A load-modulated enhanced Doherty power amplifier

Abstract

This invention discloses a load-modulated enhanced Doherty power amplifier, comprising a power divider, a main branch, an auxiliary branch, a post-matching network, a compensation branch, and a power combining network. The main branch includes a main power amplifier, the auxiliary branch includes an auxiliary power amplifier, and the compensation branch includes a compensation power amplifier. The auxiliary branch, the compensation branch, and the power combining network constitute a new auxiliary branch. The compensation branch uses the power combining network to superimpose its output current with the output current of the auxiliary branch, making the output current of the new auxiliary branch equal to the sum of the output current of the auxiliary branch and the output current of the compensation branch. This achieves synchronous saturation of the combined current of the auxiliary branch and the compensation branch with the output current of the main branch. The advantage is that it can eliminate the adverse effects of the weak current output capability and small output current of the auxiliary power amplifier caused by Class C bias, thus eliminating the need for an additional voltage control module for correction and reducing the integration difficulty of the wireless communication system.

Description

Technical Field

[0001] This invention relates to Doherty power amplifiers, and more particularly to a load-modulated enhanced Doherty power amplifier. Background Technology

[0002] With the continuous development of wireless communication standards, stringent requirements have been placed on radio frequency power amplifiers in terms of efficiency, linearity, and bandwidth. Modern wireless communication systems increasingly employ modern modulation schemes with high peak-to-average power ratio (PAPR) waveforms, such as orthogonal frequency division multiplexing (OFDM), necessitating power amplifiers capable of maintaining high efficiency over an extended dynamic range. Doherty power amplifiers, with their characteristic of maintaining high efficiency over an extended dynamic range, have thus gained widespread application.

[0003] Existing Doherty power amplifiers typically consist of a power divider, a main branch (including a primary power amplifier), an auxiliary branch (including an auxiliary power amplifier), and a post-matching network. The power divider splits the externally input RF signal into two equal signals, which are then input to the main and auxiliary branches respectively. The main and auxiliary branches amplify their respective input signals before outputting them to the post-matching network. The post-matching network matches the impedance of the junction of the main and auxiliary branches to the standard 50 ohms for wireless communication systems, thus outputting the signal to its designated point. Doherty power amplifiers achieve active load modulation between the primary and auxiliary power amplifiers by setting the auxiliary power amplifier's bias voltage to Class C, allowing it to turn on at a fixed back-off power point. This enables higher efficiency characteristics in the power back-off region. This inherent advantage has driven the widespread adoption of Doherty power amplifiers in 4G LTE systems and current 5G infrastructure, particularly in macrocell base stations requiring multi-carrier operation.

[0004] Because the auxiliary power amplifier in the Doherty power amplifier is biased to Class C and operates in Class C mode, its current output capability is weaker than that of the main power amplifier operating in Class AB mode. This phenomenon is more pronounced in actual testing of the Doherty power amplifier. The weaker current output capability of the auxiliary power amplifier (i.e., lower output current) causes the load modulation process of the Doherty power amplifier to deviate from the theoretical process, thus affecting the performance of the Doherty power amplifier, such as efficiency and gain.

[0005] Current research on Doherty power amplifiers mainly focuses on improving back-off efficiency, back-off range, and operating bandwidth. However, the acute problem of weak current output capability of the auxiliary amplifier due to Class C bias remains unavoidable. Currently, most Doherty power amplifiers rely to some extent on a large input power to push their auxiliary amplifier to its theoretical saturation value. However, in this process, the main amplifier inevitably enters the oversaturation region, increasing the risk of damage to the main amplifier and affecting the overall linearity of the Doherty power amplifier.

[0006] Researchers have proposed using dynamic biasing technology with an additional voltage control module to correct the auxiliary power amplifier in a Doherty power amplifier system. This voltage control module gradually adjusts the auxiliary power amplifier's operating voltage from Class C bias to Class B bias after the auxiliary power amplifier is turned on, thus eliminating the influence of the auxiliary power amplifier's Class C bias. This technique can push the auxiliary power amplifier to its theoretical saturation value while preventing the main power amplifier from entering the oversaturation region. However, the introduction of an additional voltage control module undoubtedly increases the integration complexity of the wireless communication system. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a load modulation enhanced Doherty power amplifier that can eliminate the adverse effects of weak current output capability and small output current caused by Class C bias of the auxiliary power amplifier, so that no additional voltage control module is needed for correction, and the integration difficulty of wireless communication system is reduced.

[0008] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: a load modulation enhanced Doherty power amplifier, including a power divider, a main branch, an auxiliary branch, and a post-matching network. The main branch includes a main power amplifier, and the auxiliary branch includes an auxiliary power amplifier. The main branch is used to amplify the input signal and output it to the post-matching network. The Doherty power amplifier also includes a compensation branch and a power combining network. The compensation branch includes a compensation power amplifier. The power divider is a three-way power divider, used to divide the externally input radio frequency signal RFin into three equal parts and input them to the main branch, the auxiliary branch, and the compensation branch respectively. The auxiliary branch and the compensation branch are respectively used to amplify the input signal and output it to the power combining network. The signal output from the compensation branch and the signal output from the auxiliary branch are combined in phase and matched to the junction point of the auxiliary branch and the compensation branch before being output to the post-matching network. The post-matching network is used to match the impedance of the junction point of the power combining network and the main branch to the 50 ohms standard of the wireless communication system, thereby outputting the signal thereto. The auxiliary branch, the compensation branch, and the power combining network constitute a new auxiliary branch. The compensation branch uses the power combining network to superimpose its output current with the output current of the auxiliary branch, so that the output current of the new auxiliary branch is equal to the sum of the output current of the auxiliary branch and the output current of the compensation branch, thereby achieving synchronous saturation of the combined current of the auxiliary branch and the compensation branch with the output current of the main branch.

