Broadband Doherty power amplifier with adaptive phase shift structure

Abstract

The invention provides a broadband Doherty power amplifier with an adaptive phase shift structure, and belongs to the technical field of power amplifiers. In order to cope with the phase mismatch problem, a self-adaptive phase shift structure is introduced and is arranged in front of an auxiliary driving amplifier unit, and nonlinear phase shift is superposed on an input signal of the auxiliary driving amplifier unit; meanwhile, the overall efficiency and linearity are prevented from being affected by insertion loss. In a broadband scene, the adaptive phase shift structure can reconstruct a phase curve in real time according to a power state of an input signal, dynamically adjust phase synthesis of a main path and an auxiliary path of the Doherty power amplifier, and ensure phase alignment and active regulation and control of load impedance in a frequency band, so that the overall efficiency of the Doherty power amplifier under the broadband is effectively improved. Moreover, the adaptive phase shift structure provides an on-chip adjustable scheme, so that the dependence on external elements is reduced, and the system complexity and the manufacturing cost are reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of power amplifiers, and particularly relates to a broadband Doherty power amplifier with an adaptive phase shift structure. Background Art

[0002] With the rapid development of 5G / 6G communication, Internet of Things, and millimeter-wave technologies, modern wireless communication systems have put forward more stringent requirements for the performance of radio frequency power amplifiers. The high peak-to-average power ratio (PAPR) characteristic of communication signals causes power amplifiers to operate in the low-power back-off region for a long time, while the efficiency of traditional power amplifiers (such as class A and class AB) drops sharply in this region. In this context, the Doherty power amplifier has become one of the mainstream architectures of high-efficiency power amplifiers. In addition, to support multi-band, multi-carrier aggregation, and ultra-wideband (such as Sub-6 GHz and millimeter-wave cooperation) communication scenarios, the bandwidth requirement of power amplifiers has expanded from the traditional several hundred MHz to several GHz, and it is difficult for traditional Doherty power amplifier designs to balance efficiency and bandwidth. Therefore, the architecture of the Doherty power amplifier needs to be innovatively optimized to meet the diverse needs of modern wireless communication systems.

[0003] The working principle of the Doherty power amplifier is divided into two states: low-power state and high-power state. These two states require different impedances, and mainly rely on λ / 4 transmission lines to achieve impedance inversion and phase compensation. However, its phase response shows significant non-linearity in a wide frequency band, resulting in the accumulation of phase deviations at different frequencies, destroying the impedance conditions required for load modulation, and making it difficult to expand the bandwidth of the Dohert y power amplifier. In the active load modulation mechanism of the Doherty power amplifier, phase is a key parameter that directly affects the effect of load modulation. Strict phase alignment is required during the modulation process to produce the required impedance transformation effect. The phase mismatch brought by the λ / 4 transmission line in the frequency band will not only reduce the efficiency of the Doherty power amplifier, but also introduce non-linear distortion and deteriorate the signal quality; and in the actual circuit, due to factors such as device non-linearity, frequency change, and process deviation, it is difficult for the phase relationship between the main and auxiliary paths of the Doherty power amplifier to always maintain an ideal state.

[0004] Existing phase alignment schemes usually adjust the output structure of the Doherty power amplifier, which requires innovation in complex load modulation networks or topologies. For example, in 2023, Kang Zhong et al. proposed a new type of output matching network, incorporating the phase degrees required at different frequency points into the design parameters of the matching network, and replacing the traditional quarter-wavelength line with a multi-section phase compensation network. This method can effectively improve the bandwidth and efficiency of the Doherty power amplifier, but it will face the problems of increased complexity and cost, and is not suitable for the requirements of future communications for low cost and miniaturization.

