Push-pull power amplifier circuit and RF front-end module

Abstract

The present invention discloses a push-pull power amplifier circuit and a radio frequency front-end module. The push-pull power amplifier circuit includes a first power amplifier transistor, a second power amplifier transistor, a first conversion balun, and a first capacitor; a first input terminal of the first conversion balun is connected to an output terminal of the first power amplifier transistor through a first inductor, and the first input terminal of the first conversion balun is connected to a first end of the first capacitor through a second inductor; a second input terminal of the first conversion balun is connected to an output terminal of the second power amplifier transistor through a third inductor, and the second input terminal of the first conversion balun is connected to a second end of the first capacitor through a fourth inductor; thereby alleviating the impedance conversion pressure of the first conversion balun for impedance conversion of the push-pull power amplifier circuit, enabling the first conversion balun to achieve impedance conversion with fewer turns of the coil, and further reducing the output loss of the push-pull power amplifier circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of radio frequency amplification, and in particular, to a push-pull power amplifier circuit and a radio frequency front-end module. Background Art

[0002] A push-pull power amplifier circuit uses two transistors with the same characteristics, and makes them both work in class B state. One transistor works in the positive half cycle, and the other transistor works in the negative half cycle. Then, the output waveforms of the two transistors are combined together on the load to obtain an amplified circuit with a complete output waveform.

[0003] The push-pull power amplifier circuit is generally connected to the subsequent load through a subsequent load balun. Among them, the subsequent load balun is used to perform impedance conversion on the output impedance of the push-pull power amplifier circuit, that is, to convert the output impedance of the push-pull power amplifier circuit into an impedance that matches the impedance of the subsequent load, so as to improve the power transmission performance of the push-pull power amplifier circuit.

[0004] However, when the output impedance of the push-pull power amplifier circuit is too different from the impedance of the subsequent load, the subsequent load balun needs to meet a large impedance conversion ratio, resulting in a large turns ratio of the subsequent load balun, and further causing a large output loss of the push-pull power amplifier circuit. Summary of the Invention

[0005] Embodiments of the present invention provide a push-pull power amplifier circuit and a radio frequency front-end module to solve the problem of large output loss of the push-pull power amplifier circuit.

[0006] A push-pull power amplifier circuit includes a first power amplifier transistor, a second power amplifier transistor, a first conversion balun, and a first capacitor; a first input terminal of the first conversion balun is connected to an output terminal of the first power amplifier transistor through a first inductor, and the first input terminal of the first conversion balun is connected to a first terminal of the first capacitor through a second inductor; a second input terminal of the first conversion balun is connected to an output terminal of the second power amplifier transistor through a third inductor, and the second input terminal of the first conversion balun is connected to a second terminal of the first capacitor through a fourth inductor.

[0007] Further, the first capacitor, the first inductor, and the second inductor cooperate to form a first impedance conversion circuit, and the first capacitor, the third inductor, and the fourth inductor cooperate to form a second impedance conversion circuit.

[0008] Further, the turns ratio of the first conversion balun is associated with the first impedance conversion circuit and the second impedance conversion circuit.

[0009] Further, the push-pull power amplifier circuit further includes a first LC filter circuit and a second LC filter circuit;

[0010] The first LC filter circuit is coupled to the output end of the first power amplifier tube and is configured to suppress harmonic signals of even harmonics of the push-pull power amplifier circuit;

[0011] The second LC filter circuit is coupled to the output end of the second power amplifier tube and is configured to suppress harmonic signals of even harmonics of the push-pull power amplifier circuit.

[0012] Further, the first LC filter circuit is configured to form a first resonance frequency point, and the second LC filter circuit is configured to form a second resonance frequency point.

[0013] Further, the first resonance frequency point and the second resonance frequency point are different.

[0014] Further, the push-pull power amplifier circuit further includes a third LC filter circuit and a fourth LC filter circuit;

[0015] The third LC filter circuit is coupled to the output end of the first power amplifier tube and is configured to form a third resonance frequency point;

[0016] The fourth LC filter circuit is coupled to the output end of the second power amplifier tube and is configured to form a fourth resonance frequency point.

[0017] Further, the third resonance frequency point and the fourth resonance frequency point are different.

[0018] Further, the first LC filter circuit includes a first capacitor and a first inductor connected in series. One end of the first capacitor is coupled to the output end of the first power amplifier tube, the other end is connected to the first end of the first inductor, and the second end of the first inductor is connected to the ground end;

[0019] The second LC filter circuit includes a second capacitor and a second inductor connected in series. One end of the second capacitor is coupled to the output end of the second power amplifier tube, the other end is connected to the first end of the second inductor, and the second end of the second inductor is connected to the ground end.

[0020] A radio frequency front-end module includes a substrate and a push-pull power amplifier chip, a first conversion balun, a first pad, and a second pad disposed on the substrate; a first input end of the first conversion balun is connected to the first pad, and a second input end is connected to the second pad; on the push-pull power amplifier chip, there are a first power amplifier tube, a second power amplifier tube, a first capacitor, a third pad, and a fourth pad, the third pad includes a first welding point and a second welding point that are separately arranged, and the fourth pad includes a third welding point and a fourth welding point that are separately arranged; an output end of the first power amplifier tube is connected to the first welding point, and an output end of the second power amplifier tube is connected to the fourth welding point; one end of the first capacitor is connected to the second welding point, and the other end is connected to the third welding point;

[0021] The first pad is connected to the first welding point through a first transmission line and to the second welding point through a second transmission line, the second pad is connected to the third welding point through a third transmission line and to the fourth welding point through a fourth transmission line.

[0022] Further, it also includes a feeding power supply disposed on the substrate, the feeding power supply is coupled to the output end of the first power amplifier tube through a first feeding inductor, and the feeding power supply is coupled to the output end of the second power amplifier tube through a second feeding inductor.

