Doherty power amplifier for dynamic linear cancellation

Abstract

The invention provides a Doherty power amplifier for dynamic linear cancellation, which comprises a power divider, a carrier power amplifier, a peak power amplifier, an input 90-degree phase shifter, an output 90-degree phase shifter, an adaptive bias circuit and an output matching circuit, and is characterized in that the power divider is configured to divide an input signal into a first input signal and a second input signal; the carrier power amplifier provides the amplified first input signal to the output 90-degree phase shifter; the output 90-degree phase shifter performs phase shifting on the amplified first input signal output by the carrier power amplifier; the input 90-degree phase shifter is connected to shift the phase of the second input signal by 90 degrees; the peak power amplifier receives the phase-shifted second input signal and amplifies the phase-shifted second input signal; the output matching circuit is configured to perform output impedance matching on the received signal; and an adaptive bias circuit configured to configure an operation type of the peak power amplifier according to the input signal.

Description

Technical Field

[0001] The present invention relates to the field of wireless communications, and more particularly to a Doherty power amplifier for dynamic configuration or dynamic linear cancellation. Background Art

[0002] The power amplifier is an important component in modern communications and is widely used in the front end of communication systems. The Doherty amplifier is a device that provides energy from a power supply to an AC signal. It is designed to solve the problem that the peak-to-average ratio of the modulated signal in the communication system is increasing, while the efficiency of the traditional amplifier is too low at the power back-off point. The Doherty power amplifier consists of two power amplifiers: a carrier power amplifier and a peak power amplifier. By adopting load modulation technology, the two power amplifiers work together to improve the back-off efficiency. The main power amplifier (carrier power amplifier) ​​usually works in class B or class AB, while the auxiliary power amplifier (peak power amplifier) ​​works in class C. When the input signal is small, only the main power amplifier is in operation, and the corresponding output impedance is a higher impedance; when the input signal increases to close to the saturation point of the main power amplifier, the auxiliary power amplifier starts to work, and the output impedance of the main power amplifier and the auxiliary power amplifier are both low impedance, and the two power amplifiers provide additional amplification capacity together. In this way, the Doherty power amplifier can reduce energy waste while maintaining a high output power. In summary, the Doherty power amplifier is a highly efficient power amplifier architecture that improves efficiency and maintains linearity through load modulation technology and the coordinated operation of two power amplifiers.

[0003] In mobile phone 5G communications, the power consumption problem caused by power increase is becoming more and more obvious. At the same time, for non-constant envelope modulation, the peak-to-average power ratio (PAPR) is high, and the power amplifier works in the back-off mode most of the time. Therefore, for the power amplifier, the back-off efficiency is more important. Through load modulation technology, the Doherty power amplifier can maintain a high efficiency at the power back-off point when processing high peak-to-average power ratio signals, so the Doherty power amplifier is more important in 5G communication applications. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a dynamically adjusted Doherty power amplifier for dynamic linear cancellation, which is used to enhance the back-off efficiency of the Doherty power amplifier and improve the linear performance of the Doherty power amplifier.

[0005] One aspect of the present invention provides a Doherty power amplifier for dynamic linear cancellation, comprising: a power divider, a carrier power amplifier, a peak power amplifier, an input 90-degree phase shifter, an output 90-degree phase shifter, an adaptive bias circuit and an output matching circuit, wherein the power divider is configured to receive an input signal and power-divide the input signal into a first input signal and a second input signal; the carrier power amplifier is configured to receive the first input signal and provide the amplified first input signal to the output 90-degree phase shifter; the output 90-degree phase shifter is configured to be connected to the output end of the carrier power amplifier to phase-shift the amplified first input signal output by the carrier power amplifier; the input 90-degree phase shifter is configured to be connected to receive the second input signal and phase-shift the second input signal by 90 degrees; the peak power amplifier is configured to receive the phase-shifted second input signal and amplify it, wherein the output end of the peak power amplifier is connected to the output end of the input 90-degree phase shifter at a junction point, and the combined signal is provided to the input end of the output matching circuit; The output matching circuit is configured to perform output impedance matching on the received signal; and the adaptive bias circuit is configured to configure the operation type of the peak power amplifier according to the input signal.

