Doherty power amplifier for improving second harmonics

Abstract

The utility model provides a Doherty power amplifier for improving second harmonics, which comprises a power divider, a carrier power amplifier, a peak power amplifier, an input 90-degree phase shifter, a composite right / left-handed transmission line and an output matching network, and is characterized in that the power divider is configured to receive an input signal; the power divider is used for dividing an 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 the first input signal to the composite right / left hand transmission line; the composite right / left hand transmission line is configured 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 shift the phase of the second input signal by 90 degrees; the peak power amplifier is configured to amplify the phase-shifted second input signal, and the output of the composite right / left hand transmission line and the output of the peak amplifier are connected to an impedance combining point to provide the signal to the output matching network.

Description

Technical Field

[0001] The utility model relates to the field of wireless communication, and more specifically, to a Doherty power amplifier for improving second harmonic. Background Art

[0002] A power amplifier is an important component in modern communication and is widely used in the front end of a communication system. The Doherty amplifier is a commonly used amplifier in a wireless communication system and is an efficient radio frequency power amplifier architecture. Generally, a Doherty amplifier consists of two power amplifiers: a carrier amplifier and a peak amplifier. The carrier amplifier usually operates in class AB, while the peak amplifier operates in class B or C. When amplifying a signal with low power, only the carrier amplifier is turned on, and its load is at a relatively high position to maintain high efficiency; when amplifying a signal with high power, the peak amplifier is turned on, and the load of the carrier amplifier is modulated to a lower position to generate a high-power output. Compared with a common amplifier, this improves the power back-off efficiency of the amplifier in wireless communication applications. However, in the design and application of a Doherty power amplifier, the second harmonic problem is an important aspect that needs attention.

[0003] The second harmonic is a signal with a frequency twice that of the original signal. When a non-linear circuit distorts a sine wave, many new signals are generated, and the signal with a frequency twice that of the original signal is called the second harmonic. The generation of the second harmonic mainly stems from the non-linear change of the internal current of non-linear elements.

[0004] In a Doherty power amplifier, the second harmonic problem mainly stems from the non-linear characteristics of the power amplifier. Since the carrier amplifier and the peak amplifier operate in class AB and class C (or class B) respectively, they both have a certain degree of non-linearity, thus generating second harmonics in the output signal. These second harmonics may affect the linearity and efficiency of the amplifier.

[0005] First, in terms of linearity, the generation of second harmonics may lead to the deterioration of the linearity of the amplifier, manifested as AM-AM distortion, AM-PM distortion, and an increase in intermodulation products. These distortions and intermodulation products may interfere with adjacent channels and reduce the performance of the communication system.

[0006] Second, in terms of efficiency, although the second harmonics themselves do not directly consume power, they may cause changes in the output power spectrum of the amplifier, thereby affecting the overall efficiency of the amplifier. In addition, in order to remove these second harmonics, additional filters may be required, which will also increase the complexity and cost of the system. Summary of the Utility Model

[0007] To solve the above problems, the present utility model provides a Doherty power amplifier structure that improves the second harmonic of a Doherty power amplifier without significantly increasing the system complexity and cost.

[0008] One aspect of the present utility model proposes a Doherty power amplifier for improving the second harmonic, comprising: a power divider, a carrier power amplifier, a peak power amplifier, an input 90-degree phase shifter, a composite right / left-handed transmission line, and an output matching network, characterized in that: the power divider is configured to receive an input signal and 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 composite right / left-handed transmission line; the composite right / left-handed transmission line 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 perform an amplification operation, and the output end of the composite right / left-handed transmission line and the output end of the peak amplifier are connected to an impedance combining point to provide the signal to the output matching network; and the output matching network is configured to receive the signals of the carrier power amplifier branch and the peak power amplifier branch and perform output impedance matching on them.

[0009] One aspect of the present utility model proposes a Doherty power amplifier for improving the second harmonic, characterized in that the power divider is configured as a Wilkinson power divider.

[0010] One aspect of the present utility model proposes a Doherty power amplifier for improving the second harmonic, characterized in that the input 90-degree phase shifter is a 1 / 4 wavelength line or its equivalent circuit.

[0011] One aspect of the present utility model proposes a Doherty power amplifier for improving the second harmonic, characterized in that the carrier power amplifier is configured as a class AB power amplifier, and the peak power amplifier is configured as a class B or class C power amplifier.

[0012] One aspect of the present utility model proposes a Doherty power amplifier for improving the second harmonic, characterized in that the Doherty power amplifier is configured as a radio frequency power amplifier for 5G communication.