[0023] In the above push-pull power amplifier circuit and radio frequency front-end module, by connecting the first input end of the first conversion balun to the output end of the first power amplifier tube through a first inductor, and connecting the first input end of the first conversion balun to the first end of the first capacitor through a second inductor; connecting the second input end of the first conversion balun to the output end of the second power amplifier tube through a third inductor, and connecting the second input end of the first conversion balun to the second end of the first capacitor through a fourth inductor, an impedance conversion circuit is formed by the first inductor, the second inductor and the first capacitor, and the third inductor, the fourth inductor and the first capacitor, and jointly participates in the impedance conversion of the push-pull power amplifier circuit with the first conversion balun, thereby alleviating the impedance conversion pressure of the first conversion balun for impedance conversion of the push-pull power amplifier circuit, enabling the first conversion balun to achieve impedance conversion with fewer turns of the coil, and further reducing the output loss of the push-pull power amplifier circuit. In addition, since the number of turns of the coil for the first conversion balun to achieve impedance conversion becomes less, the layout design of the first conversion balun can be realized on a substrate with fewer layers, reducing the design cost, and the design of the first conversion balun is thus more flexible. Description of the Drawings

[0024] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0025] Figure 1 is a circuit schematic diagram of a push-pull power amplifier circuit in an embodiment of the present invention;

[0026] Figure 2 is another circuit schematic diagram of a push-pull power amplifier circuit in an embodiment of the present invention;

[0027] Figure 3 is another circuit schematic diagram of a push-pull power amplifier circuit in an embodiment of the present invention;

[0028] Figure 4 is a circuit schematic diagram of a radio frequency front-end module in an embodiment of the present invention.

[0029] In the figure: 10, the first conversion balun; 20, the first impedance conversion circuit; 30, the second impedance conversion circuit; 40, the first LC filter circuit; 50, the second LC filter circuit; 60, the third LC filter circuit; 70, the fourth LC filter circuit; 71, the first pad; 72, the second pad; 73, the third pad; 731, the first welding point; 732, the second welding point; 74, the fourth pad; 741, the third welding point; 742, the fourth welding point; 81, the first transmission line; 82, the second transmission line; 83, the third transmission line; 84, the fourth transmission line. Detailed implementation manners

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0031] It should be understood that the present invention can be implemented in different forms and should not be construed as limited to the embodiments presented herein. On the contrary, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated. The same reference numerals denote the same elements throughout the drawings.

[0032] It should be understood that when an element or layer is referred to as "on", "adjacent to", "connected to", or "coupled to" another element or layer, it can be directly on, adjacent to, connected or coupled to the other element or layer, or there may be intervening elements or layers. In contrast, when an element is referred to as "directly on", "directly adjacent to", "directly connected to", or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Thus, without departing from the teachings of the present invention, the first element, component, region, layer, or part discussed below may be denoted as the second element, component, region, layer, or part.

[0033] Spatial relationship terms such as "under", "below", "lower", "beneath", "above", "upper", etc. are used herein for convenience in describing the relationship of one element or feature shown in the figures to other elements or features. It should be understood that, in addition to the orientation shown in the figures, spatial relationship terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figures is flipped, then an element or feature described as "under" or "beneath" or "below" other elements or features will be oriented "above" the other elements or features. Thus, the exemplary terms "under" and "below" can include both an upper and a lower orientation. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatial descriptors used herein are to be interpreted accordingly.

[0034] The purpose of the terms used herein is only to describe specific embodiments and is not a limitation of the present invention. As used herein, the singular forms "a", "an", and "the" are also intended to include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. As used herein, the term "and / or" includes any and all combinations of the associated listed items.

[0035] To fully understand the present invention, detailed structures and steps will be presented in the following description to illustrate the technical solutions proposed by the present invention. The preferred embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may have other embodiments.

[0036] This embodiment provides a push-pull power amplifier circuit, such asFigure 1 As shown in the figure, it includes a first power amplifier transistor M1, a second power amplifier transistor M2, a first conversion balun 10, and a first capacitor C11. The first input terminal of the first conversion balun 10 is connected to the output terminal of the first power amplifier transistor M1 through a first inductor L21, and the first input terminal of the first conversion balun 10 is connected to the first terminal of the first capacitor C11 through a second inductor L22. The second input terminal of the first conversion balun 10 is connected to the output terminal of the second power amplifier transistor M2 through a third inductor L31, and the second input terminal of the first conversion balun 10 is connected to the second terminal of the first capacitor C11 through a fourth inductor L32.

[0037] Among them, both the first power amplifier transistor M1 and the second power amplifier transistor M2 can be BJT transistors (for example, HBT transistors) or field effect transistors. Preferably, the first power amplifier transistor M1 and the second power amplifier transistor M2 are BJT transistors. Through the current amplification effect of the transistors, it can be applied to application scenarios with higher power amplification requirements. Specifically, the first input terminal of the first power amplifier transistor M1 in the push-pull power amplifier circuit can input a first differential signal, and the second input terminal of the second power amplifier transistor M2 can input a second differential signal. The first power amplifier transistor M1 amplifies the input first differential signal and outputs a first differential amplified signal. The first power amplifier transistor M1 amplifies the input second differential signal and outputs a second differential amplified signal. The amplification factor of the first differential signal is determined by the amplification factor of the first power amplifier transistor M1, and the amplification factor of the second differential signal is determined by the amplification factor of the second power amplifier transistor M2. The amplification factors of the first differential signal and the second differential signal are the same.

[0038] In a specific embodiment, the push-pull power amplifier circuit usually further includes an input conversion circuit. The input conversion circuit includes an input conversion balun, which is configured to receive an unbalanced radio frequency input signal and convert the unbalanced radio frequency input signal into balanced first and second differential signals. The first differential signal is input to the first input terminal of the first power amplifier transistor M1, and the second differential signal is input to the second input terminal of the second power amplifier transistor M2. The first power amplifier transistor M1 amplifies the received first differential signal, and the second power amplifier transistor M2 amplifies the received second differential signal.

