An impedance matching circuit and method

Abstract

The present invention discloses an impedance matching circuit and method. The circuit is applied to the power supply circuit of an envelope tracking radio frequency power amplifier. The envelope tracking power supply is connected to the radio frequency power amplifier through a first matching circuit, and matching is performed based on the conjugate impedance of the optimal efficiency load impedance of the envelope tracking power supply and the optimal efficiency load impedance of the radio frequency power amplifier, so that the envelope tracking radio frequency power amplifier obtains the optimal efficiency.

Description

Technical Field

[0001] This application relates to the field of wireless communication, and more specifically, to an impedance matching circuit and method. Background Art

[0002] A radio frequency power amplifier is an important part of various wireless transmitters. In the front-end circuit of the transmitter, it amplifies the radio frequency signal power generated by the modulation oscillation circuit to obtain sufficient radio frequency power, which is then fed to the antenna for radiation. Therefore, the radio frequency power amplifier is a very important module in modern communication systems. Especially in 5G communication base stations, a high-efficiency radio frequency power amplifier determines the size, overall power consumption of the 5G base station, as well as the later construction and operation costs.

[0003] Impedance matching means that during the signal transmission process, all high-frequency signals can be transmitted to the load point without any signal reflection back to the source point, thereby improving the output efficiency. It is an effective way to improve the efficiency of radio frequency power amplifiers. Traditional impedance matching technology is to design an impedance matching network to make the signal source impedance conjugate match with the load impedance to obtain the highest output power transmission.

[0004] The inventors found during the technical research process that the new generation of communication technology combines the envelope tracking technology with the radio frequency power amplifier. Only solving the power output problem by conjugate matching the source impedance and load impedance of the radio frequency power amplifier no longer meets the requirements.

[0005] Therefore, it can be seen that how to improve the power output efficiency of the envelope tracking radio frequency power amplifier is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0006] The present invention provides an impedance matching circuit to solve the technical problem that the impedance matching power output efficiency of the radio frequency power amplifier in the prior art is low and the envelope tracking radio frequency power amplifier cannot reach the qualified power output efficiency. This circuit is applied to the power supply circuit of the envelope tracking radio frequency power amplifier and includes: an envelope tracking power supply, a radio frequency power amplifier, a first matching circuit, and a blocking capacitor. Among them,

[0007] The envelope tracking power supply is used to perform envelope tracking processing on the input signal and provide electrical energy to the radio frequency power amplifier;

[0008] The first matching circuit includes a first matching unit and a capacitor;

[0009] The input ends of the first matching unit are respectively connected to the output end of the envelope tracking power supply, and the output end is connected to one end of the DC-blocking capacitor. The first matching circuit is located between the RF power amplifier and the DC-blocking capacitor, and impedance matching is performed according to the conjugate impedance of the envelope tracking power supply optimal efficiency load impedance and the RF power amplifier optimal efficiency load impedance to obtain the optimal efficiency of the envelope tracking RF power amplifier; and / or, according to the conjugate impedance of the RF power amplifier load impedance value, the envelope tracking power supply optimal efficiency load impedance is matched to obtain the optimal efficiency of the envelope tracking RF power amplifier.

[0010] Preferably, a third superposition circuit is further included.

[0011] The third superposition circuit includes a fundamental wave and its higher harmonics in the superposition circuit, and outputs a superposed signal.

[0012] Preferably, a second matching circuit is further included, including a second matching unit and a capacitor.

[0013] The second matching circuit is used to perform impedance matching according to the envelope tracking power supply optimal efficiency load impedance to obtain a specified load impedance.

[0014] Preferably, the input end of the second matching circuit is connected to the other end of the DC-blocking capacitor, and forms a matching network with the DC-blocking capacitor.

[0015] The matching network is used to perform impedance matching according to the obtained envelope tracking power supply optimal efficiency load impedance to obtain a specified load impedance.

[0016] Preferably, the first matching unit includes microstrip lines or coplanar waveguides of different specifications.

[0017] The second matching unit also includes microstrip lines or coplanar waveguides of different specifications.

[0018] The length of the microstrip line or coplanar waveguide is determined according to the matching to the specified load impedance requirement of the envelope tracking power supply optimal efficiency load impedance.