[0009] Compared with the prior art, the advantages of this invention are that by adding a compensation branch and a power combining network to form a new auxiliary branch with the auxiliary branch, the output current of the auxiliary branch is compensated by the output current of the compensation branch, so that the output current of the new auxiliary branch is equal to the sum of the output current of the auxiliary branch and the output current of the compensation branch. This makes the combined current of the auxiliary branch and the compensation branch synchronously saturate with the output current of the main branch, avoiding the main power amplifier from entering the oversaturation region. Thus, this invention itself can eliminate the adverse effects of the weak current output capability and small output current of the auxiliary power amplifier caused by Class C bias, without the need to introduce an additional voltage control module for correction, which can reduce the integration difficulty of the wireless communication system.

[0010] Furthermore, the main branch also includes a main input matching network and a main output matching network. The main input matching network is used to perform impedance matching on the signal output to it from the three-way power divider, and outputs the impedance-matched signal to the main power amplifier. The main power amplifier is used to amplify the signal output to it from the main input matching network, and outputs the amplified signal to the main output matching network. The main output matching network is used to match the signal output to it from the main power amplifier and output it to the post-matching network. The auxiliary branch also includes an auxiliary input matching network and an auxiliary output matching network. The auxiliary input matching network is used to perform impedance matching on the signal output to it from the three-way power divider, and simultaneously controls the turn-on point of the auxiliary power amplifier within the passband, outputting the impedance-matched and turn-on controlled signal to the auxiliary power amplifier. The auxiliary power amplifier is used to match the auxiliary input... The signal output from the network is amplified, and the amplified signal is output to the auxiliary output matching network. The auxiliary output matching network is used to match the signal output from the auxiliary power amplifier and then output it to the power combining network. The compensation branch also includes a compensation input matching network and a compensation output matching network. The compensation input matching network is used to perform impedance matching on the signal output from the three-way power divider, and simultaneously controls the turn-on point of the compensation power amplifier and the auxiliary power amplifier to be consistent within the passband. The signal after impedance matching and turn-on control is output to the compensation power amplifier. The compensation power amplifier is used to amplify the signal output from the compensation input matching network and then output the amplified signal to the compensation output matching network. The compensation output matching network is used to match the signal output from the compensation power amplifier and then output it to the power combining network.

[0011] Furthermore, the three-way power divider has one input terminal and three output terminals. The main input matching network, the main output matching network, the auxiliary input matching network, the auxiliary output matching network, the compensation input matching network, the compensation output matching network, and the post-matching circuit all have input terminals and output terminals. The power combining network has two input terminals and one output terminal. The input terminal of the three-way power divider serves as the input terminal of the Doherty power amplifier, used to connect to the externally input RF signal RFin. The three output terminals of the three-way power divider are connected one-to-one with the input terminals of the main input matching network, the auxiliary input matching network, and the compensation input matching network. The output terminal of the main input matching network is connected to the gate of the main power amplifier, and the source of the main power amplifier is grounded. The output terminal of the auxiliary input matching network is connected to the gate of the main power amplifier. The gate of the power amplifier is connected, the source of the auxiliary power amplifier is grounded, the output of the compensation input matching network is connected to the gate of the compensation power amplifier, the source of the compensation power amplifier is grounded, the drain of the main power amplifier is connected to the input of the main output matching network, the drain of the auxiliary power amplifier is connected to the input of the auxiliary output matching network, the drain of the compensation power amplifier is connected to the input of the compensation output matching network, the output of the main output matching network is connected to the input of the post-matching network, the outputs of the auxiliary output matching network and the compensation output matching network are connected one-to-one to the two inputs of the power combining network, the output of the power combining network is connected to the input of the post-matching network, and the output of the post-matching network is the output of the Doherty power amplifier, used to output the amplified RF signal RFout.

[0012] Furthermore, the main input matching network, the auxiliary input matching network, and the compensation input matching network all employ high-order impedance matching networks to achieve impedance transformation, thereby effectively controlling the second harmonic and improving the efficiency of the Doherty power amplifier. At the same time, they can also precisely control the turn-on points of the auxiliary power amplifier and the compensation power amplifier, ensuring that the auxiliary power amplifier and the compensation power amplifier turn on at the power back-off point.

[0013] Furthermore, the main input matching network includes nine impedance tuning lines, three capacitors, and two resistors. The nine impedance tuning lines are referred to as the first to the ninth impedance tuning lines, the three capacitors as the first to the third capacitors, and the two resistors as the first and second resistors. One end of the first impedance tuning line is the input terminal of the main input matching network. The other end of the first impedance tuning line is connected to one end of the first capacitor. The other end of the first capacitor is connected to one end of the second impedance tuning line. The other end of the second impedance tuning line is connected to one end of the third impedance tuning line. The other end of the third impedance tuning line is connected to one end of the fourth impedance tuning line. The other end of the fourth impedance tuning line is connected to one end of the fifth and seventh impedance tuning lines. The other end of the fifth impedance tuning line is connected to one end of the first resistor. The other end of the first resistor is connected to one end of the sixth impedance tuning line. The other end of the sixth impedance tuning line is connected to one end of the second capacitor, and its connection point is connected to the gate bias voltage V used to operate the main power amplifier in Class AB mode. g1 The other end of the second capacitor is grounded, the other end of the seventh impedance tuning line is connected to one end of the eighth impedance tuning line, the other end of the eighth impedance tuning line is connected to one end of the second resistor and one end of the third capacitor, the other end of the third capacitor and the other end of the second resistor are connected to one end of the ninth impedance tuning line, and the other end of the ninth impedance tuning line is the output end of the main input matching network.

