Self-powered adaptive matching circuit with closed loop control

Abstract

The application discloses a self-powered adaptive matching circuit with closed-loop control in the technical field of radio frequency circuit, and aims to solve the problem that the existing adjustable matching network depends on external bias power supply and complex control link. The adaptive matching circuit comprises a main feeding channel, a directional coupler, a rectifier circuit, a bias network and an adjustable matching branch. When a reflected wave is generated due to load mismatch, the directional coupler extracts the energy of the reflected wave, the rectifier circuit converts the energy into a direct current bias voltage, the voltage directly drives a varactor diode in the adjustable matching branch through the bias network, changes the equivalent impedance of the varactor diode, thereby adaptively adjusts the input impedance of the main feeding channel, and reduces the reflection. The application directly utilizes the reflected energy as a control source, does not need external bias power supply and a microcontroller, has the advantages of simple structure, fast response speed, low power consumption and easy integration, and is particularly suitable for a radio frequency front-end system sensitive to volume and power consumption.

Description

Technical Field

[0001] This invention relates to the field of radio frequency circuit technology, and more specifically, to an adaptive matching circuit with self-powered closed-loop control. Background Technology

[0002] The impedance matching of the power supply network has a significant impact on the power transmission efficiency, return loss, VSWR, and system stability of an RF system. In practical applications, the input impedance of the power supply network is not constant but is easily affected by factors such as the operating environment, installation conditions, nearby metal objects, human proximity, packaging structure, tolerance drift, and array mutual coupling. When the output impedance deviates from the design value, a significant mismatch occurs between the power supply network and the load, leading to worsened return loss, increased reflected power, and decreased effective radiated power. In severe cases, it may even affect the operational stability of the transmitter front-end and the overall system efficiency.

[0003] To address the aforementioned issues, existing technologies typically employ fixed or adjustable matching networks to improve port matching. Fixed matching networks have a simple structure, but their matching performance is usually optimal only under specific design conditions, exhibiting poor adaptability. To enhance adaptability, existing technologies have further proposed reconfigurable matching networks constructed using switched capacitor arrays, PIN diodes, MEMS devices, or varactor diodes.

[0004] However, most existing adaptive or automatic matching schemes employ external detection and control methods. This involves acquiring forward or reflected power information through directional couplers, power detectors, etc., and then using microcontrollers to generate control signals to drive the matching network. These schemes typically require an external bias power supply, resulting in complex circuit structures, large size, high power consumption, and long response links. Furthermore, schemes using varactor diodes also require a separate bias network and an external power supply to provide reverse bias voltage. While some schemes utilize directional couplers to extract reflected power for detection, the reflected power is only used as a detected quantity and is not directly used as the energy source for tuning. Summary of the Invention

[0005] The purpose of this invention is to provide an adaptive matching circuit with self-powered closed-loop control, which solves the technical problem of existing adjustable matching networks relying on external bias power supplies and complex control links, and achieves adaptive improvement of the return loss of the feeder network without the need for external bias power supplies and complex controllers.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: An adaptive matching circuit with self-powered closed-loop control, comprising: The main feed channel connects the RF input terminal and the antenna port, and is equipped with an impedance transformation network for transmitting the main RF signal; A directional coupler, disposed on the main feed channel, includes an input terminal, an output terminal, an isolation terminal, and a coupling terminal. The input terminal is connected to the main feed channel, the output terminal is connected to the antenna element, the isolation terminal is used to extract the reflected wave energy from the antenna end, and the coupling terminal is connected to the matching load for absorbing energy. A rectifier circuit, whose input terminal is connected to the isolation terminal of the directional coupler, is used to convert the reflected wave energy into a DC bias voltage. A bias network, the input of which is connected to the output of the rectifier circuit, An adjustable matching branch is connected to the main power supply channel and to the output of the bias network. The equivalent impedance of the adjustable matching branch is controlled by the DC bias voltage. The DC bias voltage automatically adjusts the equivalent impedance of the adjustable matching branch in response to changes in the reflected wave energy, forming a closed-loop self-adjustment that brings the main power supply channel toward an impedance-matched state.

[0007] Furthermore, the main power supply channel includes main transmission lines TL1, TL2, TL4 and adjustable matching branch TL3, forming an impedance transformation and continuously adjustable matching structure.

[0008] Furthermore, the directional coupler is a 13dB directional coupler with a coupling degree of 5% and an insertion loss of less than 0.22dB to the main channel; its coupling end is connected to a 50Ω matched load.

[0009] Furthermore, the rectifier circuit adopts a voltage doubler rectifier structure to increase the output DC voltage, with an output voltage range of 1V to 6V, which changes linearly with the reflected power.

