Doherty power amplifier and design method of Doherty power amplifier

Abstract

The present invention discloses a Doherty power amplifier and a design method of the Doherty power amplifier, wherein the Doherty power amplifier comprises: a signal input terminal, a signal output terminal, a power divider, a main power amplifier, an auxiliary power amplifier, an impedance conversion module and a phase compensator which are interconnected; wherein the impedance conversion module comprises a first coupling inductor, a second coupling inductor, a series capacitor and a parallel capacitor, and the first coupling inductor and the second coupling inductor are mutually coupled; the first end of the first coupling inductor is electrically connected to the first end of the parallel capacitor and then electrically connected to the output terminal of the main power amplifier; the second end of the first coupling inductor is electrically connected to the first end of the series capacitor, and the second end of the series capacitor is grounded; the first end of the second coupling inductor is electrically connected to the second end of the parallel capacitor and then electrically connected to the signal output terminal, and the second end of the second coupling inductor is electrically connected to the first end of the series capacitor. The harmonic suppression effect of the Doherty power amplifier is achieved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of semiconductor technology, and in particular to a Doherty power amplifier and a design method of the Doherty power amplifier. Background Art

[0002] Doherty power amplifier is a high-power amplifier that is currently the most widely used in wireless communication systems. The traditional Doherty power amplifier includes: a main power amplifier and an auxiliary power amplifier; it also includes: a quarter-wavelength transmission line placed between the main power amplifier and the power synthesis point, wherein the basic idea of ​​the Doherty power amplifier is active load pulling, specifically: the main power amplifier works in class B or class AB, the auxiliary power amplifier works in class C, the main power amplifier works all the time, and the auxiliary power amplifier works only when it reaches the set peak value. The quarter-wavelength transmission line behind the main power amplifier is mainly used for impedance transformation, the purpose is to reduce the apparent impedance of the main power amplifier when the auxiliary power amplifier is working, to ensure that the active load impedance composed of the auxiliary power amplifier and the circuit behind it becomes low when the auxiliary power amplifier is working, so that the output current of the main power amplifier becomes larger, so that the entire Doherty power amplifier is always in a high-efficiency working state.

[0003] However, the impedance transformation effect of the quarter-wavelength transmission line at the harmonic frequency point cannot be controlled, so that the Doherty power amplifier cannot achieve the harmonic suppression effect. Summary of the invention

[0004] The embodiment of the present invention provides a Doherty power amplifier and a design method of the Doherty power amplifier, so as to achieve the effect of harmonic suppression of the Doherty power amplifier.

[0005] In a first aspect, an embodiment of the present invention provides a Doherty power amplifier, the Doherty power amplifier comprising: a signal input end, a signal output end, a power divider, a main power amplifier, an auxiliary power amplifier, an impedance transformation module and a phase compensator;

[0006] The main power amplifier and the auxiliary power amplifier are connected in parallel;

[0007] The power divider comprises a power divider input terminal, a first power divider output terminal and a second power divider output terminal;

[0008] The power division input terminal is electrically connected to the signal input terminal, the first power division output terminal is electrically connected to the input terminal of the main power amplifier, and the output terminal of the main power amplifier is electrically connected to the first terminal of the impedance conversion module;

[0009] The phase compensator is provided between the second power division output terminal and the input terminal of the auxiliary power amplifier, and the second terminal of the impedance conversion module is electrically connected to the output terminal of the auxiliary power amplifier and then electrically connected to the signal output terminal;

[0010] Wherein, the impedance transformation module includes a first coupled inductor, a second coupled inductor, a series capacitor and a parallel capacitor, and the first coupled inductor and the second coupled inductor are mutually coupled;

[0011] The first end of the first coupling inductor is electrically connected to the first end of the shunt capacitor and then electrically connected to the output end of the main power amplifier; the second end of the first coupling inductor is electrically connected to the first end of the series capacitor, and the second end of the series capacitor is grounded; the first end of the second coupling inductor is electrically connected to the second end of the shunt capacitor and then electrically connected to the signal output end, and the second end of the second coupling inductor is electrically connected to the first end of the series capacitor.