[0019] Preferably, the third superimposing circuit includes microstrip lines or coplanar waveguides of different lengths, wherein the lengths of the microstrip lines or coplanar waveguides correspond to the frequencies of the output power of the radio frequency power amplifier.

[0020] Correspondingly, the present invention further provides an impedance matching method, which is applied to the envelope tracking radio frequency power amplifier power supply circuit. The method includes:

[0021] Performing impedance matching according to the conjugate impedance of the envelope tracking power supply optimal efficiency load impedance and the radio frequency power amplifier optimal efficiency load impedance to obtain the envelope tracking radio frequency power amplifier optimal efficiency;

[0022] Performing impedance matching according to the obtained envelope tracking power supply optimal efficiency load impedance to obtain a specified load impedance.

[0023] Preferably, after obtaining the specified load impedance, it further includes:

[0024] Superimposing its high-order harmonics on the fundamental wave to output a superimposed signal.

[0025] Preferably, before performing impedance matching according to the conjugate impedance of the envelope tracking power supply optimal efficiency load impedance and the radio frequency power amplifier optimal efficiency load impedance to obtain the envelope tracking radio frequency power amplifier optimal efficiency, it further includes:

[0026] Obtaining the conjugate impedance of the envelope tracking power supply optimal efficiency load impedance and / or the radio frequency power amplifier optimal efficiency load impedance according to the characteristics of the envelope tracking power supply and / or the radio frequency power amplifier.

[0027] Preferably,

[0028] The calculation methods for obtaining the optimal efficiency of the envelope tracking radio frequency power amplifier and the specified load impedance include: computer simulation, Smith chart calculation, and prior experience.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention discloses an impedance matching circuit and method. The circuit is applied to the envelope tracking radio frequency power amplifier power supply circuit. The envelope tracking power supply is connected to the radio frequency power amplifier through a first matching circuit. Matching is performed based on the conjugate impedance of the envelope tracking power supply optimal efficiency load impedance and the radio frequency power amplifier optimal efficiency load impedance, so that the envelope tracking radio frequency power amplifier obtains the optimal efficiency. By superimposing the fundamental wave of the circuit and its high-order harmonics (second harmonic or third harmonic), the output power of the circuit is further increased to meet the development requirements of signal transmission technology. Brief Description of the Drawings

[0031] To more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for the description of the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0032] Figure 1 Fig. shows a schematic structural diagram of an impedance matching circuit proposed in an embodiment of the present application;

[0033] Figure 2 Fig. shows a schematic structural diagram of an impedance matching circuit proposed in another embodiment of the present application;

[0034] Figure 3 Fig. shows a schematic structural diagram of an impedance matching circuit proposed in yet another embodiment of the present application;

[0035] Figure 4 Fig. shows a schematic structural diagram of a third superimposing circuit in an embodiment of the present application;

[0036] Figure 5 Fig. shows a schematic flow diagram of an impedance matching method proposed in an embodiment of the present application. Detailed Embodiments

[0037] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0038] As described in the background art, in the prior art, the impedance matching power output efficiency of a radio frequency power amplifier is low, and it is impossible to make the envelope tracking radio frequency power amplifier reach a qualified power output efficiency.

[0039] To solve the above problems, an embodiment of the present application proposes an impedance matching circuit, which is applied to the power supply circuit of an envelope tracking radio frequency power amplifier, as Figure 1 Fig. shows a schematic structural diagram of an impedance matching circuit proposed in an embodiment of the present application, including: an envelope tracking power supply, a radio frequency power amplifier, a first matching circuit, and a DC blocking capacitor. Among them,

[0040] The envelope tracking power supply is used to amplify the input envelope signal and provide voltage and current to the radio frequency power amplifier;

[0041] The first matching circuit includes a first matching unit and a capacitor;

[0042] The input end of the first matching unit is respectively connected to the output end of the envelope tracking power supply, and the output end is connected to one end of the DC-blocking capacitor. The first matching circuit is located between the RF power amplifier and the DC-blocking capacitor, and impedance matching is performed according to the conjugate impedance of the envelope tracking power supply's optimal efficiency load impedance and the RF power amplifier's optimal efficiency load impedance to obtain the optimal efficiency of the envelope tracking RF power amplifier; and / or, according to the conjugate impedance of the RF power amplifier's load impedance value, the envelope tracking power supply's optimal efficiency load impedance is matched to obtain the optimal efficiency of the envelope tracking RF power amplifier.

