WO2014044189A1 - 一种Doherty功放电路 - Google Patents

一种Doherty功放电路 Download PDF

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Publication number
WO2014044189A1
WO2014044189A1 PCT/CN2013/083765 CN2013083765W WO2014044189A1 WO 2014044189 A1 WO2014044189 A1 WO 2014044189A1 CN 2013083765 W CN2013083765 W CN 2013083765W WO 2014044189 A1 WO2014044189 A1 WO 2014044189A1
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Prior art keywords
power amplifier
circuit
amplifier circuit
line
coupler
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PCT/CN2013/083765
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English (en)
French (fr)
Inventor
余敏德
戴丽
秦天银
翟文宇
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中兴通讯股份有限公司
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Application filed by 中兴通讯股份有限公司 filed Critical 中兴通讯股份有限公司
Priority to US14/427,966 priority Critical patent/US9531325B2/en
Priority to IN2481DEN2015 priority patent/IN2015DN02481A/en
Priority to EP13838990.3A priority patent/EP2887542B1/en
Publication of WO2014044189A1 publication Critical patent/WO2014044189A1/zh

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/02—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/02—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation
    • H03F1/0205—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in transistor amplifiers
    • H03F1/0288—Modifications of amplifiers to raise the efficiency, e.g. gliding Class A stages, use of an auxiliary oscillation in transistor amplifiers using a main and one or several auxiliary peaking amplifiers whereby the load is connected to the main amplifier using an impedance inverter, e.g. Doherty amplifiers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/20—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers
    • H03F3/24—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers of transmitter output stages
    • H03F3/245—Power amplifiers, e.g. Class B amplifiers, Class C amplifiers of transmitter output stages with semiconductor devices only
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/60—Amplifiers in which coupling networks have distributed constants, e.g. with waveguide resonators
    • H03F3/602—Combinations of several amplifiers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2200/00—Indexing scheme relating to amplifiers
    • H03F2200/171—A filter circuit coupled to the output of an amplifier
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2200/00—Indexing scheme relating to amplifiers
    • H03F2200/204—A hybrid coupler being used at the output of an amplifier circuit
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2200/00—Indexing scheme relating to amplifiers
    • H03F2200/207—A hybrid coupler being used as power measuring circuit at the output of an amplifier circuit

Definitions

  • the utility model relates to the field of electronic circuits, in particular to a Doherty power amplifier circuit. Background technique
  • the performance of base station products is the main focus of the industry competition.
  • the power amplification unit is directly related to the quality and communication effect of the transmitted signal.
  • Doherty power amplifier technology the most widely used mature technology.
  • Most power amplifier manufacturers have started mass production and application of Doherty power amplifier. In recent years, this technology will still occupy the mainstream position in terms of cost and mass production capacity. How to further reduce the size of the power amplifier based on the power amplifier technology, and improve the linearity and efficiency of the power amplifier is more important.
  • the structure of the conventional Doherty power amplifier is as shown by reference numeral 102 in Fig. 1, and is composed of two or more power amplifier tubes, which are divided into a main power amplifier tube and an auxiliary power amplifier tube; wherein, the main power amplifier tube and the auxiliary power amplifier tube work in different working states respectively.
  • the impedance modulation technology to achieve efficiency.
  • an impedance conversion line 103 to achieve impedance modulation and matching, for example:
  • a typical Doherty power amplifier circuit there will be 35 ohm impedance transformation at the combined output of the two power amplifier tubes.
  • Line 103 is used to achieve impedance modulation and matching.
  • the method of outputting the harmonic signal is to add a filter at the output. As shown in Fig. 1, a filter 105 is provided at the combined output of the Doherty power amplifier circuit.
  • Doherty power amplifier circuits usually increase linearity by digital pre-distortion (DPD). Therefore, it is necessary to sample the power amplifier output signal for processing. DPD training, based on this, a coupler can be added to the combined output of the Doherty power amplifier circuit to implement the function of signal sampling. As shown in Fig. 1, a coupler 104 is provided in the Doherty power amplifier circuit.