[0039] Among them, the first conversion balun 10 is a device used for radio frequency signal conversion in the push-pull power amplifier circuit, or a device for impedance matching of radio frequency signals in the push-pull power amplifier circuit. In this example, the first conversion balun 10 can be a discrete balun or an integrated balun, and a suitable balun can be selected according to actual needs.

[0040] Specifically, in the related art, a push-pull power amplifier circuit generally accesses a first conversion balun 10 at the output end of a first power amplifier transistor M1 and the output end of a second power amplifier transistor M2, and performs impedance conversion through the first conversion balun 10 to achieve output impedance matching. For example, the output impedance of the push-pull power amplifier circuit needs to satisfy an impedance matching of 50 ohms.

[0041] In a specific embodiment, in the process of performing impedance conversion on the output impedance of the push-pull power amplifier circuit by using the first conversion balun 10 to achieve output impedance matching, if the impedance conversion ratio is too large, for example: it is necessary to convert an impedance of 64 ohms to an impedance of 4 ohms, that is, the impedance conversion ratio is: 16:1. Based on the property that the square of the turns ratio of the balun is equal to the impedance ratio, it is necessary to set the turns ratio of the first conversion balun 10 to 4:1; that is, it is necessary to design the first conversion balun 10 with a larger turns ratio, thereby increasing the cost and occupied area of the first conversion balun 10, which is not conducive to the integrated design of the circuit, and the larger the turns ratio of the first conversion balun 10, the greater the loss in the push-pull power amplifier circuit.

[0042] Therefore, to solve the above problems, in a specific embodiment, the present application connects the first input end of the first conversion balun 10 to the output end of the first power amplifier transistor M1 through a first inductor L21, and connects it to the first end of a first capacitor through a second inductor, and connects the second input end of the first conversion balun 10 to the output end of the second power amplifier transistor through a third inductor, and connects it to the second end of the first capacitor through a fourth inductor; the first inductor, the second inductor and the first capacitor form a first impedance conversion circuit 20, the third inductor, the fourth inductor and the first capacitor form a second impedance conversion circuit 30, and the subsequent first conversion balun jointly participates in the impedance conversion of the push-pull power amplifier circuit, thereby alleviating the impedance conversion pressure of using the first conversion balun 10 alone to perform impedance conversion on the push-pull power amplifier circuit, so that in the case of too large an impedance conversion ratio; the first conversion balun 10 can achieve impedance conversion with fewer turns of the coil, so as to reduce the cost of the first conversion balun 10, and the design of the first conversion balun 10 is also more flexible accordingly.

[0043] In a specific embodiment, for example, it is necessary to convert an impedance of 64 ohms into an impedance of 4 ohms, that is, the impedance conversion ratio of the first conversion balun 10 is 16:1. Based on the property that the square of the turn ratio of the balun is equal to the impedance ratio, in the case where the first inductor, the second inductor, the first capacitor, the third inductor, the fourth inductor, and the first capacitor do not participate in impedance conversion, the turn ratio of the first conversion balun 10 needs to be set to 4:1. In this application, by jointly participating in impedance matching with the first conversion balun 10 by the first inductor, the second inductor, the third inductor, the fourth inductor, and the first capacitor, the first conversion balun 10 can first convert an impedance of 64 ohms into an impedance of 16 ohms, and then the impedance conversion circuit composed of the first inductor, the second inductor, the third inductor, the fourth inductor, and the first capacitor is used to convert the impedance of 16 ohms into an impedance of 4 ohms. It can be seen that at this time, the impedance conversion ratio of the first conversion balun 10 changes from 16:1 to 4:1, and the turn ratio of the first conversion balun 10 only needs to be set to 2:1 accordingly, thereby greatly reducing the number of turns of the coil of the first conversion balun 10, reducing the cost of the first conversion balun 10, and making the design of the first conversion balun 10 more flexible.

[0044] In this embodiment, by connecting the first input end of the first conversion balun 10 to the output end of the first power amplifier tube M1 through the first inductor L21, and connecting the second inductor to the first end of the first capacitor, and connecting the second input end of the first conversion balun 10 to the output end of the second power amplifier tube through the third inductor, and connecting the fourth inductor to the second end of the first capacitor; the first inductor, the second inductor, and the first capacitor form the first impedance conversion circuit 20, the third inductor, the fourth inductor, and the first capacitor form the second impedance conversion circuit 30, and jointly participate in the impedance conversion of the push-pull power amplifier circuit with the subsequent first conversion balun, thereby alleviating the impedance conversion pressure of the push-pull power amplifier circuit when the first conversion balun 10 is used alone for impedance conversion, enabling the first conversion balun 10 to achieve impedance conversion with fewer turns of the coil, and reducing the output loss of the push-pull power amplifier circuit. In addition, since the number of turns of the coil for the first conversion balun 10 to achieve impedance conversion becomes smaller, the layout design of the first conversion balun 10 can be realized on a substrate with fewer layers, thereby reducing the design cost, and making the design of the first conversion balun 10 more flexible.

[0045] As an example, such as Figure 1As shown, the first input terminal of the first conversion balun 10 is connected to the output terminal of the first power amplifier transistor M1 through the first inductor L21, and is also connected to the first terminal of the first capacitor C11 through the second inductor L22. The first inductor L21, the second inductor L22, and the first capacitor C11 form a first impedance conversion circuit 20 through the above connection method. At the same time, the first input terminal of the first conversion balun 10 is connected to the output terminal of the second power amplifier transistor M2 through the third inductor L31, and is also connected to the second terminal of the first capacitor C11 through the fourth inductor L32. The third inductor L31, the fourth inductor L32, and the first capacitor C11 form a second impedance conversion circuit 30 through the above connection method.