[0005] Therefore, how to design an innovative phase alignment scheme that is generally applicable and expands the bandwidth of the Doherty power amplifier has become the focus of concern for researchers. Summary of the Invention

[0006] Aiming at the problems existing in the background technology, the purpose of the present invention is to provide a broadband Doherty power amplifier with an adaptive phase shift structure. In order to address the phase mismatch problem, the present invention introduces an adaptive phase shift structure, which is arranged in front of the auxiliary drive amplifier unit to superimpose a non-linear phase shift on the input signal of the auxiliary drive amplifier unit, while preventing the insertion loss from affecting the overall efficiency and linearity. In a broadband scenario, the adaptive phase shift structure of the present invention can reconstruct the phase curve in real time according to the input signal power state, dynamically adjust the phase synthesis of the main and auxiliary paths of the Doherty power amplifier, ensure phase alignment within the frequency band, actively regulate the load impedance, and thus effectively improve the overall efficiency of the Doherty power amplifier under broadband conditions.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] A broadband Doherty power amplifier with an adaptive phase shift structure, comprising a drive power distribution unit, a first drive amplifier unit, a second drive amplifier unit, a main path power amplifier unit, an auxiliary path power amplifier unit, and an output power synthesis unit; the broadband Doherty power amplifier further comprises an adaptive phase shift structure;

[0009] The drive power distribution unit distributes the input radio frequency signal power into two signals, one signal is injected into the main path as the main path signal, and the other signal is injected into the auxiliary path as the auxiliary path signal; the main path signal is transmitted to the output power synthesis unit through the first drive amplifier unit and the main path power amplifier unit; the auxiliary path signal is transmitted to the output power synthesis unit through the adaptive phase shift structure, the second drive amplifier unit, and the auxiliary path power amplifier unit; the output power synthesis unit synthesizes the two signals and then outputs them;

[0010] The adaptive phase shift structure superimposes a non-linear phase shift on the input auxiliary path signal to achieve real-time alignment of the phase at the synthesis point of the Doherty power amplifier.

[0011] Further, the adaptive phase shift structure includes a transformer balun, n transistors, two resistors, a choke inductor, and a DC-blocking capacitor; the n transistors are connected in series in a stacked form, and their gates are all connected to one end of the choke inductor and one end of the DC-blocking capacitor; one end of the primary coil of the transformer balun is connected to the output end of the drive power distribution unit, and the other end of the primary coil is connected to the input end of the second driver unit and the other end of the DC-blocking capacitor, and serves as the output port of the adaptive phase shift structure. One end of the secondary coil is connected to one end of the first resistor and the source of the first transistor, and the other end of the secondary coil is connected to the drain of the nth transistor and one end of the second resistor; the other ends of the first resistor and the second resistor are grounded; the other end of the choke inductor is connected to the port voltage V gate .

[0012] Further, the number of transistors n ≥ 2.

[0013] Further, the resistance values of the first resistor and the second resistor should be not less than 10 kΩ to prevent the leakage of radio frequency signals.

[0014] Further, parameters such as the number and size of transistors, the inductance value and coupling coefficient of the transformer balun coil in the adaptive phase shift structure are adjusted according to the phase shift requirement.

[0015] Further, the specific process of adjustment according to the phase shift requirement is as follows: Before using the adaptive phase shift structure, scan the initial bandwidth of the Doherty power amplifier and the phase to be compensated on the auxiliary path of the frequency band to be widened. After determining the maximum and minimum values of the phase degrees to be compensated, adjust the component parameters in the adaptive phase shift structure to compensate for the required phase degrees; after determining the parameters of the adaptive phase shift structure, for any frequency point within the band, the phase compensation curve can be changed by adjusting the value of the external control voltage; in addition, the trend of phase shift change (increase / decrease) can be adjusted by the value of the external voltage control port.