[0006] One aspect of the present invention provides a Doherty power amplifier for dynamic linear cancellation, wherein the power divider is configured as an asymmetric Wilkinson power divider.

[0007] One aspect of the present invention proposes a Doherty power amplifier for dynamic linear cancellation, wherein the adaptive bias circuit is configured to make the peak power amplifier operate in class C when the input signal is less than a first threshold, and to make the peak power amplifier operate in class B / AB when the input signal is greater than a second threshold.

[0008] One aspect of the present invention provides a Doherty power amplifier for dynamic linear cancellation, further comprising an adaptive clipping circuit, wherein the adaptive clipping circuit is configured to allocate additional power to a peak power amplifier when an input signal is greater than a second threshold.

[0009] One aspect of the present invention proposes a Doherty power amplifier for dynamic linear cancellation, wherein the adaptive limiting circuit is configured to include: a diode D1, a capacitor C1, a resistor R1 and a transistor N1, wherein the forward input terminal of the diode D1 is connected to the input signal, and its output terminal is connected to the input 90-degree phase shifter; the capacitor C1 is connected in parallel with the resistor R1 and the transistor N1 connected in series between the output terminal of the diode D1 and the ground node, and the transistor N1 is configured with the base connected to the drain.

[0010] One aspect of the present invention proposes a Doherty power amplifier for dynamic linear cancellation, wherein the peak power amplifier is configured to be configurable in size, and wherein, when the input signal is less than a first threshold, the size of the peak power amplifier is configured to be the same as the size of the carrier power amplifier; and when the input signal is greater than a second threshold, the size of the peak power amplifier is greater than the size of the carrier power amplifier.

[0011] One aspect of the present invention provides a Doherty power amplifier for dynamic linear cancellation, wherein the adaptive limiting circuit is configured to increase the number of amplifying units turned on in the peak power amplifier to increase the size of the peak power amplifier when the input signal is greater than a second threshold.

[0012] One aspect of the present invention proposes a Doherty power amplifier for dynamic linear cancellation, wherein the adaptive bias circuit is configured to make the carrier power amplifier operate in Class A and the peak power amplifier operate in Class C when the input signal is less than a first power threshold; and to make the carrier power amplifier operate in Class A and the peak power amplifier operate in Class C / B / AB when the input signal is greater than a second power threshold.

[0013] One aspect of the present invention proposes a Doherty power amplifier for dynamic linear cancellation, wherein the power divider and the input 90-degree phase shifter are configured as a coupling transformer structure, wherein the input signal is power-divided into an orthogonal first input signal and a second input signal through the coupling transformer, wherein the ports of the primary coil and the secondary coil of the coupling transformer are connected through coupling capacitors C1 and C2, the input signal is connected to one end of the primary coil of the transformer, and the first input signal is connected to the other end of the primary coil; a port in the secondary coil of the transformer connected to the primary coil through the coupling capacitor C1 is used to provide a second input signal, and the other end of the secondary coil is grounded through a resistor R1.

[0014] One aspect of the present invention provides a Doherty power amplifier for dynamic linear cancellation, wherein the carrier power amplifier and the peak power amplifier include one of an HBT amplifier, a CMOS amplifier, a SiGe amplifier, a single-ended amplifier, a differential amplifier or a Cascode structure power amplifier. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram showing a dynamically adjusted Doherty power amplifier structure according to an embodiment of the present invention;

[0016] Figure 2 is a schematic diagram showing a structure of an adaptive limiting circuit according to an embodiment of the present invention;

[0017] Figure 3 is a schematic diagram showing a dynamic input signal in a Doherty power amplifier according to an embodiment of the present invention;

[0018] Figure 4 A schematic diagram showing a third-order intermodulation product (IM3) and a fundamental wave of a Doherty power amplifier according to an embodiment of the present invention;

[0019] Figure 5 is a schematic diagram showing IM3 and PAE curves of a Doherty power amplifier according to an embodiment of the present invention;

[0020] Figure 6 is a schematic diagram showing a Doherty power amplifier structure according to another embodiment of the present invention; and

[0021] Figure 7 FIG. 4 is a schematic diagram showing a structure of a Doherty power amplifier according to another embodiment of the present invention. DETAILED DESCRIPTION

[0022] Before proceeding to the following detailed description, it may be advantageous to set forth the definitions of certain words and phrases used throughout the present invention document. The terms "coupling", "connection" and their derivatives refer to any direct or indirect communication between two or more elements, whether or not 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 with...connecting, coupling or with...coupling, communicating with, cooperating, interweaving, parallel, approaching, binding or with...binding, having, having attributes, having a relationship or with...having a relationship, 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.