[0046] Specifically, in the field of radio frequency technology, both capacitors and inductors will impede the flow of the alternating current corresponding to the radio frequency signal, thereby forming a certain impedance to the radio frequency signal. In this example, through the first impedance conversion circuit 20 formed by the first inductor L21, the second inductor L22, and the first capacitor C11, and the second impedance conversion circuit 30 formed by the third inductor L31, the fourth inductor L32, and the first capacitor C114, by utilizing the characteristic that the first impedance conversion circuit 20 and the second impedance conversion circuit 30 can form a certain impedance to the radio frequency signal, the first impedance conversion circuit 20 and the second impedance conversion circuit 30 can jointly participate in the impedance conversion of the push-pull power amplifier circuit with the first conversion balun, thereby alleviating the impedance conversion pressure of using only the first conversion balun 10 to perform impedance conversion on the push-pull power amplifier circuit. When the impedance conversion ratio is too large, the first conversion balun 10 can achieve impedance conversion with fewer turns of the coil, and the first conversion balun 10 can achieve impedance conversion with fewer turns of the coil, thereby reducing the output loss of the push-pull power amplifier circuit.

[0047] In a specific embodiment, the inductance value of the first inductor L21, the inductance value of the second inductor L22, the capacitance value of the first capacitor C11, the inductance value of the third inductor L31, and the inductance value of the fourth inductor L32 can be determined according to the total impedance conversion ratio for impedance matching of the push-pull power amplifier circuit and the impedance conversion ratio of the first conversion balun 10. So that under the combined action of the first impedance conversion circuit 20 formed by the first inductor, the second inductor, and the first capacitor, the second impedance conversion circuit 30 formed by the third inductor, the fourth inductor, and the first capacitor, and the first conversion balun, the impedance matching of the push-pull power amplifier circuit is achieved.

[0048] In this embodiment, by leveraging the characteristic that the first impedance conversion circuit 20 and the second impedance conversion circuit 30 can form a certain impedance for the radio frequency signal, the first impedance conversion circuit 20 and the second impedance conversion circuit 30 can jointly participate in the impedance conversion of the push-pull power amplifier circuit with the first conversion balun, thereby alleviating the impedance conversion pressure of solely using the first conversion balun 10 for impedance conversion of the push-pull power amplifier circuit. In the case where the impedance conversion ratio is too large, the first conversion balun 10 can achieve impedance conversion with fewer turns of the coil, reducing the cost of the first conversion balun 10, and the design of the first conversion balun 10 becomes more flexible as a result.

[0049] In one embodiment, the turn ratio of the first conversion balun 10 is associated with the first impedance conversion circuit 20 and the second impedance conversion circuit 30.

[0050] As an example, according to the above embodiment, for example, to achieve impedance matching of the push-pull power amplifier circuit, it is necessary to convert an impedance of 64 ohms to an impedance of 4 ohms at the output end, that is, the total impedance conversion ratio is 16:1. In this application, the first impedance conversion circuit 20, the second impedance conversion circuit 30, and the first conversion balun 10 jointly participate in impedance matching. First, the first conversion balun 10 can be used to convert an impedance of 64 ohms to an impedance of 16 ohms, and then the first impedance conversion circuit 20 and the second impedance conversion circuit 30 can be used to convert the impedance of 16 ohms to an impedance of 4 ohms. It can be seen that at this time, under the action of the first impedance conversion circuit 20 and the second impedance conversion circuit 30, the impedance conversion ratio of the first conversion balun 10 changes from the original 16:1 to 4:1, and the turn ratio of the first conversion balun 10 also changes from the original 4:1 to 2:1, thereby greatly reducing the number of turns of the coil of the first conversion balun 10, reducing the cost of the first conversion balun 10, and the design of the first conversion balun 10 becomes more flexible as a result.

[0051] In one embodiment, as Figure 2 shown, the push-pull power amplifier circuit further includes a first LC filter circuit 40 and a second LC filter circuit 50; the first LC filter circuit 40, coupled to the output end of the first power amplifier tube M1, is configured to suppress the even harmonic signals of the push-pull power amplifier circuit; the second LC filter circuit 50, coupled to the output end of the second power amplifier tube M2, is configured to suppress the even harmonic signals of the push-pull power amplifier circuit.

[0052] Specifically, the first LC filter circuit 40 is a circuit formed by connecting an inductor and a capacitor in series. Similarly, the second LC filter circuit 50 is also a circuit formed by connecting an inductor and a capacitor in series. Refer to the following Figure 2As shown, the first LC filter circuit 40 includes a first filter capacitor C41 and a first filter inductor L41 connected in series. Among them, the first end of the first filter capacitor C41 is coupled to the output end of the first power amplifier transistor M1, the second end is connected to the first end of the first filter inductor L41, and the second end of the first filter inductor L41 is connected to the ground terminal. The second LC filter circuit 50 includes a second filter capacitor C51 and a second filter inductor L51 connected in series. Among them, the first end of the second filter capacitor C51 is coupled to the output end of the second power amplifier transistor M2, the second end is connected to the first end of the second filter inductor L51, and the second end of the second filter inductor L51 is connected to the ground terminal.