[0016] Further, the present invention can also improve the phase shift accuracy through the following steps:

[0017] Step 1. Under the condition of the previously determined parameters, further adjust the size and number of transistors in the adaptive phase shift structure. The size and number of the transistors affect the value of the parasitic capacitance of the transistors and the inductance value of the secondary coil, so that it conforms to the formula L1 dc_on =(1 - k 2 )L1;

[0018] where k is the coupling coefficient; L1 dc_on is the inductance value of the primary coil when n transistors are turned on; L1 is the inductance value of the primary coil when n transistors are turned off;

[0019] Step 2. Then, according to the phase shift required by the actual Doherty power amplifier, adjust the coil inductance value and coupling coefficient value in the adaptive phase shift structure to make the phase shift curve close to the ideal curve while controlling the insertion loss.

[0020] Further, the drive power distribution unit includes a power distribution subunit and an input matching subunit; wherein, the power distribution subunit distributes the input radio frequency signal into two paths; the input matching subunit is used for the matching of the ports of the power distribution subunit to ensure the maximum transmission of power.

[0021] Both the first drive amplifier unit and the second drive amplifier unit include a drive amplifier subunit and an inter-stage matching subunit. The drive amplifier subunit amplifies the radio frequency input signal transmitted after power division and then transmits it to the power amplifier unit to ensure the overall gain; the inter-stage matching subunit is used for the matching between the drive amplifier subunit and the power amplifier to ensure the maximum transmission of power. Both the main path power amplifier unit and the auxiliary path power amplifier unit adopt a cascode structure. The radio frequency signal transmitted by the drive amplifier subunit is input from the gate of the common-source transistor, and the power-amplified radio frequency signal is output from the drain of the common-gate transistor; the output power combining unit includes an output matching subunit and a post-matching subunit. The output matching subunit matches the drain impedance of the transistor to the ideal impedance, and the post-matching subunit matches the combined point impedance of the broadband Doherty power amplifier to 50Ω.

[0022] Further, the power distribution subunit equally divides or unequally divides the input radio frequency signal.

[0023] Further, the core feature of the Doherty power amplifier lies in the active load modulation mechanism, and its structural types include but are not limited to basic topological structures (differential structure, single-ended structure, multi-path structure or any combination thereof), reconfigurable structures, hybrid topological structures, etc.

[0024] The active load modulation effect formed by the adaptive phase shift structure designed by the present invention is as follows: when the auxiliary path of the Doherty power amplifier is not turned on, the adaptive phase shift structure will not affect the overall efficiency; after the auxiliary path of the Doherty power amplifier is turned on, the adaptive phase shift structure detects the input power state of the auxiliary path in real time, changes the phase of the radio frequency signal input to the auxiliary path drive amplifier unit, so that the phases of the main path and the auxiliary path in the output power combining network reach real-time consistency, realizing the maximum output of power and the maximization of efficiency; in addition, when working within a broadband, the phase shift curve can be changed by changing the value of the external voltage control port of the adaptive phase shift structure to achieve high efficiency within the broadband.

[0025] The mechanism of the present invention is as follows: In the adaptive phase shift structure of the present invention, the gate of the transistor is connected to an external voltage control port after being serially connected with a choke resistor, and the working state of the transistor is adjusted through the port voltage. At the same time, the output port of the primary coil of the transformer balun is connected to the transistor gate through a DC blocking capacitor, which avoids the influence of the external control port voltage on the RF path and introduces the feedback of the input power, so as to realize that the phase shift degree of the phase shift structure changes with the input power. Specifically, by introducing the feedback of the input power, within a radio frequency signal cycle, the amplitude of the DC voltage at the transistor gate has two states of increase and decrease. These two states change the coupling state of the transformer balun, so that the effective value of the primary coil connected to the RF path changes within a radio frequency signal cycle, and then the change of the phase shift is generated.

[0026] The adaptive phase shift structure of the present invention is based on the active load modulation mechanism of the Doherty power amplifier, and uses the influence of the combined point phase on the load impedance of the Doherty power amplifier during load modulation to adjust the two combined phases; the load modulation principle of the Doherty power amplifier determines that the output signal phases of the main path and the auxiliary path fluctuate continuously during the modulation process. At the same time, due to the chip process, the transistor usually has parasitic parameters (such as capacitance and inductance), and these factors will cause the phase shift at the output end of the power amplifier to change non-linearly with the input power. Therefore, a non-linear phase compensation scheme should also be adopted when compensating the phase. The adaptive phase shift structure of the present invention is placed in front of the auxiliary path drive amplifier unit of the Doherty power amplifier, which avoids the deterioration of efficiency and linearity caused by insertion loss, and at the same time performs non-linear phase shift on the input RF signal of the auxiliary path drive amplifier unit.

