Doherty radio frequency power amplifier

Abstract

The invention provides a Doherty radio frequency power amplifier suitable for a mobile terminal, which comprises an input quadrature coupler for outputting two paths of quadrature radio frequency signals, a first input balun for receiving a first path of output and converting the first path of output into a differential signal to be provided for a main path amplifier; the second input balun is used for receiving the second path of output and converting the second path of output into a differential signal to be provided for the auxiliary path amplifier; the main amplification circuit is used for amplifying the two paths of differential radio frequency signals and providing the two paths of differential radio frequency signals to the quarter-wavelength converter; the quarter-wavelength converter is used for performing phase compensation on the differential amplification signal; the auxiliary amplifying circuit is used for amplifying the differential radio-frequency signal and combining the differential radio-frequency signal with the differential output of the main amplifying circuit, two signals in the same phase in the differential output of the main amplifying circuit and the auxiliary amplifying circuit are respectively combined to form an input balun module and an output balun module of the output balun module, and the output balun module is used for outputting the differential radio-frequency signal. The circuit comprises an output balun and a variable capacitor network.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency integrated circuits, and in particular to a Doherty radio frequency power amplifier circuit used in a mobile terminal. Background Art

[0002] In 5G communication systems (such as mobile phones or other user devices), RF power amplifiers are key modules and the main power consumption unit modules. In order to improve spectrum utilization and increase communication speed, more and more complex modulation methods such as Orthogonal Frequency Division Multiplexing (OFDM) are adopted by 5G communication systems, and their RF signal peak-to-average ratio (PAR) reaches 7dB to 9dB. When the power amplifier is amplifying power, in order to take into account the linearity of the power amplifier, the RF power amplifier is usually backed off. The larger the RF signal peak-to-average ratio (PAR), the more the RF power amplifier backs off in order to ensure the linearity of the amplified signal, and the correspondingly lower efficiency, resulting in reduced efficiency of the entire wireless communication system, excessive battery consumption of mobile devices, and shortened standby time.

[0003] At present, the solutions for improving the efficiency of power amplifiers in academia and industry are mainly divided into two categories: power supply modulation and load modulation. Power supply modulation is power envelope tracking (ET). Envelope tracking has relatively high requirements on the power supply system. The power supply voltage dynamically follows the changes in the RF signal envelope, which makes envelope tracking more complicated for the system. Compared with envelope tracking (ET), the Doherty structure power amplifier is a load modulation technology. It changes the load impedance at different output power levels through the cooperation of the main amplifier and the auxiliary amplifier. At high power, the impedance is relatively small and has a relatively large power output capacity. At low power, the impedance becomes larger to achieve high efficiency. That is, the Doherty power amplifier can effectively improve the back-off efficiency of the power amplifier and improve the average efficiency of the power amplifier. Doherty power amplifiers are widely used in base stations, and cooperate with the digital pre-distortion (DPD) system to achieve high power, high efficiency and high linearity. In most cases, the Doherty amplifiers used in base stations are built with discrete devices, and the entire power amplifier occupies a large volume.

[0004] With the arrival of 5G, the data transmission speed of the communication system will be further improved, and the peak-to-average ratio of 5G radio frequency signals will be further improved. The efficiency of traditional Class-AB power amplifier circuits is increasingly unable to meet the needs of mobile terminals, and mobile terminals have an increasingly strong demand for high-efficiency and high-linearity power amplifiers. Figure 1 FIG. 1 shows the structure of a conventional Doherty power amplifier. Figure 1 The input network uses a power divider to achieve power distribution, and a quarter-wavelength line is connected in series with the auxiliary path amplification circuit input path to achieve a 90° phase delay. The traditional Doherty power amplifier is difficult to integrate and miniaturize because the quarter-wavelength line is difficult to integrate. The traditional power divider plus quarter-wavelength line solution has the disadvantages of large space occupation, narrow bandwidth and difficulty in integration.

[0005] In addition, compared with the 3G / 4G standard, the 5G standard signal has a higher peak-to-average ratio, and the mobile terminal requires a higher transmission power and a wider signal bandwidth. In order to improve the efficiency of 5G power amplifiers, Doherty structure power amplifiers are gradually being adopted by 5G mobile terminals. Compared with traditional structure power amplifiers, the bandwidth of traditional Doherty power amplifiers is relatively narrow. The frequency range of the n77 band is 3.3GHz to 4.2GHz, such as Figure 1 The conventional Doherty structure power amplifier used in the mobile terminal shown in the figure cannot fully cover the entire bandwidth range of 3.3GHz to 4.2GHz in the n77 frequency band. At different frequencies, the efficiency of the conventional Doherty structure power amplifier varies greatly, and the advantage of high efficiency of the Doherty structure cannot be fully reflected.

