Doherty amplifier and radio frequency terminal

Abstract

This application discloses a Doherty amplifier and an RF terminal, wherein a power divider circuit is used to distribute the RF input signal into a main signal and an auxiliary signal; a first phase-shifting circuit is used to perform input matching and a first phase shift on the main signal; a second phase-shifting circuit is used to perform a second phase shift on the signal amplified by the first amplifier and suppress its harmonics; a third phase-shifting circuit is used to perform a third phase shift on the signal amplified by the second amplifier and suppress its harmonics, while ensuring that the auxiliary output presents an open-circuit impedance when the auxiliary circuit is closed; the sum of the phase values ​​of the first phase shift and the second phase shift is equal to the phase value of the third phase shift, so that the two signals are superimposed in phase at the combining point to form a combined signal. This application enables the Doherty amplifier to achieve efficient built-in harmonic suppression over a wide bandwidth without the need for any additional independent filtering devices, and avoids problems such as complex circuit structure.

Description

Technical Field

[0001] This application relates to the field of wireless communication technology, specifically to a Doherty amplifier and a radio frequency terminal. Background Technology

[0002] Power amplifiers (PAs) are a core component of the radio frequency front-end of wireless communication devices. Their efficiency directly determines the power consumption, heat dissipation design, and overall size of the communication equipment. In base station equipment, the power amplifier accounts for a particularly significant portion of the power consumption, reaching approximately 44% of the total power consumption. Therefore, improving power amplifier efficiency has become crucial for solving the power consumption problem in communication systems.

[0003] Doherty power amplifiers have become a leading representative of power amplifiers due to their simple structure and ability to maintain high efficiency in the power back-off region. With the increasing demands for high spectral efficiency and data transmission rates in 5G and future communication systems, the peak-to-average power ratio (PAPR) of transmitted signals continues to increase, placing even more stringent requirements on power amplifiers to achieve high efficiency and high linearity amplification over a wide bandwidth.

[0004] A typical Doherty amplifier employs a parallel configuration of a main amplifier and an auxiliary amplifier, using a quarter-wavelength (λ / 4) transmission line to achieve impedance inversion and load modulation. The auxiliary amplifier is switched off in the low-power range, and its output must exhibit an approximately open-circuit impedance characteristic to prevent power leakage from the main amplifier to the auxiliary branch, thus avoiding efficiency loss.

[0005] However, in traditional Doherty amplifiers, the inherent source-drain parasitic capacitance (Cds) of the RF power transistors objectively exists, causing the output impedance of the auxiliary amplifier to be capacitive rather than ideally open-circuit when it is off. This capacitive component severely disrupts the initial boundary conditions of the Doherty load modulation network, preventing the main amplifier from achieving the theoretically expected optimal load impedance in the back-off region, thus leading to a significant drop in efficiency. Although traditional solutions attempt to utilize or compensate for this parasitic capacitance, this often comes at the cost of sacrificing bandwidth or increasing circuit complexity. Furthermore, existing Doherty amplifiers typically incorporate a phase-shifting network at the auxiliary output to meet the high-impedance condition (equivalent open-circuit condition), but this phase-shifting network only focuses on impedance transformation at the fundamental frequency and lacks effective means of suppressing higher harmonics. Adding an additional independent harmonic suppression filter would result in a bulky circuit structure and increased insertion loss. Summary of the Invention

[0006] In view of this, this application provides a Doherty amplifier and RF terminal to solve the problem that traditional Doherty amplifiers are prone to complex circuit structures in the process of ensuring amplifier performance such as efficiency and / or harmonic suppression.

[0007] This application provides a Doherty amplifier, which includes a power divider circuit, a first phase shift circuit, a second phase shift circuit, a third phase shift circuit, a first amplifier, and a second amplifier. The input terminal of the power divider circuit is used to receive radio frequency input signals, the first output terminal is connected to the input terminal of the first phase shift circuit, and the second output terminal is connected to the input terminal of the second amplifier; the output terminal of the first phase shift circuit is connected to the combining point in sequence through the first amplifier and the second phase shift circuit; the output terminal of the second amplifier is connected to the combining point through the third phase shift circuit. The power divider circuit is used to divide the radio frequency input signal into a main signal and an auxiliary signal; The first phase-shifting circuit is used to perform input matching and first phase shifting on the main signal; The second phase-shifting circuit is used to perform a second phase shift on the signal amplified by the first amplifier and suppress its harmonics; The third phase-shifting circuit is used to perform a third phase shift on the signal amplified by the second amplifier and suppress its harmonics, while making the auxiliary circuit output present an open-circuit impedance when the auxiliary circuit is closed. The sum of the phase values ​​of the first phase shift and the second phase shift is equal to the phase value of the third phase shift, so that the two signals are superimposed in phase at the merging point to form a combined signal.