  • DPD digital pre-distortion
  • the Doherty power amplifier circuit needs to be equipped with a coupler on the output 50 ohm microstrip transmission line to implement the DPD training function or the power control function, and set the filter to suppress the harmonics; These devices will occupy a certain space on the printed circuit board (PCB), which will inevitably lead to an increase in the size of the microstrip transmission line at the output of the power amplifier, and an increase in the differential loss, thereby causing the overall power amplifier efficiency to be lowered, and the power amplifier circuit.
  • PCB printed circuit board
  • the PCB size is increased, and the cost of the power amplifier circuit is increased. Summary of the invention
  • the main purpose of the embodiments of the present invention is to provide a Doherty power discharge circuit, which can reduce the size of the power amplifier circuit, reduce the cost of the power amplifier circuit, and improve the efficiency of the power amplifier.
  • a Doherty power amplifier circuit includes: a power distribution circuit, and a power amplifying circuit connected to the power distribution circuit; the Doherty power amplifier circuit further includes a power amplifying circuit The connected combined output circuit, the combined output circuit is a varistor filter.
  • the varistor filter is formed by connecting n-segment microstrip transmission lines of different sizes in series, where n is an integer greater than one.
  • a Doherty power amplifier circuit includes: a power distribution circuit and a power amplifying circuit connected to the power distribution circuit; the Doherty power amplifier circuit further includes a combined output circuit connected to the power amplifying circuit, wherein the combined output circuit is a variable resistance coupler .
  • the varistor coupler includes a main line and a sub line; the main line and the sub line each adopt a microstrip transmission line, and the main line and the sub line are coupled by parallel line coupling or parallel line plus tooth structure.
  • the main line is an impedance conversion line.
  • a Doherty power amplifier circuit comprising: a power distribution circuit and a power distribution circuit a power amplifying circuit; the Doherty power amplifier circuit further includes a combined output circuit connected to the power amplifying circuit, wherein the combined output circuit is a variable resistance filter coupler.
  • the varistor filter coupler includes a main line and a sub line; the main line and the sub line each adopt a microstrip transmission line, and the main line and the sub line are coupled by a parallel line or a parallel line plus a tooth structure
  • the main line is formed by connecting microstrip transmission lines of different sizes in series.
  • the Doherty power amplifier circuit provided by the embodiment of the present invention realizes the impedance transformation line, the coupler and the filter of the combined output portion of the traditional Doherty power amplifier circuit by using a variable resistance filter coupler, and simultaneously realizes impedance transformation, The harmonic and power sampling functions are suppressed, thus reducing the size of the power amplifier circuit, increasing the power amplifier index, and reducing the cost of the power amplifier circuit.
  • the embodiment of the present invention can also implement the combined output circuit by using a varistor filter according to the needs of the actual application, to complete the function of impedance transformation and suppressing harmonics; or, the combined output circuit adopts a varistor coupler Implemented to perform the functions of impedance transformation and power sampling.
  • variable resistance filter uses pure microstrip Realized, with high reliability, low cost, easy to implement, and small size, can effectively use the PCB layout space, can significantly improve the harmonic index of the Doherty power amplifier circuit, according to the harmonic test results, each harmonic has With a certain reduction, harmonics can be effectively suppressed;
  • 1 is a schematic structural diagram of a conventional Doherty power amplifier circuit
  • FIG. 2 is a schematic structural view of a Doherty power amplifier circuit of the present invention
  • FIG. 3 is a schematic structural diagram of an example of a varistor filter in the output circuit of the utility model
  • 4 is a schematic structural diagram of an example of a varistor coupler in the output circuit of the utility model
  • FIG. 5 is a schematic structural diagram of a varistor filter coupler in the output circuit of the utility model of the present invention
  • the Doherty power amplifier circuit includes: a power distribution circuit 201, a power amplification circuit 202, and a combined output circuit 203;
  • the power distribution circuit 201 is configured to separate the input signal into N (1, 2, 3, ... N) way signals, and respectively send them into the power amplifying circuit 202 composed of the main amplifier and the slave amplifier; N is a natural number greater than or equal to 2, and N is the sum of the number of main amplifiers and slave amplifiers.