[0006] Therefore, a Doherty power amplifier with a small footprint and a wide frequency range is desired. Summary of the invention

[0007] The technical solution of the present invention adopts a transformer-based input orthogonal coupler to replace the power divider and 90° delay line of the traditional structure. The transformer-based input balun realizes single-ended differential conversion, so that the main path and the auxiliary path both adopt a fully differential structure, and the output network adopts a balun combined with a variable capacitor network to realize impedance transformation and power synthesis. It can achieve high linearity, high efficiency and high output power in the entire bandwidth of the n77 frequency band.

[0008] The technical solution of the present invention has a compact structure, is easy to integrate, and occupies a small volume; in addition, it can achieve high-linearity signal output without the assistance of digital pre-distortion, and is suitable for use in mobile terminal devices.

[0009] One aspect of the present invention provides a Doherty RF power amplifier, comprising: an input orthogonal coupler, which is configured to receive a single-ended RF input and output two orthogonal RF signals, a first input balun, which is configured to receive the orthogonal RF signal of the input orthogonal coupler, and transform the orthogonal RF signal into a differential main signal to provide to a main amplifier; a second input balun, which is configured to receive a second orthogonal RF signal of the input orthogonal coupler, and transform the second orthogonal RF signal into a differential auxiliary signal to provide to the auxiliary amplifier; a main amplifier circuit, which is configured to amplify the differential main signal output by the first input balun, and provide the amplified differential main signal to a quarter-wavelength converter; a quarter-wavelength converter, which It is configured to perform phase compensation on the differential main signal output from the main amplifier circuit; the auxiliary amplifier circuit is configured to amplify the differential auxiliary signal output by the second input balun, and combine the amplified differential auxiliary signal with the amplified differential main signal after phase compensation, wherein two in-phase signals of the amplified differential main signal and the amplified differential auxiliary signal are respectively combined to form a combined differential signal used as an input of the output balun module, the output balun module includes an output balun and a variable capacitor network, the output balun is used to receive the combined differential signal and generate a single-ended RF output signal, and the variable capacitor network is used to adjust the output impedance of the Doherty RF power amplifier at different frequencies and expand the bandwidth of the Doherty RF power amplifier.

[0010] One aspect of the present invention provides a Doherty RF power amplifier, wherein an input orthogonal coupler comprises: an input transformer including a first winding and a second winding, an input capacitor and an input resistor, wherein the first winding is connected between a single-ended RF input and one input end of a first input balun, the input capacitor is connected between the single-ended RF input and one input end of a second input balun, one end of the second winding is connected between the input capacitor and the one input end of the second input balun, and the other end of the second winding is grounded through the input resistor.

[0011] One aspect of the present invention provides a Doherty RF power amplifier, wherein the main path amplifier circuit includes a first-stage main path amplifier, a second-stage main path amplifier and a first-stage inter-stage matching circuit, and wherein the auxiliary path amplifier circuit includes a first-stage auxiliary path amplifier, a second-stage auxiliary path amplifier and a second-stage inter-stage matching circuit.

[0012] One aspect of the present invention provides a Doherty radio frequency power amplifier, wherein the first interstage matching circuit of the main amplifier circuit includes a first interstage matching transformer, and the second interstage matching circuit of the auxiliary amplifier circuit includes a second interstage matching transformer.

[0013] One aspect of the present invention provides a Doherty RF power amplifier, wherein the quarter-wavelength converter is implemented by two π-type LC networks formed by a capacitor and an inductor, which are configured to perform 90° phase compensation on the differential output signals of the main amplifier circuit respectively, and simultaneously realize impedance modulation at different power outputs.

[0014] An aspect of the present invention provides a Doherty RF power amplifier, wherein a first-stage main path amplifier of the main path amplifier circuit includes a fully differential amplifier consisting of a first transistor and a second transistor and a first capacitor and a second capacitor, wherein the first transistor is used to receive a first input and output a first output, the second transistor is used to receive a second input and output a second output, and the first capacitor is connected between the first input and the second output, and the second capacitor is connected between the second input and the first output; and wherein a first-stage auxiliary path amplifier of the auxiliary path amplifier circuit includes a fully differential amplifier consisting of a third transistor and a fourth transistor and a third capacitor and a fourth capacitor, wherein the third transistor is used to receive a third input and output a third output, the fourth transistor is used to receive a fourth input and output a fourth output, and the third capacitor is connected between the third input and the fourth output, and the fourth capacitor is connected between the fourth input and the third output.

[0015] One aspect of the present invention provides a Doherty radio frequency power amplifier, wherein the main amplifier circuit and the auxiliary amplifier circuit are formed by at least one of a BJT transistor, a FET transistor, and a MOS transistor.

[0016] One aspect of the present invention provides a Doherty radio frequency power amplifier, wherein the output balun includes an input winding and an output winding, the input winding includes two input ends, and the output winding includes two output ends.

[0017] One aspect of the present invention provides a Doherty radio frequency power amplifier, wherein the variable capacitor network includes a first variable capacitor connected between two input terminals of an output balun.

[0018] One aspect of the present invention provides a Doherty RF power amplifier, wherein the variable capacitor network includes a fifth capacitor connected between an output terminal of the output balun and a RF output of the Doherty RF power amplifier.