[0043] Specifically, for a circuit using an envelope tracking RF power amplifier, its excitation source impedance is generated by matching the conjugate impedance of the envelope tracking power supply's optimal efficiency load impedance and the RF power amplifier's optimal efficiency load impedance. If only the conjugate impedance of the RF power amplifier's optimal efficiency load impedance is matched, there will be a mismatch, that is, the excitation source cannot obtain the highest efficiency or maximum power output. Therefore, in the envelope tracking power amplifier circuit, it is necessary to conjugate-match the load impedance of the envelope tracking power supply's optimal efficiency and the load impedance of the power amplifier. The envelope tracking power supply and the RF power amplifier are connected through the first matching circuit. The first matching circuit is located between the RF power amplifier and the DC-blocking capacitor, and the first matching circuit includes a first matching unit and a capacitor. Thus, impedance matching can be performed according to the conjugate impedance of the envelope tracking power supply's optimal efficiency load impedance and the RF power amplifier's optimal efficiency load impedance to obtain the optimal efficiency of the envelope tracking RF power amplifier, and / or, according to the conjugate impedance of the RF power amplifier's load impedance value, the envelope tracking power supply's optimal efficiency load impedance is matched to obtain the optimal efficiency of the envelope tracking RF power amplifier.

[0044] To further improve the efficiency of the envelope tracking RF power amplifier, in a preferred embodiment of the present application, a third superimposing circuit is further included.

[0045] The third superimposing circuit includes a circuit for superimposing the fundamental wave and its higher harmonics (second harmonic or third harmonic) in the circuit to output a superimposed signal.

[0046] Specifically, to increase the output power of the RF power amplifier, it is necessary to have as large an output fundamental wave power as possible and as small an efficiency of the output second harmonic or other multiple harmonics as possible. The fundamental wave and its higher harmonics in the third superimposing circuit are used to output a superimposed signal, thereby further improving the efficiency of the envelope tracking RF power amplifier.

[0047] To transmit all the optimal efficiency signals to the load, in a preferred embodiment of the present application, a second matching circuit is further included, which includes a second matching unit and a capacitor;

[0048] The second matching circuit is configured to perform impedance matching according to the optimal efficiency load impedance of the envelope tracking power supply to obtain a specified load impedance.

[0049] Specifically, the conjugate impedance of the optimal efficiency load impedance of the radio frequency power amplifier and / or the optimal efficiency load impedance of the envelope tracking power supply are subjected to impedance matching to obtain a specified load impedance, that is, 50Ω or 75Ω required by industry standards, so as to reduce reflections during the signal transmission of the radio frequency power amplifier and improve the signal transmission efficiency on the basis of optimal efficiency. Additionally, in the specific application scenarios of the present application, such as Figure 3 the DC blocking capacitor shown in [reference], is only used to isolate the first matching circuit and the second matching circuit, without impedance matching function.

[0050] To further transmit all the optimal efficiency signals to the load, in a preferred embodiment of the present application, the input end of the second matching circuit is connected to the other end of the DC blocking capacitor, and together with the DC blocking capacitor, they form a matching network;

[0051] The matching network is configured to perform impedance matching according to the obtained optimal efficiency load impedance of the envelope tracking power supply to obtain a specified load impedance.

[0052] As described above, the matching network formed by the second matching circuit and the DC blocking capacitor includes the DC blocking capacitor. The DC blocking capacitor participates in impedance matching, and the conjugate impedance of the optimal efficiency load impedance of the radio frequency power amplifier and / or the optimal efficiency load impedance of the envelope tracking power supply are subjected to impedance matching to obtain a specified load impedance, thereby further transmitting all the power signals to the load.

[0053] To meet the requirements of different load impedances, in a preferred embodiment of the present application, the first matching unit includes microstrip lines or coplanar waveguides of different specifications;

[0054] The second matching unit also includes microstrip lines or coplanar waveguides of different specifications;

[0055] The lengths of the microstrip lines or coplanar waveguides are determined according to the matching to the specified load impedance requirements of the optimal efficiency load impedance of the envelope tracking power supply.