[0008] Optionally, the Doherty amplifier further includes a combining transformation network; the input terminal of the combining transformation network is connected to the combining point, and the output terminal is used to output an RF output signal; the combining transformation network is used to perform impedance transformation on the combined signal, and cooperates with the second phase shift circuit and the third phase shift circuit to perform harmonic suppression, so as to match the load impedance.

[0009] Optionally, the combining transformation network is a complex impedance network, and the impedance of the complex impedance network is located in the inductive region.

[0010] Optionally, the combining transformation network includes a first capacitor, a second capacitor, and a first inductor; the first end of the first inductor serves as the input end of the combining transformation network, and is connected to the first end of the first capacitor and the combining point respectively; the second end serves as the output end of the combining transformation network, and is connected to the first end of the second capacitor; the second end of the first capacitor is grounded; the second end of the second capacitor is grounded.

[0011] Optionally, the phase shift of the third phase shift is 180°.

[0012] Optionally, the phase shift of the first phase shift is 90°, and the phase shift of the second phase shift is 90°.

[0013] Optionally, the first phase-shifting circuit includes a third capacitor, a fourth capacitor, and a second inductor; the first end of the second inductor serves as the input terminal of the first phase-shifting circuit, and is connected to the first end of the third capacitor and the first output terminal of the power divider circuit respectively; the second end serves as the output terminal of the first phase-shifting circuit, and is connected to the first end of the fourth capacitor and the input terminal of the first amplifier respectively; the second end of the third capacitor is grounded; the second end of the fourth capacitor is grounded.

[0014] Optionally, the second phase-shifting circuit includes a fifth capacitor, a sixth capacitor, a third inductor, and a fourth inductor; the first terminal of the third inductor serves as the input terminal of the second phase-shifting circuit, and is connected to the first terminal of the fourth inductor, the first terminal of the fifth capacitor, and the output terminal of the first amplifier, respectively; the second terminal serves as the output terminal of the second phase-shifting circuit, and is connected to the first terminal of the sixth capacitor and the junction point, respectively; the second terminal of the fifth capacitor is grounded; the second terminal of the sixth capacitor is grounded; and the second terminal of the fourth inductor is used to connect a preset voltage.

[0015] Optionally, the third phase-shifting circuit includes a seventh capacitor, an eighth capacitor, and a fifth inductor; the first end of the fifth inductor serves as the input terminal of the third phase-shifting circuit, and is connected to the first end of the seventh capacitor and the output terminal of the second amplifier, respectively; the second end serves as the output terminal of the third phase-shifting circuit, and is connected to the first end of the eighth capacitor and the junction point, respectively; the second end of the seventh capacitor is grounded; the second end of the eighth capacitor is grounded.

[0016] This application also provides a radio frequency terminal, which includes any of the Doherty amplifiers described above.

[0017] The Doherty amplifier and RF terminal described in this application, by setting a first phase-shifting circuit and a second phase-shifting circuit at the main input and output terminals respectively, and a third phase-shifting circuit at the auxiliary output terminal, with the sum of the phase shifts of the first and second phase shifts equal to the phase shift of the third phase shift, ensures that at the fundamental level, the superposition of the two-stage phase shifts in the main circuit and the phase shift of the auxiliary circuit are strictly matched. This ensures that the fundamental currents of the main and auxiliary circuits are precisely in-phase vector superimposed at the junction point, thereby maximizing the power combining efficiency and maintaining the optimal impedance trajectory of the Doherty load modulation, resulting in a substantial improvement in the additional efficiency in the power back-off region. At the harmonic suppression level, the second phase-shifting circuit at the main output terminal can form a low-pass filter structure to suppress the main circuit harmonics. At the same time, the third phase-shifting circuit in the auxiliary circuit simultaneously filters out the auxiliary circuit harmonics while compensating the parasitic capacitance to a high-impedance condition (equivalent open-circuit condition). The synergy of these three components allows the corresponding Doherty amplifier to achieve efficient built-in harmonic suppression over a wide bandwidth without the need for any additional independent filtering devices, and also avoids problems such as complex circuit structures. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the Doherty amplifier structure according to an embodiment of this application; Figure 2 This is a schematic diagram of the Doherty amplifier structure according to another embodiment of this application; Figure 3 This is a schematic diagram of the Doherty amplifier structure according to another embodiment of this application. Detailed Implementation

