CN111614331A - Novel Doherty power amplifier based on rear matching structure - Google Patents
Novel Doherty power amplifier based on rear matching structure Download PDFInfo
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- CN111614331A CN111614331A CN202010666094.1A CN202010666094A CN111614331A CN 111614331 A CN111614331 A CN 111614331A CN 202010666094 A CN202010666094 A CN 202010666094A CN 111614331 A CN111614331 A CN 111614331A
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- 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
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- 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
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Abstract
The invention discloses a novel Doherty power amplifier based on a rear matching structure, which is characterized in that: the power divider comprises an equal power divider for dividing one path of radio frequency signals into multiple paths, a carrier power amplifier module for processing the signals and amplifying voltage, a peak power amplifier module for carrying out load modulation according to the carrier power amplifier module and a rear matching network; the output end of the equal power divider is divided into two paths which are respectively connected with the input ends of the carrier power amplification module and the peak power amplification module; the scheme can ensure efficiency and realize a broadband power amplifier.
Description
Technical Field
The invention relates to the technical field of communication, in particular to a novel Doherty power amplifier based on a rear matching structure.
Background
To date, Power Amplifier (PA) designs for wireless communications have focused primarily on improving radio frequency bandwidth, efficiency, and linearity. The traditional design method only can achieve high efficiency and sacrifice bandwidth, and cannot be applied to a broadband wireless communication system covering a plurality of frequency bands. Especially, both the current 4G and the future 5G communication systems need to realize a broadband power amplifier while ensuring efficiency.
For this current situation, s.c. crispps proposed a continuous wideband-like power amplifier in 2009, describing a novel formula for voltage waveform in a high-efficiency linear power amplifier. A series of continuous modes such as continuous B/J type, continuous F type and continuous inverse F type are proposed in succession, K.Chen et al synthesizes continuous F type and continuous inverse F type in 2012, and all the working modes provide relatively perfect theory and practical feasibility for designing broadband power amplifiers.
However, these operation modes still require the real part of the fundamental impedance or admittance space to be a constant value, and in order to further expand the space, j.chen et al from the university of electronics in china proposed scms (series of continuous modes) mode, which achieves the purpose of further expanding the bandwidth by expanding the equation on a continuous class basis, and thereafter, sicm (the series of inverse continuous modes) was proposed by w.shi et al. These operating modes extend the bandwidth of the continuous mode,
at present, the traditional design method only can achieve high efficiency and sacrifice bandwidth, and can not be applied to a broadband wireless communication system covering a plurality of frequency bands.
Disclosure of Invention
The invention aims to provide a novel Doherty power amplifier based on a post-matching structure, which is used for realizing a broadband power amplifier while ensuring the efficiency.
In order to achieve the purpose, the invention provides the following technical scheme:
novel Doherty power amplifier based on back matching structure, its characterized in that: the power divider comprises an equal power divider for dividing one path of radio frequency signals into multiple paths, a carrier power amplifier module for processing the signals and amplifying voltage, a peak power amplifier module for carrying out load modulation according to the carrier power amplifier module and a rear matching network;
the output end of the equal power divider is divided into two paths which are respectively connected with the input ends of the carrier power amplification module and the peak power amplification module;
the carrier power amplifier module is formed by connecting a phase compensation line, a carrier input matching network, a carrier amplifier and a carrier output matching network in series in sequence;
the peak power amplifier module comprises a peak compensation line, a peak input matching network, a peak amplifier and a peak output matching network, wherein the peak input matching network, the peak amplifier and the peak output matching network are sequentially connected in series with the peak compensation line;
the output ends of the carrier power amplifier module and the peak power amplifier module are connected with the input end of the rear matching network, and the output end of the rear matching network is used as a radio frequency output end.
Preferably, the carrier amplifier employs a carrier transistor.
Preferably, the peak power amplifier module adopts a peak transistor.
Preferably, the rear matching network includes a wavelength line module, a microstrip line and a dc blocking capacitor, the wavelength line module, the microstrip line and the dc blocking capacitor are sequentially connected in series, the microstrip line is a 50 Ω microstrip line, a resistor is installed between the microstrip line and the dc blocking capacitor, and the wavelength line module includes a plurality of resistors sequentially connected in series.
Preferably, the carrier amplifier has a carrier power amplifier circuit saturation region, the optimal load point of the carrier power amplifier circuit saturation region is 20 Ω, the load impedance of the system is selected to be 10 Ω, so that the impedance of the saturation region is matched to the impedance of a 20 Ω critical back-off region to be 10 Ω by using a relatively low-order network, and the carrier input matching network and the carrier output matching network respectively designed have characteristic load impedance, which is 20 Ω in the saturation region and 10 Ω in the critical back-off region.
