CN210780690U - Novel broadband Doherty power amplifier of way - Google Patents
Novel broadband Doherty power amplifier of way Download PDFInfo
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- CN210780690U CN210780690U CN201922483856.XU CN201922483856U CN210780690U CN 210780690 U CN210780690 U CN 210780690U CN 201922483856 U CN201922483856 U CN 201922483856U CN 210780690 U CN210780690 U CN 210780690U
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Abstract
The utility model discloses a novel broadband Doherty power amplifier of way that closes, divide ware, carrier power amplifier circuit, peak power amplifier circuit, load modulation network and back matching network including Wilkinson merit, the Wilkinson merit divide the input power to carry out after dividing equally respectively export give carrier power amplifier circuit and peak power amplifier circuit, carrier power amplifier circuit's output with peak power amplifier circuit's output with the load modulation network is connected, the load modulation network with back matching network is connected, warp the load modulation network gives power output back matching network, warp back matching network gives power output for the load. The utility model reduces the impedance transformation ratio of the impedance transformation line at the output end of the carrier power amplifier; and a rear matching network optimized by a simplified real-frequency method is used at the combining end to replace a quarter-wavelength line to realize broadband matching to the load, and the working bandwidth of the Doherty power amplifier is expanded.
Description
Technical Field
The utility model belongs to the technical field of power amplifier, a novel broadband Doherty power amplifier who closes way is related to.
Background
With the rapid development of communication technology, China formally enters the 5G commercial era. In the 5G era, a very important technical feature is the ability to connect potentially billions of everything in computation with high bandwidth, low latency. The fifth generation mobile communication also needs to satisfy high mobility, seamless roaming, and seamless coverage. In principle, it is difficult to achieve broadband high-speed data rates and high mobility, which can be very much band dependent. This puts higher demands on the power amplifier.
The power amplifier is one of the most important devices in the transmitter of the wireless communication system, and the indexes of linearity, efficiency, bandwidth, stability and the like play a key role. At present, the Doherty power amplifier is the mainstream form of the power amplifier used in the wireless communication at present because the Doherty power amplifier can efficiently amplify the modulated signal and has low cost.
However, the quarter-impedance transformation line is used in the load modulation network of the conventional Doherty power amplifier for many times, so that the Doherty power amplifier can only work normally in a narrow bandwidth, and the narrow-band characteristic is not suitable for the current wireless communication system, so that designing a wideband Doherty power amplifier suitable for the 5G frequency band becomes a hotspot of research in academia and industry.
There are many factors that limit the bandwidth in the Doherty power amplifier structure, such as a power divider, a compensation line, a matching circuit of the main and auxiliary power amplifiers, and a load modulation network, which all have the function of limiting the bandwidth. In the prior art, the following method is generally adopted to increase the bandwidth of the Doherty amplifier: (1) the bandwidth is increased by using a load modulation network for reducing the impedance transformation ratio of the quarter wavelength, but the quarter wavelength line after the combination point is still the problem of limiting the bandwidth. (2) The length of the compensation wire at the output end of the main and auxiliary power amplifiers is effectively shortened by adopting a double-impedance matching method. However, the requirement of the matching circuit of the main and auxiliary power amplifiers caused by the dual-impedance matching method is extremely high.
Therefore, in view of the above-mentioned drawbacks in the prior art, it is necessary to develop and improve a solution to solve the above-mentioned drawbacks in the prior art.
SUMMERY OF THE UTILITY MODEL
In order to solve the above problem, an object of the present invention is to provide a wideband Doherty power amplifier based on a novel combining circuit, which reduces the impedance transformation ratio at the output end of the carrier amplifier through a novel load modulation network, and uses a back matching network (simplified real frequency method synthesis) to match the combining point impedance to the load end, replacing the conventional quarter-wavelength impedance transformer, so as to extend the working bandwidth of the Doherty power amplifier.