[0013] One aspect of the present utility model proposes a Doherty power amplifier for improving the second harmonic, characterized in that the composite right / left-handed transmission line is configured to include one right-handed transmission line unit and two left-handed transmission line units.

[0014] One aspect of the present utility model provides a Doherty power amplifier for improving second harmonic, characterized in that the left-handed transmission line unit and the right-handed transmission line unit are configured to have a dual structure.

[0015] One aspect of the present utility model provides a Doherty power amplifier for improving second harmonic, characterized in that the right-handed transmission line unit is equivalent to a π-shaped network including two capacitors and an inductor; and the left-handed transmission line unit is equivalent to a π-shaped network including two inductors and a capacitor.

[0016] One aspect of the present utility model provides a Doherty power amplifier for improving second harmonic, characterized in that the composite left-handed and right-handed transmission line is configured to achieve a 90-degree phase shift for the fundamental frequency of the first input signal and a 270-degree phase shift for the second harmonic frequency of the first input signal.

[0017] One aspect of the present utility model provides a Doherty power amplifier for improving second harmonic, characterized in that 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. Description of the Drawings

[0018] Figure 1 is a schematic diagram showing a structure of a Doherty power amplifier according to an embodiment of the present utility model;

[0019] Figure 2 is a schematic diagram showing another structure of a Doherty power amplifier according to the present utility model;

[0020] Figure 3 is a schematic diagram showing an equivalent circuit model of the unit structures of a right-handed transmission line (RH_TL) and a left-handed transmission line (LH_TL);

[0021] Figure 4 is a schematic diagram showing the circuit parameters of the right-handed transmission line and the composite left-handed and right-handed transmission line; and

[0022] Figure 5 is a schematic diagram showing the circuit implementation of the composite left-handed and right-handed transmission line according to the present utility model. Detailed Description of the Invention

[0023] Before the following detailed description, it may be advantageous to set forth definitions of certain words and phrases used throughout this document of the present utility model. The terms "coupled", "connected" 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 "transmit", "receive" and "communicate" and their derivatives cover both direct and indirect communication. The terms "comprise" and "include" and their derivatives mean including but not limited to. The term "or" is inclusive and means and / or. The phrase "associated with" and its derivatives mean including, included within, interconnected, containing, contained within, connected or connected to, coupled or coupled to, communicating with, cooperating, interlacing, juxtaposing, adjacent, bound or bound to, having, having an attribute, having a relationship or having a relationship with, etc. The term "controller" refers to any device, system or part thereof that controls at least one operation. Such a controller can be implemented in hardware, or in 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", when used in conjunction with a list of items, means that different combinations of one or more of the listed items can be used, and only one item in the list may be required. For example, "at least one of A, B, C" includes any one of the following combinations: A, B, C, A and B, A and C, B and C, A and B and C.

[0024] Definitions of other specific words and phrases are provided throughout this document of the present utility model. Those of ordinary skill in the art should understand that in many cases, if not most cases, such definitions apply to the prior and future use of the words and phrases so defined.

[0025] In this document of the present utility model, the application combination of circuit blocks and the division of sub-circuit blocks are only for illustration, and within the scope of not departing from the present utility model, the application combination of circuit blocks and the division of sub-circuit blocks can have different ways.

[0026] The following discussion Figures 1 to 5 and the various embodiments for describing the principles of the present utility model in this document of the present utility model are only for illustration and should not be construed in any way as limiting the scope of the present utility model. Those skilled in the art will understand that the principles of the present utility model can be implemented in any suitably arranged system or device.

[0027] To solve the second harmonic problem in Doherty power amplifiers, the following measures can generally be taken: (1) Optimize the power amplifier setting scheme. By optimizing parameters such as the bias voltage, input matching, and output matching of the power amplifier, the non-linear characteristics of the power amplifier can be reduced, thereby reducing the generation of second harmonics; (2) Adopt the second harmonic injection technology to improve the linearity of the amplifier. It improves the amplifier linearity by injecting a second harmonic signal that is a multiple of the fundamental frequency into the input terminal. Through a carefully designed second harmonic injection circuit, the cancellation of the third-order intermodulation at the output terminal can be achieved, thereby improving the linearity of the amplifier. However, this method requires accurate modeling and analysis of the non-linear characteristics of the amplifier to ensure that the injected second harmonic signal can produce the desired effect; (3) Use filters to adjust the performance of the amplifier. By adding a filter at the output terminal of the amplifier, unwanted second harmonics and other high-frequency components can be removed. However, this method may increase the complexity and cost of the system and requires careful design to ensure that the performance of the filter meets the requirements.