[0023] Definitions for other specific words and phrases are provided throughout this 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.

[0024] In the present invention document, the application combination of circuit blocks and the division of sub-circuit blocks are only for illustration, and the application combination of circuit blocks and the division of sub-circuit blocks may have different modes without departing from the scope of the present disclosure.

[0025] The following discussion Figures 1 to 7 The various embodiments used to describe the principles of the present disclosure in this invention document are for illustration only and should not be interpreted in any way as limiting the scope of the present disclosure. Those skilled in the art will appreciate that the principles of the present disclosure can be implemented in any appropriately arranged system or device.

[0026] From a structural perspective, Doherty amplifiers can be divided into symmetrical Doherty power amplifiers and asymmetrical Doherty power amplifiers. In a symmetrical Doherty power amplifier, the carrier and peak power amplifiers are of the same size and have a 90-degree phase difference. At maximum power output, the output impedance of the carrier and peak power amplifiers are the same, and the power they provide is also the same. For an asymmetrical Doherty power amplifier, the peak power amplifier is larger than the carrier power amplifier. At maximum power output, the output impedance of the carrier power amplifier is slightly higher than that of the peak power amplifier, and the power it provides is slightly lower, thus providing the possibility of further improving added efficiency and linearity.

[0027] From the perspective of input signals, Doherty power amplifiers can be divided into two types: those with no difference in input signals and those with difference in input signals. For ordinary Doherty power amplifiers, the input signals of the carrier and peak power amplifiers are of the same size, and the operating modes of the carrier and peak power amplifiers are fixed. For improved Doherty power amplifiers, the difference between the input signals of the carrier and peak power amplifiers is constant, which has a certain effect on improving power back-off efficiency and linearity. However, since the input signals of the carrier power amplifier and the peak power amplifier cannot be adjusted dynamically, when the input signal increases to a certain level, the carrier power amplifier enters a saturation state, and the saturated power no longer increases with the increase in input power. However, due to the rectification effect of the HBT tube, the current of the carrier power amplifier still increases, which will limit the improvement of the back-off efficiency of the Doherty power amplifier. On the other hand, since the carrier power amplifier enters a saturated state, it will also limit the linear improvement effect of the amplifier.

[0028] Based on the peak power amplifier working type, Doherty amplifiers can be divided into two types: Class C and Class B / AB. For Class C Doherty power amplifiers, the peak power amplifier works in Class C, and the back-off efficiency of the Doherty power amplifier is the best. However, when the input signal is too small, it will not be able to be fully turned on and the peak power amplifier will work in a saturated state, which will weaken the load modulation effect on the carrier power amplifier, making it impossible for the Doherty power amplifier to reach the optimal saturated power, limiting the linear performance of the amplifier. For Class B / AB Doherty power amplifiers, the peak power amplifier works in Class B / AB, the back-off efficiency of the Doherty power amplifier is limited, and the carrier power amplifier will not enter the saturation state in advance, resulting in better linear performance.

[0029] In summary, for each type of Doherty power amplifier using different technologies, its efficiency and linear performance always need to be compromised (trade off). The reason is that the types of Doherty power amplifiers distinguished from different angles are fixed. However, in order to achieve the best performance, the type of Doherty power amplifier should change with the input signal. That is, the size of the carrier and peak power amplifiers, the difference in input signals between the carrier and peak power amplifiers, and the working type of the peak power amplifier should all be dynamically adjusted with the input power. Through dynamic adjustment, the amplification path can be optimized so that under small signals, the carrier power amplifier will not enter an oversaturated state to affect the back-off efficiency and linearity; and under large signals, the peak power amplifier smoothly enters a saturated state to increase the saturation power of the Doherty power amplifier, avoiding performance compromises, and thus achieving the best performance of the Doherty power amplifier.