[0019] One aspect of the present invention provides a Doherty RF power amplifier, wherein the variable capacitor network includes a second variable capacitor, one end of the second variable capacitor is connected between a fifth capacitor and the RF output, and the other end of the second variable capacitor is grounded.

[0020] One aspect of the present invention provides a Doherty radio frequency power amplifier, wherein the variable capacitor network includes a third variable capacitor connected between another output terminal of the output balun and the ground.

[0021] One aspect of the present invention provides a Doherty RF power amplifier, wherein the variable capacitor network includes a fourth variable capacitor, one end of the fourth variable capacitor is grounded, and the other end of the fourth variable capacitor is connected to the input winding of the output balun and the power supply terminal.

[0022] One aspect of the present invention provides a Doherty RF power amplifier, wherein a variable capacitor network includes a variable capacitor, the variable capacitor includes a plurality of capacitors connected in parallel, at least one of the plurality of capacitors connected in parallel can be disconnected or connected by a capacitor switch, wherein the Doherty RF power amplifier also includes a control unit, and the capacitor switch is controlled by the control unit to be disconnected or connected according to different operating frequencies.

[0023] One aspect of the present invention provides a Doherty RF power amplifier, further comprising a filter connected between a fifth capacitor and the RF output and a switch module for changing the capacitance value of a variable capacitor network, wherein the filter and the switch module are connected in series.

[0024] An aspect of the present invention provides a Doherty radio frequency power amplifier, wherein the input transformer is formed by a rectangular pattern of two layers of metal structure.

[0025] One aspect of the present invention provides a Doherty radio frequency power amplifier, wherein the output balun is formed by a pattern of a three-layer metal structure.

[0026] One aspect of the present invention provides a Doherty radio frequency power amplifier, wherein the inductor in the quarter-wave transformer is formed by a combination of a bonding wire and a substrate microstrip line.

[0027] One aspect of the present invention provides a Doherty radio frequency power amplifier, wherein the Doherty radio frequency power amplifier including the capacitor switch and the control unit is packaged by a multi-layer substrate package for multiple chips. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram showing a conventional Doherty power amplifier structure;

[0029] Figure 2 is a schematic diagram showing a Doherty radio frequency power amplifier according to an embodiment of the present invention;

[0030] Figure 3is a schematic diagram showing a Doherty radio frequency power amplifier according to an embodiment of the present invention;

[0031] Figure 4 is a circuit diagram showing a Doherty radio frequency power amplifier according to an embodiment of the present invention;

[0032] Figure 5 is a circuit diagram showing a variable capacitor according to an embodiment of the present invention;

[0033] Figure 6 is a circuit diagram showing a Doherty radio frequency power amplifier according to an embodiment of the present invention;

[0034] Figure 7 is a schematic diagram showing the relationship between the output power and the power-added efficiency (PAE) curve of the Doherty RF power amplifier according to an embodiment of the present invention and the traditional Class AB power amplifier;

[0035] Figure 8A-8C is a schematic diagram showing an implementation of an output balun according to an embodiment of the present invention;

[0036] Figure 9A-9C is a schematic diagram showing an implementation of a transformer T1 in an orthogonal coupler according to an embodiment of the present invention;

[0037] Fig.10 is a phase-frequency diagram showing an input quadrature coupler according to an embodiment of the present invention;

[0038] Fig.11 is a schematic diagram showing an implementation method of an inductor of a quarter-wavelength transformer in a Doherty radio frequency power amplifier according to an embodiment of the present invention;

[0039] Fig.12 is a plan view showing a multi-chip package of a Doherty radio frequency power amplifier according to an embodiment of the present invention; and

[0040] Fig.13 is a side view showing a multi-chip package of a Doherty RF power amplifier according to an embodiment of the present invention. DETAILED DESCRIPTION

[0041] Before proceeding to the following detailed description, it may be advantageous to set forth the definitions of certain words and phrases used throughout this patent document. The terms "coupling", "connection" and their derivatives refer to any direct or indirect communication or connection between two or more elements, regardless of whether those elements are in physical contact with each other. The terms "transmission", "reception" and "communication" and their derivatives cover direct and indirect communication. The terms "include" and "comprising" and their derivatives refer to including but not limited to. The term "or" is inclusive, meaning and / or. The phrase "associated with..." and its derivatives refer to including, including within, interconnecting, containing, contained within, connecting or connecting with, coupling or coupling with, communicating with, cooperating, interweaving, parallel, close to, binding or binding with, having, having attributes, having a relationship or having a relationship with, etc. The term "controller" refers to any device, system or part thereof that controls at least one operation. Such a controller can be implemented with hardware, or a combination of hardware and software and / or firmware. The functions associated with any particular controller can be centralized or distributed, whether local or remote. The phrase "at least one of", when used with a list of items, means that different combinations of one or more of the listed items may be used, and only one of the items in the list may be required. For example, "at least one of A, B, C" includes any of the following combinations: A, B, C, A and B, A and C, B and C, A and B and C.