[0056] As described above, both the first matching circuit and the second matching circuit include microstrip lines or coplanar waveguides with different specifications and capacitors. In the specific application scenario of this application, the specifications of the microstrip lines or coplanar waveguides in the first matching circuit, as well as the number and parameters of the capacitors, are related to the envelope tracking power supply that needs to perform impedance matching and the optimal efficiency load impedance characteristics of the radio frequency power amplifier. For the second matching circuit, it is used to match the optimal load impedance of the envelope tracking power supply to the specified industry standard of 50Ω or 75Ω. Therefore, the specifications of the microstrip lines or coplanar waveguides in its circuit, as well as the number and parameters of the capacitors, correspond to the optimal efficiency load impedance characteristics of the envelope tracking power supply that needs to perform impedance matching.

[0057] To match the output power of the radio frequency amplifier, in a preferred embodiment of this application, the third superimposing circuit includes microstrip lines or coplanar waveguides with different lengths, wherein the lengths of the microstrip lines or coplanar waveguides correspond to the frequencies of the output power of the radio frequency power amplifier.

[0058] By applying the above technical solutions, the envelope tracking power supply is connected to the radio frequency power amplifier through the first matching circuit. Based on the conjugate impedance matching between the optimal efficiency load impedance of the envelope tracking power supply and the optimal efficiency load impedance of the radio frequency power amplifier, the envelope tracking radio frequency power amplifier can obtain the optimal efficiency. By superimposing the fundamental wave and its high-order harmonics (second harmonic or third harmonic) of the circuit, the output power of the circuit is further increased, meeting the development requirements of signal transmission technology.

[0059] To achieve the above technical objectives, an embodiment of this application also proposes an impedance matching method. By matching the conjugate impedance between the optimal efficiency load impedance of the envelope tracking power supply and the optimal efficiency load impedance of the radio frequency power amplifier, the envelope tracking radio frequency power amplifier can obtain the optimal efficiency, and based on the obtained optimal efficiency load impedance of the envelope tracking power supply, such as Figure 5 As shown, the method includes:

[0060] Step S501, perform impedance matching according to the conjugate impedance between the optimal efficiency load impedance of the envelope tracking power supply and the optimal efficiency load impedance of the radio frequency power amplifier to obtain the optimal efficiency of the envelope tracking radio frequency power amplifier.

[0061] Specifically, for an envelope tracking RF power amplifier circuit, its excitation source impedance is generated by conjugate impedance matching between the envelope tracking power supply's optimal efficiency load impedance and the RF power amplifier's optimal efficiency load impedance. If only the conjugate impedance of the RF power amplifier's optimal efficiency load impedance is matched, there will be a mismatch, which means that the excitation source cannot obtain the maximum efficiency and maximum power output. Therefore, in the envelope tracking power supply power amplifier circuit, it is necessary to perform conjugate matching between the envelope tracking power supply load impedance and the power amplifier load impedance to obtain the optimal efficiency of the envelope tracking RF power amplifier.

[0062] To accurately obtain the optimal efficiency of the envelope tracking RF power amplifier, in a preferred embodiment of the present application, before performing impedance matching according to the conjugate impedance of the envelope tracking power supply's optimal efficiency load impedance and the RF power amplifier's optimal efficiency load impedance to obtain the optimal efficiency of the envelope tracking RF power amplifier, it further includes:

[0063] According to the characteristics of the envelope tracking power supply and / or the RF power amplifier, obtain the conjugate impedance of the envelope tracking power supply's optimal efficiency load impedance and / or the RF power amplifier's optimal efficiency load impedance.

[0064] As described above, since it is necessary to determine the optimal efficiency of the envelope tracking RF power amplifier based on the conjugate impedance, it is necessary to first obtain the conjugate impedance of the envelope tracking power supply's optimal efficiency load impedance and / or the RF power amplifier's optimal efficiency load impedance according to the characteristics of the envelope tracking power supply and / or the RF power amplifier.

[0065] Step S502: According to the obtained envelope tracking power supply's optimal efficiency load impedance, perform impedance matching to obtain a specified load impedance.