[0020] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. In the absence of conflict, the following embodiments and their technical features can be combined with each other.

[0021] The first aspect of this application provides a Doherty amplifier that can be located in a radio frequency terminal to amplify radio frequency input signals.

[0022] refer to Figure 1As shown, the Doherty amplifier includes a power divider circuit 110, a first phase shifter circuit 120, a second phase shifter circuit 130, a third phase shifter circuit 140, a first amplifier 150, and a second amplifier 160.

[0023] The input terminal of the power divider circuit 110 is used to receive the radio frequency input signal. The first output terminal of the power divider circuit 110 is connected to the input terminal of the first phase shifter circuit 120, and the second output terminal of the power divider circuit 110 is connected to the input terminal of the second amplifier 160. The output terminal of the first phase shifter circuit 120 is connected to the combining point through the first amplifier 150 and the second phase shifter circuit 130 in sequence; that is, the output terminal of the first phase shifter circuit 120 is connected to the input terminal of the first amplifier 150, and the output terminal of the first amplifier 150 is connected to the combining point through the second phase shifter circuit 130. The output terminal of the second amplifier 160 is connected to the combining point through the third phase shifter circuit 140.

[0024] The power divider circuit 110 is used to distribute the RF input signal into a main signal and an auxiliary signal, so as to output the main signal to the main circuit and the auxiliary signal to the auxiliary circuit; the output branch corresponding to its first output terminal is the main circuit, and the output branch corresponding to its second output terminal is the auxiliary circuit. Optionally, the power divider circuit 110 includes a Wilkinson power divider, which can be implemented using a microstrip line structure, has good port isolation, and can effectively prevent signal crosstalk between the two amplifiers.

[0025] The first phase-shifting circuit 120 is used to perform input impedance matching and first phase shifting on the main signal, and outputs the first phase-shifted signal.

[0026] The first amplifier 150 is used to amplify the phase-shifted main signal (i.e., the first phase-shifted signal) and output the first amplified signal.

[0027] The second phase-shifting circuit 130 is used to perform harmonic suppression and second phase shifting on the amplified signal (i.e., the first amplified signal) and output a second phase-shifted signal. Optionally, the second phase-shifting circuit 130 may include a low-pass filter structure to suppress harmonics.

[0028] The second amplifier 160 is used to amplify the auxiliary signal and output a second amplified signal.

[0029] The third phase-shifting circuit 140 is used to perform a third phase shift on the amplified auxiliary signal (i.e., the second amplified signal). Simultaneously, the third phase-shifting circuit 140 has the function of suppressing auxiliary harmonics, which can suppress the harmonics of the second amplified signal, and also ensure that the auxiliary output presents an open-circuit impedance when the auxiliary signal is turned off. For the fundamental signal, this network can provide the required 180° phase shift.

[0030] The sum of the phase shifts of the first and second phase shifts is equal to the phase shift of the third phase shift, so that the two input signals are superimposed in phase at the combining point to form a combined signal, maximizing the power combining efficiency and maintaining the accurate impedance trajectory of the Doherty load modulation.