The peak power amplifier is usually biased in class C to meet the requirement that the peak power amplifier is not turned on when the input power is small, the gate voltage of the peak power amplifier is biased at-6V, the output power is insufficient due to too deep bias, and the source voltage of the peak power amplifier is set at 32V to meet the requirement of the output power.
In summary, the scheme includes: the power divider is used for dividing one path of signal into multiple paths, and the design is a symmetrical design, so that the input power of the carrier power amplifier and the input power of the peak power amplifier are equal by selecting the power divider; the carrier power amplifier in the Doherty circuit determines the efficiency of a critical backspacing region of the whole circuit, so that the carrier power amplifier needs to show high-efficiency characteristics in both the critical backspacing region and a saturation region; the peak power amplifier is mainly used for carrying out load modulation on the carrier power amplifier and is matched with the carrier power amplifier to carry out power output after a power starting point; in the previous design, the impedance of the output end of the carrier power amplifier and the peak power amplifier after being combined is 10 Ω, and the standard impedance of the communication system and the test system is 50 Ω, so a back matching circuit is needed to match 10 Ω to 50 Ω; and the phase compensation line and the peak compensation line can adjust the length of the carrier phase adjusting line and the length of the peak phase adjusting line, so that the phases of the two paths of power amplifier output are the same when the power is superposed, and the maximum power output is obtained.
Aiming at the bandwidth limiting factor of the traditional Doherty power amplifier, the invention adopts a matching structure after application and designs a Doherty power amplifier working at 2.4-3.4GHz including a 4G reserved frequency band and a 5G middle frequency band in a simulation way.
Drawings
FIG. 1 is a block diagram of the structure of the novel Doherty power amplifier based on the post-matching structure;
FIG. 2 is a schematic diagram of the design of the carrier power amplifier module of FIG. 1;
FIG. 3 is a schematic diagram of the design of the peak power amplifier module of FIG. 1;
FIG. 4 is a schematic design diagram of the back matching circuit of FIG. 1;
fig. 5 is a schematic diagram of a carrier power amplifier module.
Detailed Description
The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.
Referring to fig. 1, the system of the Doherty power amplifier based on the post-matching structure includes an equal power divider, a carrier power amplifier module, a peak power amplifier module, a post-matching network, a phase compensation line, and a peak compensation line.
The radio frequency power amplifier comprises an equal power divider for dividing a path of radio frequency signals into multiple paths, a carrier power amplifier module for processing the signals and amplifying voltage, a peak power amplifier module for carrying out load modulation according to the carrier power amplifier module and a rear matching network;
the output end of the equal power divider is divided into two paths which are respectively connected with the input ends of the carrier power amplification module and the peak power amplification module;
the output ends of the carrier power amplifier module and the peak power amplifier module are connected with the input end of the rear matching network, and the output end of the rear matching network is used as a radio frequency output end.
As shown in fig. 2 and 5, the carrier power amplifier module is formed by connecting a phase compensation line, a carrier input matching network B, a carrier amplifier D and a carrier output matching network C in series in sequence; preferably, the carrier amplifier D employs a carrier transistor.
The optimal load point of the carrier power amplifier circuit in the saturation region is about 20 omega, so that the load impedance Z of the system is selectedCLIs 10 omega in order to match the impedance of the saturation region to the impedance of the 20 omega critical back-off region to 10 omega using a relatively low order network. The input and output matching networks are designed separately. The characteristic load impedance is 20 omega in a saturation region and 10 omega in a critical rollback region, the blocking capacitor of the carrier power amplifier is arranged behind the rear matching circuit, and the capacitor at the output end in the figure is only convenient for simulation and does not participate in matching, so that an ideal large capacitor of 1 muF is adopted. The length of the carrier phase adjusting line does not influence the performance of the carrier power amplifier.
The peak power amplifier in the Doherty circuit mainly plays a role in load modulation of a carrier power amplifier, and is matched with the carrier power amplifier to output power after a power starting point.
As shown in fig. 3, the peak power amplifier module includes a peak compensation line 2ZL, a peak input matching network E, a peak amplifier and a peak output matching network G, and the peak input matching network, the peak amplifier and the peak output matching network and the peak compensation line are sequentially connected in series; preferably, the peak power amplifier module adopts a peak transistor.
