Antenna matching circuit and radio frequency terminal

Abstract

The present invention proposes an antenna matching circuit and a radio frequency terminal, which are used to solve the technical problem in the prior art that once the external environment causes the antenna impedance to change or the impedance discontinuity introduced by the terminal feed point itself, the matching network will fail, which will reduce the antenna performance. The antenna matching circuit includes: a switching tube, an adjustable varactor diode, a first bias circuit, a second bias circuit, and a control unit; wherein: the first end of the first bias circuit is used to connect to the radio frequency output end and the first end of the second bias circuit, the second end of the first bias circuit is connected to the first end of the adjustable varactor diode, the control end of the first bias circuit is connected to the control unit, and the second end of the adjustable varactor diode is connected to the ground end; the first end of the second bias circuit is used to connect to the radio frequency input end, the second end of the second bias circuit is connected to the first end of the switching tube, the control end of the second bias circuit is connected to the control unit, and the second end of the switching tube is connected to the ground end.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and in particular to an antenna matching circuit and a radio frequency terminal. Background Art

[0002] Currently, broadband, multi-band, and multi-antenna terminal products have become extremely popular in wireless communication systems. It's generally assumed that the antenna input impedance is a constant. However, in practice, antenna input impedance varies due to factors such as antenna feed point design, feed network design, and environmental variations, with this variation increasing with wider operating bandwidth. The feed network takes antenna radiation into account, and feed point design introduces line impedance discontinuities. Furthermore, varying antenna feed point structures and shapes introduce parasitic inductance, which can easily cause load pull between the terminal and the antenna. Mismatched antenna impedance with the radio front-end and back-end can cause impedance pull and line signal reflections, significantly reducing the power and efficiency of the wireless link. A common solution is to embed a matching network between the antenna and transmitter / receiver.

[0003] The inventors have found that the traditional antenna matching network inserts a fixed matching network between the signal source and the antenna, which can only achieve matching for fixed frequencies. Once the external environment causes the antenna impedance to change or the impedance discontinuity introduced by the terminal feed point itself is discontinuous, the matching network will fail and the antenna performance will be reduced. Summary of the Invention

[0004] The present invention provides an antenna matching circuit and a radio frequency terminal, which are used to solve the technical problem in the prior art that once the external environment causes the antenna impedance to change or the impedance discontinuity introduced by the terminal feed point itself is discontinuous, the matching network will fail and the antenna performance will be reduced.

[0005] To solve the above technical problems, the present invention provides an antenna matching circuit in a first aspect, comprising: a switch tube, an adjustable varactor diode, a first bias circuit, a second bias circuit, and a control unit; wherein:

[0006] The first end of the first bias circuit is used to be connected to the RF output end and the first end of the second bias circuit, the second end of the first bias circuit is connected to the first end of the adjustable varactor diode, the control end of the first bias circuit is connected to the control unit, and the second end of the adjustable varactor diode is connected to the ground end;

[0007] The first end of the second bias circuit is used to connect to the RF input end, the second end of the second bias circuit is connected to the first end of the switch tube, the control end of the second bias circuit is connected to the control unit, and the second end of the switch tube is connected to the ground end.

[0008] Furthermore, the first bias circuit includes a first bypass capacitor and a first choke inductor, wherein the first end of the first bypass capacitor serves as the first end of the first bias circuit, the first end of the first choke inductor serves as the control end of the first bias circuit, and the second end of the first bypass capacitor and the second end of the first choke inductor are connected together to serve as the second end of the first bias circuit.

[0009] Furthermore, the second bias circuit includes a second bypass capacitor and a second choke inductor, wherein the first end of the second bypass capacitor serves as the first end of the second bias circuit, the first end of the second choke inductor serves as the control end of the second bias circuit, and the second end of the second bypass capacitor and the second end of the second choke inductor are connected together to serve as the second end of the second bias circuit.