[0066] To transmit all the optimal efficiency signals to the load, according to the obtained envelope tracking power supply's optimal efficiency load impedance, perform impedance matching to obtain a specified load impedance.

[0067] To further improve the efficiency of the envelope tracking RF power amplifier, in a preferred embodiment of the present application, after obtaining the specified load impedance, it further includes:

[0068] Superimpose its higher harmonics on the fundamental wave to output a superimposed signal.

[0069] Specifically, to increase the output power of the RF power amplifier, it is necessary to have as large an output fundamental wave power as possible and as small an efficiency of output second harmonic or other multiple harmonics as possible. Therefore, after obtaining the specified load impedance, other higher harmonics are superimposed on the fundamental wave to output a superimposed signal.

[0070] It should be noted that the solutions of the above preferred embodiments are only specific implementation solutions proposed by this application. Other ways to further improve the efficiency of the envelope tracking radio frequency power amplifier all fall within the protection scope of this application.

[0071] In the preferred embodiment of this application, to accurately obtain the optimal efficiency and the specified load impedance, the calculation method for obtaining the optimal efficiency of the envelope tracking radio frequency power amplifier and the specified load impedance includes: computer simulation, Smith chart calculation, and old experience.

[0072] Those skilled in the art can flexibly select other calculation methods according to actual needs, which does not affect the protection scope of this application.

[0073] By applying the above technical solution, in the power supply circuit of the envelope tracking radio frequency power amplifier, impedance matching is performed according to the conjugate impedance of the envelope tracking power supply optimal efficiency load impedance and the radio frequency power amplifier optimal efficiency load impedance to obtain the optimal efficiency of the envelope tracking radio frequency power amplifier; according to the obtained envelope tracking power supply optimal efficiency load impedance, impedance matching is performed to obtain the specified load impedance. Thus, the envelope tracking radio frequency power amplifier obtains the optimal efficiency, and through the superposition of the fundamental wave and its high-order harmonics of the circuit, the output power and efficiency of the circuit are further improved to meet the development needs of signal transmission technology.

[0074] To further elaborate on the technical idea of the present invention, the technical solution of the present invention will be described in combination with a specific application scenario.

[0075] In the field of signal transmission, especially in the field of the new generation of wireless communication, efficient signal transmission is the development trend. The embodiment of the present invention proposes an impedance matching circuit. By connecting the envelope tracking power supply to the radio frequency power amplifier through the first matching circuit and matching the conjugate impedance of the envelope tracking power supply optimal efficiency load impedance and the radio frequency power amplifier optimal efficiency load impedance, the envelope tracking radio frequency power amplifier can obtain the optimal efficiency.

[0076] Impedance matching is the mutual adaptation of the load impedance and the excitation source impedance, so that the excitation source can obtain the highest output efficiency, that is, the maximum output power. For the envelope tracking radio frequency power amplifier circuit, its excitation source impedance is generated by the conjugate impedance matching of the envelope tracking power supply's optimal efficiency load impedance and the radio frequency power amplifier's optimal efficiency load impedance. If only the conjugate impedance of the radio frequency power amplifier's optimal efficiency load impedance is matched to make the circuit obtain the industry standard 50Ω or 75Ω, there will be a mismatch, that is, the excitation source cannot obtain the highest efficiency and maximum power output. Therefore, in the envelope tracking power supply power amplifier circuit, it is necessary to conjugate-match the envelope tracking power supply load impedance and the power amplifier load impedance. When the conjugate impedance of the envelope tracking power supply's optimal efficiency load impedance and the radio frequency power amplifier's optimal efficiency load impedance is matched, the circuit will obtain the best efficiency and output the maximum power at the best efficiency, thereby further improving the efficiency of the envelope tracking radio frequency power amplifier.

[0077] As Figure 2 shown in the structural schematic diagram of the impedance matching circuit, the circuit includes an envelope tracking power supply, a radio frequency power amplifier, a first matching circuit, a DC blocking capacitor, a second matching circuit, and a third superposition circuit. The envelope tracking power supply is used to perform envelope tracking processing on the input signal and supply electrical energy to the power amplifier; the input end of the first matching circuit is respectively connected to the output end of the envelope tracking power supply, and the output end is connected to one end of the DC blocking capacitor. The first matching circuit is located between the radio frequency power amplifier and the DC blocking capacitor, and impedance matching is performed according to the conjugate impedance of the envelope tracking power supply's optimal efficiency load impedance and the radio frequency power amplifier's optimal efficiency load impedance to obtain the best efficiency of the envelope tracking radio frequency power amplifier; and / or, according to the conjugate impedance of the radio frequency power amplifier load impedance value, the envelope tracking power supply's optimal efficiency load impedance is matched to obtain the best efficiency of the envelope tracking radio frequency power amplifier.