[0014] Furthermore, the structures of the auxiliary input matching network and the compensation input matching network are basically the same as those of the main input matching network, the only difference being that the auxiliary input matching network is connected to a gate bias voltage V used to enable the auxiliary power amplifier to operate in Class C mode. g2 The compensation input matching network is connected to the gate bias voltage V used to enable the compensation power amplifier to operate in Class C mode. g3 .

[0015] Furthermore, the main output matching network includes a tenth impedance tuning line, an eleventh impedance tuning line, a twelfth impedance tuning line, a thirteenth impedance tuning line, and a fourth capacitor. One end of the tenth impedance tuning line is connected to one end of the eleventh impedance tuning line, and this connection end serves as the input terminal of the main output matching network. The other end of the tenth impedance tuning line is connected to one end of the fourth capacitor, and this connection end is connected to the drain bias voltage V used to ensure the normal operation of the main power amplifier. d1The other end of the fourth capacitor is grounded, the other end of the eleventh impedance tuning line is connected to one end of the twelfth impedance tuning line, the other end of the twelfth impedance tuning line is connected to one end of the thirteenth impedance tuning line, and the other end of the thirteenth impedance tuning line is the output terminal of the main output matching network.

[0016] Furthermore, the auxiliary output matching network includes a fourteenth impedance tuning line, a fifteenth impedance tuning line, a sixteenth impedance tuning line, a seventeenth impedance tuning line, a fifth capacitor, and a sixth capacitor. One end of the fourteenth impedance tuning line is connected to one end of the fifteenth impedance tuning line, and its connection end is the input terminal of the auxiliary output matching network. The other end of the fourteenth impedance tuning line is connected to one end of the fifth capacitor, and its connection terminal is connected to the drain bias voltage V used to enable the auxiliary power amplifier to operate normally. d2 The other end of the fifth capacitor is grounded. The other end of the fifteenth impedance tuning line is connected to one end of the sixteenth impedance tuning line. The other end of the sixteenth impedance tuning line is connected to one end of the sixth capacitor. The other end of the sixth capacitor is connected to one end of the seventeenth impedance tuning line. The other end of the seventeenth impedance tuning line is the output terminal of the auxiliary output matching network. The structure of the compensation output matching network is basically the same as that of the auxiliary output matching network, except that the compensation output matching network is connected to the drain bias voltage V used to enable the compensation power amplifier to operate normally. d3 .

[0017] Furthermore, the power combining network adopts a Wilkinson power divider structure, including an eighteenth impedance tuning line, a nineteenth impedance tuning line, a twentieth impedance tuning line, and a third resistor. One end of the eighteenth impedance tuning line is the output terminal of the power combining network. The other end of the eighteenth impedance tuning line is connected to one end of the nineteenth impedance tuning line and one end of the twentieth impedance tuning line, respectively. The other end of the nineteenth impedance tuning line is connected to one end of the third resistor. The other end of the third resistor is connected to the other end of the twentieth impedance tuning line. The connection point between the other end of the nineteenth impedance tuning line and one end of the third resistor, and the connection point between the other end of the third resistor and the other end of the twentieth impedance tuning line, are the two input terminals of the power combining network.

[0018] Furthermore, the post-matching network includes a 21st impedance tuning line, a 22nd impedance tuning line, a 23rd impedance tuning line, a 24th impedance tuning line, a 25th impedance tuning line, and a 7th capacitor. One end of the 21st impedance tuning line is the input terminal of the post-matching network. The other end of the 21st impedance tuning line is connected to one end of the 22nd impedance tuning line, the other end of the 22nd impedance tuning line is connected to one end of the 23rd impedance tuning line, the other end of the 23rd impedance tuning line is connected to one end of the 24th impedance tuning line, the other end of the 24th impedance tuning line is connected to one end of the 7th capacitor, and the other end of the 7th capacitor is connected to one end of the 25th impedance tuning line. The other end of the 25th impedance tuning line is the output terminal of the post-matching network. Attached Figure Description

[0019] Figure 1 This is a structural diagram of the Doherty power amplifier with load modulation enhancement according to the present invention;

[0020] Figure 2 The circuit diagram shows the main input matching network of the load modulation enhanced Doherty power amplifier of the present invention.

[0021] Figure 3 The circuit diagram shows the main output matching network of the load modulation enhanced Doherty power amplifier of the present invention.

[0022] Figure 4 The circuit diagram shows the auxiliary output matching network of the load modulation enhanced Doherty power amplifier of the present invention.

[0023] Figure 5 The circuit diagram shows the power combining network of the load modulation enhanced Doherty power amplifier of the present invention.

[0024] Figure 6 The circuit diagram shows the post-matching network of the load modulation enhanced Doherty power amplifier of the present invention.

[0025] Figure 7 The graph shows the efficiency and gain of the load-modulated enhanced Doherty power amplifier of the present invention as a function of output power.