[0010] Furthermore, the switching tube is a PIN diode, the positive end of the PIN diode is connected to the second end of the second bias circuit, the negative end of the PIN diode is connected to the ground end, the positive end of the adjustable varactor diode is the positive end of the adjustable varactor diode, and the negative end of the adjustable varactor diode is the first end of the adjustable varactor diode.

[0011] Furthermore, the line matching circuit also includes a first coupling capacitor and a second coupling capacitor, wherein the first end of the first coupling capacitor is connected to the RF input end, the second end of the first coupling capacitor is connected to the second bias circuit, the first end of the first bias circuit and the first end of the second coupling capacitor, and the second end of the second coupling capacitor is connected to the RF output end.

[0012] Furthermore, the first end of the first coupling capacitor is connected to the RF input terminal through a 50Ω input microstrip connection line, the second end of the second coupling capacitor is connected to the RF output terminal through a microstrip transmission line, and the second end of the first coupling capacitor, the first end of the second bias circuit, the first end of the first bias circuit and the first end of the second coupling capacitor are connected through a microstrip transmission line.

[0013] Furthermore, the antenna matching circuit also includes a microstrip open branch, wherein the first end of the microstrip open branch is connected to the first end of the second coupling capacitor and the first end of the first bias circuit through a microstrip transmission line, and the second end of the microstrip open branch is open.

[0014] In a second aspect, a matching control method for an antenna matching circuit is provided, wherein the antenna matching circuit is the antenna matching circuit as described in the first aspect, the method comprising:

[0015] collecting a real-time load impedance value of an antenna connected to the radio frequency input terminal;

[0016] Acquire the impedance value of the radio frequency input port, and obtain the reflection coefficient of the radio frequency input port according to the impedance value of the radio frequency input port and the real-time load value;

[0017] determining the capacitance values ​​of the adjustable varactor diode and the switch tube when the reflection coefficient reaches a preset value;

[0018] According to the capacitance values ​​of the adjustable varactor diode and the switch tube, the first bias circuit and the second bias circuit are respectively controlled to generate corresponding bias voltages to respectively change the equivalent capacitance values ​​of the adjustable varactor diode and the switch tube.

[0019] In a third aspect, a radio frequency terminal is provided, comprising an antenna and the antenna matching circuit mentioned in the first aspect, wherein the antenna is connected to a radio frequency output end of the antenna matching circuit.

[0020] Furthermore, the radio frequency terminal further includes a dielectric substrate and a feeder, the antenna matching circuit is provided on the dielectric substrate, and the radio frequency output end is connected to the antenna via the feeder.

[0021] The present invention provides an antenna matching circuit and a radio frequency terminal, which combine the on and off control of the second bias circuit capacitor by a switch tube switch and the adjustable electrical tuning by a varactor diode switch to broaden the circuit's broadband full-frequency impedance matching, reduce radio frequency signal loss, and achieve high linearity of the radio frequency circuit. It can be flexibly tuned within a wide frequency band, and ensures that the load pulling problem existing in current communication products is solved and that the broadband impedance matching of multiple antennas is supported to be consistent, thereby improving antenna performance. In addition, a new design of a port and antenna of a radio frequency terminal is provided to realize a new radio frequency terminal product with a simple circuit, low cost, and small PCB area occupation, which is conducive to low cost and miniaturization of the product, greatly simplifies the port design of the radio frequency terminal, and improves the terminal receiving performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is a schematic structural diagram of an antenna matching circuit provided by an embodiment of the present invention;

[0024] Figure 2 is another structural schematic diagram of an antenna matching circuit provided by an embodiment of the present invention;

[0025] Figure 3 is another structural schematic diagram of an antenna matching circuit provided by an embodiment of the present invention;

[0026] Figure 4 This is a schematic structural diagram of a radio frequency terminal provided by an embodiment of the present invention;

[0027] Figure 5 The present invention is a flowchart of a matching control method for an antenna matching circuit provided by an embodiment of the present invention.