[0012] Optionally, the first coupled inductor, the second coupled inductor, the series capacitor, and the parallel capacitor satisfy the following relationship:

[0013]

[0014]

[0015] Among them, the Z apn is the preset characteristic impedance value of the impedance transformation module; M is the coupling coefficient between the first coupled inductor and the second coupled inductor; L is the inductance value of the first coupled inductor and the second coupled inductor; C p is the capacitance value of the parallel capacitor, the C s is the capacitance value of the series capacitor; is the insertion phase of the impedance transformation module; and f is the preset working base frequency of the impedance transformation module.

[0016] Optionally, the power divider includes a Wilkinson power divider.

[0017] Optionally, the phase compensator comprises a quarter wavelength transmission line.

[0018] Optionally, the main power amplifier operates in class AB, and the auxiliary power amplifier operates in class B.

[0019] In a second aspect, an embodiment of the present invention further provides a design method of a Doherty power amplifier, wherein the Doherty power amplifier comprises: a signal input end, a signal output end, a power divider, a main power amplifier, an auxiliary power amplifier, an impedance conversion module and a phase compensator;

[0020] The main power amplifier and the auxiliary power amplifier are connected in parallel;

[0021] The power divider comprises a power divider input terminal, a first power divider output terminal and a second power divider output terminal;

[0022] The power division input terminal is electrically connected to the signal output terminal, the first power division output terminal is electrically connected to the input terminal of the main power amplifier, and the output terminal of the main power amplifier is provided with the impedance conversion module;

[0023] The phase compensator is provided between the second power division output terminal and the input terminal of the auxiliary power amplifier;

[0024] The impedance transformation module includes a first coupled inductor, a second coupled inductor, a series capacitor and a parallel capacitor, and the first coupled inductor and the second coupled inductor are mutually coupled;

[0025] The first end of the first coupling inductor is electrically connected to the first end of the shunt capacitor and then electrically connected to the output end of the main power amplifier; the second end of the first coupling inductor is electrically connected to the first end of the series capacitor, and the second end of the series capacitor is grounded; the first end of the second coupling inductor is electrically connected to the second end of the shunt capacitor and then electrically connected to the signal output end, and the second end of the second coupling inductor is electrically connected to the first end of the series capacitor;

[0026] The method comprises: determining a preset characteristic impedance value of the impedance transformation module, an operating fundamental frequency of the impedance transformation module, a target harmonic frequency, a preset insertion phase of the impedance transformation module at the operating fundamental frequency, and an insertion phase of the impedance transformation module at the target harmonic frequency;

[0027] According to the preset characteristic impedance value of the impedance transformation module, the working fundamental frequency of the impedance transformation module, the target harmonic frequency, the preset insertion phase of the impedance transformation module at the working fundamental frequency, the insertion phase of the impedance transformation module at the target harmonic frequency and a preset formula, the inductance values ​​of the first coupled inductor and the second coupled inductor, the coupling coefficient between the first coupled inductor and the second coupled inductor, the capacitance value of the parallel capacitor, and the capacitance value of the series capacitor are determined.

[0028] Optionally, the preset formula includes:

[0029]

[0030] Among them, the Z apnis the preset characteristic impedance value of the impedance transformation module; M is the coupling coefficient between the first coupled inductor and the second coupled inductor; L is the inductance value of the first coupled inductor and the second coupled inductor; C p is the capacitance value of the parallel capacitor, the C s is the capacitance value of the series capacitor; is the preset insertion phase of the impedance transformation module; and f is the preset working base frequency of the impedance transformation module.

[0031] Optionally, determining a preset characteristic impedance value of the impedance transformation module includes:

[0032] The preset characteristic impedance value of the impedance transformation module is determined according to the load impedance.

[0033] Optionally, determining the impedance transformation module insertion phase at the target harmonic frequency includes:

[0034] The insertion phase of the target harmonic frequency is determined by a simulation scanning method according to the working fundamental frequency of the impedance transformation module, the target harmonic frequency, and the preset insertion phase of the impedance transformation module at the working fundamental frequency.

[0035] Optionally, determining the insertion phase of the target harmonic frequency by using a simulation scanning method according to the working fundamental frequency of the impedance transformation module, the target harmonic frequency, and the preset insertion phase of the impedance transformation module at the working fundamental frequency specifically includes:

[0036] Determine the preset insertion phase of the impedance transformation module at the working fundamental frequency Calculate the first intermediate quantity γ1, where

[0037] Set the insertion phase of the target harmonic frequency to a variable Set the second intermediate variable γ2, where

[0038] Calculate the scanning range H2 of γ2, where

[0039] Determine γ2 within the scanning range H2;

[0040] The insertion phase of the target harmonic frequency is calculated based on γ2

[0041] Among them, f1 is the working fundamental frequency of the impedance transformation module, and f2 is the target harmonic frequency.