In order to achieve the above purpose, the technical scheme of the utility model is that:
a novel combined broadband Doherty power amplifier comprises a Wilkinson power divider, a carrier power amplifying circuit, a peak power amplifying circuit, a load modulation network and a rear matching network, wherein,
the Wilkinson power divider equally divides input power and then respectively outputs the divided input power to the carrier power amplifying circuit and the peak power amplifying circuit, the output end of the carrier power amplifying circuit and the output end of the peak power amplifying circuit are connected with the load modulation network, the load modulation network is connected with the rear matching network, power is output to the rear matching network through the load modulation network, and the power is output to a load through the rear matching network;
the carrier power amplification circuit comprises a carrier input matching circuit, a carrier power amplifier and a carrier output matching circuit which are sequentially connected in series, and the carrier output matching circuit is connected with a load modulation network; the peak power amplification circuit comprises a peak input matching circuit, a peak power amplifier and a peak output matching circuit which are sequentially connected in series;
the load modulation network comprises a first impedance transformer T1 of 1/4 wavelength and a peak compensation line T2; the carrier amplifying circuit is connected with a peak value compensation line T2 in the peak value amplifying circuit through the first impedance converter T1, and outputs power to a load through the rear matching network.
Preferably, the wilkinson power divider is in an equal division mode.
Preferably, the carrier power amplifier is a class AB power amplifier, and the peak power amplifier is a class C power amplifier.
Preferably, the impedance of the first impedance transformer T1 is 43.3 Ω.
Preferably, the impedance of the peak compensation line T2 is 75 Ω.
Preferably, the impedance of the first impedance transformer T1 is 50 Ω.
Preferably, the impedance of the peak compensation line T2 is 50 Ω.
Preferably, the back matching network comprises a multi-stage LC configuration high-low impedance converter.
Preferably, a 50 Ω phase compensation line is provided between the wilkinson power divider and the peak power amplifying circuit.
Compared with the prior art, the utility model discloses divide ware is exported respectively for carrier power amplifier circuit and peak power amplifier circuit after dividing equally to input power to the partition Wilkinson merit, and carrier power amplifier circuit's output termination 43.3 omega quarter wavelength impedance transformer T1 to be connected with peak power amplifier circuit's output 75 omega peak compensation line T2 and combine the output with power and export for back matching network, back matching network exports for the load through the broadband matching network.
Compared with the prior art, the utility model discloses an improve traditional Doherty power amplifier's load modulation network, reduce the impedance transformation ratio of carrier power amplifier output end impedance transformation line; and a rear matching network optimized by a simplified real-frequency method is used at the combining end to replace a quarter-wavelength line to realize broadband matching to the load, so that the working bandwidth of the Doherty power amplifier is expanded. The method at least comprises the following beneficial effects:
1. the impedance value of the quarter-wave line is changed, so that the transformation ratio is reduced;
2. a peak value compensation line is added behind the peak value output matching circuit, which is beneficial to realizing the impedance of a combining point and enables the power amplifier to keep a high-impedance open circuit at low power;
3. and a rear matching circuit is arranged behind the combining point to replace a quarter-wave line in the prior art, so that the bandwidth is favorably expanded, and a simplified real-frequency technology is applied to the rear matching circuit, so that the bandwidth is further favorably expanded.
Drawings
Fig. 1 is a block diagram of a wideband Doherty power amplifier with a novel combiner according to an embodiment of the present invention;
fig. 2 is a block diagram of a load modulation network in a prior art Doherty power amplifier;
fig. 3 is a block diagram of a load modulation network structure of a wideband Doherty power amplifier with a novel combiner according to an embodiment of the present invention;
fig. 4 is a diagram of a matching network for implementing scattering parameters by a simplified real-frequency method in the wideband Doherty power amplifier with a novel combiner according to the embodiment of the present invention;
fig. 5 is a simulation diagram of the S parameter of the back matching network circuit of the wideband Doherty power amplifier of the novel combiner according to the embodiment of the present invention;
fig. 6 is a simulation result diagram of the saturated drain efficiency and the 6dB output back-off efficiency of the wideband Doherty power amplifier with a novel combiner according to the embodiment of the present invention;
fig. 7 is a flowchart illustrating steps of a method for designing a wideband Doherty power amplifier with a novel combiner according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
On the contrary, the invention is intended to cover alternatives, modifications, equivalents and alternatives which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in order to provide a better understanding of the present invention to the public, certain specific details are set forth in the following detailed description of the invention. It will be apparent to those skilled in the art that the present invention may be practiced without these specific details.