[0053] In this embodiment, the even harmonic signal can be at least one of any even harmonics such as a second harmonic signal, a fourth harmonic signal, or a sixth harmonic signal. The odd harmonic signal can be at least one of any odd harmonics such as a third harmonic signal, a fifth harmonic signal, or a seventh harmonic signal. It can be understood that the first LC filter circuit 40 and the second LC filter circuit 50 in this embodiment can filter out the second harmonic signal in the push-pull power amplifier circuit, or filter out the fourth harmonic signal in the push-pull power amplifier circuit, or filter out the sixth harmonic signal in the push-pull power amplifier circuit, or filter out any one or any combination of even harmonic signals in the push-pull power amplifier circuit. It should be noted that the even harmonic signals filtered out by the first LC filter circuit 40 and the even harmonic signals filtered out by the second LC filter circuit 50 can be the same or different. For example: the first LC filter circuit 40 filters out the second harmonic signal in the push-pull power amplifier circuit, and the second LC filter circuit 50 filters out the fourth harmonic signal in the push-pull power amplifier circuit; or, the first LC filter circuit 40 filters out the second harmonic signal in the push-pull power amplifier circuit, and the second LC filter circuit 50 filters out the second harmonic signal in the push-pull power amplifier circuit.

[0054] Specifically, due to the influence of some non-linear elements (such as: amplifier transistors) in the push-pull power amplifier circuit, harmonic signals are generated in the push-pull power amplifier circuit, which affects the overall performance of the push-pull power amplifier circuit. In this example, the first differential amplification signal amplified by the first power amplifier transistor M1 and the second differential amplification signal amplified by the second power amplifier transistor M2 are mixed with harmonic signals that need to be filtered out. Therefore, by coupling the first LC filter circuit 40 to the output end of the first power amplifier transistor M1, and at the same time, coupling the second LC filter circuit 50 to the output end of the second power amplifier transistor M2, the even harmonic signals are filtered to the ground through the resonance of the first LC filter circuit 40 and the second LC filter circuit 50, realizing the filtering of the even harmonic signals in the push-pull power amplifier circuit.

[0055] In the actual application scenario of the push - pull power amplifier circuit, the second - harmonic signal has a relatively large impact on the linearity and stability of the push - pull power amplifier circuit. Therefore, the main functions of the first LC filter circuit 40 and the second LC filter circuit 50 in this embodiment are to filter out the second - harmonic signal. For example, the resonance frequency points of the first LC filter circuit 40 and the second LC filter circuit 50 can be set to the resonance frequency points corresponding to the second - harmonic signal, so as to filter the even - harmonic signals in the push - pull power amplifier circuit to ground and improve the harmonic performance of the push - pull power amplifier circuit.

[0056] In this embodiment, the first LC filter circuit 40 is coupled to the output terminal of the first power amplifier tube M1, and at the same time, the second LC filter circuit 50 is coupled to the output terminal of the second power amplifier tube M2. Through the resonance effect of the first LC filter circuit 40 and the second LC filter circuit 50 with the even - harmonic signal, the even - harmonic signal is filtered to ground, realizing the filtering of the even - harmonic signals in the push - pull power amplifier circuit.

[0057] In one embodiment, the first LC filter circuit 40 is configured to form a first resonance frequency point, and the second LC filter circuit 50 is configured to form a second resonance frequency point.

[0058] Among them, the first resonance frequency point is the resonance frequency point formed by the first filter capacitor C41 and the first filter inductor L41 in the first LC filter circuit 40. The first resonance frequency point mainly depends on the capacitance value of the first filter capacitor C41 and the inductance value of the first filter inductor L41. The second resonance frequency point is the resonance frequency point formed by the second filter capacitor C51 and the second filter inductor L51 in the second LC filter circuit 50. The second resonance frequency point mainly depends on the capacitance value of the second filter capacitor C51 and the inductance value of the second filter inductor L51. In this embodiment, the first resonance frequency point and the second resonance frequency point can be the same or different. If the capacitance value of the first filter capacitor C41 and the inductance value of the first filter inductor L41 are the same as the capacitance value of the second filter capacitor C51 and the inductance value of the second filter inductor L51, the formed first resonance frequency point and second resonance frequency point are the same; if the capacitance value of one capacitor and the inductance value of the first filter inductor L41 are different from the capacitance value of the second filter capacitor C51 and the inductance value of the second filter inductor L51, the formed first resonance frequency point and second resonance frequency point are different.

[0059] In this embodiment, since the first LC filter circuit 40 and the second LC filter circuit 50 are mainly used for harmonic suppression of the even - harmonic signals of the push - pull power amplifier circuit, the first resonance frequency point and the second resonance frequency point formed by them both belong to the frequency points corresponding to the even - harmonic signals.

[0060] In a specific embodiment, if the frequency point corresponding to the second harmonic signal is known as 2f0 and the frequency point corresponding to the fourth harmonic signal is 4f0, then in order to achieve harmonic suppression of the second harmonic signal and the fourth harmonic signal, according to the calculation formula of the resonance frequency: , reasonably set the inductance value of the first filter inductor L41 and the capacitance value of the first filter capacitor C41 in the first LC filter circuit 40, so that the first resonance frequency point formed by the first filter inductor L41 and the first filter capacitor C41 is the same as the frequency point 2f0 corresponding to the second harmonic signal, and reasonably set the inductance value of the second filter inductor L51 and the capacitance value of the second filter capacitor C51 in the second LC filter circuit 50, so that the second resonance frequency point formed by the second filter inductor L51 and the second filter capacitor C51 is the same as the frequency point 4f0 corresponding to the fourth harmonic signal, thereby achieving harmonic suppression of the second harmonic signal and the fourth harmonic signal of the push-pull power amplifier circuit.

[0061] In another specific embodiment, if it is found that the second harmonic signal has a greater impact on the push-pull power amplifier circuit and the impact of other even harmonic signals on the push-pull power amplifier circuit is very small and can almost be ignored, then the inductance value of the first filter inductor L41 and the capacitance value of the first filter capacitor C41 in the first LC filter circuit 40 can be reasonably set so that the first resonance frequency point formed by the first filter inductor L41 and the first filter capacitor C41 is the same as the frequency point 2f0 corresponding to the second harmonic signal, and the inductance value of the second filter inductor L51 and the capacitance value of the second filter capacitor C51 in the second LC filter circuit 50 can be reasonably set so that the second resonance frequency point formed by the second filter inductor L51 and the second filter capacitor C51 is also the same as the frequency point 2f0 corresponding to the second harmonic signal. The second harmonic signal of the push-pull power amplifier circuit is subjected to harmonic suppression through the first LC filter circuit 40 and the second LC filter circuit 50, thereby enhancing the effect of harmonic suppression of the second harmonic signal.