The peak power amplifier module is usually biased in class C to meet the requirement that the peak power amplifier is not turned on when the input power is small. The section biases the grid voltage of the peak power amplifier to-6V, and the output power is insufficient due to too deep bias. Because the output capability of the transistor in the high frequency band is not ideal, the drain-source voltage is set at 32V to meet the output power requirement.
In the foregoing design, the impedance of the output end after the carrier power amplifier and the peak power amplifier are combined is 10 Ω, and the standard impedance of the communication system and the test system is 50 Ω, so a back matching circuit is required to match 10 Ω to 50 Ω.
As shown in fig. 4, a flattest low-pass filter prototype is used to perform matching from 10 Ω to 50 Ω, three quarter-wavelength lines are used to perform impedance conversion, and simultaneously, the function of filtering high-frequency harmonics is achieved, and after the three lines are designed, a 50 Ω microstrip line and a dc blocking capacitor are added, wherein the dc blocking capacitor is 9.1 uf.
The square connections in fig. 2-4 are all microstrip lines, the numbers above are microstrip line parameter width (mm)/length (mm), and the size of the first microstrip line in fig. 4 is: namely, the microstrip line with the width of 8.8mm and the length of 0.2mm, the size of the microstrip line is obtained in the same way for other microstrip lines, and meanwhile, all microstrip lines adopt 50 omega microstrip lines. The peak power amplifier module is similar to the carrier power amplifier module, and the principle can be referred to.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (7)
1. Novel Doherty power amplifier based on back matching structure, its characterized in that: the power divider comprises an equal power divider for dividing one path of radio frequency signals into multiple paths, a carrier power amplifier module for processing the signals and amplifying voltage, a peak power amplifier module for carrying out load modulation according to the carrier power amplifier module and a rear matching network;
the output end of the equal power divider is divided into two paths which are respectively connected with the input ends of the carrier power amplification module and the peak power amplification module;
the carrier power amplifier module is formed by connecting a phase compensation line, a carrier input matching network, a carrier amplifier and a carrier output matching network in series in sequence;
the peak power amplifier module comprises a peak compensation line, a peak input matching network, a peak amplifier and a peak output matching network, wherein the peak input matching network, the peak amplifier and the peak output matching network are sequentially connected in series with the peak compensation line;
the output ends of the carrier power amplifier module and the peak power amplifier module are connected with the input end of the rear matching network, and the output end of the rear matching network is used as a radio frequency output end.
2. The novel Doherty power amplifier based on post-matching structure of claim 1, wherein: the carrier amplifier employs a carrier transistor.
3. The novel Doherty power amplifier based on post-matching structure of claim 1, wherein: the peak power amplification module adopts a peak transistor.
4. The novel Doherty power amplifier based on post-matching structure of claim 1, wherein: the rear matching network comprises a wavelength line module, a microstrip line and a blocking capacitor, wherein the wavelength line module is used for converting 10 omega impedance to 50 omega impedance, the wavelength line module, the microstrip line and the blocking capacitor are sequentially connected in series, and the microstrip line is a 50 omega microstrip line.
5. The novel Doherty power amplifier based on post-matching structure of claim 1, wherein: the carrier amplifier is provided with a carrier power amplifier circuit saturation area, the optimal load point of the carrier power amplifier circuit saturation area is 20 omega, the output end of the carrier output matching network is connected with load impedance, the selected load impedance is 10 omega, the carrier input matching network is provided with characteristic load impedance, the characteristic load impedance of the carrier input matching network is 20 omega in the saturation area, and is 10 omega in a critical rollback area.
6. The novel Doherty power amplifier based on post-matching structure of claim 1 or 2, characterized in that: the peak power amplifier module is usually biased in class C to meet the requirement that the peak power amplifier is not turned on when the input power is small, the gate voltage of the peak amplifier is biased at-6V, the output power is insufficient due to too deep bias, and the source voltage of the peak amplifier is set at 32V to meet the requirement of the output power.
7. The novel Doherty power amplifier based on post-matching structure of claim 5, wherein: the carrier output matching network is connected in series with a blocking capacitor, the blocking capacitor is arranged behind the rear matching network, and the blocking capacitor is 1 muF.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113839621A (en) * | 2021-11-26 | 2021-12-24 | 华南理工大学 | Doherty power amplifier |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113839621A (en) * | 2021-11-26 | 2021-12-24 | 华南理工大学 | Doherty power amplifier |
| CN113839621B (en) * | 2021-11-26 | 2022-04-01 | 华南理工大学 | Doherty power amplifier |
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