Example 1
Referring to fig. 1, a wideband Doherty power amplifier with a novel combiner according to an embodiment of the present invention is shown, which includes a wilkinson power divider 10, a carrier power amplifier circuit, a peak power amplifier circuit, a load modulation network 60 and a back matching network 70, wherein,
the Wilkinson power divider 10 equally divides the input power and respectively outputs the power to the carrier power amplifying circuit and the peak power amplifying circuit, the output end of the carrier power amplifying circuit and the output end of the peak power amplifying circuit are connected with the load modulation network 60, the load modulation network 60 is connected with the rear matching network 70, the power is output to the rear matching network 70 through the load modulation network 60, and the power is output to the load through the rear matching network 70;
the carrier power amplifying circuit comprises a carrier input matching circuit 31, a carrier power amplifier 41 and a carrier output matching circuit 51 which are sequentially connected in series, wherein the carrier output matching circuit 51 is connected with the load modulation network 60; the peak power amplifying circuit comprises a peak input matching circuit 32, a peak power amplifier 42 and a peak output matching circuit 52 which are sequentially connected in series;
the load modulation network 60 comprises a first impedance transformer T1 of 1/4 wavelength and a peak compensation line T2; the carrier amplifying circuit is connected with a peak value compensation line T2 in the peak value amplifying circuit through a first impedance converter T1, and outputs power to a load through a rear matching network 70.
Detailed description of the preferred embodiments
The wilkinson power divider 10 is of an equal division type.
The carrier power amplifier 41 is a class AB power amplifier and the peak power amplifier 42 is a class C power amplifier.
The impedance of the first impedance transformer T1 is 43.3 Ω or 50 Ω.
The impedance of the peak compensation line T2 is 75 Ω or 50 Ω.
The back matching network 70 comprises a multi-stage LC configuration high-low impedance converter.
A 50 Ω phase compensation line 20 is provided between the wilkinson power divider 10 and the peak power amplifier circuit.
The carrier power amplifier 41 and the peak power amplifier 42 are implemented using transistors.
The impedance transformation ratio of the quarter-wavelength first impedance transformer T1 in the load modulation network 60 is a major factor limiting the bandwidth of the Doherty power amplifier, and the approximate expression of the operating bandwidth of the quarter-wavelength transmission line is:
wherein, Δ f/f0Representing the relative bandwidth of a quarter-wavelength transmission line; gamma-shapedmIs the maximum acceptable reflection coefficient; zinAnd ZLRepresenting the impedance values of the input and output two ports of the quarter-wave transmission line; according to the formula (1), when Z isinAnd ZLThe closer the impedance value of (a), i.e., the smaller the impedance transformation ratio of the quarter-wavelength impedance transformation line, the wider the operating bandwidth thereof. Therefore, to increase Δ f/f0By decreasing ZinAnd ZLI.e. the impedance transformation ratio of the reduced quarter-wave transmission line. Referring to fig. 2, the T1 and T3 impedances of the quarter-wave lines in the prior art Doherty power amplifier load modulation network 60 are 50 Ω and 35.3 Ω, respectively, and the impedance transformation ratio is 4:1 (from 100 Ω to 25 Ω).
Therefore, the applicant applies the above theoretical analysis to the circuit design, and improves the load modulation network 60 of the Doherty power amplifier in the prior art, referring to fig. 3, by using the first impedance transformer T1 of a quarter wavelength of 43.3 Ω at the output of the carrier power amplifier 41, using the peak compensation line T2 at the output of the peak power amplifier 42, transforming the load impedance of 50 Ω to 75 Ω, and using the simplified real-frequency optimized post-matching network 70 at the combining end instead of the quarter wavelength line T3 in the prior art, thereby further expanding the bandwidth.
The impedance transformation before and after the transmission line can be calculated according to the formula (2), so that the impedance transformation of each structure of the Doherty power amplifier when low-power and high-power signals are input is analyzed, and the purpose of controlling the current in the main path and the auxiliary path (carrier and peak value) in the active load traction theory is realized.
Z in the formula (2)inRepresenting the input impedance of the transmission line; zLRepresenting the output impedance of the transmission line; z0Representing the characteristic impedance of the transmission line, and β l representing the electrical length of the transmission line.