  • the power amplifying circuit 202 is connected to the power distribution circuit and includes a main amplifier, one or more slave amplifiers, and an input/output matching circuit corresponding to each of the amplifiers; the main amplifier and the slave amplifier respectively amplify the input signals and output the signals to the combined output.
  • Circuit 203 Generally, the main amplifier and the slave amplifier are in different working states, for example: the main amplifier can work in the class AB state, and the auxiliary amplifier can work in the class C state; wherein the conduction angle of the class AB amplifier is slightly greater than 90 degrees, It can reduce the crossover distortion that tends to be cut off; Class C amplifiers have a conduction angle of less than 90 degrees and are nonlinear and highly efficient.
  • the power distribution circuit 201 and the power amplifying circuit 202 are the same as those of the conventional Doherty power amplifier circuit, and are not described herein again.
  • the combined output circuit 203 is configured to synthesize the amplified N-channel signals into one signal output, and complete impedance conversion at the output end.
  • the final output of the Doherty power amplifier circuit is required to be matched to 50 ohms. Therefore, the combined output circuit 203 has an impedance conversion function.
  • the combined output circuit 203 is further configured to implement suppression of harmonics and/or signal sampling work. can. Therefore, the combined output circuit 203 may be a varistor filter coupler, a varistor filter, or a varistor coupler; the combined output circuit 203 shown in FIG. 2 is a varistor filter coupler. .
  • the combined output circuit 203 is a variable resistance filter coupler
  • the varistor filter and the varistor coupler are integrated into one circuit, and the main line impedance conversion of the variable resistance coupler is implemented by using a varistor filter.
  • the combined output circuit 203 has impedance conversion, harmonic suppression and signal sampling functions simultaneously; when the combined output circuit 203 is a varistor filter, it has impedance transformation and harmonic suppression function; the combined output circuit 203 is a varistor coupler It has impedance transformation and signal sampling.
  • the Doherty power amplifier circuit of the embodiment of the present invention realizes the change of the working state by impedance modulation under different signal states, so as to improve the efficiency power amplifier when the signal is small, and ensure the linearity of the large signal. Moreover, the Doherty power amplifier circuit of the embodiment of the present invention integrates the functions of the impedance conversion line, the coupler and the filter, and according to the actual application requirements, the combined output circuit satisfies the impedance transformation and realizes the suppression of harmonics and/or Or signal sampling function.
  • the structure of the varistor filter is as shown in FIG. 3, and the varistor filter is formed by connecting microstrip transmission lines 301, 302, 303, and 304 of different sizes in series, here four
  • the length of the segment microstrip transmission line is 1/16 wavelength
  • the characteristic impedance is 53 ohms, 13 ohms, 96 ohms, and 23 ohms.
  • the length and width of each microstrip transmission line can be converted according to the electrical length and impedance parameter values.
  • the microstrip transmission line enables impedance transformation and harmonic suppression. Of course, in practical applications, the size can be slightly changed without affecting the implementation of the function.
  • the microstrip transmission line constituting the varistor filter may not be four segments, and may be n segments, and n may be an integer greater than one.
  • the specific use of several microstrip transmission lines may be based on bandwidth and standing waves in practical applications. It is different than the requirements of other indicators.
  • the microstrip transmission line is a microwave transmission line
  • the microstrip transmission lines of different sizes and forms can be equivalent to corresponding inductance and capacitance. Therefore, the microstrip transmission line can constitute a microwave for various purposes. Component.