[0042] The technical solution provided in this embodiment replaces the traditional quarter-wavelength transmission line with an impedance transformation module including a first coupled inductor, a second coupled inductor, a series capacitor and a parallel capacitor. Since the characteristic impedance of the impedance transformation module is set to be the same as the characteristic impedance of the traditional quarter-wavelength transmission line used in the design, it can not only play the role of impedance transformation, but also suppress harmonics. Moreover, by adjusting the relevant parameters of the first coupled inductor, the second coupled inductor, the series capacitor and the parallel capacitor, the effect of suppressing harmonics at different frequencies can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 is a structural schematic diagram of a Doherty power amplifier provided by an embodiment of the present invention;

[0044] Figure 2 is a structural schematic diagram of an impedance transformation module provided by an embodiment of the present invention;

[0045] Figure 3 is a flow chart of a design method of a Doherty power amplifier provided by an embodiment of the present invention;

[0046] Figure 4 is a structural schematic diagram of another Doherty power amplifier provided by an embodiment of the present invention;

[0047] Figure 5 It is an output amplitude diagram of a simulated output of third-order and fifth-order harmonics provided by an embodiment of the present invention;

[0048] Figure 6 It is an output spectrum diagram of a Doherty power amplifier in the prior art;

[0049] Figure 7 This is an output spectrum diagram of a Doherty power amplifier provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0050] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0051] Figure 1 is a structural schematic diagram of a Doherty power amplifier provided by an embodiment of the present invention, Figure 2 is a schematic diagram of the structure of an impedance conversion module provided by an embodiment of the present invention, such as Figure 1 and Figure 2As shown, the Doherty power amplifier comprises: a signal input terminal 10, a signal output terminal 20, a power divider 30, a main power amplifier 40, an auxiliary power amplifier 50, an impedance transformation module 60 and a phase compensator 70; the main power amplifier 40 and the auxiliary power amplifier 50 are connected in parallel; the power divider 30 comprises a power divider input terminal, a first power divider output terminal and a second power divider output terminal; the power divider input terminal is electrically connected to the signal input terminal 10, the first power divider output terminal is electrically connected to the input terminal of the main power amplifier 40, and the output terminal of the main power amplifier 40 is electrically connected to the first terminal of the impedance transformation module 60; a phase compensator 70 is arranged between the second power divider output terminal and the input terminal of the auxiliary power amplifier 50, and the second terminal of the impedance transformation module 60 is electrically connected to the auxiliary power The output end of the amplifier 50 is electrically connected to the signal output end 20; wherein the impedance transformation module 60 includes a first coupling inductor 61, a second coupling inductor 62, a series capacitor 63 and a parallel capacitor 64, and the first coupling inductor 61 and the second coupling inductor 62 are mutually coupled; the first end of the first coupling inductor 61 is electrically connected to the first end of the parallel capacitor 64 and then electrically connected to the output end of the main power amplifier 40; the second end of the first coupling inductor 61 is electrically connected to the first end of the series capacitor 63, and the second end of the series capacitor 63 is grounded; the first end of the second coupling inductor 62 is electrically connected to the second end of the parallel capacitor 64 and then electrically connected to the signal output end 20, and the second end of the second coupling inductor 62 is electrically connected to the first end of the series capacitor 63.

[0052] Among them, the main signal input to the input signal terminal 10 of the Doherty power amplifier is divided into two paths by the power divider 30, and output from the first power divider output terminal and the second power divider output terminal of the power divider 30 respectively to complete the power distribution function. The sum of the powers of the first power divider output terminal and the second power divider output terminal of the power divider 30 is the same as the power of the input signal of the power divider input terminal; one of the paths is composed of a main power amplifier 40 and an impedance transformation module 60, and the other path is composed of a phase compensator 70 and an auxiliary power amplifier 50.