[0027] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows:

[0028] By adopting the adaptive phase shift structure, the present invention introduces a function with adjustable phase shift degree in the original Doherty power amplifier, and can adjust the control voltage of the transistor in the adaptive phase shift structure according to the required phase shift degree of the actual circuit to achieve phase alignment at different frequency points, effectively improving the efficiency of the Doherty power amplifier at out-of-band frequency points, making it meet the in-band working requirements, and solving the bandwidth limitation brought by the λ / 4 transmission line of the traditional Doherty power amplifier, that is, expanding the bandwidth of the Doherty power amplifier. In addition, the adaptive phase shift structure provides an on-chip adjustable solution, reduces the dependence on external components, and reduces the system complexity and manufacturing cost. Brief Description of the Drawings

[0029] Figure 1 It is the system block diagram of the Doherty power amplifier of the present invention.

[0030] Figure 2This is a schematic diagram of the drive power distribution network in the present invention.

[0031] Among them, (a) is a schematic diagram of the differential structure, and (b) is a schematic diagram of the single-ended structure.

[0032] Figure 3 This is a schematic diagram of the adaptive phase shift structure in the present invention.

[0033] Figure 4 This is a schematic diagram of the drive amplifier unit in the present invention.

[0034] Among them, (a) is a schematic diagram of the differential structure, and (b) is a schematic diagram of the single-ended structure.

[0035] Figure 5 This is a schematic diagram of the power amplifier unit in the present invention.

[0036] Among them, (a) is a schematic diagram of the differential structure, and (b) is a schematic diagram of the single-ended structure.

[0037] Figure 6 This is a schematic diagram of the output power combining unit in the present invention.

[0038] Among them, (a) is a schematic diagram of the differential structure, and (b) is a schematic diagram of the single-ended structure.

[0039] Figure 7 This is a schematic diagram of the parameter selection process of the adaptive phase shift structure in the present invention.

[0040] Figure 8 This is a schematic diagram of the operation process of the adaptive phase shift structure in the present invention.

[0041] Figure 9 This is a schematic diagram of the principle of the adaptive phase shift structure in the present invention.

[0042] Among them, (a) is a schematic diagram of the principle of the theoretical analysis of the phase shift structure, and (b) is a schematic diagram of the change in the phase shifter degree.

[0043] Figure 10 This is a schematic diagram of the adaptive phase shift structure in Embodiment 2 of the present invention. Specific implementation manners

[0044] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the implementation manners and the accompanying drawings.

[0045] Embodiment 1

[0046] A differential Doherty power amplifier based on CMOS 65nm process, operating at 24 - 32GHz with an adaptive phase shift structure, includes an adaptive phase shift structure, a drive power distribution unit for the main path and the auxiliary path, a drive amplifier unit, a power amplifier unit, and an output power combining unit; it also includes an adaptive bias unit.

[0047] The Doherty power amplifier is of differential structure. The drive power distribution unit is as shown in the schematic Figure 2 (a), and includes a power distribution sub - unit and an input matching sub - unit. First, a 90° coupled - line hybrid divides the input RF signal power equally into two paths. Then, at the end of each path, a transformer balun converts the single - ended input to differential input and performs input matching.

[0048] In this embodiment, the structure of the adaptive phase shift structure is as shown in Figure 3 . The primary coil of the transformer balun is connected to the RF path of the Doherty power amplifier. The two ends of the secondary coil are respectively connected to the source and drain of the transistor. At the same time, a 50kΩ large resistor is connected in series between the source and drain of the transistor to ground. The gate of the transistor is connected to the external voltage control port after being connected in series with a choke resistor. At the same time, the output port of the primary coil of the transformer balun is connected to a DC - blocking capacitor to the gate of the transistor to realize the feedback of the input power.