  • the varistor filter coupler, the varistor filter and the varistor coupler as the combined output circuit are implemented in the form of a microstrip transmission line.
  • the number of sections of the microstrip transmission line and the size of each section of the microstrip transmission line are mainly determined by various condition parameter variables such as a filter type, an operating frequency, a board parameter, a matching impedance, a bandwidth, a suppression amount, a ripple, and a transmission power.
  • condition parameter variables such as a filter type, an operating frequency, a board parameter, a matching impedance, a bandwidth, a suppression amount, a ripple, and a transmission power.
  • the varistor filter in the example of the utility model is mainly used for suppression
  • the 3rd harmonic of the Doherty amplifier is due to the Doherty amplifier's working frequency range of 920MHz ⁇ 960MHz, and the 3rd harmonic frequency band is 2760MHz ⁇ 2880MHz. Therefore, the interference caused by the 3rd harmonic and the waveform of the Doherty amplifier are greatly affected.
  • the form of the low-pass filter can be used as a prototype, and then converted into a microstrip transmission line by software calculation.
  • the attenuation in the 3rd harmonic band is more than 10dB, and the attenuation in the Doherty power amplifier operating band is less than 0.06dB.
  • the output impedance is matched from 25 ohms to 50 ohms to suppress the third harmonic of the Doherty power amplifier.
  • the specific internal design of the varistor filter belongs to the prior art and will not be described again.
  • the varistor coupler When the combined output circuit 203 is a varistor coupler, the varistor coupler also uses a microstrip transmission line to achieve impedance transformation and power sampling.
  • the structure of the varistor coupler is as shown in FIG. 4.
  • the varistor coupler includes a main line 401 and a sub line 403.
  • the main line 401 and the sub line 403 both use a microstrip transmission line, and the main line 401 and the sub line 403 are toothed by parallel lines.
  • the structure 402 is coupled; the main line 401 is an impedance conversion line capable of transmitting power, implementing impedance transformation, and matching non-50 ohm impedance to 50 ohms.
  • the main line 401 can couple its own power to a part of the sub-line 403 through multiple ways, and interfere with each other, wherein the multiple paths may be parallel line coupling or parallel lines plus toothed Structural coupling, such as: rectangular coupling on parallel lines, triangular coupling on parallel lines, etc., generally parallel line coupling can be used, coupled with the coupling of the tooth structure can further improve the performance of the coupler.
  • Power is transmitted in only one direction in the secondary line 403, power sampling is achieved, and is ultimately output by the 50 ohm transmission line 404.
  • variable resistance filter coupler When the combined output circuit 203 is a variable resistance filter coupler, the variable resistance filter and the variable resistance coupler are Integrated into a circuit, the main line impedance transformation of the varistor coupler is implemented using a varistor filter.
  • the structure of the variable resistance filter coupler is as shown in FIG. 5, and is composed of microstrip transmission lines having different lengths and widths.
  • variable resistance filter coupler includes a main line and a sub line 305, and the main line and the sub line 305 each adopt a microstrip transmission line, and the main line and the sub line 305 are coupled by a parallel line plus a tooth structure 306; wherein the main line is different in size
  • the microstrip transmission lines 301, 302, 303, and 304 are connected in series for implementing impedance transformation and suppressing harmonics, that is, using a varistor filter microstrip transmission line as a main line; and a sub-line 305 for implementing power sampling, and finally
  • the 50 ohm transmission line 307 is output, that is, the sub line of the varistor coupler microstrip transmission line is used as the sub line 305 of the varistor filter coupler.