[0053] Specifically, the phase compensator 70 is used to achieve phase matching between the main power amplifier 40 and the auxiliary power amplifier 50. The impedance transformation module 60 has a certain characteristic impedance value, and the characteristic impedance of the impedance transformation module 60 is set to be the same as the characteristic impedance of the traditional quarter-wavelength transmission line, and is used for impedance transformation. When the auxiliary power amplifier 50 is working, it plays a role in reducing the apparent impedance of the main power amplifier 40, ensuring that the active load impedance composed of the auxiliary power amplifier 50 and the resistor behind it becomes low when the auxiliary power amplifier 50 is working, so that the output current of the main power amplifier becomes larger, so that the entire Doherty power amplifier is always in a high-efficiency working state.

[0054] Specifically, in this embodiment, the impedance transformation module 60 includes a first coupling inductor 61, a second coupling inductor 62, a series capacitor 63 and a parallel capacitor 64. According to the target harmonics to be suppressed, the first coupling inductor 61, the second coupling inductor 62, the series capacitor 63 and the parallel capacitor 64 related parameters are obtained to achieve the effect of suppressing harmonics. That is, in this embodiment, by setting the characteristic impedance of the impedance change module 60 to be the same as the characteristic impedance of the traditional quarter transmission line, the impedance can be transformed, and when the auxiliary power amplifier is working, the apparent impedance of the main power amplifier is reduced to ensure that the active load impedance composed of the auxiliary power amplifier and the subsequent circuit becomes low; at the same time, the effect of suppressing harmonics can be achieved; and by adjusting the related parameters of the first coupling inductor 61, the second coupling inductor 62, the series capacitor 63 and the parallel capacitor 64, the effect of suppressing harmonics at multiple frequency points can be achieved.

[0055] Optionally, the power divider 30 includes a Wilkinson power divider.

[0056] Optionally, the phase compensator 70 comprises a quarter wavelength transmission line.

[0057] Optionally, there are many design methods for the main power amplifier 40 and the auxiliary power amplifier 50. For example, the main power amplifier 40 adopts a CLASS AB power amplifier, and the auxiliary power amplifier 50 adopts a CLASS B power amplifier.

[0058] The technical solution provided in this embodiment replaces the traditional quarter-wavelength transmission line with an impedance transformation module including a first coupled inductor, a second coupled inductor, a series capacitor and a parallel capacitor. Since the characteristic impedance of the impedance transformation module is set to be the same as the characteristic impedance of the traditional quarter-wavelength transmission line used in the design, it can not only play the role of impedance transformation, but also suppress harmonics. Moreover, by adjusting the relevant parameters of the first coupled inductor, the second coupled inductor, the series capacitor and the parallel capacitor, the effect of suppressing harmonics at different frequencies can be achieved, thereby expanding the application range of the Doherty power amplifier.

[0059] Optionally, the first coupling inductor 61, the second coupling inductor 62, the series capacitor 63 and the parallel capacitor 64 satisfy the following relationship:

[0060]

[0061] Among them, Z apn is the preset characteristic impedance value of the impedance transformation module; M is the coupling coefficient between the first coupled inductor and the second coupled inductor; L is the inductance value of the first coupled inductor and the second coupled inductor; C p is the capacitance value of the parallel capacitor, C s is the capacitance value of the series capacitor; is the preset insertion phase of the impedance transformation module; f is the preset working base frequency of the impedance transformation module.

[0062] Specifically, when determining the preset characteristic impedance value Z of the impedance transformation module apn , the working fundamental frequency of the impedance transformation module, the preset insertion phase of the impedance transformation module at the working fundamental frequency After the target harmonic frequency to be suppressed and the impedance transformation module at the target harmonic frequency are inserted into the phase, the capacitance value of the parallel capacitor 64, the capacitance value of the series capacitor 63, the inductance value of the first coupling inductor 61 and the second coupling inductor 62 and the coupling coefficient M can be determined by the above formula. apn , the working fundamental frequency of the impedance transformation module and the preset insertion phase of the impedance transformation module at the working fundamental frequency It can be directly determined that the first coupling inductor 61, the second coupling inductor 62, the series capacitor 63 and the parallel capacitor 64 can be inserted into the phase adjustment according to the target harmonic frequency to be suppressed and the impedance transformation module at the target harmonic frequency, so as to achieve the effect of suppressing harmonics at different frequencies.