When a low-power signal is input, the peak power amplifier 42 is in a class C state, and the signal strength is not enough to enable the peak power amplifier 42 to work, so that the peak power amplifier 42 is cut off and in a high-impedance state; at this time, the carrier power amplifier 41 operating in class AB operates, and since the 1/4 wavelength conversion line changes the load to a load impedance 1.5 times, that is, Z1 is 75 Ω, the load voltage increases, so that the carrier power amplifier 41 enters a pre-saturation state in advance, and the efficiency is improved.
When a high-power signal is input, the peak power amplifier 42 is turned on, an active modulation effect occurs, at this time, the equivalent load of the carrier power amplifier 41 decreases from the optimal impedance 75 Ω of 1.5 times to the optimal impedance 50 Ω, at this time, the voltage of the carrier power amplifier 41 is kept in a pre-saturation state under the control of the peak power amplifier 42, and the load of the peak power amplifier 42 also changes from an open circuit state to the optimal load impedance 50 Ω. When the peak power amplifier 42 is saturated, the currents of the carrier power amplifier 41 and the peak power amplifier 42 reach the maximum value, the load impedance of the main circuit (the carrier power amplifying circuit) is 37.5 Ω, the load impedance of the auxiliary circuit (the peak power amplifying circuit) is 75 Ω, the impedance value of the combining point is 25 Ω, the two paths of power are combined, and the output reaches the maximum value.
By analysis, the first impedance transformer T1 of the quarter-wave line in the load modulation network 60 has an impedance transformation ratio of 3:1 (from 75 Ω to 25 Ω), reducing ZinAnd ZLThus extending the operating bandwidth of the Doherty power amplifier.
The input/output matching networks of the carrier power amplifier 41 and the peak power amplifier 42 and the post-matching network 70 are circuit structures designed and optimized by a simplified real frequency method, and here, the broadband matching of the post-matching network 70 is taken as an example.
The applicant carried out a wideband design of the above five-part matching circuit using a simplified real frequency method (SRFT) that optimizes the Transmission Power Gain (TPG) by building a matching network with reference to the scattering parameters (S-parameters) in fig. 4, which is expressed as:
e in the formula (3)LRepresenting the load ZLS parameter network of (1).
The parameter TPG reflects the power transmission degree of the matching circuit, and the maximum value is 1; when the value of TPG is 1, the matching circuit is completely matched, a lossless network is established, and the power can be transmitted to the load by 100 percent; conversely, the smaller the TPG, the less the matching circuit is completely matched, and the loss is caused.
After the simplified real-frequency method is used for optimization, a circuit with an LC series-parallel structure can be obtained, and since the circuit is composed of discrete components, the circuit needs to be converted into a microstrip line form, and the physical length of the microstrip line is calculated according to the following formula:
omega in the formulae (4) and (5)cIs the center frequency, λ, of the designed matching networkIs the wavelength at the center frequency, ZOLAnd ZOCHigh and low characteristic impedance, respectively.
And performing S parameter simulation on the obtained matching circuit in ADS software.
Referring to FIG. 5, the m2 curve represents the post-matching network 70S1170S of rear matching network represented by m1 curve floating about-48 dB in the frequency band of 2.8 GHz-3.8 GHz21Almost approaches to 0dB in the frequency range of 2.8 GHz-3.8 GHz, and the value of TPG reaches 0.9. The simulation result shows that the matching network 70 has a good broadband matching effect.
And carrying out efficiency simulation in ADS software.
Referring to fig. 6, in the frequency band range of 2.8GHz to 3.8GHz, the saturation drain efficiency of the wideband Doherty power amplifier of the novel combiner is 60% to 62%, and the 6dB output back-off efficiency is 44% to 46%.
Through obtaining circuit simulation analysis, the utility model discloses not only improved at load modulation network 60 and the way of combining of back matching network 70 and realized the broadband effect, this Doherty power amplifier satisfies the frequency requirement of contemporary 5G communication (3.3GHz ~ 3.6GHz) base station power amplifier moreover.