[0031] Specifically, the phase shift of the third phase shift is 180°. This is because the first capacitor characterizing the auxiliary circuit is the transistor's parasitic capacitance. Due to this capacitance, the transistor's output impedance is inherently in the capacitive region, not an open circuit. The Doherty structure requires the auxiliary circuit's output impedance to be open when it is off. Setting a 180° phase-shifting network at the auxiliary circuit output ensures an open-circuit output impedance while also suppressing auxiliary circuit harmonics. Furthermore, setting a 180° phase-shifting network at the auxiliary circuit output allows for a streamlined design that integrates three functions: compensating for parasitic capacitance, constructing a high-impedance condition (equivalent open-circuit condition), and suppressing harmonics. First, this network precisely transforms the auxiliary circuit transistor's inherent output parasitic capacitance (capacitive) along with its output impedance to a high-impedance point (equivalent open-circuit point), thus strictly meeting the stringent requirements of Doherty load modulation for the auxiliary circuit's off-state impedance, fundamentally eliminating the main amplifier efficiency drop caused by capacitive components. Second, this 180° phase-shifting network... While completing the 180° phase shift of the fundamental frequency (in conjunction with the main circuit phase shift to ensure in-phase synthesis of the two circuits), its frequency selectivity characteristics are used to synchronously filter out the high-order harmonics generated by the auxiliary circuit, improving linearity without the need for additional independent filtering units. Finally, this integrated design avoids the insertion loss and area increase caused by additional compensation networks. While ensuring that the fundamental currents of the main and auxiliary circuits are in-phase vector superimposed at the combining point and maximizing the synthesis efficiency, it significantly improves the power-added efficiency (PAE) of the amplifier over a wide bandwidth, demonstrating a high degree of unity between functional integration and performance optimization.

[0032] Specifically, the first phase shift has a phase shift of 90°, applying a first 90° phase delay to the main signal, contributing half of the total phase shift (input 90° + output 90° = 180°) to the main signal. The second phase shift has a phase shift of 90° to complete the remaining 90° phase delay, ensuring the total phase shift of the main signal reaches 180°, which is strictly equal to the total phase shift of the auxiliary signal, thus satisfying the Doherty load modulation requirement for fundamental phase consistency. The second phase shift circuit 130 includes a low-pass filter structure, whose low-pass filtering characteristics can suppress harmonics generated by the active devices in the main signal.

[0033] The aforementioned Doherty amplifier, by setting a first phase-shifting circuit 120 and a second phase-shifting circuit 130 at the main input and output terminals respectively, and a third phase-shifting circuit 140 at the auxiliary output terminal, ensures that the sum of the phase shifts of the first and second phase shifts equals the phase shift of the third phase shift. This ensures that at the fundamental level, the superposition of the two phase shifts in the main circuit and the phase shift of the auxiliary circuit are strictly matched, guaranteeing that the fundamental currents of the main and auxiliary circuits are precisely in-phase vector superimposed at the junction point. This maximizes the power combining efficiency and maintains the optimal impedance trajectory of the Doherty load modulation, resulting in a substantial improvement in the power back-off efficiency (PAE). At the harmonic suppression level, the second phase-shifting circuit 130 at the main output terminal can form a low-pass filter structure to suppress the main circuit harmonics. At the same time, the third phase-shifting circuit 140 in the auxiliary circuit simultaneously filters out the auxiliary circuit harmonics while compensating the parasitic capacitance to a high-impedance condition (equivalent open-circuit condition). The synergy of these three components allows the corresponding Doherty amplifier to achieve efficient built-in harmonic suppression over a wide bandwidth without the need for any additional independent filtering devices, and also avoids problems such as complex circuit structures.

[0034] In some embodiments, reference Figure 2 As shown, the Doherty amplifier also includes a combining network 180. The input of the combining network 180 is connected to the combining point, and its output is used to output an RF signal. The combining network 180 performs impedance transformation on the combined signal and, in conjunction with the second phase-shifting circuit 130 and the third phase-shifting circuit 140, performs harmonic suppression to match the load impedance. The combining network 180 can be a low-pass filter structure, transforming the impedance from 50Ω to the combined impedance while suppressing harmonics.

[0035] Specifically, the combiner network 180 is a complex impedance network. Since the impedance of a complex impedance network is located in the inductive region, the combiner network 180 requires larger values ​​for L (inductance) and C (capacitor) to achieve better low-pass rejection. The inductive complex impedance design of the output combiner network 180 allows for larger values ​​of inductor L and capacitor C in the combiner network to enhance the low-pass roll-off steepness. Ultimately, this results in a comprehensive performance improvement across a wide bandwidth, achieving high efficiency, high linearity, and compact circuit integration.