[0026] Figure 8 The graph shows the saturation efficiency and back-off efficiency of the Doherty power amplifier with load modulation enhancement according to the present invention as a function of frequency. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0028] Example 1: As Figure 1 As shown, a load-modulated enhanced Doherty power amplifier includes a power divider, a main branch, an auxiliary branch, and a post-matching network. The main branch includes a main power amplifier, and the auxiliary branch includes an auxiliary power amplifier. The main branch amplifies the input signal and outputs it to the post-matching network. The Doherty power amplifier also includes a compensation branch and a power combining network. The compensation branch includes a compensation power amplifier. The power divider is a three-way power divider, used to divide the externally input RF signal RFin into three equal parts and input them to the main branch, auxiliary branch, and compensation branch respectively. The auxiliary branch and compensation branch amplify the input signals and output them to the power combining network. The power combining network is used to amplify the compensation signal. The signals output from the compensation branch and the auxiliary branch are combined in phase and matched to the junction point of the auxiliary branch and the compensation branch before being output to the post-matching network. The post-matching network is used to match the impedance of the junction point of the power combining network and the main branch to the 50 ohms standard of the wireless communication system, thereby outputting the signal to that point. The auxiliary branch, the compensation branch, and the power combining network constitute a new auxiliary branch. The compensation branch uses the power combining network to superimpose its output current with the output current of the auxiliary branch, so that the output current of the new auxiliary branch is equal to the sum of the output current of the auxiliary branch and the output current of the compensation branch, thereby achieving synchronous saturation of the combined current of the auxiliary branch and the compensation branch with the output current of the main branch.

[0029] For a traditional Doherty power amplifier, to achieve an ideal active load modulation trajectory, the rate of change of current in the auxiliary power amplifier should be twice that of the main power amplifier. This ensures synchronous saturation of the auxiliary and main power amplifiers. This rate of change of current is called the transconductance. gm The concept is expressed by equation (1):

[0030] (1)

[0031] △Ic The slope representing the drain current of a transistor (power amplifier transistor). △V in This represents the slope of the input voltage of a transistor (power amplifier tube).

[0032] Due to the late start-up of the auxiliary power amplifier and the influence of Class C bias, for traditional Doherty power amplifiers, the main power amplifier and the auxiliary power amplifier cannot reach synchronous saturation to achieve ideal active load modulation if the main power amplifier is not oversaturated, thus limiting the performance of the Doherty power amplifier.

[0033] This invention injects compensation current by setting up a compensation branch, thereby correcting the weak current output capability and small output current of the auxiliary branch caused by Class C bias. This allows the output current of the newly formed auxiliary branch to achieve synchronous saturation with the output current of the main branch. The compensation branch, the auxiliary branch, and the power combining network are combined to form a new auxiliary branch. In this case, the transconductance of the new auxiliary branch is still physically the derivative of the overall output current with respect to the input voltage. The transconductance of the main power amplifier is denoted as gm,m, the transconductance of the auxiliary power amplifier as gm,a, and the transconductance of the compensation power amplifier as gm,c. The load-modulated enhanced Doherty power amplifier of this invention essentially compensates for and corrects the gm,a of the auxiliary power amplifier, theoretically achieving the effect of gm,m = gm,c + gm,a. This fundamentally corrects the current output capability of the auxiliary power amplifier and eliminates the adverse effects caused by its weak current output capability.

[0034] Example 2: This example is basically the same as Example 1, except that: In this example, the main branch also includes a main input matching network and a main output matching network. The main input matching network is used to perform impedance matching on the signal output from the three-way power divider, and the impedance-matched signal is output to the main power amplifier. The main power amplifier is used to amplify the signal output from the main input matching network, and the amplified signal is output to the main output matching network. The main output matching network is used to match the signal output from the main power amplifier and output it to the post-matching network. The auxiliary branch also includes an auxiliary input matching network and an auxiliary output matching network. The auxiliary input matching network is used to perform impedance matching on the signal output from the three-way power divider, and simultaneously controls the turn-on point of the auxiliary power amplifier within the passband, obtaining an impedance-matched signal with turn-on control, which is then output to the auxiliary power amplifier. The auxiliary power amplifier amplifies the signal output from the auxiliary input matching network and outputs the amplified signal to the auxiliary output matching network. The auxiliary output matching network then matches the signal output from the auxiliary power amplifier and outputs it to the power combining network. The compensation branch also includes a compensation input matching network and a compensation output matching network. The compensation input matching network performs impedance matching on the signal output from the three-way power divider and simultaneously controls the turn-on point of the compensation power amplifier within the passband to be consistent with the turn-on point of the auxiliary power amplifier. The signal after impedance matching and turn-on control is output to the compensation power amplifier. The compensation power amplifier amplifies the signal output from the compensation input matching network and outputs the amplified signal to the compensation output matching network. The compensation output matching network then matches the signal output from the compensation power amplifier and outputs it to the power combining network.