[0030] Figure 1 It is a schematic diagram showing the structure of a dynamically adjusted Doherty power amplifier according to an embodiment of the present invention.

[0031] like Figure 1 As shown, the Doherty power amplifier according to the embodiment of the present invention includes: a power divider, a carrier power amplifier, a peak power amplifier, an input 90-degree phase shifter, an output 90-degree phase shifter, an adaptive bias circuit, an adaptive limiting circuit and an output matching circuit.

[0032] The power divider is configured to receive an input signal and power-divide the input signal into a first input signal and a second input signal. According to an embodiment of the present invention, the power divider is configured as an asymmetric Wilkinson power divider to generate a first input signal and a second input signal with different powers.

[0033] The carrier power amplifier is configured to receive a first input signal and provide an amplified first input signal to an output 90 degree phase shifter.

[0034] The output 90-degree phase shifter is configured to be connected to the output terminal of the carrier power amplifier to shift the phase of the amplified first input signal output by the carrier power amplifier.

[0035] The input 90 degree phase shifter is configured to be connected to receive the second input signal and to shift the phase of the second input signal by 90 degrees.

[0036] The peak power amplifier is configured to receive a second input signal that has been phase-shifted and to amplify it, wherein the output end of the peak power amplifier is connected to the output end of the input 90-degree phase shifter and the combined signal is provided to the input end of the output matching circuit; the output matching circuit is configured to perform output matching on the received signal.

[0037] The input 90-degree phase shifter and the output 90-degree phase shifter are configured as a 1 / 4 wavelength line.

[0038] The carrier power amplifier is configured as a class A power amplifier, and the peak power amplifier is configured as a class C / B / AB power amplifier.

[0039] According to an embodiment of the present invention, the carrier power amplifier is configured as a two-stage differential power amplifier, which includes: a carrier single-ended-to-differential converter, a driver stage amplifier 1, an interstage matching network 1, and a carrier power stage amplifier. The carrier single-ended-to-differential converter is configured to receive a first input signal and convert the first input signal into a differential first input signal; the interstage matching circuit 1 is configured between the driver stage amplifier 1 and the carrier power stage amplifier to provide interstage impedance matching; the carrier power stage amplifier is configured to include a power stage amplifier 1 and a power stage amplifier 2, and the power stage amplifier 1 and the power stage amplifier 2 are configured to respectively amplify one of the differential first input signals, and respectively provide the amplified differential signals to the signal combining point through the output 90-degree phase shifter.

[0040] According to an embodiment of the present invention, the peak power amplifier is configured as a two-stage differential power amplifier, which includes: a peak single-ended-to-differential converter, a driver stage amplifier 2, an interstage matching network 2, and a peak power stage amplifier. The peak single-ended-to-differential converter is configured to receive a second input signal that has undergone phase shifting, and convert the second input signal into a differential second input signal; the interstage matching circuit 2 is configured between the driver stage amplifier 2 and the peak power stage amplifier to provide interstage impedance matching; the peak power stage amplifier is configured to include a power stage amplifier 3 and a power stage amplifier 4, and the power stage amplifier 3 and the power stage amplifier 4 are configured to respectively amplify one of the differential second input signals, and respectively provide the amplified differential signals to the signal combining point of the Doherty power amplifier.

[0041] The bias signals of the driver stage amplifier 2 and the peak power stage amplifier in the peak power amplifier are configured according to the input signal through an adaptive bias circuit to optimize the performance under different powers.

[0042] The peak power stage amplifier in the peak power amplifier can be configured to have a variable size (size) so as to configure the size of the power stage amplifier according to the input signal. For example, the size of the power stage amplifier 3 and the power stage amplifier 4 in the peak power stage amplifier can be configured to be adjustable according to the input signal.

[0043] According to an embodiment of the present invention, a capacitor C may be further configured between two signal combining points of the carrier power amplifier and the peak power amplifier to further suppress common mode signals.