[0049] The drive amplifier unit is as shown in the schematic Figure 4 (a), and is composed of a pair of differential common - source transistors, and uses cross - coupled capacitors to improve gain and stability. Inter - stage matching uses a transformer balun for impedance matching. The power amplifier unit is as shown in the schematic Figure 5 (a), and is composed of a pair of differential Cascode structures. Cross - coupled capacitors are used on the common - source transistors to improve gain and stability. The RF signal is superimposed on the gate of the common - source transistors. The output power combining unit includes an output matching sub - unit and a post - matching sub - unit. The structure of the differential - structure output power combining unit is as shown in the schematic Figure 6 (a). The output matching sub - unit is composed of a transformer balun, which is connected between the output port of the power amplifier unit and the synthesis port of the main path and the auxiliary path, and realizes the functions of differential - to - single - ended conversion and impedance matching at the same time. The post - matching sub - unit matches the synthesis - point impedance of the Doherty power amplifier to 50Ω.

[0050] The adaptive bias unit structure is divided into two levels: the first level functions as a detector; the second level is used to output the control voltages for the drive amplifier unit and the power amplifier unit of the Doherty power amplifier. The input port of the first level is connected to the output end of the drive power distribution unit, the output port of the first level is connected to the input port of the second level, and the output port of the second level is connected to the gate power supply port of the transistor of the second drive amplifier unit and the gate power supply port of the common-source transistor of the auxiliary path power amplifier unit.

[0051] The combined phase of the two paths of the Doherty power amplifier can be adjusted by the adaptive phase shift structure. By adjusting the external voltage control port of the adaptive phase shift structure, the combined point phase of the Doherty power amplifier within the frequency band can be effectively improved, thereby enhancing the efficiency and output power.

[0052] The principle of the adaptive phase shift structure is as follows. Let the inductance value of the primary coil be L1, the inductance value of the secondary coil be L2, and the coupling coefficient be k. At this time, the inductance values of the primary coil when the transistor is off and on are respectively:

[0053] L1 dc_off = L1; (1)

[0054] L1 dc_on = (1 - k 2 )L1; (2)

[0055] When the transistor is off, there is no coupling between the primary coil and the secondary coil. Therefore, the value of the primary coil is the coil inductance value. When the transistor is fully on, due to the limited coupling coefficient, the inductance value of the primary coil will decrease. Under the on and off conditions, the coupling coefficient depends on the impedance of the transistor. The impedance of the transistor decreases during the process from off to on, and the mutual inductance between the coils increases, resulting in an increase in the coupling coefficient k. Therefore, L1 shows a downward trend between the off and on stages. Through mathematical analysis, it can be known that when changing the gate bias of the transistor, the phase shift degree and the phase shift trend of the phase shift structure with respect to the input power can be changed.

[0056] Figure 7 It is a schematic diagram of the parameter selection process for the adaptive phase shift structure. First, scan the phases that should be compensated for the auxiliary path of the Doherty power amplifier within the frequency band and the frequency band to be extended. After determining the maximum and minimum values of the phase degrees to be compensated, adjust the parameters of the adaptive phase shift structure to compensate for the required phase degrees. After determining the parameters of the adaptive phase shift structure, for any frequency point within the frequency band, the phase compensation curve can be changed by adjusting the value of the external control voltage. In addition, the trend of phase shift change (increase / decrease) can be adjusted by the value of the external voltage control port.