[0063] Based on the same inventive concept, an embodiment of the present invention further provides a design method for a Doherty power amplifier, the method being used to determine the inductance values ​​of the first coupled inductor and the second coupled inductor, the capacitance values ​​of the series capacitor and the parallel capacitor in the impedance conversion module in the above embodiment. Figure 3 As shown, the design method of the Doherty power amplifier includes:

[0064] S110, determining a preset characteristic impedance value of the impedance transformation module, an operating fundamental frequency of the impedance transformation module, a target harmonic frequency, a preset insertion phase of the impedance transformation module at the operating fundamental frequency, and an insertion phase of the impedance transformation module at the target harmonic frequency;

[0065] The Doherty power amplifier includes: a signal input terminal, a signal output terminal, a power divider, a main power amplifier, an auxiliary power amplifier, an impedance conversion module and a phase compensator; the main power amplifier and the auxiliary power amplifier are connected in parallel; the power divider includes a power divider input terminal, a first power divider output terminal and a second power divider output terminal; the power divider input terminal is electrically connected to the signal output terminal, the first power divider output terminal is electrically connected to the input terminal of the main power amplifier, and an impedance conversion module is provided at the output terminal of the main power amplifier; a phase compensator is provided between the second power divider output terminal and the input terminal of the auxiliary power amplifier; the impedance conversion module includes a first coupling inductor, a second coupling inductor, a series capacitor and a parallel capacitor, and the first coupling inductor and the second coupling inductor are mutually coupled; the first end of the first coupling inductor is electrically connected to the first end of the parallel capacitor and then electrically connected to the output terminal of the main power amplifier; the second end of the first coupling inductor is electrically connected to the first end of the series capacitor, and the second end of the series capacitor is grounded; the first end of the second coupling inductor is electrically connected to the second end of the parallel capacitor and then electrically connected to the signal output terminal, and the second end of the second coupling inductor is electrically connected to the first end of the series capacitor.

[0066] Specifically, the preset characteristic impedance value of the impedance transformation module can be determined according to the load impedance, and the characteristic impedance of the impedance transformation module is the same as the characteristic impedance of the traditional quarter-wavelength transmission line; for example, after the impedance transformation design of the main power amplifier based on the traditional quarter-wavelength transmission line is completed, the quarter-wavelength transmission line of the main power amplifier can be replaced with the impedance transformation module with independent adjustment of harmonic frequency impedance proposed by the present invention.

[0067] Specifically, the target harmonic frequency may be a selected frequency point greater than the working fundamental frequency, such as a third-order harmonic. The impedance transformation module at the working fundamental frequency presets an insertion phase that is the same as the insertion phase of a conventional quarter transmission line, such as ±90°.

[0068] Specifically, the insertion phase of the impedance transformation module at the target harmonic frequency may be determined by calculation based on the working fundamental frequency of the impedance transformation module, the target harmonic frequency, and the preset insertion phase of the impedance transformation module at the working fundamental frequency.

[0069] Optionally, determining the insertion phase of the impedance transformation module at the target harmonic frequency includes: determining the insertion phase of the impedance transformation module at the target harmonic frequency by using a simulation scanning method according to the working fundamental frequency of the impedance transformation module, the target harmonic frequency, and the preset insertion phase of the impedance transformation module at the working fundamental frequency. That is, this embodiment uses a simulation scanning method to determine the insertion phase of the impedance transformation module at the target harmonic frequency, which can simplify the calculation steps.

[0070] On the basis of the above scheme, optionally, according to the working fundamental frequency of the impedance transformation module, the target harmonic frequency, and the preset insertion phase of the impedance transformation module at the working fundamental frequency, the impedance transformation module insertion phase at the target harmonic frequency is determined by a simulation scanning method, specifically including: determining the preset insertion phase of the impedance transformation module at the working fundamental frequency Calculate the first intermediate quantity γ1, where Set the impedance transformation module at the target harmonic frequency to insert the phase as a variable Set the second intermediate variable γ2, where Calculate the scanning range H2 of γ2, where Determine γ2 in the scanning range H2; calculate the impedance transformation module at the target harmonic frequency according to γ2 and insert the phase Among them, f1 is the selected operating frequency of the impedance transformation module, and f2 is the target harmonic frequency.

[0071] Specifically, in order to simplify the calculation, the first intermediate variable γ1 and the second intermediate variable γ2 are introduced; specifically, the impedance transformation module at the working base frequency is set to preset the insertion phase Calculate the first intermediate quantity γ1, where Set the insertion phase of the target harmonic frequency as a variable Set the second intermediate variable γ2, where Calculate the scanning range H2 of γ2, where Simulate and scan the output amplitude of the target harmonic point corresponding to different γ2 values ​​in the H2 range, find the scan of γ2 that meets the design requirements, select γ2, and then That is, this embodiment determines the impedance transformation module insertion phase at the target harmonic frequency by means of simulation scanning. Compared with the calculation method in the prior art, the steps are simplified and the efficiency is improved.