[0062] In this embodiment, the first LC filter circuit 40 is configured to form a first resonance frequency point, and the second LC filter circuit 50 is configured to form a second resonance frequency point. In this example, the first resonance frequency point and the second resonance frequency point may be different or the same. When the first resonance frequency point and the second resonance frequency point are different, even harmonic signals with different frequencies in the push-pull power amplifier circuit can be filtered out, thereby achieving even harmonic suppression in a wider frequency band range.

[0063] In one embodiment, as Figure 3As shown, the push-pull power amplifier circuit further includes a third LC filter circuit 60 and a fourth LC filter circuit 70; the third LC filter circuit 60 is coupled to the output terminal of the first power amplifier tube M1 and is configured to form a third resonance frequency point; the fourth LC filter circuit 70 is coupled to the output terminal of the second power amplifier tube M2 and is configured to form a fourth resonance frequency point.

[0064] Specifically, the third LC filter circuit 60 includes a third filter capacitor C61 and a third filter inductor L61 connected in series. Among them, the first end of the third filter capacitor C61 is coupled to the output terminal of the first power amplifier tube M1, the second end is connected to the first end of the third filter inductor L61, and the second end of the third filter inductor L61 is connected to the ground terminal. The fourth LC filter circuit 70 includes a fourth filter capacitor C71 and a fourth filter inductor L71 connected in series. Among them, the first end of the fourth filter capacitor C71 is coupled to the output terminal of the second power amplifier tube M2, the second end is connected to the first end of the fourth filter inductor L71, and the second end of the fourth filter inductor L71 is connected to the ground terminal.

[0065] Similarly, by reasonably setting the capacitance value of the third filter capacitor C61 and the inductance value of the third filter inductor L61 in the third LC filter circuit 60, and the capacitance value of the fourth filter capacitor C71 and the inductance value of the fourth filter inductor L71 in the fourth LC filter circuit 70, a third resonance frequency point and a fourth resonance frequency point can be formed to suppress the even harmonics in the push-pull power amplifier circuit.

[0066] In this embodiment, in order to further suppress even harmonics in a wider frequency band range, in this example, the third LC filter circuit 60 is coupled to the output terminal of the first power amplifier tube M1 and is configured to form a third resonance frequency point, and the fourth LC filter circuit 70 is coupled to the output terminal of the second power amplifier tube M2 and is configured to form a fourth resonance frequency point. Similarly, the third resonance frequency point and the fourth resonance frequency point can be the same or different. In this embodiment, the principle of harmonic suppression of the third LC filter circuit 60 and the fourth LC filter circuit 70 is the same as that of the above-mentioned first LC filter circuit 40 and second LC filter circuit 50, and will not be redundantly described here.

[0067] In a specific embodiment, if the first resonance frequency point, the second resonance frequency point, the third resonance frequency point, and the fourth resonance frequency point are all different; then under the combined action of the first LC filter circuit 40, the second LC filter circuit 50, the third LC filter circuit 60, and the fourth LC filter circuit 70, harmonic suppression of four different frequency even harmonic signals in the push-pull power amplifier circuit can be achieved, thereby realizing even harmonic suppression in a wider frequency band range.

[0068] In another specific embodiment, if the first resonance frequency point is the same as the second resonance frequency point, and the third resonance frequency point is the same as the fourth resonance frequency point, but the first resonance frequency point and the second resonance frequency point are different from the third resonance frequency point and the fourth resonance frequency point, then under the combined action of the first LC filter circuit 40, the second LC filter circuit 50, the third LC filter circuit 60, and the fourth LC filter circuit 70, the harmonic suppression of the even harmonic signals of two different frequencies in the push-pull power amplifier circuit can be achieved. Thus, while ensuring the effect of harmonic suppression, the suppression of even harmonics can also be achieved in a wider frequency band range.

[0069] It should be noted that, without considering the cost and the occupied area of the push-pull power amplifier circuit, in order to achieve the suppression of even harmonics in a wider frequency band range, multiple LC filter circuits can also be connected to the output terminals of the first power amplifier tube M1 and the second power amplifier tube M2 to form multiple different resonance frequency points, so as to achieve the suppression of harmonics in a wider frequency band range and enhance the effect of harmonic suppression.

[0070] This embodiment provides a radio frequency front-end module, as Figure 4 shown, which includes a substrate, a push-pull power amplifier chip, a first conversion balun 10, a first pad 71, and a second pad 72 disposed on the substrate; the first input terminal of the first conversion balun 10 is connected to the first pad 71, and the second input terminal is connected to the second pad 72; on the push-pull power amplifier chip, there are a first power amplifier tube M1, a second power amplifier tube M2, a first capacitor C11, a third pad 73, and a fourth pad 74. The third pad 73 includes a first welding point 731 and a second welding point 732 that are separately arranged, and the fourth pad 74 includes a third welding point 741 and a fourth welding point 742 that are separately arranged; the output terminal of the first power amplifier tube M1 is connected to the first welding point 731, and the output terminal of the second power amplifier tube M2 is connected to the fourth welding point 742; one end of the first capacitor C11 is connected to the second welding point 732, and the other end is connected to the third welding point 741; the first pad 71 is connected to the first welding point 731 through a first transmission line 81 and to the second welding point 732 through a second transmission line 82. The second pad 72 is connected to the third welding point 741 through a third transmission line 83 and to the fourth welding point 742 through a fourth transmission line 84.