[0042] Definitions for other specific words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior and future uses of such defined words and phrases.

[0043] In this patent document, the application combination of modules and the division level of sub-modules are only used for illustration, and the application combination of modules and the division level of sub-modules may have different forms without departing from the scope of the present disclosure.

[0044] The Doherty RF power amplifier according to the embodiment of the present invention adopts a transformer-based orthogonalizer to replace the power divider and 90° delay line of the traditional structure, so it is easier to integrate and has a relatively wide bandwidth. In addition, the Doherty RF power amplifier according to the embodiment of the present invention adopts a transformer-based balun to achieve single-ended to differential conversion, and adopts a fully differential structure in the main path and the auxiliary path, so as to achieve higher gain, higher efficiency and better linearity. The output network of the technical solution of the present invention adopts a balun combined with a variable capacitor network to achieve impedance transformation and power synthesis. It can achieve high linearity, high efficiency and high output power in the entire bandwidth of the n77 frequency band. The technical solution of the present invention has a compact structure, is easy to integrate, and occupies a small volume; in addition, it does not require digital pre-distortion assistance to achieve high linearity signal output, and is suitable for use in mobile terminal devices.

[0045] Figure 2 FIG. 4 is a schematic diagram showing a Doherty radio frequency power amplifier according to an embodiment of the present invention.

[0046] refer to Figure 2 According to an embodiment of the present invention, the Doherty RF power amplifier includes an input quadrature coupler, an input balun module T2, an input balun module T3, an output balun module, a main amplifier circuit, an auxiliary amplifier circuit, and a quarter-wavelength converter. The RF input is connected to the Doherty RF power amplifier through the input quadrature coupler. The input quadrature coupler adopts a transformer-based structure to achieve single-end input and dual-end output of RF signals, and further achieves two-way orthogonal 90° output.

[0047] The two orthogonal signals output by the input orthogonal coupler are respectively provided to the input balun module T2 and the input balun module T3, wherein the input balun module T2 receives one output (main path output) of the input orthogonal coupler, and transforms the signal into a differential signal to provide it to the main path amplifier; the input balun module T3 receives the other output (auxiliary path output) of the input orthogonal coupler, and transforms the signal into a differential signal to provide it to the auxiliary path amplifier. The input balun module T2 and the input balun module T3 are both configured based on a transformer form to achieve single-ended input and two differential outputs.

[0048] The main amplifier circuit and the auxiliary amplifier circuit are multi-stage fully differential power amplifier circuits to respectively amplify two signals. The use of a fully differential amplifier structure enables further suppression of common mode noise.

[0049] Thereafter, the output of the main amplifier circuit passes through a quarter-wavelength converter, which is configured to perform phase compensation on the differential output signals of the main amplifier circuit respectively, and realize impedance modulation at different power outputs. After the signal is phase compensated (for example, 90° phase compensation) and impedance modulated, the output of the output of the main amplifier circuit is combined with the output of the auxiliary amplifier circuit, and the combined signal is output to the output balun module. Among them, the two signals of the same phase in the differential output of the main amplifier circuit and the differential output of the auxiliary amplifier circuit are respectively combined together to form a combined differential signal used as the input of the output balun module. The output balun module includes an output balun and a variable capacitor network. The output balun is used to receive the combined differential signal and generate a single-ended RF output signal. The variable capacitor network is used to adjust the output impedance of the Doherty RF power amplifier at different frequencies and expand the bandwidth of the Doherty RF power amplifier. For example, the variable capacitor network can realize impedance transformation and power synthesis, and reduce the chip area. Although Figure 2 Not shown, but Figure 2 The Doherty RF power amplifier may further include a control unit, which may be configured to control the variable capacitor network at different frequency points to achieve corresponding capacitance values, thereby broadening the Doherty bandwidth and achieving high efficiency and high linearity within the entire n77 frequency band.

[0050] Figure 3 is a circuit diagram showing a Doherty RF power amplifier according to an embodiment of the present invention.

[0051] refer to Figure 3 According to an embodiment of the present invention, the Doherty RF power amplifier includes an input orthogonal coupler, an input balun module T2, an input balun module T3, an output balun module, a main amplifier circuit, an auxiliary amplifier circuit, and a quarter-wavelength converter.

[0052] refer to Figure 3 , both the main amplifier circuit and the auxiliary amplifier circuit adopt a two-stage fully differential structure power amplifier.