[0036] In some examples, reference Figure 3 As shown, the combining network 180 includes a first capacitor C1, a second capacitor C2, and a first inductor L1. The input terminal of the first inductor L1 serves as the input terminal of the combining network 180, connected to the first terminal of the first capacitor C1 and the combining point. The second terminal of the first inductor L1 serves as the output terminal of the combining network 180, connected to the first terminal of the second capacitor C2. The second terminal of the first capacitor C1 is grounded. The second terminal of the second capacitor C2 is grounded.

[0037] The first capacitor C1 and the second capacitor C2 clamp harmonics from both ends, while the first inductor L1 intercepts frequency components other than the fundamental frequency in the middle. The values ​​of these three capacitors can be increased as a whole under the constraint of the inductive complex impedance, causing the combining network 180 to exhibit a much steeper low-pass filtering characteristic than traditional purely resistive designs. Thus, without adding an additional filter, the Doherty amplifier achieves efficient fundamental frequency synthesis and synchronous harmonic suppression over a wide bandwidth, while maximizing fundamental power transmission and minimizing harmonic leakage.

[0038] In some embodiments, such as Figure 3 As shown, the first phase-shifting circuit 120 includes a third capacitor C3, a fourth capacitor C4, and a second inductor L2. The first terminal of the second inductor L2 serves as the input terminal of the first phase-shifting circuit 120, connected to the first terminal of the third capacitor C3 and the first output terminal of the power divider circuit 110. The second terminal of the second inductor L2 serves as the output terminal of the first phase-shifting circuit 120, connected to the first terminal of the fourth capacitor C4 and the input terminal of the first amplifier 150. The second terminal of the third capacitor C3 is grounded. The second terminal of the fourth capacitor C4 is grounded.

[0039] The second inductor L2 can serve as the core component for phase shifting and impedance transformation. Together with the third capacitor C3 and the fourth capacitor C4, it determines the phase response slope of the first phase shifting circuit 120, accurately realizing the 90° fundamental phase shift at the input end, and providing half of the phase basis for the total phase shift of the main circuit.

[0040] The fourth capacitor C4 and the second inductor L2 together complete the output impedance matching of the network, smoothly coupling the phase-shifted signal to the input impedance of the main circuit first amplifier 150, so as to maximize the signal transmission power and reduce the mismatch loss.

[0041] In this embodiment, the first phase shifting circuit 120 can ensure low-loss transmission of the fundamental signal and accurately achieve a 90° phase shift.

[0042] In some embodiments, such as Figure 3 As shown, the second phase-shifting circuit 130 includes a fifth capacitor C5, a sixth capacitor C6, a third inductor L3, and a fourth inductor L4. The first terminal of the third inductor L3 serves as the input terminal of the second phase-shifting circuit 130, connected to the first terminal of the fourth inductor L4, the first terminal of the fifth capacitor C5, and the output terminal of the first amplifier 150. The second terminal of the third inductor L3 serves as the output terminal of the second phase-shifting circuit 130, connected to the first terminal of the sixth capacitor C6 and the junction point. The second terminal of the fifth capacitor C5 is grounded. The second terminal of the sixth capacitor C6 is grounded. The second terminal of the fourth inductor L4 is used to connect a preset voltage V0.

[0043] The third inductor L3, as the core series element for phase shifting and impedance transformation in the second phase shifting circuit 130, together with the various capacitor elements in the network, determines the phase delay of the fundamental signal and accurately contributes the required 90° phase shift component. At the same time, the third inductor L3 exhibits high inductive reactance to higher harmonics and forms a strong blocking effect on harmonic currents in the series path, which is the main barrier to intercept high-frequency stray components from the transmission path.

[0044] The inductive reactance of the fourth inductor L4 shares the "voltage-to-current" conversion task of impedance transformation with the third inductor L3. By finely adjusting the value of the fourth inductor L4, the phase flatness (group delay characteristic) of the network in a wide frequency range can be optimized, ensuring that the 90° phase shift remains stable within the operating bandwidth.

[0045] The capacitive reactance of the fifth capacitor C5 decreases as the frequency increases, providing a low-impedance discharge path for the high-order harmonics generated by the main amplifier. This bypasses the harmonic components to ground before they enter the series-connected third inductor L3, achieving pre-suppression at the first end. This effectively reduces the harmonic energy entering the subsequent series-connected inductive reactance components, preventing them from generating additional voltage drops on the inductive reactance and interfering with the fundamental phase.