[0035] In this embodiment, the three-way power divider has one input terminal and three output terminals. The main input matching network, main output matching network, auxiliary input matching network, auxiliary output matching network, compensation input matching network, compensation output matching network, and post-matching circuit all have input terminals and output terminals. The power combining network has two input terminals and one output terminal. The input terminal of the three-way power divider serves as the input terminal of the Doherty power amplifier, used to receive the externally input RF signal RFin. The three output terminals of the three-way power divider are connected one-to-one with the input terminals of the main input matching network, auxiliary input matching network, and compensation input matching network. The output terminal of the main input matching network is connected to the gate of the main power amplifier, and the source of the main power amplifier is grounded. The output terminal of the auxiliary input matching network... The auxiliary power amplifier's gate is connected to the power amplifier's gate, and the power amplifier's source is grounded. The output of the compensation input matching network is connected to the compensation power amplifier's gate, and the compensation power amplifier's source is grounded. The main power amplifier's drain is connected to the main output matching network's input, the auxiliary power amplifier's drain is connected to the auxiliary output matching network's input, the compensation power amplifier's drain is connected to the compensation output matching network's input, the main output matching network's output is connected to the post-matching network's input, the auxiliary output matching network's output and the compensation output matching network's output are connected one-to-one to the two inputs of the power combining network, the power combining network's output is connected to the post-matching network's input, and the post-matching network's output is the Doherty power amplifier's output, used to output the amplified RF signal.

[0036] Example 3: This example is basically the same as Example 2, except that in this example, the main input matching network, the auxiliary input matching network and the compensation input matching network all use high-order impedance matching networks to achieve impedance transformation.

[0037] like Figure 2As shown, in this embodiment, the main input matching network includes nine impedance tuning lines, three capacitors, and two resistors. The nine impedance tuning lines are referred to as the first impedance tuning line TL1 to the ninth impedance tuning line TL9, the three capacitors as the first capacitor C1 to the third capacitor C3, and the two resistors as the first resistor R1 and the second resistor R2. One end of the first impedance tuning line TL1 is the input terminal of the main input matching network. The other end of the first impedance tuning line TL1 is connected to one end of the first capacitor C1, and the other end of the first capacitor C1 is connected to one end of the second impedance tuning line TL2. The other end of line 2 is connected to one end of the third impedance tuning line TL3. The other end of the third impedance tuning line TL3 is connected to one end of the fourth impedance tuning line TL4. The other end of the fourth impedance tuning line TL4 is connected to one end of the fifth impedance tuning line TL5 and one end of the seventh impedance tuning line TL7. The other end of the fifth impedance tuning line TL5 is connected to one end of the first resistor R1. The other end of the first resistor R1 is connected to one end of the sixth impedance tuning line TL6. The other end of the sixth impedance tuning line TL6 is connected to one end of the second capacitor C2, and its connection point is connected to the gate bias voltage V used to make the main power amplifier operate in Class AB mode. g1 The other end of the second capacitor C2 is grounded. The other end of the seventh impedance tuning line TL7 is connected to one end of the eighth impedance tuning line TL8. The other end of the eighth impedance tuning line TL8 is connected to one end of the second resistor R2 and one end of the third capacitor C3. The other end of the third capacitor C3 and the other end of the second resistor R2 are connected to one end of the ninth impedance tuning line TL9. The other end of the ninth impedance tuning line TL9 is the output terminal of the main input matching network. The structure of the auxiliary input matching network and the compensation input matching network is basically the same as that of the main input matching network, except that the auxiliary input matching network is connected to the gate bias voltage V used to make the auxiliary power amplifier operate in Class C mode. g2 The compensation input matching network is connected to the gate bias voltage V used to enable the compensation power amplifier to operate in Class C mode. g3 .

[0038] In this embodiment, when the main input matching network, auxiliary input matching network, and compensation input matching network perform impedance transformation, they can effectively control the second harmonic and improve the efficiency of the Doherty power amplifier. At the same time, the auxiliary input matching network and compensation input matching network can also precisely control the turn-on point of the auxiliary power amplifier and the compensation power amplifier, ensuring that the auxiliary power amplifier and the compensation power amplifier are turned on at the power back-off point.

[0039] Example 4: This example is basically the same as Example 2, except that: Figure 3As shown, in this embodiment, the main output matching network includes a tenth impedance tuning line TL10, an eleventh impedance tuning line TL11, a twelfth impedance tuning line TL12, a thirteenth impedance tuning line TL13, and a fourth capacitor C4. One end of the tenth impedance tuning line TL10 is connected to one end of the eleventh impedance tuning line TL11, and this connection point is the input terminal of the main output matching network. The other end of the tenth impedance tuning line TL10 is connected to one end of the fourth capacitor C4, and this connection point is connected to the drain bias voltage V used to ensure the normal operation of the main power amplifier. d1 The other end of the fourth capacitor C4 is grounded. The other end of the eleventh impedance tuning line TL11 is connected to one end of the twelfth impedance tuning line TL12. The other end of the twelfth impedance tuning line TL12 is connected to one end of the thirteenth impedance tuning line TL13. The other end of the thirteenth impedance tuning line TL13 is the output terminal of the main output matching network.

[0040] In this embodiment, the main power amplifier output matching network is implemented with a simplified structure consisting of four anti-tuning lines and one capacitor. The main power amplifier output matching network is equivalent to a quarter wavelength line at the center frequency f0 of the Doherty power amplifier's operating frequency band. This ensures the high efficiency and high output power characteristics of the Doherty power amplifier under both saturated power operation and back-off power operation conditions. At the same time, it further regulates the second harmonic of the main power amplifier to further improve efficiency.