  • the Doherty power amplifier circuit provided by the embodiment of the present invention realizes the impedance transformation line, the coupler and the filter of the combined output portion of the traditional Doherty power amplifier circuit by using a variable resistance filter coupler, and simultaneously realizes impedance transformation, The harmonic and power sampling functions are suppressed, thus reducing the size of the power amplifier circuit, increasing the power amplifier index, and reducing the cost of the power amplifier circuit.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Amplifiers (AREA)

Abstract

本实用新型公开了一种Doherty功放电路，包括：功率分配电路、与功率分配电路连接的功率放大电路；关键是，该Doherty功放电路还包括与功率放大电路连接的合路输出电路，所述合路输出电路为变阻滤波耦合器、或变阻滤波器、或变阻耦合器。采用本实用新型能够减小功放电路尺寸，降低功放电路的成本，提高功放效率。

Description

一种 Dohert 功放电路 技术领域
本实用新型涉及电子电路领域， 尤其涉及一种 Doherty功放电路。 背景技术
随着日益激烈的市场竟争， 基站产品的性能高低是业内竟争的主要焦 点， 功率放大单元作为基站的重要组成部分， 直接关系着发射信号的质量 和通信效果。 目前， 最为广泛应用的一种成熟技术就是 Doherty功放技术， 大部分功放厂家都已开始批量生产、 应用 Doherty功放， 近年来这种技术无 论在成本方面还是批量生产能力方面仍将占据主流地位， 因此， 如何在该 功放技术的基础上进一步减小功放尺寸， 提高功放的线性和效率显得更加 重要。
传统的 Doherty功率放大器的结构如图 1中标号 102所示， 由两个以上功 放管组成， 分为主功放管和辅助功放管； 其中， 主功放管和辅助功放管分 别工作在不同的工作状态， 通过阻抗调制技术实现效率的提升。 在功放电 路的合路输出端，通常会有阻抗变换线 103来实现阻抗的调制和匹配，例如： 一个典型 Doherty功放电路， 在两个功放管输出的合路输出处会有 35欧姆的 阻抗变换线 103来实现阻抗调制和匹配。
由于收发信机发出的小信号经功率放大器放大后通常会伴随产生一些 谐波信号， 这些谐波信号会对其他设备产生干扰， 因此， 功率放大器对输 出谐波大小都有一定的要求， 一般减小输出谐波信号的方法是在输出端增 加滤波器， 如图 1中在 Doherty功放电路的合路输出端设置有滤波器 105。
另夕卜， Doherty功放电路通常通过数字预失真 ( DPD， Digital Pre-Distortion )来提高线性， 因此， 需要对功放输出信号进行取样， 以进行 DPD训练， 基于此， 可以在 Doherty功放电路的合路输出端增加一个耦合器 来实现信号取样的功能，如图 1所示在 Doherty功放电路中设置有耦合器 104。