[0010] Furthermore, the bias network employs an RF choke inductor to transmit the DC bias voltage output by the rectifier circuit to the adjustable matching branch and to block RF signals from the main feed channel.

[0011] Furthermore, the adjustable matching branch includes a varactor diode connected in reverse series and a microstrip line connected in series with the varactor diode, the other end of which is connected to the main power supply channel.

[0012] Furthermore, the adaptive matching circuit operates at a frequency of 12 GHz, which is in the Ku band.

[0013] An adaptive matching method for self-powered closed-loop control includes the following steps: The radio frequency signal is transmitted to the antenna port through the main feed channel; When an impedance mismatch occurs at the antenna port, the reflected wave energy generated by the mismatch is obtained through the isolation terminal of the directional coupler; The reflected wave energy is converted into DC bias voltage through a rectifier circuit; The DC bias voltage is applied directly to the adjustable matching branch through the bias network to change its equivalent impedance, thereby adaptively adjusting the input impedance of the main feed channel and reducing the energy reflected back to the RF input terminal.

[0014] By adopting the above technical solution, the present invention has the following advantages: 1. This invention provides an adaptive matching circuit with self-powered closed-loop control. It does not require an external bias power supply. Instead, it directly utilizes the energy reflected from the antenna port to form a DC bias voltage through rectification, which drives the varactor diode to work, thus achieving energy self-sufficiency.

[0015] 2. This invention provides an adaptive matching circuit for self-powered closed-loop control, which has no complex control link, does not rely on microcontrollers, analog-to-digital converters or digital algorithms, and directly forms closed-loop control through analog circuits. The circuit structure is simple and the response speed is fast.

[0016] 3. This invention provides an adaptive matching circuit with self-powered closed-loop control. When the antenna load changes, it can automatically adjust the impedance of the feed network according to the magnitude of the reflected power to form negative feedback, effectively improve the return loss, and has strong adaptive adjustment capability.

[0017] 4. This invention provides an adaptive matching circuit with self-powered closed-loop control. Because it uses reflected energy for self-powered operation, the overall power consumption of the system is low, which is beneficial for miniaturization and integration with array units. It is especially suitable for RF front-end systems with limited size, power consumption and wiring complexity, and features low power consumption and easy integration. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the circuit structure of the adaptive matching circuit for self-powered closed-loop control of the present invention. Figure 2 This is a circuit diagram of the voltage doubler rectifier circuit in an embodiment of the present invention; Figure 3 This is a graph showing the change of the output voltage of the rectifier circuit with the input power in an embodiment of the present invention. Figure 4 This is a graph showing the change of the equivalent capacitance of the varactor diode with DC bias voltage in an embodiment of the present invention. Figure 5 The figure shows the simulation results of the S-parameters as a function of load impedance at a fixed operating frequency according to an embodiment of the present invention. Figure 6 The figure shows the simulation results of the S-parameters changing with the operating frequency under a fixed load impedance according to an embodiment of the present invention. Detailed Implementation

[0019] The technical solution of the present invention will be specifically described below with reference to the accompanying drawings. It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0020] This invention provides an adaptive matching circuit for self-powered closed-loop control, specifically as follows: Figure 1 As shown, its core lies in constructing a closed-loop feedback path from "mismatched reflection energy extraction" to "energy conversion" and then to "impedance adaptive adjustment". The adaptive matching circuit of this self-powered closed-loop control includes: main feed channel, directional coupler, rectifier circuit, bias network and adjustable matching branch.

[0021] Main feed channel: Connecting the RF input terminal and the antenna port, it is the transmission path for the main RF signal. The main feed channel is equipped with an impedance transformation network, including at least the main transmission lines TL1, TL2, and TL4, as well as an adjustable matching branch TL3 that participates in adaptive adjustment. (Specific details are as follows...) Figure 1 As shown, its characteristic impedance is typically designed to be the system impedance (e.g., 50Ω). In this embodiment, the main feed channel is an impedance transformation network consisting of transmission lines TL1, TL2, and TL4 connected in sequence, and an adjustable matching branch TL3 connected in parallel with TL2. Its input is connected to the radio frequency transmitter, and its output is connected to the load (e.g., an antenna).