[0046] The sixth capacitor C6 complements the fifth capacitor C5, providing a second bypass discharge channel for the residual harmonic components after transmission through the series path of the third inductor L3 and the fourth inductor L4, further attenuating high-frequency spurious components and ensuring a highly pure signal spectrum at the output to the combining point. At the same time, the sixth capacitor C6, together with each inductor, completes the output impedance matching of the network, smoothly coupling the signal after phase shifting and impedance transformation to the combining point, providing an accurate fundamental phase reference and a low spurious spectrum environment for the subsequent combining network.

[0047] The fifth capacitor C5 and the sixth capacitor C6 perform a pincer bypass attenuation of harmonics from both ends of the network. The third inductor L3 and the fourth inductor L4 form a dual inductive reactance interception in the series channel, together constituting a low-pass filter structure. Its cutoff frequency can be set between the fundamental frequency and the second harmonic. The four components work together to enable the second phase shift circuit 130 to achieve low-loss 90° precise phase shift and impedance inversion in the fundamental frequency band, and provide deep suppression in the harmonic frequency band. Thus, without the need for an independent filter, the fundamental signal output from the main amplifier is delivered to the combining point with optimal phase and pure spectrum. This creates a precise phase reference and low harmonic excitation environment for the inductive complex impedance design of the subsequent combining network, and ultimately achieves a unified high-efficiency, high-linearity and compact circuit integration over a wide range.

[0048] In some embodiments, such as Figure 3As shown, the third phase-shifting circuit 140 includes a seventh capacitor C7, an eighth capacitor C8, and a fifth inductor L5. The first terminal of the fifth inductor L5 serves as the input terminal of the third phase-shifting circuit 140, connected to the first terminal of the seventh capacitor C7 and the output terminal of the second amplifier 160. The second terminal of the fifth inductor L5 serves as the output terminal of the third phase-shifting circuit 140, connected to the first terminal of the eighth capacitor C8 and the second input terminal of the combining point. The second terminal of the seventh capacitor C7 is grounded. The second terminal of the eighth capacitor C8 is grounded.

[0049] The fifth inductor L5, as the core series component for phase shifting and impedance transformation in the third phase-shifting circuit 140, together with the seventh capacitor C7 and the eighth capacitor C8, determines the phase delay of the fundamental signal, precisely contributing the required 180° phase shift. The fifth inductor L5 can exhibit high inductive reactance to higher harmonics, forming a strong blocking effect on the harmonic current generated by the auxiliary circuit in the series path, and is the main barrier to intercept high-frequency spurious components from the transmission path. The fifth inductor and the seventh capacitor C7 work together to accurately map the originally capacitive parasitic capacitance (Cds) and output impedance of the auxiliary circuit transistor output terminal to a high-resistance point (equivalent open circuit point) through network transformation, thereby strictly meeting the stringent requirements of Doherty load modulation for the auxiliary circuit's off-state impedance and preventing power leakage from the main amplifier to the auxiliary circuit.

[0050] The seventh capacitor C7 can be connected in parallel with the transistor parasitic capacitance Cds to work together. By selecting a reasonable value, the parasitic capacitance can be absorbed as part of the network, so that the total equivalent capacitance seen from the network input terminal, together with the fifth inductor L5, constitutes the initial conditions for phase shift and impedance transformation. The seventh capacitor C7 can also provide a low-impedance discharge path for the high-order harmonics generated by the auxiliary transistor. The harmonics are bypassed to ground before entering the series inductor, achieving pre-suppression at the first end and effectively reducing the harmonic energy entering the fifth inductor L5.

[0051] The eighth capacitor C8 and the seventh capacitor C7 complement each other, providing a second bypass discharge channel for the residual harmonic components after being transmitted in series through the fifth inductor L5, further attenuating high-frequency spurious components and ensuring a highly pure signal spectrum at the output to the combining point. At the same time, the eighth capacitor C8 and the fifth inductor L5 together complete the output impedance matching of the network, smoothly coupling the signal after phase shifting and open-circuit transformation to the combining point, providing an accurate fundamental phase reference and a low spurious spectrum environment for the subsequent combining network.