[0072] S120, determining the inductance values ​​of the first coupled inductor and the second coupled inductor, the coupling coefficient between the first coupled inductor and the second coupled inductor, the capacitance value of the parallel capacitor, and the capacitance value of the series capacitor according to the preset characteristic impedance value of the impedance transformation module, the working fundamental frequency of the impedance transformation module, the target harmonic frequency, the preset insertion phase of the impedance transformation module at the working fundamental frequency, the insertion phase of the impedance transformation module at the target harmonic frequency, and a preset formula.

[0073] Optional, preset formulas include:

[0074]

[0075] Among them, Z apnis the preset characteristic impedance value of the impedance transformation module; M is the coupling coefficient between the first coupled inductor and the second coupled inductor; L is the inductance value of the first coupled inductor and the second coupled inductor; C p is the capacitance value of the parallel capacitor, C s is the capacitance value of the series capacitor; is the preset insertion phase of the impedance transformation module; f is the preset working base frequency of the impedance transformation module.

[0076] Specifically, after determining the characteristic impedance of the impedance transformation module, the working fundamental frequency of the impedance transformation module, the target harmonic frequency, the preset insertion phase of the impedance transformation module at the working fundamental frequency, and the insertion phase of the target harmonic frequency, it should be noted that in order to simplify the calculation, this step also introduces the first intermediate variable γ1 and the second intermediate variable γ2, where, The characteristic impedance of the impedance transformation module, the working fundamental frequency of the impedance transformation module, the target harmonic frequency, the preset insertion phase of the impedance transformation module at the working fundamental frequency, and the insertion phase of the target harmonic frequency are brought into the following formula calculated based on the preset formula:

[0077]

[0078] Calculate intermediate variables:

[0079]

[0080] Then we get:

[0081]

[0082] Among them, Z T is the characteristic impedance of the impedance transformation module; f1 is a selected working fundamental frequency of the impedance transformation module; f2 is the target harmonic frequency; is the insertion phase of the impedance transformation module; is the insertion phase of the impedance transformation module at the target harmonic frequency. That is, the inductance value L of the first coupling inductor 61 and the second coupling inductor 62, the capacitance value C of the series capacitor 63 are obtained. s and the capacitance value C of the parallel capacitor 64 p ;

[0083] The following description is given in conjunction with specific implementation methods, but does not constitute a limitation to the present application.

[0084] For example, the values ​​of the first coupling inductor 61, the second coupling inductor 62, the series capacitor 63 and the parallel capacitor 64 of the impedance transformation module in the 850MHz Doherty power amplifier are set. Figure 4FIG. 1 is a schematic diagram of the structure of another Doherty power amplifier provided by an embodiment of the present invention. This embodiment provides an 850MHz Doherty power amplifier with harmonic suppression. Figure 4 As shown, the Doherty power amplifier not only includes the signal input terminal 10, the signal output terminal 20, the power divider 30, the main power amplifier 40, the auxiliary power amplifier 50, the impedance transformation module 60 and the phase compensator 70 in the above-mentioned embodiment, but also includes a main path driving amplifier 80 and an auxiliary path driving amplifier 90, wherein the main path driving amplifier 80 is arranged between the first power divider output terminal and the input terminal of the main power amplifier 40, and the auxiliary path driving amplifier 90 is arranged between the phase compensator 70 and the input terminal of the auxiliary power amplifier 50.

[0085] After the impedance transformation design of the main power amplifier based on the traditional quarter-wavelength transmission line is completed, the quarter-wavelength transmission line of the main power amplifier can be replaced by the impedance transformation module with independent harmonic frequency impedance adjustment in the above embodiment.