从图 1所示的 Doherty功放电路可以看出， Doherty功放电路在设计中需 要在输出 50欧姆微带传输线上设置耦合器来实现 DPD训练功能或功率控制 功能，设置滤波器来抑制谐波；而这些器件都会在印制线路板（PCB， Printed Circuit Board )上占用一定的空间， 如此， 必然会导致功放输出端微带传输 线尺寸增大、差损增大， 进而造成整个功放效率降低、 功放电路的 PCB尺寸 增大、 以及功放电路的成本提高。 发明内容
有鉴于此， 本实用新型实施例的主要目的在于提供一种 Doherty功放电 路， 能够减小功放电路尺寸， 降低功放电路的成本， 提高功放效率。
为达到上述目的， 本实用新型实施例的技术方案是这样实现的： 一种 Doherty功放电路， 包括： 功率分配电路、 与功率分配电路连接的 功率放大电路； 该 Doherty功放电路还包括与功率放大电路连接的合路输出 电路， 所述合路输出电路为变阻滤波器。
所述变阻滤波器由不同尺寸的 n段微带传输线串联而成， 其中， n为大 于 1的整数。
一种 Doherty功放电路， 包括： 功率分配电路、 与功率分配电路连接的 功率放大电路； 该 Doherty功放电路还包括与功率放大电路连接的合路输出 电路， 所述合路输出电路为变阻耦合器。
所述变阻耦合器包括主线和副线； 所述主线和所述副线均采用微带传 输线， 所述主线和所述副线之间通过平行线耦合、 或平行线加齿状结构耦 合。
所述主线为阻抗变换线。
一种 Doherty功放电路， 包括： 功率分配电路、 与功率分配电路连接的 功率放大电路； 该 Doherty功放电路还包括与功率放大电路连接的合路输出 电路， 所述合路输出电路为变阻滤波耦合器。
所述变阻滤波耦合器包括主线和副线； 所述主线和所述副线均采用微 带传输线， 所述主线和所述副线之间通过平行线耦合、 或平行线加齿状结 构耦合； 所述主线由不同尺寸的微带传输线串联而成。
本实用新型实施例所提供的 Doherty功放电路， 将传统 Doherty功放电路 中合路输出部分的阻抗变换线、 耦合器和滤波器三种器件采用变阻滤波耦 合器来实现， 同时实现了阻抗变换、 抑制谐波和功率取样功能， 如此， 能 够减少功放电路尺寸、 提高功放指标、 降低功放电路的成本。
本实用新型实施例还可以根据实际应用的需要， 将合路输出电路采用 变阻滤波器来实现， 以完成阻抗变换和抑制谐波的功能； 或者， 将合路输 出电路采用变阻耦合器来实现， 以完成阻抗变换和功率取样的功能。
合路输出电路采用变阻滤波器时， 能在达到阻抗匹配标准的同时有效 抑制带外谐波的干扰， 这种实现方案具有面积小、 差损低的优点； 变阻滤 波器采用纯微带实现， 具有可靠性高、 成本低、 易于实现的优点， 并且尺 寸小， 能有效利用 PCB布局空间， 可以明显改善 Doherty功放电路的谐波指 标， 根据谐波测试结果显示， 各次谐波均有一定的减小， 谐波能得到有效 抑制；
合路输出电路采用变阻耦合器时， 输出差损降低， 0.015db-0.03db之间 的功放效率有提高； 并且， 能够大大缩小功放电路尺寸， 极大地降低功放 电路的整体成本。 附图说明
图 1为传统 Doherty功放电路的组成结构示意图；
图 2为本实用新型 Doherty功放电路的一种组成结构示意图；
图 3为本实用新型中合路输出电路为变阻滤波器的实例结构示意图； 图 4为本实用新型中合路输出电路为变阻耦合器的实例结构示意图； 图 5为本实用新型中合路输出电路为变阻滤波耦合器的实例结构示意
具体实施方式
本实用新型实施例 Doherty功放电路的一种组成结构， 如图 2所示， 该 Doherty功放电路包括： 功率分配电路 201、 功率放大电路 202、 合路输出电 路 203; 具体的，
功率分配电路 201， 配置为将输入信号分离为 N ( 1， 2， 3， ... ... N )路 信号， 分别送入由主放大器和从放大器构成的功率放大电路 202中； 其中， N为大于等于 2的自然数， N为主放大器和从放大器个数之和。