[0078] The first matching circuit is connected to the envelope tracking power supply and is located between the RF power amplifier and the DC-blocking capacitor. Its purpose is to match the conjugate impedance of the optimal efficiency load impedance of the RF power amplifier to the optimal efficiency load impedance of the envelope tracking power supply, so as to maximize the output efficiency of the envelope tracking RF power amplifier. By means of the first matching circuit, the efficiency of the envelope tracking RF power amplifier can be improved. This is different from the prior art where only the conjugate impedance of the optimal efficiency load impedance of the RF power amplifier is matched to a specified load impedance, i.e., 50Ω or 75Ω required by the industry, to improve the output efficiency of the RF power amplifier. The prior art can only be used for RF power amplifier circuits without an envelope tracking power supply, aiming to transmit the RF power amplifier signal to the load without a large amount of signal reflection. However, the impedance matching circuit in this embodiment can not only be used to solve the problem of RF power amplifier signal transmission, but also to solve the problem of the output efficiency of the envelope tracking RF power amplifier, that is, to obtain the optimal efficiency through the first matching circuit, output the optimal efficiency signal to the load without reflection through the second matching circuit, and further improve the efficiency of the envelope tracking RF power amplifier through the third superposition circuit, so as to be more suitable for the signal transmission requirements of high peak-to-average ratio, large bandwidth, and high efficiency.

[0079] Through the above embodiments, the optimal efficiency of the envelope tracking RF power amplifier can be obtained. However, how to transmit all the optimal efficiency signals to the load is also a problem that needs to be considered in the present invention. As Figure 3 shown in the structural schematic diagram of an impedance matching circuit proposed in another embodiment of the present application, which includes an envelope tracking power supply, an RF power amplifier, a first matching circuit, a DC-blocking capacitor, a second matching circuit, and a third superposition circuit. The first matching circuit includes a first matching unit and a capacitor, and the second matching circuit includes a second matching unit and a capacitor. Through the matching network composed of the second matching circuit and the DC-blocking capacitor, the conjugate impedance of the optimal efficiency load impedance of the RF power amplifier and / or the optimal efficiency load impedance of the envelope tracking power supply is impedance-matched to obtain a specified load impedance, that is, 50Ω or 75Ω required by the industry standard, so as to reduce the reflection during the signal transmission process of the RF power amplifier and improve the signal transmission efficiency on the basis of the optimal efficiency.

[0080] In the specific application scenario of the present application, the second matching circuit can also perform impedance matching without including the DC-blocking capacitor. The second matching circuit performs impedance matching according to the optimal efficiency load impedance of the envelope tracking power supply to obtain a specified load impedance. At this time, the DC-blocking capacitor is only used to isolate the first matching circuit and the second matching circuit and has no impedance matching function.

[0081] The first matching circuit and the second matching circuit both include microstrip lines or coplanar waveguides with different specifications and capacitors. The first matching circuit is used to obtain the best efficiency. The first matching circuit is affected by the conjugate impedances of the best efficiency load impedances of different envelope tracking power supplies and the best efficiency load impedance of the radio frequency power amplifier. It requires microstrip lines or coplanar waveguides with different specifications to meet the requirements of different load impedances. That is to say, the specifications of the microstrip lines or coplanar waveguides in the first matching circuit, as well as the number and parameters of the capacitors, are related to the best efficiency load impedance characteristics of the envelope tracking power supply and the radio frequency power amplifier that need impedance matching.

[0082] For the second matching circuit, it is used to match the best load impedance of the envelope tracking power supply to the specified industry standard of 50Ω or 75Ω. Therefore, the specifications of the microstrip lines in its circuit, as well as the number and parameters of the capacitors, correspond to the best efficiency load impedance characteristics of the envelope tracking power supply that need impedance matching.