[0041] Example 5: This example is basically the same as Example 2, except that: Figure 4 As shown, in this embodiment, the auxiliary output matching network includes a fourteenth impedance tuning line TL14, a fifteenth impedance tuning line TL15, a sixteenth impedance tuning line TL16, a seventeenth impedance tuning line TL17, a fifth capacitor C5, and a sixth capacitor C6. One end of the fourteenth impedance tuning line TL14 is connected to one end of the fifteenth impedance tuning line TL15, and its connection end is the input terminal of the auxiliary output matching network. The other end of the fourteenth impedance tuning line TL14 is connected to one end of the fifth capacitor C5, and its connection end is connected to the drain bias voltage V used to enable the auxiliary power amplifier to operate normally. d2 The other end of the fifth capacitor C5 is grounded. The other end of the fifteenth impedance tuning line TL15 is connected to one end of the sixteenth impedance tuning line TL16. The other end of the sixteenth impedance tuning line TL16 is connected to one end of the sixth capacitor C6. The other end of the sixth capacitor C6 is connected to one end of the seventeenth impedance tuning line TL17. The other end of the seventeenth impedance tuning line TL17 is the output terminal of the auxiliary output matching network. The structure of the compensation output matching network is basically the same as that of the auxiliary output matching network, except that the compensation output matching network is connected to the drain bias voltage V used to enable the compensation power amplifier to operate normally. d3 Normally, V d1 = Vd2 = V d3 .

[0042] In this embodiment, both the auxiliary output matching network and the compensation output matching network adjust the output impedance of the corresponding power amplifier to the high-efficiency, high-power operating region within the passband range, ensuring the operation of the auxiliary power amplifier and the compensation power amplifier in the high-efficiency, high-output-power mode, thereby improving the overall efficiency and output power of the Doherty power amplifier.

[0043] Example 6: This example is basically the same as Example 2, except that: Figure 5 As shown, the power combining network adopts a Wilkinson power divider structure, including an eighteenth impedance tuning line TL18, a nineteenth impedance tuning line TL19, a twentieth impedance tuning line TL20, and a third resistor R3. One end of the eighteenth impedance tuning line TL18 is the output terminal of the power combining network. The other end of the eighteenth impedance tuning line TL18 is connected to one end of the nineteenth impedance tuning line TL19 and one end of the twentieth impedance tuning line TL20, respectively. The other end of the nineteenth impedance tuning line TL19 is connected to one end of the third resistor R3, and the other end of the third resistor R3 is connected to the other end of the twentieth impedance tuning line TL20. The connection between the other end of the nineteenth impedance tuning line TL19 and one end of the third resistor R3, and the connection between the other end of the third resistor R3 and the other end of the twentieth impedance tuning line TL20, are the two input terminals of the power combining network.

[0044] In this embodiment, the power combining network further fine-tunes the phase of the signals output from the auxiliary power amplifier and the compensation power amplifier to achieve a state of two in-phase combined circuits, reducing the loss caused by power combining, thereby improving the overall output power and operating efficiency of the Doherty power amplifier.

[0045] Example 7: This example is basically the same as Example 2, except that: Figure 6As shown, the post-matching network includes the twenty-first impedance tuning line TL21, the twenty-second impedance tuning line TL22, the twenty-third impedance tuning line TL23, the twenty-fourth impedance tuning line TL24, the twenty-fifth impedance tuning line TL25, and the seventh capacitor C7. One end of the twenty-first impedance tuning line TL21 is the input terminal of the post-matching network. The other end of the twenty-first impedance tuning line TL21 is connected to one end of the twenty-second impedance tuning line TL22. The other end of the twenty-second impedance tuning line TL22 is connected to one end of the twenty-third impedance tuning line TL23. The other end of the twenty-third impedance tuning line TL23 is connected to one end of the twenty-fourth impedance tuning line TL24. The other end of the twenty-fourth impedance tuning line TL24 is connected to one end of the seventh capacitor C7. The other end of the seventh capacitor C7 is connected to one end of the twenty-fifth impedance tuning line TL25. The other end of the twenty-fifth impedance tuning line TL25 is the output terminal of the post-matching network.

[0046] In this embodiment, the post-matching network adopts a high-order impedance transformation network, which matches the fundamental impedance of the junction point of the main output matching network and the power combining network to the standard 50 ohms of the wireless communication system. At the same time, it strictly suppresses the second harmonic and tunes the second harmonic to the high-efficiency region, so that the signal input to it is output to the output terminal of the Doherty power amplifier with the highest efficiency and maximum power, thus ensuring the high-performance operation of the overall Doherty power amplifier.

[0047] To verify the performance of the load-modulated enhanced Doherty power amplifier of this invention, the amplifier was actually fabricated and tested. During testing, a copper block was tightly secured beneath the amplifier with screws to ensure good grounding and heat dissipation. A fan was used for auxiliary cooling during testing. The laboratory temperature and humidity were approximately 25°C and 50%, respectively, during testing. A 40dB attenuator was placed between the Doherty power amplifier and the spectrum analyzer to prevent damage to the analyzer.

[0048] The Doherty power amplifier was tested using a single-tone continuous wave (SCH) test. The signal frequencies were set at five specific points: 1.3 GHz, 1.4 GHz, 1.5 GHz, 1.6 GHz, 1.7 GHz, and 1.8 GHz. A linear power scan was performed at these frequencies, yielding the following results: Figure 7 The graph shown illustrates the efficiency versus gain of the load-modulated enhanced Doherty power amplifier of the present invention as a function of output power. From... Figure 7As can be seen, within the operating frequency range of 1.3-1.8 GHz, the load-modulated enhanced Doherty power amplifier of this invention exhibits a saturated drain efficiency of 69.1%-71.9%, a 6dB back-off efficiency of 62.9%-69.4%, and an output power of 43.7-44.5 dBm. These performance indicators demonstrate that the load-modulated enhanced Doherty power amplifier of this invention exhibits excellent efficiency and power output capability over a wide bandwidth. Thanks to the three-channel Doherty architecture employed in the load-modulated enhanced Doherty power amplifier of this invention, which compensates for the current output capability of the auxiliary power amplifier, the saturated output efficiency exceeding 69.1% and the 6dB back-off efficiency exceeding 62.9% within the passband demonstrate excellent energy conversion efficiency, placing it at the forefront of the industry. Furthermore, the output power range of 43.7-44.5 dBm fully meets the high power output requirements of modern wireless communication systems.