[0028] Description of reference numerals:

[0029] 1- Antenna;

[0030] 2 - antenna matching circuit; 21 - first bias circuit; 211 - first choke inductor; 212 - first bypass capacitor; 22 - second bias circuit; 221 - second choke inductor; 222 - first bypass capacitor; 23 - control unit; 210 - first control voltage input terminal; 220 - second control voltage input terminal; D1 - switch tube; D2 - adjustable varactor diode;

[0031] 3- dielectric substrate; 4- feeder line. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0033] It should be noted that when an element is referred to as being “fixed on” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0034] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0035] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0036] like Figure 1 As shown, the present invention provides an antenna matching circuit 2, including a radio frequency input terminal and a radio frequency output terminal, wherein the radio frequency output terminal is used to connect to the antenna 1, and the antenna matching circuit 2 includes: a switch tube D1, an adjustable varactor diode D2, a first bias circuit 21, a second bias circuit 22 and a control unit 23; wherein:

[0037] The first end of the first bias circuit 21 is used to be connected to the RF output end and the first end of the second bias circuit 22, the second end of the first bias circuit 21 is connected to the first end of the adjustable varactor diode D2, the control end of the first bias circuit 21 is connected to the control unit 23, and the second end of the adjustable varactor diode D2 is connected to the ground end;

[0038] The first end of the second bias circuit 22 is used to connect to the RF input end, the second end of the second bias circuit 22 is connected to the first end of the switch tube D1, the control end of the second bias circuit 22 is connected to the control unit 23, and the second end of the switch tube D2 is connected to the ground end.

[0039] In the invention, two bias circuits are provided, controlled by a control unit 23. The switching of the second bias circuit 22 capacitor is controlled by the switch D1, and the variable capacitance diode switch D2 is used for adjustable electrical tuning. This combines to broaden the circuit's broadband full-band impedance matching, reduce RF signal loss, and achieve high linearity in the RF circuit. Flexible tuning is possible over a wide bandwidth, ensuring consistent impedance matching for multiple antennas while resolving the load-pull problem of current communication products. This improves antenna performance. The circuit design method for the switch D1 and the adjustable variable capacitance diode D1 effectively expands bandwidth, provides good consistency, and occupies a small circuit structure area, ensuring excellent RF signal transmission integrity. This effectively addresses current antenna feed access issues. As the frequency of antenna 1 increases, and as the load of antenna 1 changes, circuit linearity is achieved by controlling the switch D1 and the adjustable capacitance diode D2, resolving the linear bottleneck problem associated with a single variable capacitance diode circuit. This technology offers advantages such as bandwidth expansion, ease of tuning and matching, high linearity, and direct reduction in impedance matching, thereby improving antenna performance.

[0040] In one embodiment, the switch D1 may be a PIN diode, the positive terminal of the PIN diode being connected to the second terminal of the second bias circuit 22, and the negative terminal of the PIN diode being connected to the ground terminal. It should be noted that the switch D1 may also be another switch, such as another power switch, and the present invention is not limited thereto. The positive terminal of the adjustable varactor diode D2 is the second terminal of the adjustable varactor diode, and the negative terminal of the adjustable varactor diode D2 is the first terminal of the adjustable varactor diode. In other words, the positive terminal of the adjustable varactor diode D2 is connected to the ground terminal, and the negative terminal is connected to the second terminal of the first bias circuit 21. For ease of description, the following embodiment will describe the switch D1 and the adjustable varactor diode D2 in this embodiment, but this does not limit the present invention.

[0041] In one embodiment, please refer to Figure 2-Figure 3 The first bias circuit 21 includes a first bypass capacitor 212 and a first choke inductor 211. The first end of the first bypass capacitor 212 serves as the first end of the first bias circuit 21, the first end of the first choke inductor 211 serves as the control end of the first bias circuit 21, and the second end of the first bypass capacitor and the second end of the first choke inductor 211 are connected together to serve as the second end of the first bias circuit 21. In other words, the embodiment of the present invention provides a specific capacitor bias circuit serving as an adjustable varactor diode D2, wherein one end of the first bypass capacitor 212 is connected to the RF output end and the first end of the second bias circuit 22, the other end of the first bypass capacitor 212 and one end of the first choke inductor 211 are connected together and then connected to the negative end of the adjustable varactor diode D2, the positive end of the adjustable varactor diode D2 is connected to the ground, and the other end of the first choke inductor 211 is used to connect to the control unit 23. In this way, the control unit 23 can adjust the equivalent capacitance of the adjustable varactor diode D2 in combination with the switch tube D1 through the voltage at one end of the first choke inductor 211, thereby achieving optimal impedance matching in the antenna matching circuit.