[0083] Those skilled in the art can obtain the calculation methods of the best efficiency and the specified load impedance through computer simulation, Smith chart calculation, old experience, etc.

[0084] To further improve the efficiency of the envelope tracking radio frequency power amplifier, as Figure 3 shown, the present application designs a third superposition circuit including a shunt short-circuit stub circuit and an open-circuit stub circuit in the circuit. The input ends of the short-circuit stub circuit and the open-circuit stub circuit are both connected to the output end of the second matching circuit, and are used to superpose the fundamental wave and its higher harmonics in the circuit to output a superposed signal.

[0085] To increase the output power of the radio frequency power amplifier, it is necessary to have as large an output fundamental wave f0 power as possible and as small an efficiency of the output second harmonic or other higher harmonics as possible. Reducing the output power of the second harmonic or other multiple harmonics requires the harmonic load to be short-circuited, open-circuited, or purely reactive. In practical applications, it is difficult to achieve the feasibility of a purely reactive load. Designing a shunt short-circuit stub circuit and an open-circuit stub circuit in the circuit design for the harmonic load short-circuit and open-circuit is the most effective way. Therefore, it is feasible to design a shunt short-circuit stub circuit and an open-circuit stub circuit to improve the output efficiency of the radio frequency power amplifier.

[0086] Taking the second harmonic 2f0 as an example, for a short - circuit stub circuit including a microstrip line or a coplanar waveguide, the length of the microstrip line or the coplanar waveguide corresponds to the frequency of the output power of the RF power amplifier, that is, it corresponds to the wavelength λ of the fundamental wave. Therefore, the length of the microstrip line or the coplanar waveguide of the short - circuit stub circuit is λ / 4. If the short - circuit stub circuit is short - circuited, point A is short - circuited (impedance 0), and the second harmonic 2f0 is transformed to an open - circuit (impedance ∞) after passing through λ / 4 impedance transformation. Then, the impedance at point B with respect to the fundamental wave f0 is very large, and the energy of the fundamental wave f0 cannot leak from point B to point A, and the energy can only be transmitted to the subsequent load or leak to point C.

[0087] For the path stub circuit including a microstrip line or a coplanar waveguide, and its microstrip line or coplanar waveguide length is also λ / 4. Since it is an open - circuit, point C is open - circuited (impedance ∞), and after passing through λ / 4 impedance transformation, it becomes a short - circuit (impedance value is very small). Similarly, the energy cannot leak to point C. That is to say, the energy of the fundamental wave f0 at point B cannot leak to point A or point C, and it can only be transmitted to the load. For point B, it is both the open - circuit point of the load for 2f0 and the short - circuit point of the load for 2f0. Therefore, the high - efficiency output of the RF power amplifier is finally realized. It should be noted that the energy of the fundamental wave f0 at point B cannot leak to point A or point C, and it can only be transmitted to the load. Therefore, the designed parallel short - circuit stub circuit and open - circuit stub circuit in the present invention have no influence on the transmission of the fundamental wave f0.

[0088] An embodiment of the present application also proposes an impedance matching method. By matching the conjugate impedance of the envelope - tracking power supply optimal - efficiency load impedance and the RF power amplifier optimal - efficiency load impedance, the envelope - tracking RF power amplifier can obtain the optimal efficiency, and according to the obtained envelope - tracking power supply optimal - efficiency load impedance, it includes the following steps:

[0089] Step a: Obtain the conjugate impedance of the envelope - tracking power supply optimal - efficiency load impedance and / or the RF power amplifier optimal - efficiency load impedance according to the characteristics of the envelope - tracking power supply and / or the RF power amplifier.

[0090] Step b: Perform impedance matching according to the conjugate impedance of the envelope - tracking power supply optimal - efficiency load impedance and the RF power amplifier optimal - efficiency load impedance to obtain the optimal efficiency of the envelope - tracking RF power amplifier;

[0091] Step c: Based on the load impedance for achieving the optimal efficiency of the envelope tracking power supply, perform impedance matching to obtain the specified load impedance.

[0092] Among them, in Step b and Step c, methods such as computer simulation, Smith chart calculation, and old experience can be used to calculate and obtain the optimal efficiency and the specified load impedance.