[0049] Simultaneously, tests were conducted under the same test conditions, and graphs showing the saturation efficiency and back-off efficiency of the load-modulated enhanced Doherty power amplifier of this invention as a function of frequency were obtained, as shown below. Figure 8 As shown. From Figure 8 As can be seen, the load modulation enhanced Doherty power amplifier of the present invention exhibits consistent and stable performance within the frequency band, and can maintain efficient operation throughout the passband, demonstrating great application potential.

Claims

1. A load-modulated enhanced Doherty power amplifier, comprising a power divider, a main branch, an auxiliary branch, and a post-matching network, wherein the main branch includes a main power amplifier, the auxiliary branch includes an auxiliary power amplifier, and the main branch is used to amplify the input signal and output it to the post-matching network, characterized in that... The Doherty power amplifier further includes a compensation branch and a power combining network. The compensation branch includes a compensation power amplifier, and the power divider is a three-way power divider, used to divide the externally input RF signal RFin into three equal parts and input them to the main branch, the auxiliary branch, and the compensation branch respectively. The auxiliary branch and the compensation branch are used to amplify the input signals and output them to the power combining network. The power combining network is used to combine the signals output from the compensation branch and the auxiliary branch in phase, and then match them to the combining point of the auxiliary branch and the compensation branch before outputting them to the post-matching network. The network, the post-matching network, is used to match the impedance of the power combining network and the main branch's junction point to the 50 ohms standard of the wireless communication system, thereby outputting the signal to that point. The auxiliary branch, the compensation branch, and the power combining network constitute a new auxiliary branch. The compensation branch uses the power combining network to superimpose its output current with the output current of the auxiliary branch, so that the output current of the new auxiliary branch is equal to the sum of the output current of the auxiliary branch and the output current of the compensation branch, thereby achieving synchronous saturation of the combined current of the auxiliary branch and the compensation branch with the output current of the main branch.

2. The Doherty power amplifier with load modulation enhancement according to claim 1, characterized in that... The main branch further includes a main input matching network and a main output matching network. The main input matching network performs impedance matching on the signal output to it before outputting it to the main power amplifier. The main power amplifier amplifies the signal output to it before outputting it to the main output matching network. The main output matching network matches the signal output to it before outputting it to the post-matching network. The auxiliary branch further includes an auxiliary input matching network and an auxiliary output matching network. The auxiliary input matching network performs impedance matching on the signal output to it and simultaneously controls the turn-on point of the auxiliary power amplifier within the passband before outputting it to the auxiliary power amplifier. The auxiliary power amplifier matches the signal output to it. The signal is amplified and then output to the auxiliary output matching network. The auxiliary output matching network is used to match the signal output to it before outputting it to the power combining network. The compensation branch also includes a compensation input matching network and a compensation output matching network. The compensation input matching network is used to perform impedance matching on the signal output to it, and simultaneously controls the turn-on point of the compensation power amplifier and the auxiliary power amplifier in the passband to be consistent before outputting to the compensation power amplifier. The compensation power amplifier is used to amplify the signal output to it before outputting it to the compensation output matching network. The compensation output matching network is used to match the signal output to it before outputting it to the power combining network.

3. The Doherty power amplifier with load modulation enhancement according to claim 2, characterized in that... The three-way power divider has one input terminal and three output terminals. The main input matching network, the main output matching network, the auxiliary input matching network, the auxiliary output matching network, the compensation input matching network, the compensation output matching network, and the post-matching network all have input terminals and output terminals. The power combining network has two input terminals and one output terminal. The three output terminals of the three-way power divider are connected one-to-one with the input terminals of the main input matching network, the auxiliary input matching network, and the compensation input matching network. The output terminal of the main input matching network is connected to the gate of the main power amplifier, and the output terminal of the auxiliary input matching network is connected to the gate of the auxiliary power amplifier. The output terminal of the compensation input matching network is connected to the gate of the compensation power amplifier. The sources of the main power amplifier, the auxiliary power amplifier, and the compensation power amplifier are all grounded. The drain of the main power amplifier is connected to the input terminal of the main output matching network. The drain of the auxiliary power amplifier is connected to the input terminal of the auxiliary output matching network. The drain of the compensation power amplifier is connected to the input terminal of the compensation output matching network. The output terminal of the main output matching network is connected to the input terminal of the post-matching network. The output terminals of the auxiliary output matching network and the compensation output matching network are connected one-to-one to the two input terminals of the power combining network. The output terminal of the power combining network is connected to the input terminal of the post-matching network.

4. The Doherty power amplifier with load modulation enhancement according to claim 3, characterized in that... The main input matching network, the auxiliary input matching network, and the compensation input matching network all employ high-order impedance matching networks to achieve impedance transformation.