[0044] According to an embodiment of the present invention, the carrier amplification path and the peak amplification path are respectively composed of two stages, namely a fully differential driving stage and an amplification stage. The carrier amplification path performs load modulation impedance transformation by outputting a 90-degree phase shifter, and the two amplification paths perform power synthesis through a differential-single-ended converter connected to a junction point, and convert the power into a single-ended signal and output it to a matching circuit. The differential-single-ended converter is configured as a transformer to achieve impedance matching and power synthesis through the turns ratio of the primary / secondary coil.

[0045] According to an embodiment of the present invention, the Doherty power amplifier further comprises an adaptive clipping circuit (adaptive Clipper clipping circuit). The adaptive clipping circuit is configured to adjust the power of the input signal of the peak amplification path according to the input signal to optimize the performance under different powers.

[0046] According to an embodiment of the present invention, the Doherty power amplifier further comprises a mode control circuit and an adaptive bias circuit, wherein the mode control circuit and the adaptive bias circuit are configured to adjust the bias signals of the driver stage amplifier 2 and the peak power stage amplifier in the peak amplification path according to the input signal, so as to optimize the performance under different powers.

[0047] According to an embodiment of the present invention, there is provided a structure for adjusting the amplifier structure in the peak amplification path of a Doherty power amplifier by an adaptive limiting circuit, a mode control circuit and an adaptive bias circuit to optimize the performance of the Doherty power amplifier at different powers. The adaptive limiting circuit, the mode control circuit and the adaptive bias circuit can be configured in the following manner:

[0048] 1) According to an embodiment of the present invention, when the input signal is a small signal (for example, when the input signal is less than a first threshold), the amplifiers in the carrier and peak amplification paths are configured to be the same size to improve the efficiency of the carrier power amplifier, and when the input signal is a large signal (for example, when the input signal is greater than a second threshold), the size of the peak power amplifier is configured to be larger than the carrier power amplifier so that the output current of the amplifier in the peak amplification path increases. For example, when the input signal is a large signal, the size of the peak power amplifier is increased by increasing the number of amplification units that are turned on in the power stage amplifier 3 and the power stage amplifier 4 through an adaptive bias circuit. By increasing the size of the peak power amplifier when the input signal is a large signal, load modulation is enhanced and the saturation power of the Doherty power amplifier is increased.

[0049] 2) According to an embodiment of the present invention, when the input signal is a small signal, since the peak power amplifier does not need to perform load modulation on the carrier power amplifier, more power can be allocated to the carrier power amplifier; when the input signal is a large signal, more power can be allocated to the peak power amplifier to enhance load modulation and improve Doherty linear performance.

[0050] For example, according to an embodiment of the present invention, the Doherty power amplifier may further include a driver amplifier. By adjusting the working type of the driver amplifier, the input signals of the carrier and peak amplification paths may be dynamically adjusted.

[0051] In addition, according to the embodiment of the present invention, the input signal (second input signal) of the peak amplification path may be adjusted by an adaptive limiting circuit. Figure 2 2 is a schematic diagram showing a structure of an adaptive amplitude limiting circuit according to an embodiment of the present invention. Figure 2As shown, the adaptive limiting circuit includes: a diode D1, a capacitor C1, a resistor R1 and a transistor N1. The forward input terminal of the diode D1 is connected to the input signal, and the output terminal thereof is connected to the input 90-degree phase shifter. The capacitor C1 is connected in parallel with the resistor R1 and the transistor N1 connected in series between the output terminal of the diode D1 and the ground node. The transistor N1 is configured to connect the base to the drain. The adaptive limiting circuit according to an embodiment of the present invention can be configured to provide an additional input signal to the peak power amplifier in the case of a large signal to enhance load modulation and improve Doherty linear performance.

[0052] Figure 3 is a schematic diagram showing a dynamic input signal in a Doherty power amplifier according to an embodiment of the present invention.

[0053] The dynamic changes of the input signals of the carrier amplifier path and the peak amplifier path are as follows: Figure 3 Reference Figure 3 In the graphs (a) and (b), in the case of small signals, the input signal of the carrier amplification path (first input signal) is about 1.2dB larger than the input signal of the peak amplification path (second input signal). At this time, the Doherty power amplifier is mainly operated by the carrier power amplifier and provides power. As the input signal increases and the driving amplifier enters the saturation state, the input signal of the carrier amplification path (first input signal) is about 2dB smaller than the input signal of the peak amplification path (second input signal), making the load modulation of the peak power amplifier on the carrier power amplifier more obvious.