[0028] In summary, the second harmonic problem in Doherty power amplifiers is an important aspect that needs attention. However, by optimizing the power amplifier design, adopting the second harmonic injection technology, and using filters and other methods, although this problem can be solved, the system complexity and cost will also increase.

[0029] The present utility model provides a structure for improving the second harmonics of a Doherty power amplifier without significantly increasing the system complexity and cost.

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

[0031] As Figure 1 shown, Figure 1A Doherty power amplifier structure based on a right - hand transmission line is shown, which includes: a power divider, a carrier power amplifier, a peak power amplifier, an input 90 - degree phase shifter, a right - hand transmission line, and an output matching network. The power divider is configured to receive an input signal and 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 right - hand transmission line; the right - hand transmission line 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 perform an amplification operation, wherein the output end of the right - hand transmission line is connected to the output end of the peak amplifier and is connected to the input end of the output matching network; the output matching network is configured to receive the signals of the carrier power amplifier branch and the peak power amplifier branch and perform output matching on them.

[0032] Wherein, the power divider can be configured as a Wilkinson power divider.

[0033] Wherein, the input 90 - degree phase shifter is a 1 / 4 - wavelength line or its equivalent circuit.

[0034] Wherein, the carrier power amplifier is configured as a class - AB power amplifier, and the peak power amplifier is configured as a class - B or class - C power amplifier.

[0035] Due to the non - linear distortion of the right - hand transmission line at high frequencies, when the power amplifier is configured for 5G communication, while the right - hand transmission line phase - shifts the original signal frequency (fundamental frequency) by 90 degrees, it phase - shifts the second - harmonic by 180 degrees. Therefore, the phase of the second - harmonic of the carrier amplifier differs from that of the peak amplifier by 90 degrees, resulting in a deterioration of the final second - harmonic performance. Thus, it is necessary to consider further optimizing the second - harmonic problem.

[0036] Figure 2 It is a schematic diagram showing another Doherty power amplifier structure according to the present utility model.

[0037] As Figure 2 shown, Figure 2Shows a Doherty power amplifier structure based on a right-handed transmission line, which includes: a power divider, a carrier power amplifier, a peak power amplifier, an input 90-degree phase shifter, a composite right / left-handed transmission line, and an output matching network. The power divider is configured to receive an input signal and 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 composite right / left-handed transmission line; the composite right / left-handed transmission line 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 perform an amplification operation, wherein the output end of the composite right / left-handed transmission line is connected to the output end of the peak amplifier and connected to the input end of the output matching network; the output matching network is configured to receive the signals of the carrier power amplifier branch and the peak power amplifier branch and perform output matching on them.

[0038] Wherein, the power divider can be configured as a Wilkinson power divider.

[0039] Wherein, the input 90-degree phase shifter is a 1 / 4 wavelength line or its equivalent circuit.

[0040] Wherein, the carrier power amplifier is configured as a class AB power amplifier, and the peak power amplifier is configured as a class B or class C power amplifier.

[0041] Wherein, the Doherty power amplifier is configured as a radio frequency power amplifier for 5G communication.

[0042] Wherein, the composite right / left-handed transmission line is configured to include one right-handed transmission line unit and two left-handed transmission line units.

[0043] Figure 3 Is a schematic diagram showing an equivalent circuit model of the unit structures of a right-handed transmission line (RH_TL) and a left-handed transmission line (LH_TL).

[0044] Reference Figure 3 , the right-handed transmission line (RH_TL) can be equivalently regarded as including a π-shaped network of two capacitors and one inductor; and the left-handed transmission line (LH_TL) can be equivalently regarded as including a π-shaped network of two inductors and one capacitor. According to an embodiment of the present invention, the left-handed transmission line and the right-handed transmission line are configured as a dual structure.

[0045] Due to the characteristics of the composite left-handed and right-handed transmission line, which includes the characteristics of the left-handed transmission line (LH_TL) and the right-handed transmission line (RH_TL), the unit phase response is non-linear, making the composite left-handed and right-handed transmission line exhibit the characteristics of metamaterial or traditional medium in different frequency bands respectively.

[0046] Figure 4 It is a schematic diagram showing the circuit parameters of the right-handed transmission line and the composite left-handed and right-handed transmission line.