[0042] In one embodiment, the second bias circuit 22 includes a second bypass capacitor 222 and a second choke inductor 221, wherein the first end of the second bypass capacitor 222 serves as the first end of the second bias circuit 22, the first end of the second choke inductor 221 serves as the control end of the second bias circuit 22, and the second end of the second bypass capacitor 222 and the second end of the second choke inductor 221 are connected together to serve as the second end of the second bias circuit 22. In other words, this embodiment of the present invention further provides a specific capacitor bias circuit serving as a switchable transistor D1, wherein one end of the second bypass capacitor 222 is connected to the RF input end and the first end of the first bias circuit 21, that is, one end of the second bypass capacitor 222 is connected to the RF input end and one end of the first bypass capacitor 212, the other end of the second bypass capacitor 222 and one end of the second choke inductor 221 are connected together and then connected to the positive end of a PIN diode, the negative end of the PIN diode is connected to ground, and the other end of the second choke inductor 221 is connected to the control unit 23. In this way, the control unit 23 can control the on or off of the PIN diode through the voltage at one end of the second choke inductor 221, and combine it with the switch-adjusted varactor diode D2 to broaden the broadband full-frequency impedance matching, reduce RF signal loss, and achieve high linearity of the RF circuit.

[0043] In the above embodiment, two bias circuits are used to control the conduction and disconnection of the capacitor of the second bias circuit 22 by switching PIN diode D1, and the switching of variable capacitance diode D2 for electrical tuning. This combines to achieve wideband full-band impedance matching, reduce RF signal loss, and achieve high RF circuit linearity. This technology provides flexible tuning across a wide frequency band, while ensuring consistent support for multi-antenna broadband impedance matching while resolving the load-pull problem currently encountered in current communications products.

[0044] In one embodiment, the control unit 23 may be a DAC source and includes a first control voltage input terminal 210 and a second control voltage input terminal 220. One end of the first control unit input terminal 210 is connected to one end of a first choke inductor 211, and the other end is connected to the DAC source output terminal; one end of the second control voltage input terminal 220 is connected to one end of a second choke inductor 221, and the other end is connected to the DAC output terminal.

[0045] In one embodiment, the line matching circuit 2 further includes a first coupling capacitor 101 and a second coupling capacitor 102, wherein a first end of the first coupling capacitor 101 is connected to the RF input end, a second end of the first coupling capacitor 101 is connected to the second bias circuit 22, a first end of the first bias circuit 21, and a first end of the second coupling capacitor 102, and a second end of the second coupling capacitor 102 is connected to the RF output end. Specifically, in combination with the above embodiment, one end of the first coupling capacitor 101 serves as the RF input end, the other end of the second coupling capacitor 101 is connected to the second bypass capacitor 222, the first bypass capacitor 212, and one end of the second coupling capacitor 102, and the other end of the second coupling capacitor 102 serves as the RF output end for connection to the antenna 1.

[0046] In one embodiment, the first end of the first coupling capacitor 101 is connected to the RF input terminal via a 50Ω input microstrip line, the second end of the second coupling capacitor 102 is connected to the RF output terminal via a microstrip transmission line, and the second end of the first coupling capacitor 101, the first end of the second bias circuit 22, the first end of the first bias circuit 21, and the first end of the second coupling capacitor 102 are connected via the microstrip transmission line. It should be noted that the 50Ω input microstrip line may have other resistance values, which can be determined through experiments and are not limited here.

