled line is used as a two-port network (diagonal ports open-circuited, i.e., the second and third ports are open-circuited, the first port is the input and the fourth port is the output), and its ABCD matrix is: ; in, This represents the transmission matrix of the coupled line. This represents the odd-mode impedance of the coupled line. The even-mode resistance of the coupling line. It is the imaginary unit.

[0044] (3) Input-side open-circuit stub (impedance) Electrical length ) The input impedance of the open stub is: ; in, The input impedance of the open stub line. It is the imaginary unit.

[0045] Step-by-step calculation of input impedance: Step 1: Calculate the input load impedance at the output of the coupled line. ; A short-circuited stub is connected in parallel to the output of the coupled line, therefore the input load at the output is: ; in, This indicates the output load impedance of the coupled line.

[0046] Step 2: Calculate the input impedance of the coupled line

[0047] Connect the ABCD matrix of the coupling line and the input load at the output end. Substituting into the impedance formula, we get: ; ; Step 3: Calculate the total input impedance of the output matching network of the high-power amplifier.

[0048] Input impedance of the coupled line Input impedance of open stub line Since they are connected in parallel, the total input impedance is: ; Step 4: Substitute each part into the equation to obtain the complete formula for the final total input impedance: ; in, .

[0049] The electrical length of the coupling line at the center frequency of 3.5 GHz It has specific odd-mode impedance ( and This is the core component for achieving broadband matching and filtering functions. Open-circuit stub 120 (characteristic impedance) Electrical length ), used for auxiliary impedance adjustment. Short-circuit stub 130 (characteristic impedance) The electrical length of the short-circuit stub at the center frequency is This is used to further optimize matching and tuning. This output matching network structure enables complex transformation (21.3-j6.2 Ω) to 50 Ω, while simultaneously ensuring efficient fundamental frequency transmission and harmonic suppression.

[0050] , , , and electrical length The design method is as follows: 1. Extract the optimal load impedance Zopt=21.3-j6.2 Ω of the transistor at the target operating frequency through load pulling simulation.

[0051] 2. Using ADS microwave simulation software, with Zopt→50Ω as the target, scan the characteristic impedance and electrical length of the coupled line, open stub 120, and short stub 130 to obtain the optimal parameter combination.

[0052] Third, verify whether the fundamental impedance trajectory falls within the target contour line, and check the harmonic suppression effect at the same time.

[0053] It has been verified that through optimization , , , and electrical length This allows for precise matching of the transistor's optimal load impedance (extracted as (21.3-j6.2 Ω)) to a 50Ω load through load pulling simulation. Simulation results... Figure 3 The data shows that the fundamental impedance trajectory falls entirely within the contour region of high output power Pout (≥41dBm) and high efficiency (PAE ≥70%), ensuring maximum power transmission and efficiency.

[0054] The coupled-line structure itself has a bandpass filter response. The output matching network designed in this invention ensures that the second harmonic impedance trajectories all fall within the high-efficiency region of the second harmonic corresponding to the load pull (e.g., Figure 4As shown in the figure, this is the optimal second harmonic termination region found from load traction simulation. This design achieves fundamental frequency matching while tuning the second harmonic to present an open or short-circuit state conducive to high-efficiency operation, thereby suppressing harmonic components, improving drain efficiency, and acting as a filter without the need for an additional filter.

[0055] The operation process of the wireless transmission system is as follows: Signal generation and pre-tuning: The host computer sets the target power via the RS232 interface. The ARM processor controls the PLL to generate a microwave signal of the required frequency and sets the initial gain of the digitally controlled amplifier.

[0056] Multi-stage amplification: The signal passes through a linear amplifier, a driver amplifier, and a final high-power amplifier in sequence, and is finally amplified to 10W.

[0057] Power sampling and feedback: A portion of the signal is coupled from the output of the directional coupler. This signal is then fed into a logarithmic amplifier after passing through a digitally controlled attenuator (controlled by an ARM to adjust the range). The logarithmic amplifier outputs a DC voltage that is logarithmically proportional to the input RF power.