[0053] The main path amplifier circuit includes a first-stage main path amplifier, an interstage matching transformer T4, and a second-stage main path amplifier, wherein the first-stage main path amplifier is configured to adjust the power input to the main path, the interstage matching transformer T4 is configured to adjust the voltage and impedance, and the second-stage main path amplifier is configured to perform a second-stage amplification on the boosted signal. The auxiliary path amplifier circuit includes a first-stage auxiliary path amplifier, an interstage matching transformer T5, and a second-stage auxiliary path amplifier, wherein the first-stage auxiliary path amplifier is configured to adjust the power input to the auxiliary path, the interstage matching transformer T5 is configured to adjust the voltage and impedance, and the second-stage auxiliary path amplifier is configured to perform a second-stage amplification on the boosted signal. According to an embodiment of the present invention, the second-stage main path amplifier and the second-stage auxiliary path amplifier are respectively configured to operate under Class AB and deep Class AB bias conditions to achieve better linearity and smoothness.

[0054] Thereafter, the output of the main amplifier circuit passes through a quarter-wavelength converter, which is configured to perform phase compensation on the differential output signals of the main amplifier circuit respectively, and to achieve impedance modulation at different power outputs. After the signal is phase compensated (for example, 90° phase compensation) and impedance modulated, the output of the main amplifier circuit is combined with the output of the auxiliary amplifier circuit, and the combined signal is output to the output balun module. Among them, the two signals of the same phase in the differential output of the main amplifier circuit and the differential output of the auxiliary amplifier circuit are respectively combined together to form a combined differential signal used as the input of the output balun module. The output balun module includes an output balun and a variable capacitor network. The output balun is used to receive the combined differential signal and generate a single-ended RF output signal. The variable capacitor network is used to adjust the output impedance of the Doherty RF power amplifier at different frequencies and to expand the bandwidth of the Doherty RF power amplifier. Although Figure 3 Not shown, but Figure 3 The Doherty RF power amplifier may further include a control unit, which may be configured to control the variable capacitor network at different frequency points to achieve corresponding capacitance values, thereby broadening the Doherty bandwidth and achieving high efficiency and high linearity within the entire n77 frequency band.

[0055] Figure 4 is a circuit diagram showing a Doherty RF power amplifier according to an embodiment of the present invention.

[0056] refer to Figure 4 According to an embodiment of the present invention, the Doherty RF power amplifier includes an input orthogonal coupler, an input balun module T2, an input balun module T3, an output balun module, a main amplifier circuit, an auxiliary amplifier circuit, and a quarter-wavelength converter.

[0057] refer to Figure 4 The input quadrature coupler includes a transformer T1, a capacitor C1, and a resistor R1. The transformer T1 includes a first winding ( Figure 4 The upper winding in transformer T1) and the second winding ( Figure 4 The first winding may be connected between the single-ended RF input and one input terminal of the input balun module T2, and the capacitor C1 may be connected between the single-ended RF input and one input terminal of the input balun module T3. One end of the second winding may be connected between the capacitor C1 and the above-mentioned one input terminal of the input balun module T3, and the other end of the second winding may be grounded through the resistor R1.

[0058] refer to Figure 4 , the main amplifier circuit and the auxiliary amplifier circuit both adopt a two-stage fully differential structure power amplifier. Among them, transistors P1 and P2 constitute the first-stage main path amplifier of the main amplifier circuit, which receives two inputs from the input balun module T2 and provides the differential output to the inter-stage matching circuit T4. In addition, capacitor C2 is connected between the base of transistor P1 and the collector of transistor P2, and capacitor C3 is connected between the base of transistor P2 and the collector of transistor P1. Capacitor C2 and capacitor C3 are set as neutralizing capacitors to offset part of the transistor parasitic capacitance, so that the gain can be increased and the linearity of the amplifier can be improved.

[0059] According to the embodiment of the present invention, the inter-stage matching circuit is formed by the transformer T4. However, those skilled in the art should understand that the inter-stage matching circuit can be formed by other forms, for example, by an LC network, without departing from the scope of the present invention.

[0060] Transistors P5 and P6 form the second stage of the main path amplifier of the main path amplifier circuit, which receives the differential input from the interstage matching circuit and provides the differential signal to the output balun module through the quarter-wave transformer. The quarter-wave transformer is formed by two π-type LC networks. For example, see Figure 4 The quarter-wavelength converter is formed by two π-type LC networks including capacitor C6, capacitor C7 and inductor L1, and capacitor C8, capacitor C9 and inductor L2. Among them, capacitor C6, capacitor C7 and inductor L1 form a π-type LC network to be connected between the collector of transistor P5 and one input terminal of the output balun module; capacitor C8, capacitor C9 and inductor L2 form a π-type LC network to be connected between the collector of transistor P6 and the other input terminal of the output balun module.

[0061] Transistors P3 and P4 form the first stage auxiliary path amplifier of the auxiliary path amplifier circuit, which receives the other two inputs from the input balun module T3 and provides the differential output to the interstage matching circuit T5. In addition, capacitor C4 is connected between the base of transistor P3 and the collector of transistor P4, and capacitor C5 is connected between the base of transistor P4 and the collector of transistor P3. Capacitor C4 and capacitor C5 are set as neutralizing capacitors to offset part of the transistor parasitic capacitance, so that the gain can be increased and the linearity of the amplifier can be improved.