[0047] In one embodiment, the antenna matching circuit 2 further includes a microstrip open-circuit stub 103, wherein a first end of the microstrip open-circuit stub 103 is connected to a first end of the second coupling capacitor 102 and a first end of the first bias circuit via a microstrip transmission line, while a second end of the microstrip open-circuit stub is open. In other words, the first end of the microstrip open-circuit stub 103 is connected to the first coupling capacitor 101, the second bypass capacitor 222, one end of the first bypass capacitor 212, and the second coupling capacitor 102, while the other end is open. It can be seen that the microstrip open-circuit stub 103 is connected in parallel with the bias circuit, rather than being connected in series with the circuit. It should be noted that in some embodiments, when the circuit does not have the second coupling capacitor 102, one end of the microstrip open-circuit stub 103 is connected to the first coupling capacitor 101, the second bypass capacitor 222, one end of the first bypass capacitor 212, and the antenna, while the other end of the microstrip open-circuit stub 103 is open.

[0048] In this embodiment, by providing the microstrip open-circuit branch circuit 103 , the limitation of the small capacitance value of the corresponding capacitor under the influence of high frequency can be effectively reduced, the consistency can be improved, and the circuit design cost can be reduced.

[0049] In one embodiment, if Figure 4As shown, a radio frequency terminal is also provided, which includes an antenna 1 and an antenna matching circuit 2 as described in the above embodiment, wherein the antenna 1 is connected to the radio frequency output end of the antenna matching circuit 2. It should be noted that the radio frequency terminal can specifically refer to various radio frequency terminals, which are not specifically limited in the present invention, such as WiFi products, 5G and other radio frequency electronic products.

[0050] In one embodiment, the RF terminal further includes a dielectric substrate 3 and a feeder 4, the antenna matching circuit 2 is arranged on the dielectric substrate 3, and the RF output end is connected to the antenna through the feeder 4. Connecting to the antenna through the feeder can further reduce interference.

[0051] In the above embodiment, the feed port of the RF input end can be connected to the RF output and antenna connection via IPEX, PCB pad, SMA, BNC, etc. In addition, the impedance of the microstrip line is 50 ohms.

[0052] In some embodiments, the dielectric substrate 13 may be made of conventional FR-4 common Tg130 glass fiber KB-6160, without any specific limitation.

[0053] like Figure 5 As shown, in one embodiment, based on the antenna matching circuit 2 provided in the above embodiment, a matching control method for an antenna matching circuit is provided, and the method includes the following steps:

[0054] S10: collecting a real-time load impedance value of the antenna connected to the RF input terminal;

[0055] S20: Acquire the impedance value of the RF input port, and obtain the reflection coefficient of the RF input port according to the impedance value of the RF input port and the real-time load value;

[0056] During the impedance matching process for the antenna, the real-time load impedance value of the antenna connected to the RF input port must first be collected. In some embodiments, the real-time load impedance value of antenna 1 can be measured or calculated using a Smith chart tool or a port measurement network analyzer. After obtaining the real-time load impedance value of antenna 1, the impedance value of the RF input port is calculated based on the circuit relationship using the following formula:

[0057]

[0058] Among them, Z L is the real-time load impedance value of the antenna, Z0 is the characteristic impedance of 50Ω, l is the electrical length from the RF input port to antenna 1, and β is the phase shift constant.

[0059] Then use the formula

[0060]

[0061] Where Γ is the reflection coefficient.

[0062] S30: determining the capacitance values ​​of the adjustable varactor diode and the switch tube when the reflection coefficient reaches a preset value;

[0063] S40: According to the capacitance values ​​of the adjustable varactor diode and the switch tube, respectively controlling the first bias circuit and the second bias circuit to generate corresponding bias voltages, so as to respectively change the equivalent capacitance values ​​of the adjustable varactor diode and the switch tube.