[0022] The directional coupler, which serves as both a "sensor" and an "energy harvester" in this invention, is positioned on the main feed channel, near the output end. A 13dB directional coupler is placed within this coupler, which is directional and includes an input end, an output end, an isolation end, and a coupling end. The input end is connected to the main feed channel, the output end is connected to the antenna element, and the isolation end is used to extract reflected wave energy from the antenna end, specifically for extracting reflected wave energy reflected back from the load end due to load mismatch. The coupling end is connected to a 50Ω matching load for energy absorption. This directional coupler, by coupling 5% of the energy, has a 0.22dB impact on the main channel.

[0023] In a preferred embodiment, a directional coupler with a coupling degree of 13dB is selected, which means that it extracts only about 5% of the reflected energy from the main channel for self-powered control, while the insertion loss introduced to the main signal channel is extremely low (less than 0.22dB), ensuring the overall efficiency of the system.

[0024] The rectifier circuit is the "energy converter" of this invention, specifically as follows: Figure 2 As shown, its input terminal is connected to the isolation terminal of the directional coupler to receive the extracted RF reflected wave energy. The isolation terminal of the directional coupler is connected to a rectifier circuit to convert the energy reflected from the output port into DC, providing DC bias voltage for the varactor diode. The rectifier circuit uses a voltage multiplier structure to increase the DC voltage, specifically as follows: Figure 2 As shown, this structure can efficiently convert weak radio frequency AC signals into higher DC bias voltages to meet the bias voltage requirements of subsequent varactor diodes. Figure 3 The curve showing the change of the rectifier circuit output voltage with input power is shown. Figure 3 It can be seen that the output DC voltage of the rectifier circuit increases linearly with the increase of the input reflected power, and the output voltage range is between 1V and 6V.

[0025] The bias network, which is the "signal isolator" of this invention, has its input connected to the DC output of the rectifier circuit and its output connected to the adjustable matching branch. Its main function is to achieve "AC-DC separation." The bias network uses an RF choke inductor to transmit the DC bias voltage output from the rectifier circuit to the adjustable matching branch TL3 and to block RF signals from the main feed channel. In a specific embodiment, the bias network uses an RF choke inductor, which acts as a low-impedance path for DC signals, allowing the rectified DC bias voltage to be smoothly applied across the varactor diode; while it acts as a high-impedance path for high-frequency RF signals, effectively preventing RF signals from the main feed channel from entering the rectifier circuit and ensuring the normal operation of the system.

[0026] Adjustable matching branch: This is the "actuator" of the present invention, comprising two parts: a varactor diode and a microstrip line connected in series with the varactor diode. The varactor diode is connected in reverse series and then to the main feed channel via the series microstrip line. In this embodiment, the core components of this adjustable matching branch are two varactor diodes (using SKYWORKS SMV1232) connected in reverse series and the microstrip line TL3 connected in series with them. A varactor diode is a semiconductor device whose equivalent junction capacitance changes with the applied reverse bias voltage. Figure 4 The graph shows the equivalent capacitance of a varactor diode as a function of DC bias voltage; for example... Figure 4 As shown, when the DC bias voltage varies from 1V to 6V, the equivalent capacitance of the SMV1232 can vary continuously between approximately 0.5pF and 1.4pF. By connecting the two varactor diodes in reverse series, the nonlinear effects that may occur under large RF signals can be effectively reduced.

[0027] The adaptive matching circuit of this self-powered closed-loop control operates at a frequency of 12 GHz, which is in the Ku band.

[0028] The working principle of the adaptive matching circuit closed-loop control of this self-powered closed-loop control is as follows: When the load impedance at the antenna port deviates from 50Ω, some RF energy is reflected back to the main feed channel. The directional coupler extracts this reflected energy and sends it to the voltage doubler rectifier circuit. The rectifier circuit converts the RF energy into a DC bias voltage proportional to the reflected power. This DC bias voltage is applied directly to the varactor diode connected in reverse series through the RF choke inductor, changing its junction capacitance and thus altering the equivalent reactance of the adjustable matching branch TL3. This change brings the overall input impedance of the main feed channel closer to the conjugate value of the antenna port impedance, thereby reducing further reflection. This is a negative feedback closed-loop control process: the more severe the mismatch, the greater the reflected power, the higher the rectified DC bias voltage, the greater the change in the varactor diode's capacitance, and the stronger the impedance adjustment, until the reflected power is reduced to a lower level.

[0029] An adaptive matching method for self-powered closed-loop control according to the present invention includes the following steps: The radio frequency signal is transmitted to the antenna port through the main feed channel; When an impedance mismatch occurs at the antenna port, the reflected wave energy generated by the mismatch is obtained through the isolation terminal of the directional coupler; The reflected wave energy is converted into DC bias voltage through a rectifier circuit; The DC bias voltage is applied directly to the adjustable matching branch through the bias network to change its equivalent impedance, thereby adaptively adjusting the input impedance of the main feed channel and reducing the energy reflected back to the RF input terminal.