[0062] According to the embodiment of the present invention, the inter-stage matching circuit is formed by the transformer T5. However, those skilled in the art should understand that the inter-stage matching circuit can be formed by other forms, for example, by an LC network, without departing from the scope of the present invention.

[0063] Transistors P7 and P8 form a second-stage auxiliary path amplifier of the auxiliary path amplifier circuit, which receives a differential input from the interstage matching circuit and provides an amplified differential signal to the output balun module, wherein the output balun module is configured as a balun in the form of a single transformer.

[0064] refer to Figure 4 The two signals of the same phase in the differential output of the main amplifier circuit and the differential output of the auxiliary amplifier circuit are respectively combined together to serve as an input end of the output balun module, so that the output balun module outputs the RF output according to the two differential signals provided by the main amplifier circuit and the auxiliary amplifier circuit.

[0065] refer to Figure 4 The output balun module may include an output balun T6 and a variable capacitor network. The output balun T6 may be used to receive a combined differential signal and generate a single-ended RF output signal. The variable capacitor network may be used to adjust the output impedance of the Doherty RF power amplifier at different frequencies and to expand the bandwidth of the Doherty RF power amplifier. The output balun T6 may include an input winding ( Figure 4 The output balun T6 has a winding on the left) and an output winding ( Figure 4 The input winding may include two input terminals, and the output winding may include two output terminals.

[0066] The variable capacitor network may include capacitor C10, capacitor C11, capacitor C12, capacitor C13, and capacitor C14. One or more of capacitor C10, capacitor C11, capacitor C12, capacitor C13, and capacitor C14 may be variable capacitors. For example, Figure 5 The example of a variable capacitor shown in FIG. 1 is used to implement a variable capacitor in a variable capacitor network. Figure 5is a circuit diagram showing a variable capacitor according to an embodiment of the present invention. Figure 5 The variable capacitor in may include four capacitors C0-C3 connected in parallel, and those skilled in the art will appreciate that more or fewer capacitors may be included, and these capacitors may be connected in other forms such as series connection. Figure 5 As shown, one or more of the four capacitors C0-C3 connected in parallel (e.g., capacitors C1-C3) can be controlled to be disconnected or connected through the corresponding capacitor switches (e.g., capacitor switches K1-K3) connected in series. In this way, the capacitance value of the corresponding variable capacitor can be controlled to change according to different frequency points.

[0067] Return to reference Figure 4 , capacitor C10 may be a variable capacitor. Capacitor C10 may be connected between the two input ends of the input winding of the output balun T6. Capacitor C11 may be a fixed capacitor. Capacitor C11 may be connected between one output end of the output winding of the output balun T6 (the upper output end of the output winding of the output balun T6) and the RF output of the Doherty RF power amplifier. Capacitor C12 may be a variable capacitor. One end of capacitor C12 may be connected between capacitor C11 and the RF output, and the other end of capacitor C12 may be grounded. Capacitor C12 may be a variable capacitor. Capacitor C12 may be connected between the other output end of the output balun T6 (the lower output end of the output winding of the output balun T6) and the ground. Capacitor C14 may be a variable capacitor. One end of capacitor C14 may be grounded, and the other end of capacitor C14 may be connected to the input winding of the output balun and the power supply end.

[0068] although Figure 4 Not shown, but Figure 4 The Doherty RF power amplifier may also include a control unit, which may be configured to control the variable capacitor network to achieve corresponding capacitance values ​​at different frequencies. For example, the control unit may control the disconnection or connection of capacitor switches (e.g., capacitor switches K1-K3) according to different operating frequencies to control the capacitance value change of the corresponding variable capacitor. In this way, the bandwidth of Doherty can be widened to achieve high efficiency and high linearity in the entire n77 frequency band.

[0069] By controlling the capacitance values ​​of capacitors C10, C12, C13, and C14, the bandwidth of Doherty can be widened to achieve high efficiency and high linearity in the entire n77 frequency band. For example, the control unit can control the size of the variable capacitor according to different operating frequencies to achieve different output impedances of the main channel amplifier and the auxiliary channel amplifier at different frequencies, so that the Doherty amplifier has an optimal impedance point at each frequency point, and finally achieves high linearity and high efficiency in the entire frequency band (for example, n77 frequency).

[0070] Those skilled in the art should understand that the amplifier circuit of the present invention can be implemented by an amplifier formed by processes such as BJT transistors, FET transistors, and MOS transistors.

[0071] Figure 6 is a circuit diagram showing a Doherty RF power amplifier according to an embodiment of the present invention.

[0072] Figure 6 Zhongyu Figure 5 The same components will not be described repeatedly. Figure 6 The Doherty RF power amplifier also includes a filter and a switch module to meet the application scenarios of out-of-band suppression and multi-antenna transmission. The filter and the switch module can be connected between the capacitor C11 and the RF output. The filter and the switch module can be connected in series. The filter can filter the signal output by the output balun module. The switch module can be used to switch different antenna ports.