[0047] Compared with the right-handed transmission line, through the composite left-handed and right-handed transmission line, a 90-degree phase shift at the fundamental frequency can be achieved, while a 270-degree shift at the second harmonic frequency can be achieved, making the phase of the fundamental frequency of the carrier power amplifier branch differ by 180 degrees from the phase of the second harmonic frequency. And the phase of the fundamental frequency of the peak power amplifier branch is in phase with the phase of the second harmonic frequency. Therefore, cancellation of the second harmonic can be achieved at the impedance combining point of the carrier power amplifier and the peak power amplifier, thereby optimizing the harmonic performance of the Doherty power amplifier. As Figure 4 shown, the abscissa is the signal frequency and the ordinate is the phase. The right-handed transmission line and the composite left-handed and right-handed transmission line have the same phase shift at the original signal frequency (fundamental frequency), both being 90 degrees, while the phase shift at the second harmonic frequency differs by 90 degrees. That is, compared with the right-handed transmission line, through the composite left-handed and right-handed transmission line, a 90-degree phase shift at the fundamental frequency can be achieved, while a 270-degree shift at the second harmonic frequency can be achieved, making the phase of the fundamental frequency of the carrier power amplifier branch differ by 180 degrees from the phase of the second harmonic frequency. And the phase of the fundamental frequency of the peak power amplifier branch is in phase with the phase of the second harmonic frequency. Therefore, cancellation of the second harmonic can be achieved at the impedance combining point of the carrier power amplifier and the peak power amplifier. Compared with using the right-handed transmission line, the second harmonic at the impedance combining point of the carrier power amplifier and the peak power amplifier differs by 90 degrees. The composite left-handed and right-handed transmission line in the present invention can optimize the second harmonic performance of the Doherty power amplifier.

[0048] Figure 5 It is a schematic diagram showing the circuit implementation of the composite left-handed and right-handed transmission line according to the present invention. As Figure 5 shown, the composite left-handed and right-handed transmission line according to the present invention includes a series-connected right-handed transmission line unit and two left-handed transmission line units.

[0049] The architecture of the present invention is applicable to Doherty power amplifiers implemented in differential, single-ended or Cascode structures using various CMOS, HBT, and SiGe processes.

[0050] Although the present invention has been described with exemplary embodiments, various changes and modifications can be proposed to those skilled in the art. The present invention is intended to cover such changes and modifications that fall within the scope of the appended claims.

[0051] No description in this utility model shall be construed as implying that any particular element, step, or function is an essential element that must be included within the scope of the claims. The scope of the subject matter of the utility model is defined solely by the claims.

Claims

1. A Doherty power amplifier for improving second harmonics, comprising: A power divider, a carrier power amplifier, a peak power amplifier, an input 90-degree phase shifter, a composite left-handed and right-handed transmission line, and an output matching network, characterized in that: 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 a first input signal and provide an amplified first input signal to the composite left-right-handed transmission line; The composite left-right-handed transmission line is configured to be connected to an output of a carrier power amplifier to phase shift the amplified first input signal output by the carrier power amplifier, and to achieve a 90-degree phase shift for the fundamental frequency of the amplified first input signal, and to achieve a 270-degree phase shift for the second harmonic frequency of the amplified first input signal; The input 90 degree phase shifter is configured to be connected to receive a second input signal and shift the phase of the second input signal by 90 degrees; The peak power amplifier is configured to receive the phase-shifted second input signal and amplify the second input signal. The output end of the composite left-handed transmission line and the output end of the peak amplifier are connected to an impedance junction to provide a signal to an output matching network; and The output matching network is configured to receive signals of the carrier power amplifier branch and the peak power amplifier branch and perform output impedance matching thereon.

2. The Doherty power amplifier according to claim 1, characterized in that: The power divider is configured as a Wilkinson power divider.

3. The Doherty power amplifier according to claim 1, characterized in that: The input 90-degree phase shifter is a 1 / 4 wavelength line or its equivalent circuit.

4. The Doherty power amplifier according to claim 1, characterized in that: The carrier power amplifier is configured as a class AB power amplifier, and the peak power amplifier is configured as a class B or class C power amplifier.

5. The Doherty power amplifier according to claim 1, characterized in that: The Doherty power amplifier is configured as a radio frequency power amplifier for 5G communications.

6. The Doherty power amplifier according to claim 1, characterized in that: The composite left-right-handed transmission line is configured to include one right-handed transmission line unit and two left-handed transmission line units.

7. The Doherty power amplifier according to claim 6, characterized in that: The left-hand transmission line unit and the right-hand transmission line unit are configured to have a dual structure.

8. The Doherty power amplifier according to claim 6, characterized in that: The right-hand transmission line unit is equivalent to a π-shaped network including two capacitors and one inductor; and the left-hand transmission line unit is equivalent to a π-shaped network including two inductors and one capacitor.

9. The Doherty power amplifier according to claim 1, characterized in that: 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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