[0058] Closed-loop amplitude stabilization: The ARM processor acquires this voltage and compares it with the voltage value corresponding to the preset target power. Based on the error, the processor adjusts the gain of the digitally controlled amplifier or the attenuation of the digitally controlled attenuator in real time until the output power reaches and stabilizes at the set value. For example, if excessive power is detected, the ARM will reduce the gain of the digitally controlled amplifier.

[0059] The microwave wireless power transmission system constructed in this invention not only achieves broadband, high efficiency and high power output of the core power amplifier through an innovative filter-type matching network, but also ensures long-term power stability and precise adjustability by relying on an intelligent closed-loop control mechanism. At the same time, the compact circuit structure creates conditions for the miniaturization and integration of the system.

[0060] Example 1 (Prototype of Microwave Wireless Power Transmission System) constitute: Circuit board: using dielectric constant ε r The entire transmission system circuitry was fabricated using an F4B high-frequency substrate with a diameter of 2.65 mm and a thickness of 0.5 mm.

[0061] Core components: High power amplifier: Layout as shown Figure 5As shown, the high-power amplifier consists of an input matching network, a gate bias and stabilization circuit, a CGH40010F power transistor, a drain bias circuit, and an output matching network. All microstrip line parameters in the circuit are characterized by width / length in mm. After the input signal enters through the port, it passes sequentially through 1.36 / 5 and 1 / 2-inch microstrip lines, then through a 10pF DC blocking capacitor, and then through a stabilization network consisting of a 1 / 2-inch microstrip line, a 10Ω resistor, and a 1pF capacitor in parallel, before being connected to the gate input matching network. The gate bias circuit provides a -2.8V gate voltage, and power supply decoupling and filtering are achieved through a parallel capacitor of 470pF, 47nF, and 4.7μF. Simultaneously, a stabilization network consisting of a 1 / 4.5-inch microstrip line, a 100Ω resistor, and a 1 / 9-inch microstrip line suppresses circuit self-oscillation. The CGH40010F is the core amplifying device. Its source is grounded, and the drain is powered by 28V. The drain bias terminal also uses parallel capacitors of 470pF, 47nF, and 4.7μF for power supply filtering, which is then connected to the drain output matching network via a 1 / 12-inch microstrip line. The input matching network consists of multiple microstrip lines (including 1 / 2-inch, 1.95 / 2.5-inch, 0.35 / 5.64-inch, 1.34 / 5-inch, and 6.42 / 6.95-inch microstrip lines). The output matching network consists of a coupling line (0.37 / 0.2 / 12.7-inch), an open-circuit stub line (0.23 / 1.8-inch), and a short-circuit stub line (0.22 / 7.48-inch). The output is connected via a 10pF DC blocking capacitor and a 1.36 / 5-inch microstrip line, achieving output impedance matching and harmonic suppression, ultimately completing the output of the power amplified signal.

[0062] Final stage power amplifier transistor: Cree CGH40010F GaN HEMT.

[0063] PLL frequency synthesizer: Select a wideband PLL chip with an output frequency coverage of 3.2-3.8 GHz.

[0064] Logarithmic amplifier: Select a logarithmic amplifier chip with a dynamic range greater than 40dB.

[0065] Processor: NXP's LPC2100 series microcontroller (based on the ARM7TDMI core).

[0066] Digitally controlled attenuator / amplifier: Select digitally controlled attenuator chips (such as the HMC series) and digitally controlled amplifier chips for the corresponding frequency band.

[0067] Peripheral circuitry includes power management circuitry to supply power to each chip, gate and drain bias circuitry to provide bias to GaN transistors, and RS232 level conversion circuitry.

[0068] Structure and Interfaces: The entire circuit is housed in a metal shielded box and equipped with an SMA interface for RF input / output, a DB9 interface for RS232 communication, and a power input interface.