[0073] Figure 7 Schematic diagram showing the relationship between the output power and the power-added efficiency (PAE) curve of the Doherty RF power amplifier according to an embodiment of the present invention and the conventional Class AB power amplifier. Figure 7 It can be seen that the Doherty RF power amplifier according to the embodiment of the present invention can obtain a higher power added efficiency below 35 dBm output power compared with the traditional Class AB power amplifier.

[0074] Figure 8A-8C is a schematic diagram showing an implementation of an output balun according to an embodiment of the present invention. Figure 9A-9C is a schematic diagram showing an implementation of the transformer T1 in the orthogonal coupler according to an embodiment of the present invention.

[0075] like Fig. 8A As shown, the output balun T6 can be formed by patterning a three-layer metal structure. Figure 8B As shown, the first metal layer may include a circular shape with an upper portion being open and a lower portion extending downward. Figure 8BThe pattern in can correspond to the input winding of the output balun T6. Figure 8C As shown, the second metal layer may include an arc pattern, and the third metal layer may include a pattern that connects the arc pattern in the second metal layer at a connection region. Figure 8C The pattern in can correspond to the output winding in the output balun.

[0076] Fig. 9A As shown, the transformer T1 of the input quadrature coupler can be formed by a rectangular pattern of a two-layer metal structure. The transformer T1 used in the input quadrature coupler can be realized on a GaAs wafer by two layers of metal. Fig. 9A The RF input 1 and RF input 2 in the input balun T2 can be connected to the single-ended RF input, and a capacitor C1 can be connected between one of the RF input 1 and the RF input 2 (for example, the RF input 2) and the single-ended RF input. One input terminal of the input balun T2 can be connected to Fig. 9A One of the input terminals of the input balun T3 can be connected between capacitor C1 and RF input 2. The isolated port can be grounded through resistor R1. Fig. 9B and Fig. 9C As shown, the first metal layer and the second metal layer may include rectangular patterns to form the transformer T1.

[0077] Fig.10 is a phase-frequency diagram showing an input quadrature coupler according to an embodiment of the present invention. Fig.10 It can be seen that within the frequency range of the n77 frequency band, two outputs with a phase difference of basically 90° can be achieved. Therefore, the Doherty RF power amplifier according to an embodiment of the present invention can be applied to 5G communication systems, especially to the frequency range of the n77 frequency band in the 5G communication frequency band.

[0078] Fig.11 is a schematic diagram showing an implementation of an inductor of a quarter-wavelength transformer in a Doherty RF power amplifier according to an embodiment of the present invention. Fig.11 In order to reduce the area and cost of the entire module, the inductor in the quarter-wavelength transformer can be realized by a combination of bonding wires and substrate microstrip lines.

[0079] Fig.12 is a plan view showing a multi-chip package of a Doherty RF power amplifier according to an embodiment of the present invention, and Fig.13 is a side view showing a multi-chip package of a Doherty RF power amplifier according to an embodiment of the present invention.

[0080] Multi-Chip Module Doherty structure power amplifiers are gradually being used in mobile terminals. Fig.12 and Fig.13 , multiple chips (e.g., controller (e.g., control unit), capacitor switch, power amplifier, low noise amplifier, switch module, output balun module) are integrated into a module through a multi-layer substrate, and multiple chips can be interconnected by bonding wires. For example, refer to Fig.12 The power amplifier chip and the output balun module are interconnected by bonding wires. By adopting a multi-chip integrated module structure, the Doherty power amplifier according to the embodiment of the present invention can be further applied to a mobile terminal.

[0081] Although the present disclosure has been described with exemplary embodiments, various changes and modifications may be suggested to one skilled in the art. The present disclosure is intended to encompass such changes and modifications as fall within the scope of the appended claims.

[0082] Any description in the present invention should not be construed as implying that any particular element, step, or function is an essential element that must be included in the claims scope. The scope of the patented subject matter is limited solely by the claims.

Claims

1. A Doherty radio frequency power amplifier, include: An input quadrature coupler configured to receive a single-ended RF input and output two orthogonal RF signals; A first input balun configured to receive the orthogonal RF signal of the input orthogonal coupler and transform the orthogonal RF signal into a differential main signal to provide it to the main amplifier; A second input balun is configured to receive a second orthogonal RF signal of the input orthogonal coupler, and transform the second orthogonal RF signal into a differential auxiliary signal to provide it to the auxiliary amplifier; a main-path amplification circuit configured to amplify the differential main-path signal output by the first input balun and provide the amplified differential main-path signal to the quarter-wavelength converter; A quarter-wavelength converter configured to perform phase compensation on a differential main signal output from the main amplifier circuit; An auxiliary amplifier circuit is configured to amplify the differential auxiliary signal output by the second input balun, and combine the amplified differential auxiliary signal with the phase-compensated amplified differential main signal, wherein two signals of the amplified differential main signal and the amplified differential auxiliary signal that are in phase are respectively combined to form a combined differential signal used as an input of the output balun module; An output balun module includes an output balun and a variable capacitor network. The output balun is used to receive a combined differential signal and generate a single-ended RF output signal. The variable capacitor network is used to adjust the output impedance of the Doherty RF power amplifier at different frequencies and expand the bandwidth of the Doherty RF power amplifier.