[0054] 3) According to an embodiment of the present invention, when the input signal is a small signal, the peak power amplifier operates in Class C to improve the back-off efficiency of the Doherty power amplifier. When the input signal is a large signal, the peak power amplifier operates in Class B / AB to enhance load modulation and increase the saturation power of the Doherty power amplifier.

[0055] For example, the working type of the peak power amplifier can be adjusted by an adaptive bias circuit. According to an embodiment of the present invention, the working type of the driver stage amplifier 2 and the peak power stage amplifier can be controlled by adjusting the bias voltage provided by the adaptive bias circuit to the driver stage amplifier 2 and the peak power stage amplifier. When the input signal is a small signal, the driver stage amplifier 2 and the peak power stage amplifier work in Class C; and when the input signal is a large signal, the driver stage amplifier 2 and the peak power stage amplifier work in Class B / AB.

[0056] 4) In the process of realizing a linear Doherty power amplifier, eliminating the third-order intermodulation distortion (IMD3) generated by the carrier power amplifier and the peak power amplifier is the most important design issue. According to an embodiment of the present invention, in order to further improve the linearity of the amplifier, when the input signal is a small signal (for example, when the input power of the input signal is less than the first power threshold), the carrier power amplifier is operated in class A and the peak power amplifier is operated in class C; when the input signal is a large signal (for example, when the input power of the input signal is greater than the second power threshold), the carrier power amplifier is operated in class A, and the peak power amplifier is dynamically adjusted in class C / B / AB through adaptive biasing. At the same time, the dynamic change of the size of the peak power amplifier and the dynamic allocation mechanism of the input power can also be combined to offset the third-order intermodulation distortion (IMD3) generated by the carrier power amplifier at different power levels, thereby improving the linearity of the power amplifier while improving the efficiency of the power amplifier. By combining multiple dynamic adjustment mechanisms, the third-order intermodulation distortion can be adjusted at each power level to improve the flexibility and adjustment range of the adjustment, so that the Doherty power amplifier according to the present invention can achieve an effect that cannot be achieved in a single adjustment method.

[0057] Figure 4 A schematic diagram showing a third-order intermodulation product (IM3) and a fundamental wave of a Doherty power amplifier according to an embodiment of the present invention is shown.

[0058] refer to Figure 4 For the carrier power amplifier, when gain compression occurs, the third-order intermodulation product (IM3) of the carrier power amplifier with class A bias and the fundamental signal are in anti-phase. For the peak power amplifier, when gain expansion begins, the IM3 of the peak power amplifier with class C / B / AB bias and the fundamental signal are in phase. Therefore, Figure 4 As shown in the graph (a), within a specific power range (for example, when the input power of the input signal is greater than the second power threshold), the IM3 of the carrier power amplifier and the peak power amplifier can cancel each other (IM3 cancellation), thereby improving the linearity of the Doherty power amplifier. At the same time, since the fundamental waves of the two amplifiers remain in the same direction, the efficiency is not affected. Figure 4 As can be seen in the graph (b) of Figure 1, the fundamental waves of the carrier and peak power amplifier are in phase in both the high and low power regions. Therefore, by utilizing the complementary gain characteristics of the two amplifiers and dynamically optimizing the bias conditions, better AM-AM distortion performance can be achieved.

[0059] Figure 5 FIG. 4 is a schematic diagram showing IM3 and PAE curves of a Doherty power amplifier according to an embodiment of the present invention.

[0060] like Figure 5As shown, after adopting the dynamic input power adjustment technology, by comparing the conventional class AB PA and the IM3 cancellation DPA, it can be seen that the linear IM3 and efficiency are significantly improved compared with the conventional power amplifier structure.

[0061] According to an embodiment of the present invention, by adaptively adjusting the operating sizes of the carrier and peak power amplifiers, the input signal power difference, and the peak power amplifier operating type, the combination of the three can achieve a linear IM3 dynamic cancellation effect at various power levels, thereby achieving the purpose of improving the back-off efficiency and linearity of the Doherty power amplifier, and avoiding the compromise between linearity and efficiency of other Doherty power amplifiers.