[0057] For this embodiment, the initial bandwidth of the Doherty power amplifier is 25 - 30 GHz, and the required operating bandwidth is 24 - 32 GHz. After compensating the phases of the Doherty power amplifier's auxiliary path within the scanning band of 25 - 30 GHz and the bandwidths of 24, 31, and 32 GHz that need to be expanded, the maximum phase to be compensated is 78°, and the minimum is 26°. Therefore, in this embodiment, 2 transistors are used, the gate index is 26, the gate channel length is 60 nm, and the gate width is 4.2 um. The values of the primary coil, secondary coil, and coupling coefficient of the transformer balun are 121 pH, 176 pH, and 0.61, respectively.

[0058] Figure 8 It is a schematic diagram of the operation process of the adaptive phase shift structure. For the phase compensation of any frequency point within the band and the bandwidths that need to be expanded, it can be achieved by switching the bias voltage Vgate of the transistor gate; after determining Vgate (①), the input signal is first injected into one end of the primary coil of the transformer balun in the adaptive phase shift structure (at this time, the initial phase of the input signal is θ) (②), and then the signal is output from the other end of the primary coil. Since it passes through the primary coil (the value of the primary coil is set as L1 at this time), the phase of the output signal at this time is Through the DC blocking capacitor, the output signal is fed back to the gate of the transistor (③), that is, the voltage at Vgate will be superimposed with the AC voltage of the input signal, causing the value of Vgate to fluctuate, thereby affecting the working state of the transistor (④); according to formula (2), the effective inductance value of the primary coil of the transformer balun will change with the fluctuation of the working state of the transistor, changing from the original L1 to L1' (⑤); finally, the phase of the output signal will also change due to the change of the inductance value of the primary coil, from to to achieve the phase shift change (⑥).

[0059] When the values of the primary coil, secondary coil, and coupling coefficient of the transformer balun are 121 pH, 176 pH, and 0.61 respectively, within one RF cycle, the minimum effective value of the primary coil is 76 pH, and the maximum is 121 pH. When the transistor is biased in the AB class mode, with the injection of RF power, the voltage superimposed on the transistor in the phase shift structure will have a large swing, causing the value of the primary coil to increase, so that the phase shift degree of the phase shift structure increases with the increase of the input power, resulting in a non-linear phase shift change. The theoretical analysis is as shown in the schematic Figure 9 (a), and the change of the phase shift degree is as shown in the schematic Figure 9 (b).

[0060] On the premise that all parameters in the formula are greater than 0, the trend of the degree change of the phase shift structure is controllable. However, considering the parasitic parameters of actual transistors and process fluctuations, the degree of the adaptive phase shift structure usually deviates from the principle. The accuracy of the adaptive phase shift structure can be improved through the following operations:

[0061] Step 1. By designing and adjusting the size and number of transistors in the adaptive phase shift structure, comprehensively consider the value of the transistor parasitic capacitance and the value of the secondary coil inductance, and substitute them into the formula for calculation;

[0062] Step 2. Then adjust the coil inductance value and coupling coefficient value of the adaptive phase shift structure according to the phase shift required by the actual Doherty power amplifier, and make the phase shift curve close to the ideal curve under the condition of controlling the insertion loss;

[0063] In this embodiment, the initial bandwidth of the Doherty power amplifier is 25 - 30 GHz. After adding the adaptive phase shift structure, the bandwidth is expanded to 24 - 32 GHz, and the relative bandwidth is increased from 18% to 28%. The maximum efficiency at the saturation point within the bandwidth can reach 28%, and the efficiency at the 6 dB back-off point is 15% - 22%; The overall efficiency of the Doherty power amplifier within the frequency band has been significantly improved.

[0064] Embodiment 2

[0065] A single-ended Doherty power amplifier based on 22nm CMOS process and operating at 2.2 - 2.8 GHz with an adaptive phase shift structure, including an adaptive phase shift structure, a driving power distribution network for the main path and the auxiliary path, a driving amplifier unit, a power amplifier unit, and an output power combining network.

[0066] The Doherty power amplifier is a single-ended structure, and the matching circuit structure is replaced by LC lumped parameter elements. The driving power distribution unit is as shown in the schematic Figure 2 (b), the driving amplifier unit is as shown in the schematic Figure 4 (b), the power amplifier unit is as shown in the schematic Figure 5 (b), and the output power combining unit is as shown in the schematic Figure 6 (b).