[0064] For steps S30-S40, in one embodiment, a Smith chart tool or a port measurement network analyzer can be used to measure or calculate the capacitance of the variable capacitance diode D2 and the switch D1 when the reflection coefficient Γ approaches a preset value. By varying the corresponding equivalent capacitance values ​​through the respective bias circuit voltages, impedance matching at the optimal frequency is achieved, thereby widening the antenna's tuning bandwidth and the circuit's linearity. Specifically, preferably, by measuring or calculating the capacitance of the adjustable variable capacitance diode D2 and the switch D1 when the reflection coefficient Γ approaches 0, the corresponding equivalent capacitance values ​​through the respective bias circuit voltage changes are achieved, thereby achieving impedance matching at the optimal frequency, widening the antenna's tuning bandwidth and the circuit's linearity.

[0065] It can be seen that in the embodiment of the present invention, based on the above embodiment, the on and off control of the second bias circuit capacitor by a PIN diode switch and the adjustable electrical tuning by a varactor diode switch are combined to broaden the full-band impedance matching of the circuit, reduce RF signal loss, and achieve high linearity of the RF circuit. It can be flexibly tuned within a wide frequency band, and ensures that the load pulling problem of current communication products is solved and that the impedance matching of multiple antennas with wideband is supported. In addition, a new design of the port and antenna of the RF terminal is provided to realize a new RF terminal product with simple circuit, low cost, and small PCB area occupation, which is conducive to low cost and miniaturization of the product, greatly simplifies the port design of the RF terminal, and improves antenna performance.

[0066] In one embodiment, the present invention also provides a computer storage medium having computer program instructions stored thereon. When the computer program instructions are used, the processor executes or implements the steps or functions of the above-mentioned antenna matching circuit matching control method. For details, please refer to the above-mentioned process, which will not be repeated here.

[0067] The inventors applied the design solution of the present invention to a WiFi product as an example. Assuming that the operating frequency of the WiFi product is 2412MHz to 2482MHz, the comparative data of the impedance matching S parameters are shown in Table 1 below:

[0068]

[0069]

[0070] Table 1 Comparison of S-parameter indicators of RF terminal ports and antennas

[0071] It can also be clearly seen from the test data in Table 1 above that the products designed using the technology of the present invention can solve the load pulling and impedance matching problems caused by the parasitic inductance introduced by the current RF terminal port and antenna structure, reduce the loss of RF signals, and widen the operating frequency bandwidth.

[0072] In summary, the present invention provides an antenna matching circuit and a corresponding radio frequency terminal, in which an adjustable varactor diode D2 is connected in series with a fixed capacitor, and the capacitance change effect under an applied voltage (through a bias circuit) is used to tune the impedance matching of high and low frequencies, and the capacitance of the corresponding bias circuit is controlled by the switch tube D1 to expand the wideband matching and improve the linearity of the circuit. The control unit of the antenna matching circuit mainly controls the on and off of the bias circuit by loading a quantized voltage to tune the overall bias capacitance to slowly increase or decrease, thereby achieving ideal matching of the tuned impedance; in addition, the design of the microstrip open-circuit branch 103 can also effectively solve the problem of impedance mismatch caused by load pulling of the connection structure between the feeding point port of the radio frequency terminal and the feeding point structure of the antenna, as well as the design of a small capacitor value for impedance matching of the antenna high-frequency effect.

[0073] The solution provided by the present invention can effectively solve the problem of discontinuous load impedance in the design of current RF products, reduce RF power loss, and improve RF power efficiency. At the same time, the use of open microstrip branch circuits can reduce the limitation of the corresponding small capacitance value under high frequency influence, improve consistency and reduce circuit design costs. In specific implementation, the wider the antenna frequency and the higher the frequency, if the antenna load changes, the equivalent small capacitance value designed by the open microstrip branch 103 of the circuit can achieve the best matching of high frequency, the capacitance value of the adjustable capacitance diode D2 of the first bias circuit 21 and the capacitance value of the second bias circuit 22 can achieve the best matching of ultra-low frequency, effectively expand the bandwidth, and control the switch tube D1 and the adjustable capacitance diode D2 by the control unit to achieve the linearity of the line, solving the problem of linear screen neck of the variable capacitance diode in the current antenna matching circuit. This technology expands the bandwidth, is easy to tune and match, has high linearity, directly reduces impedance matching, and has strong application scenarios.