[0071] In a specific embodiment, when the push-pull power amplifier chip disposed on the substrate is connected to the first conversion balun 10 disposed on the substrate, since a transmission line (such as a bonding wire) is required for the connection, usually two pads connected to the output end of the first power amplifier transistor M1 and the output end of the second power amplifier transistor M2 are provided on the push-pull power amplifier chip, and two pads connected to the first input end and the second input end of the first conversion balun 10 are provided on the substrate; then the pad connected to the output end of the first power amplifier transistor M1 and the pad connected to the first input end of the first conversion balun 10 are connected by the first transmission line 81, and the pad connected to the output end of the second power amplifier transistor M2 and the pad connected to the second input end of the first conversion balun 10 are connected by the second transmission line 82. It can be seen that in practical applications, the functions of the first transmission line 81 and the second transmission line 82 are only used for the connection of pads (ports), and since the transmission line is substantially equivalent to an inductor in practical applications, therefore, in order to avoid the problem of increased transmission loss caused by the transmission line, it is necessary to ensure that the first transmission line 81 and the second transmission line 82 cannot be too long. If the length of the transmission line is too long, the problem of increased transmission loss will occur.

[0072] In view of the above problems, the radio frequency front-end module of the present application improves the structure of the pads on the push-pull power amplifier chip connected to the first conversion balun 10. Specifically, the pads on the push-pull power amplifier chip connected to the first conversion balun 10 are separated into two welding points. Specifically, refer to the following Figure 4As shown, the third pad 73 disposed on the push-pull power amplifier chip includes a separately disposed first welding point 731 and a second welding point 732, and the fourth pad 74 includes a separately disposed third welding point 741 and a fourth welding point 742; the output end of the first power amplifier tube is connected to the first welding point 731, and the output end of the second power amplifier tube is connected to the fourth welding point 742; one end of the first capacitor C11 is connected to the second welding point 732, and the other end is connected to the third welding point 741; the first input end of the first conversion balun 10 disposed on the substrate is connected to the first pad 71, and the second input end is connected to the second pad 72; the first pad 71 is connected to the first welding point 731 through the first transmission line 81 and to the second welding point 732 through the second transmission line 82, and the second pad 72 is connected to the third welding point 741 through the third transmission line 83 and to the fourth welding point 742 through the fourth transmission line 84. Due to the manufacturing process of the transmission line, the transmission line can generally be equivalent to an inductor. Therefore, a first impedance conversion circuit 20 can be formed between the first transmission line 81, the second transmission line 82 and the first capacitor C11, and a second impedance conversion circuit 30 can be formed between the third transmission line 83, the fourth transmission line 84 and the first capacitor C11, thereby not only solving the problem of increased transmission loss caused by the transmission line during the RF signal transmission process, but also enabling the first impedance conversion circuit 20 and the second impedance conversion circuit 30 formed thereby to participate in the impedance conversion of the push-pull power amplifier circuit together with the first conversion balun, thus alleviating the impedance conversion pressure of using only the first conversion balun 10 for impedance conversion of the push-pull power amplifier circuit, so that in the case of an excessive impedance conversion ratio; the first conversion balun 10 can achieve impedance conversion with fewer turns of the coil, so as to reduce the cost of the first conversion balun 10, and the design of the first conversion balun 10 is also more flexible accordingly.

[0073] In another specific embodiment, the first welding point 731 and the second welding point 732 can also be separately disposed on two different and separately disposed pads (for example: the third pad 73 and the fifth pad). Similarly, the third welding point 741 and the fourth welding point 742 can also be separately disposed on two different and separately disposed pads (for example: the fourth pad 74 and the sixth pad), so that the first pad 71 connected to the first conversion balun 10 is connected to the first welding point 731 on the third pad 73 through the first transmission line 81 and to the second welding point 732 on the fifth pad through the second transmission line 82; the second pad 72 connected to the first conversion balun 10 is connected to the third welding point 741 on the fourth pad 74 through the third transmission line 83 and to the fourth welding point 742 on the sixth pad through the fourth transmission line 84.

[0074] In this embodiment, by setting the third pad 73 disposed on the push-pull power amplifier chip to include a first welding point 731 and a second welding point 732 that are separately disposed, and setting the fourth pad 74 to include a third welding point 741 and a fourth welding point 742 that are separately disposed; and by utilizing the equivalent inductances of the first transmission line 81, the second transmission line 82, the third transmission line 83, and the fourth transmission line 84, the first transmission line 81 and the second transmission line 82 form a first impedance conversion circuit 20 with the first capacitor C11, and the third transmission line 83 and the fourth transmission line 84 form a second impedance conversion circuit 30 with the first capacitor C11. This not only solves the problem of increased transmission loss caused by the transmission line during the RF signal transmission process, but also the formed first impedance conversion circuit 20 and second impedance conversion circuit 30 can participate in the impedance conversion of the push-pull power amplification circuit together with the first conversion balun; thus alleviating the impedance conversion pressure of using only the first conversion balun 10 to perform impedance conversion on the push-pull power amplification circuit, such that in the case of an excessive impedance conversion ratio; the first conversion balun 10 can achieve impedance conversion with fewer turns of the coil, so as to reduce the cost of the first conversion balun 10, and the design of the first conversion balun 10 is thus more flexible.

[0075] In one embodiment, it further includes a feeding power supply disposed on the substrate, and the feeding power supply is coupled to the output end of the first power amplifying transistor M1 through a first feeding inductor, and the feeding power supply is coupled to the output end of the second power amplifying transistor M2 through a second feeding inductor.