5. The Doherty power amplifier with load modulation enhancement according to claim 4, characterized in that... The main input matching network includes a first impedance tuning line to a ninth impedance tuning line, a first capacitor to a third capacitor, a first resistor, and a second resistor. One end of the first impedance tuning line is the input terminal of the main input matching network, and the other end is connected to one end of the first capacitor. The other end of the first capacitor is connected to one end of the second impedance tuning line. The other end of the second impedance tuning line is connected to one end of the third impedance tuning line. The other end of the third impedance tuning line is connected to one end of the fourth impedance tuning line. The other end of the fourth impedance tuning line, one end of the fifth impedance tuning line, and one end of the seventh impedance tuning line are connected. The other end of the fifth impedance tuning line is connected to one end of the first resistor. The other end of the first resistor is connected to one end of the sixth impedance tuning line. The other end of the sixth impedance tuning line is connected to one end of the second capacitor, and its connection terminal is connected to the gate bias voltage V used to make the main power amplifier operate in Class AB mode. g1 The other end of the second capacitor is grounded, the other end of the seventh impedance tuning line is connected to one end of the eighth impedance tuning line, the other end of the eighth impedance tuning line is connected to one end of the second resistor and one end of the third capacitor, the other end of the third capacitor and the other end of the second resistor are connected to one end of the ninth impedance tuning line, and the other end of the ninth impedance tuning line is the output end of the main input matching network.

6. The Doherty power amplifier with load modulation enhancement according to claim 5, characterized in that... The structure of the auxiliary input matching network and the compensation input matching network is basically the same as that of the main input matching network, except that the auxiliary input matching network is connected to the gate bias voltage V used to enable the auxiliary power amplifier to operate in Class C mode. g2 The compensation input matching network is connected to the gate bias voltage V used to enable the compensation power amplifier to operate in Class C mode. g3 .

7. The Doherty power amplifier with load modulation enhancement according to claim 3, characterized in that... The main output matching network includes a tenth impedance tuning line, an eleventh impedance tuning line, a twelfth impedance tuning line, a thirteenth impedance tuning line, and a fourth capacitor. One end of the tenth impedance tuning line is connected to one end of the eleventh impedance tuning line, and this connection point serves as the input terminal of the main output matching network. The other end of the tenth impedance tuning line is connected to one end of the fourth capacitor, and this connection point is connected to the drain bias voltage V used to ensure the normal operation of the main power amplifier. d1 The other end of the fourth capacitor is grounded, the other end of the eleventh impedance tuning line is connected to one end of the twelfth impedance tuning line, the other end of the twelfth impedance tuning line is connected to one end of the thirteenth impedance tuning line, and the other end of the thirteenth impedance tuning line is the output terminal of the main output matching network.

8. The Doherty power amplifier with load modulation enhancement according to claim 3, characterized in that... The auxiliary output matching network includes a fourteenth impedance tuning line, a fifteenth impedance tuning line, a sixteenth impedance tuning line, a seventeenth impedance tuning line, a fifth capacitor, and a sixth capacitor. One end of the fourteenth impedance tuning line is connected to one end of the fifteenth impedance tuning line, and this connection end serves as the input terminal of the auxiliary output matching network. The other end of the fourteenth impedance tuning line is connected to one end of the fifth capacitor, and this connection end is connected to the drain bias voltage V used to ensure the normal operation of the auxiliary power amplifier. d2 The other end of the fifth capacitor is grounded. The other end of the fifteenth impedance tuning line is connected to one end of the sixteenth impedance tuning line. The other end of the sixteenth impedance tuning line is connected to one end of the sixth capacitor. The other end of the sixth capacitor is connected to one end of the seventeenth impedance tuning line. The other end of the seventeenth impedance tuning line is the output terminal of the auxiliary output matching network. The structure of the compensation output matching network is basically the same as that of the auxiliary output matching network, except that the compensation output matching network is connected to the drain bias voltage V used to enable the compensation power amplifier to operate normally. d3 .

9. The Doherty power amplifier with load modulation enhancement according to claim 3, characterized in that... The power combining network adopts a Wilkinson power divider structure, including an eighteenth impedance tuning line, a nineteenth impedance tuning line, a twentieth impedance tuning line, and a third resistor. One end of the eighteenth impedance tuning line is the output terminal of the power combining network. The other end of the eighteenth impedance tuning line is connected to one end of the nineteenth impedance tuning line and one end of the twentieth impedance tuning line, respectively. The other end of the nineteenth impedance tuning line is connected to one end of the third resistor. The other end of the third resistor is connected to the other end of the twentieth impedance tuning line. The connection point between the other end of the nineteenth impedance tuning line and one end of the third resistor, and the connection point between the other end of the third resistor and the other end of the twentieth impedance tuning line, are the two input terminals of the power combining network.

10. The Doherty power amplifier with load modulation enhancement according to claim 3, characterized in that... The post-matching network includes a 21st impedance tuning line, a 22nd impedance tuning line, a 23rd impedance tuning line, a 24th impedance tuning line, a 25th impedance tuning line, and a 7th capacitor. One end of the 21st impedance tuning line is the input terminal of the post-matching network. The other end of the 21st impedance tuning line is connected to one end of the 22nd impedance tuning line, the other end of the 22nd impedance tuning line is connected to one end of the 23rd impedance tuning line, the other end of the 23rd impedance tuning line is connected to one end of the 24th impedance tuning line, the other end of the 24th impedance tuning line is connected to one end of the 7th capacitor, and the other end of the 7th capacitor is connected to one end of the 25th impedance tuning line. The other end of the 25th impedance tuning line is the output terminal of the post-matching network.

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