Method embodiment
Fig. 7 is a flow chart showing the steps of the design method of the wideband Doherty power amplifier of the combiner of the present invention, which includes the following steps:
s10, debugging a standard AB type power amplifier as a carrier power amplifier; designing an input and output matching circuit of a carrier power amplifier; meanwhile, the output matching circuit is adjusted, so that the output impedance of the carrier power amplifier is 75 omega when the carrier power amplifier is in low-power input, and the load impedance is 50 omega when the carrier power amplifier is in high-power input;
s20, debugging a standard C-type power amplifier as a peak power amplifier; designing an input/output matching circuit of the peak power amplifier; adjusting an output matching network of the peak power amplifier to enable the output impedance of the peak power amplifier to be infinite when the peak power amplifier is in low-power input and enable the load impedance to be 50 omega when the peak power amplifier is in high-power input;
s30, adjusting a peak compensation line at the output end of the peak power amplifier to enable the load impedance of the peak power amplifier at high power input to be matched to 75 omega;
s40, adjusting a phase compensation line at the input end of the peak power amplifier to ensure that the phases of the carrier power amplifier and the peak power amplifier are consistent;
and S50, adjusting the post-matching network after combination, so that the impedance of the combination point is matched to the load output end of 50 omega from 25 omega through the impedance transformer.
S60, combining the debugged carrier power amplifier, the peak power amplifier, the load modulation network and the rear matching network to form a novel combined broadband Doherty power amplifier;
and the load impedances of the carrier power amplifier and the peak power amplifier are both 50 omega.
The specific embodiment of the method is the same as the power amplifier embodiment described above, and is not described again.
The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, as any modifications, equivalents, improvements and the like made within the spirit and principles of the present invention are intended to be included within the scope of the present invention.
Claims (9)
1. A novel broadband Doherty power amplifier with a combined circuit is characterized by comprising a Wilkinson power divider, a carrier power amplifying circuit, a peak power amplifying circuit, a load modulation network and a rear matching network, wherein,
the Wilkinson power divider equally divides input power and then respectively outputs the divided input power to the carrier power amplifying circuit and the peak power amplifying circuit, the output end of the carrier power amplifying circuit and the output end of the peak power amplifying circuit are connected with the load modulation network, the load modulation network is connected with the rear matching network, power is output to the rear matching network through the load modulation network, and the power is output to a load through the rear matching network;
the carrier power amplification circuit comprises a carrier input matching circuit, a carrier power amplifier and a carrier output matching circuit which are sequentially connected in series, and the carrier output matching circuit is connected with a load modulation network; the peak power amplification circuit comprises a peak input matching circuit, a peak power amplifier and a peak output matching circuit which are sequentially connected in series;
the load modulation network comprises a first impedance transformer T1 of 1/4 wavelength and a peak compensation line T2; the carrier amplifying circuit is connected with a peak value compensation line T2 in the peak value amplifying circuit through the first impedance converter T1, and outputs power to a load through the rear matching network.
2. The novel combined wideband Doherty power amplifier of claim 1 in which the wilkinson power divider is an equal-division.
3. The novel combined wideband Doherty power amplifier of claim 1 wherein the carrier power amplifier is a class AB power amplifier and the peaking power amplifier is a class C power amplifier.
4. The novel combined wideband Doherty power amplifier of claim 1 wherein the impedance of said first impedance transformer T1 is 43.3 Ω.
5. The novel combined wideband Doherty power amplifier of claim 1 wherein the impedance of said peak compensation line T2 is 75 Ω.
6. The novel combined wideband Doherty power amplifier of claim 1 wherein the impedance of said first impedance transformer T1 is 50 Ω.
7. The novel combined wideband Doherty power amplifier of claim 1 wherein the impedance of said peak compensation line T2 is 50 Ω.
8. The combined wideband Doherty power amplifier of claim 1 wherein the back-matching network includes a multi-stage LC configuration high-low impedance transformer.
9. The novel combined broadband Doherty power amplifier of claim 1, wherein a 50 Ω phase compensation line is provided between the wilkinson power divider and the peak power amplifying circuit.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2023206868A1 (en) * | 2022-04-26 | 2023-11-02 | 深圳清华大学研究院 | Signal transmission circuit, amplifier and transceiver |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2023206868A1 (en) * | 2022-04-26 | 2023-11-02 | 深圳清华大学研究院 | Signal transmission circuit, amplifier and transceiver |
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