2. The Doherty RF power amplifier according to claim 1, in, The input quadrature coupler comprises: an input transformer including a first winding and a second winding, an input capacitor and an input resistor, wherein: The first winding is connected between the single-ended RF input and one input of the first input balun. The input capacitor is connected between the single-ended RF input and one input of the second input balun, One end of the second winding is connected between the input capacitor and the one input end of the second input balun, and the other end of the second winding is grounded via an input resistor.

3. The Doherty RF power amplifier according to claim 1, in, The main path amplifier circuit includes a first-stage main path amplifier, a second-stage main path amplifier and a first-stage inter-stage matching circuit, and The auxiliary path amplifier circuit includes a first-stage auxiliary path amplifier, a second-stage auxiliary path amplifier and a second-stage inter-stage matching circuit.

4. The Doherty RF power amplifier according to claim 3, in, The first inter-stage matching circuit of the main amplifier circuit includes a first inter-stage matching transformer, and The second inter-stage matching circuit of the auxiliary amplifier circuit includes a second inter-stage matching transformer.

5. The Doherty RF power amplifier according to claim 1, wherein: in, The quarter-wavelength converter is realized by two π-type LC networks formed by capacitors and inductors, and is configured to perform 90° phase compensation on the amplified differential main channel signals respectively, and realize impedance modulation at different power outputs.

6. The Doherty RF power amplifier according to claim 1, in, The first-stage main path amplifier of the main path amplifier circuit includes a fully differential amplifier composed of a first transistor and a second transistor, and a first capacitor and a second capacitor, wherein the first transistor is used to receive a first input and output a first output, the second transistor is used to receive a second input and output a second output, and the first capacitor is connected between the first input and the second output, and the second capacitor is connected between the second input and the first output; and In which, the first-stage auxiliary path amplifier of the auxiliary path amplifier circuit includes a fully differential amplifier composed of a third transistor and a fourth transistor and a third capacitor and a fourth capacitor, wherein the third transistor is used to receive a third input and output a third output, the fourth transistor is used to receive a fourth input and output a fourth output, and the third capacitor is connected between the third input and the fourth output, and the fourth capacitor is connected between the fourth input and the third output.

7. The Doherty RF power amplifier according to claim 1, in, The main amplifier circuit and the auxiliary amplifier circuit are formed by at least one of a BJT transistor, a FET transistor, and a MOS transistor.

8. The Doherty RF power amplifier according to claim 1, in, The output balun includes an input winding and an output winding, wherein the input winding includes two input terminals and the output winding includes two output terminals.

9. The Doherty RF power amplifier according to claim 8, in, The variable capacitor network includes a first variable capacitor connected between two input terminals of the output balun.

10. The Doherty radio frequency power amplifier according to claim 8, in, The variable capacitor network includes a fifth capacitor connected between an output terminal of the output balun and a radio frequency output of the Doherty radio frequency power amplifier.

11. The Doherty radio frequency power amplifier according to claim 10, in, The variable capacitor network includes a second variable capacitor, one end of the second variable capacitor is connected between the fifth capacitor and the RF output, and the other end of the second variable capacitor is grounded.

12. The Doherty radio frequency power amplifier according to claim 10, in, The variable capacitor network includes a third variable capacitor connected between another output terminal of the output balun and the ground.

13. The Doherty RF power amplifier according to claim 8, in, The variable capacitor network includes a fourth variable capacitor, one end of which is grounded, and the other end of which is connected to the input winding of the output balun and the power supply terminal.

14. The Doherty radio frequency power amplifier according to claim 1, in, The variable capacitor network includes a variable capacitor, the variable capacitor includes a plurality of capacitors connected in parallel, at least one of the plurality of capacitors connected in parallel can be disconnected or connected by a capacitor switch, The Doherty RF power amplifier further includes a control unit, and the capacitor switch is controlled by the control unit to be disconnected or connected according to different operating frequencies.

15. The Doherty RF power amplifier according to claim 10, further comprising a filter connected between the fifth capacitor and the RF output and a switch module for changing the capacitance value of the variable capacitor network. in, The filter and the switch module are connected in series.

16. The Doherty radio frequency power amplifier according to claim 2, in, The input transformer is formed by a rectangular pattern of two-layer metal structures.

17. The Doherty RF power amplifier according to claim 1, in, The output balun is formed by patterning a three-layer metal structure.

18. The Doherty radio frequency power amplifier according to claim 1, in, The inductor in the quarter-wave transformer is formed by a combination of bonding wires and substrate microstrip lines.

19. The Doherty RF power amplifier according to claim 14, in, The Doherty radio frequency power amplifier including the capacitor switch and the control unit is packaged through a multi-layer substrate package for multiple chips.

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