[0069] Connect the power supply, the radio frequency signal source (such as a vector network analyzer or signal generator, set to a frequency point within 3.2-3.8 GHz, with an output power of approximately -10 dBm), and the spectrum analyzer (connected via a high-power attenuator).

[0070] Send a command via the host computer software to set the target output power to 40 dBm.

[0071] After the system powers on, the ARM processor initializes each chip, and the PLL is locked at a specified frequency. The signal is then amplified three times before being output.

[0072] Figure 6 For this embodiment (e.g.) Figure 5 The simulation results of the drain efficiency DE, output power Pout, and gain Gain of a high-power amplifier as a function of frequency are shown in the figure. Figure 6 As shown, within the design operating frequency band of 3.2GHz-3.8GHz, the drain efficiency (DE) is 58%~79%, and the output power (P) is... out The power efficiency is 40.8~41.9 dBm, and the gain is 11.6~12.8 dB. The above simulation results verify the effectiveness of the high-power amplifier provided by this invention.

[0073] In this embodiment, the output power of the microwave wireless power transmission system is stabilized at around 40 dBm. By changing the frequency via the host computer, the output power remains stable above 40 dBm within the range of 3.2-3.8 GHz. The drain efficiency is calculated by measuring DC power consumption and RF output power. Changing the ambient temperature shows no significant drift in output power, proving the effectiveness of the closed-loop control system.

[0074] The microwave wireless power transmission system constructed in this invention has superior power amplifier performance: achieving a high drain efficiency of 58%-79% and a stable high output power of 40.8-41.9dBm in the 3.2GHz-3.8GHz frequency band, while also possessing broadband operation capability and good gain flatness; it can achieve high stability and intelligent control: through a closed-loop feedback mechanism, it effectively suppresses the influence of factors such as temperature and aging on power, and combined with a remote communication interface, it achieves precise and stable adjustment and intelligent monitoring of output power; it has a compact structure: the output matching network integrates filtering function, eliminating the need for additional filters and helping to reduce system size and weight.

[0075] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A high-power amplifier, characterized in that, include: transistor; An output matching network, the input of which is connected to the output of the transistor; The output matching network includes: The coupling line consists of a coupled first transmission line and a coupled second transmission line; the two ends of the first transmission line are a first port and a second port, respectively, and the two ends of the second transmission line are a third port and a fourth port, respectively. Wherein, the first port is connected to the input terminal, and the third port is open circuit; An open-circuit short wire is connected to the second port; Short-circuit stub wire, which is connected to the fourth port; The output load is connected to the fourth port.

2. The high-power amplifier according to claim 1, characterized in that, The transistor is a GaN HEMT transistor.

3. The high-power amplifier according to claim 2, characterized in that, The electrical length of the coupling line at the center frequency is 90°.

4. The high-power amplifier according to claim 3, characterized in that, The electrical length of the short-circuit stub at the center frequency is 90°.

5. The high-power amplifier according to claim 1 or 2, characterized in that, The static operating point of the transistor is set to Vds = 28V and Vgs = -2.8V.

6. A microwave wireless transmission system, using a high-power amplifier as described in any one of claims 1-5, characterized in that, The microwave wireless transmission system includes, from the signal input end to the transmitter end, a closed-loop power control module, a signal generation and conditioning module, a power amplification link, and a transmitting antenna connected in sequence. The closed-loop power control module includes: a digitally controlled attenuator, a logarithmic amplifier, and a processor; The signal generation and conditioning module includes: a phase-locked loop frequency synthesizer and a digitally controlled amplifier; The power amplification link includes a linear amplifier, a driver amplifier, and the high-power amplifier connected in sequence.

7. The microwave wireless transmission system according to claim 6, characterized in that, The processor used is an ARM7TDMI processor.

8. The microwave wireless transmission system according to claim 7, characterized in that, The ARM7TDMI processor is connected to the host computer via an RS232 interface.

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