[0052] The aforementioned seventh capacitor C7, connected in parallel with the parasitic capacitance Cds of the auxiliary tube, together with the fifth inductor L5 and the eighth capacitor C8, forms a multifunctional network integrating parasitic capacitance absorption compensation, 180° precise phase shift, and second-order low-pass filtering. The seventh and eighth capacitors C7 and C8 perform a pincer-style bypass attenuation of harmonics from both ends of the network, while the fifth inductor L5 forms inductive reactance interception in the series path and dominates phase shift and open-circuit transformation. These three are tightly coupled. Their cooperation ensures that the auxiliary circuit presents perfect high-impedance conditions (equivalent to open-circuit conditions) in the off state and provides a pure 180° phase-shifted fundamental frequency in the on state. Simultaneously, no additional independent filtering or compensation units are required, thus achieving the integrated function of "phase shift + open-circuit compensation + harmonic suppression" in the auxiliary circuit. This creates a precise phase reference, a clean spectral environment, and ideal open-circuit boundary conditions for the combining network to achieve high-efficiency broadband power combining.

[0053] The aforementioned Doherty amplifier constructs a three-in-one collaborative architecture of "phase shifting-filtering-impedance transformation" by setting 90° phase shifting networks at the main input and output terminals, setting 180° phase shifting networks at the auxiliary output terminal, and designing the junction impedance as an inductive complex impedance to increase the values ​​of inductance L and capacitance C in the junction network. At the fundamental level, the total phase shift of 180° in the main circuit is strictly matched with that of the auxiliary circuit, ensuring that the two fundamental currents achieve precise in-phase vector superposition at the junction point, maximizing power combining efficiency and maintaining the optimal impedance trajectory of Doherty load modulation, thereby substantially improving the power back-off efficiency (PAE). At the harmonic suppression level, the core suppression function is achieved through the collaboration of the second phase-shifting circuit 130 at the main output and the third phase-shifting circuit 140 at the auxiliary output. Without adding other independent filtering devices, deep harmonic suppression can be achieved in a wide bandwidth, significantly improving the adjacent channel leakage ratio (ACLR). At the broadband performance level, the phase flatness design of each phase-shifting network, together with the low-pass filtering characteristics of the combining network, expands the high-efficiency operating bandwidth. At the same time, since no additional filtering unit is required, the circuit structure is more compact and the insertion loss is lower.

[0054] A second aspect of this application provides a radio frequency (RF) terminal, which includes the Doherty amplifier described in any of the above embodiments.

[0055] The aforementioned radio frequency terminal includes the Doherty amplifier described in any of the above embodiments, and has all the beneficial effects of the Doherty amplifier described in any of the aforementioned embodiments, which will not be repeated here.

[0056] Although this application has been shown and described with respect to one or more implementations, equivalent variations and modifications will occur to those skilled in the art based on a reading and understanding of this specification and the accompanying drawings. This application includes all such modifications and variations and is limited only by the scope of the appended claims. In particular, with respect to the various functions performed by the aforementioned components, the terminology used to describe such components is intended to correspond to any component (unless otherwise indicated) that performs the specified function of said component (e.g., is functionally equivalent to it), even if structurally not equivalent to the disclosed structure performing the functions in the exemplary implementations of this specification shown herein.

[0057] That is, the above description is only an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural changes made using the content of this application’s specification and drawings, such as the combination of technical features between different embodiments, or direct or indirect application in other related technical fields, are similarly included within the patent protection scope of this application.

[0058] Furthermore, it should be understood that in the description of this application, the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Additionally, for structural elements with the same or similar characteristics, this application may use the same or different reference numerals for identification. Moreover, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more features. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0059] In this application, the term "exemplary" is used to mean "serving as an example, illustration, or description." Any embodiment described as "exemplary" in this application is not necessarily to be construed as more preferred or advantageous than other embodiments. This application has been provided above to enable any person skilled in the art to implement and use it. Various details have been set forth in the above description for purposes of explanation. It should be understood that those skilled in the art will recognize that this application can be implemented without using these specific details. In other embodiments, well-known structures and processes will not be described in detail to avoid obscuring the description of this application with unnecessary detail. Therefore, this application is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed herein.