[0067] Due to the change of the working bandwidth, the parameter selection values of the power amplifier unit and the output power combining unit change. In this embodiment, due to the change of the working bandwidth and the change of the power unit size, the required phase of the Doherty power amplifier within the frequency band also changes, and the required phase is different at each frequency point. At this time, it is necessary to re-consider the parameters in the adaptive phase shift structure, such as the coil inductance value, coupling factor, transistor parameters, etc., and adjust the parameters according to the actual required phase compensation.

[0068] The adaptive phase shift structure used in this embodiment is shown schematically Figure 10 As shown, the initial bandwidth of the Doherty power amplifier is 2.35 - 2.6 GHz, and the operating bandwidth is 2.2 - 2.8 GHz.

[0069] After scanning the in-band 2.35 - 2.6 GHz of the Doherty power amplifier and the bandwidths to be extended, 2.2 - 2.35 GHz and 2.6 - 2.8 GHz, the maximum phase to be compensated is 87°, and the minimum is 23°. In this embodiment, the number of transistors is increased to 3 to increase the voltage resistance of the transistors. The transistor gate index is 32, the gate channel length is 60 nm, and the gate width is 4.5 um. The values of the primary coil, secondary coil, and coupling coefficient are 172 pH, 205 pH, and 0.69 respectively. The minimum effective value of the primary coil is 90 pH, and the maximum is 172 pH. After the coupling factor increases, the values of the primary coil transistor when it is turned off and on change more greatly, which can generate a greater phase change. And with the change of the transistor gate voltage, it can adapt to the phase curve required by the frequency band. This reduces the power combination insertion loss in the frequency band and improves the efficiency and linearity.

[0070] The initial bandwidth of the Doherty power amplifier in this embodiment is 2.35 - 2.6 GHz. After adding the adaptive phase shift structure, the bandwidth is extended to 2.2 - 2.8 GHz, and the relative bandwidth is increased from 10% to 24%. The highest efficiency at the saturation point within the bandwidth can reach 35%, and the efficiency at the 6 dB back-off point is 23% - 28.6%. The overall efficiency of the Doherty power amplifier within the frequency band has been significantly improved.

[0071] As described above, it is only the specific implementation manner of the present invention. Any feature disclosed in this specification, unless specifically described, can be replaced by other equivalent or similar-purpose alternative features; all the features disclosed, or all the steps in all the methods or processes, except for the mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A broadband Doherty power amplifier with an adaptive phase shift structure, comprising a drive power distribution unit, a first drive amplifier unit, a second drive amplifier unit, a main path power amplifier unit, a secondary path power amplifier unit, and an output power combining unit; characterized in that, The broadband Doherty power amplifier further includes an adaptive phase shift structure; The drive power distribution unit distributes the input radio frequency signal power into two signals. One signal is injected into the main path as the main path signal, and the other signal is injected into the auxiliary path as the auxiliary path signal. The main path signal is transmitted to the output power combining unit through the first drive amplifier unit and the main path power amplifier unit. The auxiliary path signal is transmitted to the output power combining unit through the adaptive phase shift structure, the second drive amplifier unit, and the auxiliary path power amplifier unit. The output power combining unit combines the two signals and then outputs them; The adaptive phase shift structure superimposes a non-linear phase shift on the input auxiliary path signal to achieve real-time alignment of the phase at the synthesis point of the Doherty power amplifier.