功率放大电路 202， 与功率分配电路连接， 包括一个主放大器、 一个以 上从放大器以及每个放大器对应的输入输出匹配电路； 主放大器和从放大 器分别将输入自身的信号进行放大后输出至合路输出电路 203; 通常， 主放 大器和从放大器分别处于不同的工作状态， 比如： 主放大器可以工作在 AB 类状态， 辅助放大器可以工作在 C类状态； 其中， AB类放大器导通角略大 于 90度， 能减少趋于截止时出现的交越失真； C类放大器导通角小于 90度， 具有非线性、 效率高的特性。
上述功率分配电路 201和功率放大电路 202与传统 Doherty功放电路结构 和功能均相同， 在此不再赘述。
合路输出电路 203， 配置为将放大后的 N路信号合成为一路信号输出， 并完成输出端的阻抗变换。 而 Doherty功放电路最终输出端要求匹配为 50欧姆， 因此，合路输出电路 203 具备阻抗变换功能。
进一步的， 合路输出电路 203还配置为实现抑制谐波和 /或信号取样功 能。 因此， 所述合路输出电路 203可以是变阻滤波耦合器， 也可以是变阻滤 波器， 还可以是变阻耦合器； 图 2中示出的合路输出电路 203为变阻滤波耦 合器。
具体的， 合路输出电路 203为变阻滤波耦合器时， 是将变阻滤波器和变 阻耦合器集成到一个电路中， 变阻耦合器的主线阻抗变换采用变阻滤波器 来实现， 这种合路输出电路 203同时具有阻抗变换、 抑制谐波和信号取样功 能； 合路输出电路 203为变阻滤波器时， 具有阻抗变换和抑制谐波功能； 合 路输出电路 203为变阻耦合器时， 具有阻抗变换和信号取样功能。
本实用新型实施例的 Doherty功放电路， 通过不同信号状态下的阻抗调 制， 实现工作状态的改变， 以提高小信号时的效率功放， 并保证大信号时 的线性。 并且， 本实用新型实施例的 Doherty功放电路是将阻抗变换线、 耦 合器和滤波器的功能融为一体， 根据实际应用需要， 使合路输出电路在满 足阻抗变换同时， 实现抑制谐波和 /或信号取样功能。
下面结合附图和具体实施例对本实用新型做进一步的说明。
合路输出电路 203为变阻滤波器时， 变阻滤波器的结构如图 3所示， 该 变阻滤波器由不同尺寸的微带传输线 301、 302、 303、 304串联而成， 这里 的四段微带传输线电长度 1/16波长， 特性阻抗分别为 53欧姆、 13欧姆、 96 欧姆、 23欧姆， 具体每段微带传输线的长度和宽度可以根据电长度和阻抗 参数值换算得出， 整个微带传输线能实现阻抗变换和抑制谐波的功能。 当 然， 在实际应用中， 尺寸可以略有变化， 不会影响功能的实现。
在实际应用中， 构成变阻滤波器的微带传输线也可以不是四段， 可以 为 n段， n为大于 1的整数即可， 具体使用几段微带传输线可以根据实际应用 中带宽和驻波比等指标要求的不同而不同。
这里， 所述微带传输线是一种微波传输线， 不同尺寸和形式的微带传 输线可等效成相应的电感电容， 因此， 微带传输线可构成各种用途的微波 元件。 本实用新型实施例中， 作为合路输出电路的变阻滤波耦合器、 变阻 滤波器和变阻耦合器均采用微带传输线形式实现。
其中， 所述微带传输线的节数和各节微带传输线的尺寸， 主要由滤波 类型、 工作频率、 板材参数、 匹配阻抗、 带宽、 抑制量、 波紋、 传输功率 等多种条件参数变量决定。 本实用新型实例中的变阻滤波器主要用于抑制
Doherty功放中 的 3次谐波， 由 于 Doherty功放的工作频段为 920MHz~960MHz， 3次谐波的频段为 2760MHz~2880MHz， 因此， 3次谐波 产生的干扰及对 Doherty功放的波形影响较大。 通常， 可采用低通滤波器的 形式作为原型， 再经过软件计算， 变型转换成微带传输线的形式， 最终实 现在 3次谐波频段衰减 10dB以上， 在 Doherty功放工作频带内衰减小于 0.06dB, 同时输出端阻抗由 25欧姆匹配到 50欧姆， 以达到抑制 Doherty功放 中 3次谐波的作用。 这里， 变阻滤波器具体的内部设计属于现有技术， 不再 赘述。