[0076] As an example, the RF front-end module further includes a feeding power supply disposed on the substrate. In this example, the feeding power supply is coupled to the output end of the first power amplifying transistor M1 through a first feeding inductor L91, and the feeding power supply is coupled to the output end of the second power amplifying transistor M2 through a second feeding inductor L92, and is configured to feed the first power amplifying transistor M1 and the second power amplifying transistor M2. It should be noted that since the occupied areas of the first feeding inductor L91 and the second feeding inductor L92 are often very large, the first feeding inductor L91 and the second feeding inductor L92 are disposed outside the push-pull power amplifier chip on the substrate, that is, the first feeding inductor L91 and the second feeding inductor L92 are disposed on the substrate, thereby reducing the area of the push-pull power amplifier chip and reducing the manufacturing cost of the push-pull power amplifier chip.

[0077] In this embodiment, the RF front-end module further includes a feeding power supply disposed on the substrate. The feeding power supply is coupled to the output end of the first power amplifying transistor M1 through a first feeding inductor L91, and the feeding power supply is coupled to the output end of the second power amplifying transistor M2 through a second feeding inductor L92, and is configured to feed the first power amplifying transistor M1 and the second power amplifying transistor M2 to ensure the normal operation of the push-pull power amplifier chip.

[0078] In another specific embodiment, the first feeding inductor L91 and the second feeding inductor L92 can also be replaced by transmission lines. Since in chip or circuit board design, the area occupied by transmission lines is much smaller than that occupied by inductors, which is beneficial to meeting the requirements of the integration of the RF front-end module. Moreover, replacing the first feeding inductor L91 and the second feeding inductor L92 with transmission lines can effectively avoid the problem of the deterioration of the load line insertion loss caused by the first feeding inductor L91 and the second feeding inductor L92, and can effectively reduce the insertion loss, thereby ensuring the overall power conversion efficiency and output power of the push-pull power amplifier circuit.

[0079] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention 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 recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A push-pull power amplifier circuit, characterized in that, It includes a first power amplifier tube, a second power amplifier tube, a first conversion balun, and a first capacitor; a first input end of the first conversion balun is connected to an output end of the first power amplifier tube through a first inductor, and the first input end of the first conversion balun is connected to a first end of the first capacitor through a second inductor; a second input end of the first conversion balun is connected to an output end of the second power amplifier tube through a third inductor, and the second input end of the first conversion balun is connected to a second end of the first capacitor through a fourth inductor; The first inductor, the second inductor, and the first capacitor form a first impedance conversion circuit, the third inductor, the fourth inductor, and the first capacitor form a second impedance conversion circuit, and the first impedance conversion circuit and the second impedance conversion circuit are configured to jointly participate in impedance conversion of a push-pull power amplifier circuit with a subsequent first conversion balun.

2. The push-pull power amplifier circuit according to claim 1, characterized in that A turns ratio of the first conversion balun is associated with the first impedance conversion circuit and the second impedance conversion circuit.

3. The push-pull power amplifier circuit according to claim 1, characterized in that The push-pull power amplifier circuit further includes a first LC filter circuit and a second LC filter circuit; The first LC filter circuit, coupled to the output end of the first power amplifier tube, is configured to suppress harmonic signals of even harmonics of the push-pull power amplifier circuit; The second LC filter circuit, coupled to the output end of the second power amplifier tube, is configured to suppress harmonic signals of even harmonics of the push-pull power amplifier circuit.

4. The push-pull power amplifier circuit according to claim 3, characterized in that, The first LC filter circuit is configured to form a first resonance frequency point, and the second LC filter circuit is configured to form a second resonance frequency point.

5. The push-pull power amplifier circuit according to claim 4, wherein The first resonance frequency point and the second resonance frequency point are different.

6. The push-pull power amplifier circuit according to claim 3, wherein The push-pull power amplifier circuit further includes a third LC filter circuit and a fourth LC filter circuit; The third LC filter circuit, coupled to the output end of the first power amplifier tube, is configured to form a third resonance frequency point; The fourth LC filter circuit, coupled to the output end of the second power amplifier tube, is configured to form a fourth resonance frequency point.

7. The push-pull power amplifier circuit according to claim 6, wherein, The third resonance frequency point and the fourth resonance frequency point are different.

8. The push-pull power amplifier circuit according to claim 3, wherein The first LC filter circuit includes a first capacitor and a first inductor connected in series, one end of the first capacitor is coupled to the output end of the first power amplifier tube, the other end is connected to a first end of the first inductor, and a second end of the first inductor is connected to a ground terminal; The second LC filter circuit includes a second capacitor and a second inductor connected in series, one end of the second capacitor is coupled to the output end of the second power amplifier tube, the other end is connected to a first end of the second inductor, and a second end of the second inductor is connected to a ground terminal.

9. A radio frequency front-end module, characterized in that, It includes a substrate, a push-pull power amplifier chip, a first conversion balun, a first pad, and a second pad disposed on the substrate; a first input end of the first conversion balun is connected to the first pad, and a second input end is connected to the second pad; on the push-pull power amplifier chip, there are a first power amplifier tube, a second power amplifier tube, a first capacitor, a third pad, and a fourth pad, the third pad includes a separately arranged first welding point and a second welding point, and the fourth pad includes a separately arranged third welding point and a fourth welding point; an output end of the first power amplifier tube is connected to the first welding point, and an output end of the second power amplifier tube is connected to the fourth welding point; one end of the first capacitor is connected to the second welding point, and the other end is connected to the third welding point; The first pad is connected to the first welding point through a first transmission line and to the second welding point through a second transmission line, and the second pad is connected to the third welding point through a third transmission line and to the fourth welding point through a fourth transmission line.

10. The RF front-end module according to claim 9, wherein It further includes a feeding power supply disposed on the substrate, and the feeding power supply is coupled to an output end of the first power amplifier tube through a first feeding inductor, and the feeding power supply is coupled to an output end of the second power amplifier tube through a second feeding inductor.

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