[0062] Figure 6 FIG. 4 is a schematic diagram showing a structure of a Doherty power amplifier according to another embodiment of the present invention.

[0063] like Figure 6 As shown, the Doherty power amplifier according to the embodiment of the present invention includes: a power divider, a carrier power amplifier, a peak power amplifier, an input 90-degree phase shifter, an output 90-degree phase shifter, an adaptive bias circuit, a limiting circuit and an output matching circuit.

[0064] and Figure 1 The embodiment of the Doherty power amplifier shown differs in that the Figure 1 In the embodiment, the mode control circuit is configured as a MIPI control circuit, and the process used by the mode control circuit and the adaptive bias circuit is different from the process used by the Doherty power amplifier chip, so that the mode control circuit and the adaptive bias circuit are configured as different chips from the Doherty power amplifier.

[0065] exist Figure 6 In the Doherty power amplifier shown, the adaptive bias circuit is configured to be implemented using the same process as the Doherty power amplifier, so that the adaptive bias circuit and the Doherty power amplifier can be implemented in the same chip. The adaptive bias circuit is configured to adjust the bias signal generated by the mode control circuit according to the input signal to dynamically configure the peak power amplifier in the peak amplification path. For example, the adaptive bias circuit can be configured to include a comparator, which adjusts the bias signal provided by the mode control circuit based on the comparison result by comparing the input signal with the threshold signal.

[0066] By integrating the adaptive bias circuit into the chip of the Doherty power amplifier, the cost can be further reduced and the stability of the amplifier can be improved.

[0067] Figure 7 FIG. 4 is a schematic diagram showing a structure of a Doherty power amplifier according to another embodiment of the present invention.

[0068] like Figure 7 As shown, the Doherty power amplifier according to the embodiment of the present invention includes: a power divider, a carrier power amplifier, a peak power amplifier, an output 90-degree phase shifter, an adaptive bias circuit, a limiting circuit and an output matching circuit.

[0069] and Figure 1 The embodiment shown is different. Figure 7 In the Doherty power amplifier shown, the power divider and the input 90-degree phase shifter are configured as a coupling transformer structure. In it, the input signal is power-divided into a first input signal and a second input signal in quadrature through the coupling transformer. In it, the ports of the primary coil and the secondary coil of the coupling transformer are connected through coupling capacitors C1 and C2, the input signal is connected to one end of the primary coil of the transformer, and the first input signal is connected to the other end of the primary coil; a port in the secondary coil of the transformer connected to the primary coil through the coupling capacitor C1 is used to provide a second input signal, the second input signal is orthogonal to the first input signal, and the other end of the secondary coil is grounded through a resistor R1.

[0070] By implementing the structure of the power divider and the 90-degree phase shifter through a transformer, the area of ​​the circuit can be further reduced, thereby saving the cost of the circuit.

[0071] In addition, Figure 1 Unlike the embodiment shown in Figure 1 In the carrier amplification path and the peak amplification path, the driver stage power amplifier adopts a fully differential amplifier structure. Figure 7 In the example shown, the driver stage power amplifier in the carrier and peak amplification paths is implemented in a single-ended manner, and the interstage transformer is in a single-ended to differential form to provide a differential input signal for the power stage amplifier. Through the above structure, the area and complexity of the circuit structure can be further reduced, and the cost of the circuit can be reduced.

[0072] exist Figure 7 In the Doherty power amplifier according to the embodiment of the present invention shown, the adaptive bias circuit is also configured to be implemented using the same process as the Doherty power amplifier, and is configured to adjust the bias voltage of the peak power amplifier according to the input signal. The adaptive bias circuit is configured to respectively configure the bias signal of the driver stage amplifier and the bias signal of the power stage amplifier in the peak power amplifier according to the second input signal. For example, the adaptive bias circuit is configured to respectively configure the bias signal of the driver stage amplifier according to the input signal of the driver stage amplifier, and configure the bias power stage amplifier signal according to the input signal of the power stage amplifier. Through the above structure, the bias signal can be configured more accurately to achieve more precise adjustment of the circuit performance.

[0073] The framework of the present invention is applicable to Doherty power amplifiers of differential, single-ended or cascode structures made by various CMOS, HBT and SiGe processes.