[0074] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. An antenna matching circuit, characterized in that: include: A switching tube, an adjustable varactor diode, a first bias circuit, a second bias circuit and a control unit; wherein: The first end of the first bias circuit is used to be connected to the RF output end and the first end of the second bias circuit, the second end of the first bias circuit is connected to the first end of the adjustable varactor diode, the control end of the first bias circuit is connected to the control unit, and the second end of the adjustable varactor diode is connected to the ground end; The first end of the second bias circuit is used to be connected to the RF input end, the second end of the second bias circuit is connected to the first end of the switch tube, the control end of the second bias circuit is connected to the control unit, and the second end of the switch tube is connected to the ground end; The antenna matching circuit further includes a second coupling capacitor and a microstrip open-circuit stub. The first end of the first bias circuit is connected to the first end of the second coupling capacitor, and the second end of the second coupling capacitor is connected to the RF output terminal. The first end of the microstrip open-circuit stub is connected to the first end of the second coupling capacitor and the first end of the first bias circuit via a microstrip transmission line, and the second end of the microstrip open-circuit stub is open. The first bias circuit includes a first bypass capacitor and a first choke inductor, wherein the first end of the first bypass capacitor serves as the first end of the first bias circuit, the first end of the first choke inductor serves as the control end of the first bias circuit, and the second end of the first bypass capacitor and the second end of the first choke inductor are commonly connected to serve as the second end of the first bias circuit; The second bias circuit includes a second bypass capacitor and a second choke inductor, wherein the first end of the second bypass capacitor serves as the first end of the second bias circuit, the first end of the second choke inductor serves as the control end of the second bias circuit, and the second end of the second bypass capacitor and the second end of the second choke inductor are connected together to serve as the second end of the second bias circuit.

2. The antenna matching circuit according to claim 1, wherein: The switching tube is a PIN diode, the positive end of the PIN diode is connected to the second end of the second bias circuit, the negative end of the PIN diode is connected to the ground end, the positive end of the adjustable varactor diode is the positive end of the adjustable varactor diode, and the negative end of the adjustable varactor diode is the first end of the adjustable varactor diode.

3. The antenna matching circuit according to any one of claims 1 to 2, wherein: The antenna matching circuit further includes a first coupling capacitor, wherein a first end of the first coupling capacitor is connected to the RF input end, and a second end of the first coupling capacitor is connected to a first end of the second bias circuit.

4. The antenna matching circuit according to claim 3, wherein: The first end of the first coupling capacitor is connected to the RF input terminal through a 50Ω input microstrip connection line, the second end of the second coupling capacitor is connected to the RF output terminal through a microstrip transmission line, and the second end of the first coupling capacitor, the first end of the second bias circuit, the first end of the first bias circuit, and the first end of the second coupling capacitor are connected through a microstrip transmission line.

5. A control method for an antenna matching circuit, characterized in that: The antenna matching circuit is the antenna matching circuit according to any one of claims 1 to 4, and the method includes: collecting a real-time load impedance value of an antenna connected to the radio frequency input terminal; Acquire the impedance value of the radio frequency input end, and obtain the reflection coefficient of the radio frequency input end according to the impedance value of the radio frequency input end and the real-time load value; determining the capacitance values ​​of the adjustable varactor diode and the switch tube when the reflection coefficient reaches a preset value; According to the capacitance values ​​of the adjustable varactor diode and the switch tube, the first bias circuit and the second bias circuit are respectively controlled to generate corresponding bias voltages to respectively change the equivalent capacitance values ​​of the adjustable varactor diode and the switch tube.

6. A radio frequency terminal, characterized in that: The invention comprises an antenna and the antenna matching circuit according to any one of claims 1 to 4, wherein the antenna is connected to a radio frequency output end of the antenna matching circuit.

7. The radio frequency terminal according to claim 6, wherein: The radio frequency terminal further includes a dielectric substrate and a feeder line. The antenna matching circuit is arranged on the dielectric substrate. The radio frequency output end is connected to the antenna through the feeder line.

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