[0030] Technical effectiveness verification: The adaptive matching circuit of the self-powered closed-loop control is connected through its various structural components. The final system simulation results are as follows: Figure 5 and Figure 6 As shown, Figure 5 As shown, simulation verification shows that when the operating frequency is fixed at 12GHz and the load impedance varies over a wide range from 35Ω to 163Ω, the adaptive matching network of this invention can automatically adjust, keeping the return loss S11 at the input port below -10dB, thus achieving good matching. Figure 6 As shown, when the load impedance is 50Ω, this network can maintain an S11 better than -10dB in a wide bandwidth from 11.5GHz to 13.8GHz. The system simulation results fully demonstrate that the present invention has good adaptive matching capability and wide bandwidth operating characteristics without relying on external power supply and controller.

[0031] In summary, this invention provides a compact adaptive matching circuit and method that requires no external bias or controller. By cleverly utilizing reflected energy as a driving source, it achieves closed-loop adaptive adjustment of the feed network impedance, making it particularly suitable for high-performance, miniaturized RF systems.

[0032] Finally, it should be noted that although the present invention has been described with reference to specific embodiments, those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. Various equivalent changes or substitutions can be made without departing from the concept of the present invention. Therefore, any changes or modifications to the above embodiments within the essential spirit of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A self-powered closed loop controlled adaptive matching circuit, characterized by, include: The main feed channel connects the RF input terminal and the antenna port, and is equipped with an impedance transformation network for transmitting the main RF signal; A directional coupler, disposed on the main feed channel, includes an input terminal, an output terminal, an isolation terminal, and a coupling terminal. The input terminal is connected to the main feed channel, the output terminal is connected to the antenna element, the isolation terminal is used to extract the reflected wave energy from the antenna end, and the coupling terminal is connected to the matching load for absorbing energy. A rectifier circuit, whose input terminal is connected to the isolation terminal of the directional coupler, is used to convert the reflected wave energy into a DC bias voltage. A bias network, the input of which is connected to the output of the rectifier circuit, An adjustable matching branch is connected to the main power supply channel and to the output of the bias network. The equivalent impedance of the adjustable matching branch is controlled by the DC bias voltage. The DC bias voltage automatically adjusts the equivalent impedance of the adjustable matching branch in response to changes in the reflected wave energy, forming a closed-loop self-adjustment that brings the main power supply channel toward an impedance-matched state.

2. A self-powered closed loop controlled adaptive matching circuit according to claim 1, wherein, The main power supply channel includes main transmission lines TL1, TL2, TL4 and adjustable matching branch TL3, forming an impedance transformation and continuously adjustable matching structure.

3. A self-powered closed loop controlled adaptive matching circuit according to claim 1, wherein, The directional coupler is a 13dB directional coupler with a coupling degree of 5% and an insertion loss of less than 0.22dB to the main channel; its coupling end is connected to a 50Ω matched load.

4. A self-powered closed loop controlled adaptive matching circuit according to claim 1, wherein, The rectifier circuit adopts a voltage doubler rectifier structure to boost the output DC voltage, with an output voltage range of 1V to 6V that varies linearly with the reflected power.

5. A self-powered closed loop controlled adaptive matching circuit according to claim 1, wherein, The bias network employs an RF choke inductor to transmit the DC bias voltage output from the rectifier circuit to the adjustable matching branch and to block RF signals from the main feed channel.

6. A self-powered closed loop controlled adaptive matching circuit according to claim 1, wherein, The adjustable matching branch includes a varactor diode connected in reverse series and a microstrip line connected in series with the varactor diode, the other end of which is connected to the main power supply channel.

7. A self-powered closed loop controlled adaptive matching circuit according to claim 1, wherein, The adaptive matching circuit operates at a frequency of 12 GHz, which is in the Ku band.

8. A self-powered closed loop controlled adaptive matching method, characterized in that, An adaptive matching circuit applied to the self-powered closed-loop control according to any one of claims 1 to 7, comprising the following steps: The radio frequency signal is transmitted to the antenna port through the main feed channel; When an impedance mismatch occurs at the antenna port, the reflected wave energy generated by the mismatch is obtained through the isolation terminal of the directional coupler; The reflected wave energy is converted into DC bias voltage through a rectifier circuit; The DC bias voltage is applied directly to the adjustable matching branch through the bias network to change its equivalent impedance, thereby adaptively adjusting the input impedance of the main feed channel and reducing the energy reflected back to the RF input terminal.

Images