[0093] Step d: Superimpose other multiple harmonics on the fundamental wave to output a superimposed signal.

[0094] By applying the above technical solution, matching the conjugate impedance of the load impedance for achieving the optimal efficiency of the envelope tracking power supply with the load impedance for achieving the optimal efficiency of the radio frequency power amplifier can enable the envelope tracking radio frequency power amplifier to achieve the optimal efficiency; by superimposing the fundamental wave and harmonics of the circuit, the output power of the circuit can be further increased to meet the development requirements of signal transmission technology.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the various embodiments of the present application.

Claims

1. A method for impedance matching of an impedance matching circuit, applied to the power supply circuit of an envelope tracking radio frequency power amplifier, characterized in that The method includes: performing impedance matching according to the conjugate impedance of the envelope tracking power supply's optimal efficiency load impedance and the radio frequency power amplifier's optimal efficiency load impedance to obtain the optimal efficiency of the envelope tracking radio frequency power amplifier; performing impedance matching according to the obtained envelope tracking power supply's optimal efficiency load impedance to obtain a specified load impedance; wherein, the impedance matching circuit includes an envelope tracking power supply, a radio frequency power amplifier, a first matching circuit, and a DC blocking capacitor. The envelope tracking power supply is used to amplify the input envelope signal and provide voltage and current to the radio frequency power amplifier. The first matching circuit includes a first matching unit and a capacitor. The input end of the first matching unit is respectively connected to the output end of the envelope tracking power supply, and the output end is connected to one end of the DC blocking capacitor. The first matching circuit is located between the radio frequency power amplifier and the DC blocking capacitor, and performs impedance matching according to the conjugate impedance of the envelope tracking power supply's optimal efficiency load impedance and the radio frequency power amplifier's optimal efficiency load impedance to obtain the optimal efficiency of the envelope tracking radio frequency power amplifier; and / or, matches the envelope tracking power supply's optimal efficiency load impedance according to the conjugate impedance of the radio frequency power amplifier's load impedance value to obtain the optimal efficiency of the envelope tracking radio frequency power amplifier.

2. The impedance matching method according to claim 1, characterized in that, After obtaining the specified load impedance, it further includes: superimposing its higher harmonics on the fundamental wave to output a superimposed signal.

3. The impedance matching method according to claim 2, wherein Before performing impedance matching according to the conjugate impedance of the envelope tracking power supply's optimal efficiency load impedance and the radio frequency power amplifier's optimal efficiency load impedance to obtain the optimal efficiency of the envelope tracking radio frequency power amplifier, it further includes: obtaining the conjugate impedance of the envelope tracking power supply's optimal efficiency load impedance and / or the radio frequency power amplifier's optimal efficiency load impedance according to the characteristics of the envelope tracking power supply and / or the radio frequency power amplifier.

4. An impedance matching method according to claim 3, characterized in that The calculation methods for obtaining the optimal efficiency of the envelope tracking radio frequency power amplifier and the specified load impedance include: computer simulation, Smith chart calculation, and previous experience.

5. An impedance matching method according to claim 1, characterized in that, The impedance matching circuit further includes a third superimposing circuit, and the third superimposing circuit is used to superimpose the fundamental wave and its higher harmonics in the circuit to output a superimposed signal.

6. The impedance matching method according to claim 5, characterized in that, The impedance matching circuit further includes a second matching circuit, and the second matching circuit includes a second matching unit and a capacitor. The second matching circuit is used to perform impedance matching according to the envelope tracking power supply's optimal efficiency load impedance to obtain a specified load impedance.

7. The impedance matching method according to claim 6, wherein The input end of the second matching circuit is connected to the other end of the DC blocking capacitor and forms a matching network with the DC blocking capacitor. The matching network is used to perform impedance matching according to the obtained envelope tracking power supply's optimal efficiency load impedance to obtain a specified load impedance.

8. The impedance matching method according to claim 6, wherein The first matching unit includes microstrip lines or coplanar waveguides (coplanarwaveguide) of different specifications; the second matching unit also includes microstrip lines (microstripline) or coplanar waveguides (coplanarwaveguide) of different specifications; the length of the microstrip line is determined according to the need to match the envelope tracking power supply's optimal efficiency load impedance to the specified load impedance.

Images