Claims

1. A Doherty amplifier, characterized in that, The Doherty amplifier includes a power divider circuit, a first phase-shifting circuit, a second phase-shifting circuit, a third phase-shifting circuit, a first amplifier, and a second amplifier. The input terminal of the power divider circuit is used to receive radio frequency input signals, the first output terminal is connected to the input terminal of the first phase shift circuit, and the second output terminal is connected to the input terminal of the second amplifier; the output terminal of the first phase shift circuit is connected to the combining point in sequence through the first amplifier and the second phase shift circuit; the output terminal of the second amplifier is connected to the combining point through the third phase shift circuit. The power divider circuit is used to divide the radio frequency input signal into a main signal and an auxiliary signal; The first phase-shifting circuit is used to perform input matching and first phase shifting on the main signal; The second phase-shifting circuit is used to perform a second phase shift on the signal amplified by the first amplifier and suppress its harmonics; The third phase-shifting circuit is used to perform a third phase shift on the signal amplified by the second amplifier and suppress its harmonics, while making the output of the auxiliary circuit present an open-circuit impedance when the auxiliary circuit is closed. The sum of the phase values ​​of the first phase shift and the second phase shift is equal to the phase value of the third phase shift, so that the two signals are superimposed in phase at the merging point to form a combined signal.

2. The Doherty amplifier according to claim 1, characterized in that, The Doherty amplifier also includes a combining converter network; The input of the combining network is connected to the combining point, and the output is used to output a radio frequency output signal. The combining transformation network is used to perform impedance transformation on the combined signal and cooperate with the second phase shifting circuit and the third phase shifting circuit to suppress harmonics and match the load impedance.

3. The Doherty amplifier according to claim 2, characterized in that, The combining transformation network is a complex impedance network, and the impedance of the complex impedance network is located in the inductive region.

4. The Doherty amplifier according to claim 2, characterized in that, The combining and transforming network includes a first capacitor, a second capacitor, and a first inductor; The first end of the first inductor serves as the input end of the combining transformation network, and is connected to the first end of the first capacitor and the combining point respectively. The second end serves as the output end of the combining transformation network, and is connected to the first end of the second capacitor. The second end of the first capacitor is grounded. The second end of the second capacitor is grounded.

5. The Doherty amplifier according to claim 1, characterized in that, The phase shift of the third phase shift is 180°.

6. The Doherty amplifier according to claim 5, characterized in that, The phase shift of the first phase shift is 90°, and the phase shift of the second phase shift is 90°.

7. The Doherty amplifier according to claim 1, characterized in that, The first phase-shifting circuit includes a third capacitor, a fourth capacitor, and a second inductor; The first end of the second inductor serves as the input terminal of the first phase-shifting circuit, and is connected to the first end of the third capacitor and the first output terminal of the power divider circuit, respectively. The second end serves as the output terminal of the first phase-shifting circuit, and is connected to the first end of the fourth capacitor and the input terminal of the first amplifier, respectively. The second end of the third capacitor is grounded. The second end of the fourth capacitor is grounded.

8. The Doherty amplifier according to claim 1, characterized in that, The second phase-shifting circuit includes a fifth capacitor, a sixth capacitor, a third inductor, and a fourth inductor; The first end of the third inductor serves as the input terminal of the second phase-shifting circuit, and is connected to the first end of the fourth inductor, the first end of the fifth capacitor, and the output terminal of the first amplifier, respectively. The second end serves as the output terminal of the second phase-shifting circuit, and is connected to the first end of the sixth capacitor and the junction point, respectively. The second end of the fifth capacitor is grounded. The second end of the sixth capacitor is grounded. The second end of the fourth inductor is used to connect to a preset voltage.

9. The Doherty amplifier according to claim 1, characterized in that, The third phase-shifting circuit includes a seventh capacitor, an eighth capacitor, and a fifth inductor; The first end of the fifth inductor serves as the input end of the third phase-shifting circuit, and is connected to the first end of the seventh capacitor and the output end of the second amplifier, respectively. The second end serves as the output end of the third phase-shifting circuit, and is connected to the first end of the eighth capacitor and the combining point, respectively. The second end of the seventh capacitor is grounded. The second end of the eighth capacitor is grounded.

10. A radio frequency terminal, characterized in that, The radio frequency terminal includes the Doherty amplifier as described in any one of claims 1 to 9.

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