[0074] 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.

[0075] 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 inventive subject matter is limited only by the claims.

Claims

1. A Doherty power amplifier for dynamic linear cancellation, comprising: A power divider, a carrier power amplifier, a peak power amplifier, an input 90-degree phase shifter, an output 90-degree phase shifter, an adaptive bias circuit, and an output matching circuit, wherein: The power splitter is configured to receive an input signal and power split the input signal into a first input signal and a second input signal; The carrier power amplifier is configured to receive a first input signal and provide an amplified first input signal to an output 90 degree phase shifter; The output 90 degree phase shift is configured to be connected to the output terminal of the carrier power amplifier to perform phase shift on the amplified first input signal output by the carrier power amplifier; The input 90 degree phase shifter is configured to be connected to receive the second input signal and to shift the phase of the second input signal by 90 degrees; The peak power amplifier is configured to receive the second input signal after phase shifting and perform an amplification operation on it, wherein the output end of the peak power amplifier is connected to the output end of the input 90-degree phase shifter at a combining point, and the combined signal is provided to the input end of the output matching circuit; The output matching circuit is configured to perform output impedance matching on a received signal; and The adaptive bias circuit is configured to configure the operation type of the peak power amplifier according to the input signal.

2. The Doherty power amplifier according to claim 1, wherein: The power divider is configured as an asymmetric Wilkinson power divider.

3. The Doherty power amplifier according to claim 1, wherein: The adaptive bias circuit is configured to make the peak power amplifier operate in class C when the input signal is less than a first threshold, and to make the peak power amplifier operate in class B / AB when the input signal is greater than a second threshold.

4. The Doherty power amplifier according to claim 1, further comprising an adaptive limiting circuit, wherein: The adaptive clipping circuit is configured to allocate additional power to the peak power amplifier when the input signal is greater than a second threshold.

5. The Doherty power amplifier according to claim 4, wherein: The adaptive amplitude limiting circuit is configured to include: a diode D1, a capacitor C1, a resistor R1 and a transistor N1, Wherein, the forward input terminal of the diode D1 is connected to the input signal, and its output terminal is connected to the input 90 degree phase shifter; A capacitor C1 is connected in parallel with a resistor R1 and a transistor N1 connected in series between the output terminal of the diode D1 and the ground node, and The transistor N1 is configured such that the base and the drain are connected.

6. The Doherty power amplifier according to claim 1, wherein: The peak power amplifier is configured to be configurable in size, and wherein, When the input signal is less than a first threshold, the size of the peak power amplifier is configured to be the same as that of the carrier power amplifier; and when the input signal is greater than a second threshold, the size of the peak power amplifier is greater than that of the carrier power amplifier.

7. The Doherty power amplifier according to claim 6, wherein: The adaptive bias circuit is configured to increase the number of amplification units turned on in the peak power amplifier to increase the size of the peak power amplifier when the input signal is greater than a second threshold.

8. The Doherty power amplifier according to claim 1, wherein: The adaptive bias circuit is configured to make the carrier power amplifier operate in class A and the peak power amplifier operate in class C when the input signal is less than a first power threshold; and to make the carrier power amplifier operate in class A and the peak power amplifier operate in class C / B / AB when the input signal is greater than a second power threshold.

9. The Doherty power amplifier according to claim 1, wherein: The power divider and the input 90-degree phase shifter are configured as a coupled transformer structure. The input signal is split into a first input signal and a second input signal in quadrature by a coupling transformer. Among them, the ports of the primary coil and the secondary coil of the coupling transformer are connected through coupling capacitors C1 and C2, the input signal is connected to one end of the primary coil of the transformer, and the first input signal is connected to the other end of the primary coil; a port in the secondary coil of the transformer connected to the primary coil through the coupling capacitor C1 is used to provide a second input signal, and the other end of the secondary coil is grounded through a resistor R1.

10. The Doherty power amplifier according to claim 1, wherein: The carrier power amplifier and the peak power amplifier include one of an HBT amplifier, a CMOS amplifier, a SiGe amplifier, a single-ended amplifier, a differential amplifier or a Cascode structure power amplifier.

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