合路输出电路 203为变阻耦合器时， 变阻耦合器也采用微带传输线， 实 现阻抗变换和功率取样。 变阻耦合器的结构如图 4所示， 变阻耦合器包括主 线 401和副线 403，主线 401和副线 403均采用微带传输线，主线 401和副线 403 之间通过平行线加齿状结构 402耦合； 所述主线 401为阻抗变换线， 能传输 功率、 实现阻抗变换， 将非 50欧姆的阻抗匹配成 50欧姆。
实际应用中， 所述主线 401可以通过多种途径将自身的功率耦合到副线 403上一部分， 且相互干涉， 其中， 所述多种途径可以是平行线耦合， 也可 以是平行线加齿状结构耦合， 如： 平行线上加矩形耦合、 平行线上加三角 形耦合等等， 一般采用平行线耦合即可， 加上齿状结构耦合可以进一步提 高耦合器的性能。 功率在副线 403中只沿一个方向传输， 实现功率取样， 并 最终由 50欧姆传输线 404输出。
合路输出电路 203为变阻滤波耦合器时， 是将变阻滤波器和变阻耦合器 集成到一个电路， 将变阻耦合器的主线阻抗变换采用变阻滤波器实现。 变 阻滤波耦合器的结构如图 5所示， 由多节长宽尺寸不同的微带传输线组成。
具体的， 变阻滤波耦合器包括主线和副线 305， 主线和副线 305均采用 微带传输线， 主线和副线 305之间通过平行线加齿状结构 306耦合； 其中， 主线由不同尺寸的微带传输线 301、 302、 303、 304串联而成， 用于实现阻 抗变换和抑制谐波， 即： 采用变阻滤波器微带传输线作为主线； 副线 305， 用于实现功率取样， 并最终由 50欧姆传输线 307输出， 即： 采用变阻耦合器 微带传输线的副线作为变阻滤波耦合器的副线 305。
以上所述， 仅为本实用新型的较佳实施例而已， 并非用于限定本实用 新型的保护范围。 工业实用性
本实用新型实施例所提供的 Doherty功放电路， 将传统 Doherty功放电路 中合路输出部分的阻抗变换线、 耦合器和滤波器三种器件采用变阻滤波耦 合器来实现， 同时实现了阻抗变换、 抑制谐波和功率取样功能， 如此， 能 够减少功放电路尺寸、 提高功放指标、 降低功放电路的成本。

Claims

权利要求书
1、 一种 Doherty功放电路， 包括： 功率分配电路、 与功率分配电路连接 的功率放大电路； 该 Doherty功放电路还包括与所述功率放大电路连接的合 路输出电路， 所述合路输出电路为变阻滤波器。
2、 根据权利要求 1所述 Doherty功放电路， 其中， 所述变阻滤波器由不 同尺寸的 n段微带传输线串联而成， 其中， n为大于 1的整数。
3、 一种 Doherty功放电路， 包括： 功率分配电路、 与功率分配电路连接 的功率放大电路； 该 Doherty功放电路还包括与所述功率放大电路连接的合 路输出电路， 所述合路输出电路为变阻耦合器。
4、 根据权利要求 3所述 Doherty功放电路， 其中，
所述变阻耦合器包括主线和副线；
所述主线和所述副线均采用微带传输线，
所述主线和所述副线之间通过平行线耦合、 或平行线加齿状结构耦合。
5、 根据权利要求 3所述 Doherty功放电路， 其中， 所述主线为阻抗变换 线。
6、 一种 Doherty功放电路， 包括： 功率分配电路、 与功率分配电路连接 的功率放大电路； 该 Doherty功放电路还包括与所述功率放大电路连接的合 路输出电路， 所述合路输出电路为变阻滤波耦合器。
7、 根据权利要求 6所述 Doherty功放电路， 其中，
所述变阻滤波耦合器包括主线和副线； 所述主线和所述副线均采用微 带传输线， 所述主线和所述副线之间通过平行线耦合、 或平行线加齿状结 构耦合；
所述主线由不同尺寸的微带传输线串联而成。
PCT/CN2013/083765 2012-09-18 2013-09-18 一种Doherty功放电路 WO2014044189A1 (zh)

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