[0086] Specifically, step 1, first set the characteristic impedance of the impedance transformation module to be the same as the characteristic impedance of the quarter-wavelength transmission line used in the design;

[0087] Step 2, then set the base frequency f1 = 850MHz, here pay attention to the third-order harmonic and the fifth-order harmonic, set f2 = 2.55GHz = 3*f1;

[0088] Step 3, then set the baseband insertion phase The first intermediate quantity γ1 = ±1 can be obtained by calculation;

[0089] Step 4: Set the inserted phase at the target harmonic frequency f2 as a variable Set the second intermediate variable γ2;

[0090] Step 5: Calculate the scanning range of γ2 or

[0091] Step 6: In the range described in step 5, scan γ2 to simulate the output amplitudes of the third-order and fifth-order harmonics.

[0092] like Figure 5 As shown, m8 represents the third harmonic output amplitude, m9 represents the fifth harmonic output amplitude, and the lowest point of the third harmonic output amplitude appears at γ2 = -1.54, where the third-order harmonic output is suppressed by 36dBc relative to the fundamental wave.

[0093] Step 7: Calculation

[0094]

[0095] Step 8: Then insert the characteristic impedance of the impedance transformation module, the working fundamental frequency f1 of the impedance transformation module, the target harmonic frequency f2, and the impedance transformation module preset at the working fundamental frequency into the phase and the insertion phase of the target harmonic frequency Substitute into the following formula calculated based on the preset formula:

[0096]

[0097] Get C P =51.56pF, C S =8.475pF, L=534.1pH, M=-110.4pH, thus completing the setting of the impedance transformation module.

[0098] Figure 6 It is an output spectrum diagram of a Doherty power amplifier in the prior art. Figure 7 This is an output spectrum diagram of a Doherty power amplifier provided by an embodiment of the present invention. Figure 6 and Figure 7 Where m2 represents the output amplitude of the fundamental wave, m3 represents the output amplitude of the third-order harmonic, and m4 represents the output amplitude of the fifth-order harmonic. Figure 6 and Figure 7 It can be seen that in the output spectrum of the Doherty power amplifier using the conventional quarter-wavelength transmission line as the impedance transformation module, the output amplitudes of the fundamental wave, the third-order harmonic, and the fifth-order harmonic are 34.006 dBm, 3.971 dBm, and 6.709 dBm, respectively. Figure 7 As shown in the output spectrum of the Doherty power amplifier, the output amplitudes of the fundamental wave, third-order harmonic, and fifth-order harmonic are 34.007dBm, 4.075dBm, and -2.474dBm, respectively. Figure 6 and Figure 7 It can be seen that compared with the traditional quarter-wavelength transmission line as an impedance transformation module, the impedance transformation module used in the present invention reduces the fifth-order harmonic amplitude by 9 dB while ensuring that the amplitudes of the fundamental wave and the third-order harmonic remain unchanged, thereby achieving the effect of harmonic suppression.

[0099] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A Doherty power amplifier, characterized in that: include: Signal input terminal, signal output terminal, power divider, main power amplifier, auxiliary power amplifier, impedance conversion module and phase compensator; The main power amplifier and the auxiliary power amplifier are connected in parallel; The power divider comprises a power divider input terminal, a first power divider output terminal and a second power divider output terminal; The power division input terminal is electrically connected to the signal input terminal, the first power division output terminal is electrically connected to the input terminal of the main power amplifier, and the output terminal of the main power amplifier is electrically connected to the first terminal of the impedance conversion module; The phase compensator is provided between the second power division output terminal and the input terminal of the auxiliary power amplifier, and the second terminal of the impedance conversion module is electrically connected to the output terminal of the auxiliary power amplifier and then electrically connected to the signal output terminal; Wherein, the impedance transformation module includes a first coupled inductor, a second coupled inductor, a series capacitor and a parallel capacitor, and the first coupled inductor and the second coupled inductor are mutually coupled; The first end of the first coupling inductor is electrically connected to the first end of the shunt capacitor and then electrically connected to the output end of the main power amplifier; the second end of the first coupling inductor is electrically connected to the first end of the series capacitor, and the second end of the series capacitor is grounded; the first end of the second coupling inductor is electrically connected to the second end of the shunt capacitor and then electrically connected to the signal output end, and the second end of the second coupling inductor is electrically connected to the first end of the series capacitor; The first coupled inductor, the second coupled inductor, the series capacitor and the parallel capacitor satisfy the following relationship: Among them, the Z apn is the preset characteristic impedance value of the impedance transformation module; M is the coupling coefficient between the first coupled inductor and the second coupled inductor; L is the inductance value of the first coupled inductor and the second coupled inductor; C p is the capacitance value of the parallel capacitor, the C s is the capacitance value of the series capacitor; φ is the insertion phase of the impedance transformation module; f is the preset working base frequency of the impedance transformation module; The power divider comprises a Wilkinson power divider.