2. The broadband Doherty power amplifier according to claim 1, characterized in that, The adaptive phase shift structure includes a transformer balun, n transistors, two resistors, a choke inductor, and a blocking capacitor. The n transistors are connected in series in a stacked form, and their gates are all connected to one end of the choke inductor and one end of the blocking capacitor. One end of the primary coil of the transformer balun is connected to the output end of the drive power distribution unit, and the other end of the primary coil is connected to the input end of the second driver unit and the other end of the blocking capacitor, and serves as the output port of the adaptive phase shift structure. One end of the secondary coil is connected to one end of the first resistor and the source electrode of the first transistor, and the other end of the secondary coil is connected to the drain of the nth transistor and one end of the second resistor; The other end of the first resistor and the other end of the second resistor are grounded; the other end of the choke inductor is connected to the port voltage V gate .

3. The broadband Doherty power amplifier according to claim 2, wherein The number of transistors n≥2.

4. The broadband Doherty power amplifier according to claim 2, wherein The resistance values of the first resistor and the second resistor should be not less than 10 kΩ.

5. The broadband Doherty power amplifier according to claim 2, characterized in that, The number and size of the transistors, the inductance value and coupling coefficient of the transformer balun coil in the adaptive phase shift structure are adjusted according to the phase shift requirements.

6. The broadband Doherty power amplifier according to claim 5, characterized in that, The specific process of adjustment according to the phase shift requirements is as follows: Before using the adaptive phase shift structure, scan the initial bandwidth of the Doherty power amplifier and the phase to be compensated for the auxiliary path of the frequency band to be widened. After determining the maximum and minimum values of the phase degrees to be compensated, adjust the component parameters in the adaptive phase shift structure to compensate for the required phase degrees. After determining the parameters of the adaptive phase shift structure, for any frequency point within the band, the curve of phase compensation can be changed by adjusting the value of the external control voltage. In addition, the trend of phase shift change is adjusted through the value of the external voltage control port.

7. The broadband Doherty power amplifier according to claim 6, characterized in that, The specific process of improving the phase shift accuracy includes the following steps: Step 1. Under the condition of adjusting the initially determined parameters according to the phase shift requirement in claim 6, further adjust the size and number of transistors in the adaptive phase shift structure, where the size and number of the transistors affect the value of the parasitic capacitance of the transistors and the inductance value of the secondary coil, so that it conforms to the formula L1 dc_on =(1-k 2 )L1; where k is the coupling coefficient; L1 dc_on is the inductance value of the primary coil when n transistors are turned on; L1 is the inductance value of the primary coil when n transistors are turned off; Step 2. Then, according to the phase shift required by the actual Doherty power amplifier, adjust the coil inductance value and coupling coefficient value in the adaptive phase shift structure to make the phase shift curve close to the ideal curve while controlling the insertion loss.

8. The broadband Doherty power amplifier according to claim 1, wherein The drive power distribution unit includes a power distribution subunit and an input matching subunit. Among them, the power distribution subunit distributes the input radio frequency signal into two paths. The input matching subunit is used for matching the ports of the power distribution subunit to ensure the maximum transmission of power; Both the first drive amplifier unit and the second drive amplifier unit include a drive amplifier subunit and an inter-stage matching subunit. The drive amplifier subunit amplifies the radio frequency input signal transmitted after power splitting and then transmits it to the power amplifier unit to ensure the overall gain. The inter-stage matching subunit is used to match between the drive amplifier subunit and the power amplifier to ensure the maximum power transmission. Both the main path power amplifier unit and the auxiliary path power amplifier unit adopt a cascode structure. The radio frequency signal transmitted by the drive amplifier subunit is input from the gate of the cascode transistor, and the radio frequency signal after power amplification is output from the drain of the cascode transistor. The output power combining unit includes an output matching subunit and a post-matching subunit. The output matching subunit matches the drain impedance of the transistor to the ideal impedance, and the post-matching subunit matches the combining point impedance of the broadband Doherty power amplifier to 50Ω.

9. The broadband Doherty power amplifier according to claim 8, characterized in that, The power distribution subunit divides the input radio frequency signal equally or unequally.

10. The broadband Doherty power amplifier according to any one of claims 1-9, characterized in that, The structural type of the broadband Doherty power amplifier is a basic topology structure, a reconfigurable structure, or a hybrid topology structure.

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