2. The Doherty power amplifier according to claim 1, characterized in that: The phase compensator includes a quarter wavelength transmission line.

3. The Doherty power amplifier according to claim 1, characterized in that: The main power amplifier operates in class AB, and the auxiliary power amplifier operates in class B.

4. A design method for a Doherty power amplifier, characterized in that: The Doherty power amplifier comprises: a signal input end, a signal output end, a power divider, a main power amplifier, an auxiliary power amplifier, an impedance conversion module and a phase compensator; The main power amplifier and the auxiliary power amplifier are connected in parallel; The power divider comprises a power divider input terminal, a first power divider output terminal and a second power divider output terminal; The power division input terminal is electrically connected to the signal output terminal, the first power division output terminal is electrically connected to the input terminal of the main power amplifier, and the output terminal of the main power amplifier is provided with the impedance conversion module; The phase compensator is provided between the second power division output terminal and the input terminal of the auxiliary power amplifier; The impedance transformation module includes a first coupled inductor, a second coupled inductor, a series capacitor and a parallel capacitor, and the first coupled inductor and the second coupled inductor are mutually coupled; The first end of the first coupling inductor is electrically connected to the first end of the shunt capacitor and then electrically connected to the output end of the main power amplifier; the second end of the first coupling inductor is electrically connected to the first end of the series capacitor, and the second end of the series capacitor is grounded; the first end of the second coupling inductor is electrically connected to the second end of the shunt capacitor and then electrically connected to the signal output end, and the second end of the second coupling inductor is electrically connected to the first end of the series capacitor; The method comprises: determining a preset characteristic impedance value of the impedance transformation module, an operating fundamental frequency of the impedance transformation module, a target harmonic frequency, a preset insertion phase of the impedance transformation module at the operating fundamental frequency, and an insertion phase of the impedance transformation module at the target harmonic frequency; Determine the inductance values ​​of the first coupled inductor and the second coupled inductor, the coupling coefficient between the first coupled inductor and the second coupled inductor, the capacitance value of the parallel capacitor, and the capacitance value of the series capacitor according to the preset characteristic impedance value of the impedance transformation module, the working fundamental frequency of the impedance transformation module, the target harmonic frequency, the preset insertion phase of the impedance transformation module at the working fundamental frequency, the insertion phase of the impedance transformation module at the target harmonic frequency, and a preset formula; The preset formula includes: Among them, the Z apn is the preset characteristic impedance value of the impedance transformation module; M is the coupling coefficient between the first coupled inductor and the second coupled inductor; L is the inductance value of the first coupled inductor and the second coupled inductor; C p is the capacitance value of the parallel capacitor, the C s is the capacitance value of the series capacitor; is the preset insertion phase of the impedance transformation module; and f is the working fundamental frequency of the impedance transformation module.

5. The design method of a Doherty power amplifier according to claim 4, characterized in that: Determining a preset characteristic impedance value of the impedance transformation module includes: The preset characteristic impedance value of the impedance transformation module is determined according to the load impedance.

6. The design method of a Doherty power amplifier according to claim 5, characterized in that: Determining the impedance transformation module insertion phase at the target harmonic frequency includes: According to the working fundamental frequency of the impedance transformation module, the target harmonic frequency, and the preset insertion phase of the impedance transformation module at the working fundamental frequency, the insertion phase of the target harmonic frequency is determined by a simulation scanning method.

7. The design method of a Doherty power amplifier according to claim 6, characterized in that: According to the working fundamental frequency of the impedance transformation module, the target harmonic frequency, and the preset insertion phase of the impedance transformation module at the working fundamental frequency, the insertion phase of the target harmonic frequency is determined by a simulation scanning method, specifically comprising: Determine the preset insertion phase of the impedance transformation module at the working fundamental frequency Calculate the first intermediate quantity γ1, where Set the insertion phase of the target harmonic frequency to a variable Set the second intermediate variable γ2, where Calculate the scanning range H2 of γ2, where Determine γ2 within the scanning range H2; The insertion phase of the target harmonic frequency is calculated based on γ2 Among them, f1 is the working fundamental frequency of the impedance transformation module, and f2 is the target harmonic frequency.

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