Doherty power amplifier with enhanced load modulation

Abstract

The invention discloses a load modulation enhanced Doherty power amplifier, which comprises a power divider, a main branch, an auxiliary branch, a post-matching network, a compensation branch and a power synthesis network, the main branch comprises a main power amplifier, the auxiliary branch comprises an auxiliary power amplifier, the compensation branch comprises a compensation power amplifier, the auxiliary branch, the compensation branch and the power synthesis network form a new auxiliary branch, and the power synthesis network is connected with the auxiliary branch. The compensation branch circuit superposes the output current of the compensation branch circuit and the output current of the auxiliary branch circuit through a power synthesis network, so that the output current of the new auxiliary branch circuit is equal to the sum of the output current of the auxiliary branch circuit and the output current of the compensation branch circuit, and the combined current of the auxiliary branch circuit and the compensation branch circuit and the output current of the main branch circuit achieve the effect of synchronous saturation; the auxiliary power amplifier has the advantages that the adverse effects of weak current output capability and small output current of the auxiliary power amplifier caused by the C-type bias voltage can be eliminated, so that an additional voltage control module is not required to be introduced for correction, and the integration difficulty of a wireless communication system can be reduced.

Description

Technical Field

[0001] The present invention relates to a Doherty power amplifier, in particular to a Doherty power amplifier with enhanced load modulation. Background Art

[0002] The continuous evolution of wireless communication standards places stringent demands on RF 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). This demands power amplifiers that can maintain high efficiency over an extended dynamic range. Doherty power amplifiers, due to their ability to maintain high efficiency over an extended dynamic range, have found widespread application.

[0003] Existing Doherty power amplifiers typically consist of a power splitter, a main branch including a main power amplifier, an auxiliary branch including an auxiliary power amplifier, and a post-matching network. The power splitter is used to split the external input RF signal into two equal signals, which are then input into the main branch and the auxiliary branch respectively. The main branch and the auxiliary branch respectively amplify the input signals and output them to the post-matching network. The post-matching network is used to match the impedance of the junction point of the main branch and the auxiliary branch to the standard 50 ohms of the wireless communication system, thereby outputting the signal input thereto. The Doherty power amplifier sets the bias voltage of the auxiliary power amplifier to a Class C bias voltage, so that it turns on at a fixed back-off power point, achieving active load modulation between the main power amplifier and the auxiliary power amplifier, thereby achieving higher efficiency characteristics in the power back-off region. This inherent advantage has promoted the widespread application of Doherty power amplifiers in 4G LTE systems and current 5G infrastructure, especially in macrocell base stations that require multi-carrier operation.

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

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

[0006] Researchers have proposed using dynamic bias technology to correct the auxiliary power amplifier of a Doherty power amplifier through an additional voltage control module. After the auxiliary power amplifier is turned on, the voltage control module gradually adjusts its operating voltage from Class C bias to Class B bias, thereby eliminating the effects of the auxiliary power amplifier's Class C bias. This technology 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 wireless communication systems. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide a Doherty power amplifier with enhanced load modulation that can eliminate the adverse effects of weak current output capability and small output current caused by Class C bias in the auxiliary power amplifier, thereby eliminating the need to introduce an additional voltage control module for correction and reducing the difficulty of integrating wireless communication systems.

[0008] The technical solution adopted by the present invention to solve the above technical problems is: a load modulation enhanced Doherty power amplifier, including a power splitter, a main branch, an auxiliary branch and a post-matching network, the main branch includes a main power amplifier, the auxiliary branch includes an auxiliary power amplifier, the main branch is used to amplify the signal input thereto and then output it to the post-matching network, the Doherty power amplifier also includes a compensation branch and a power synthesis network, the compensation branch includes a compensation power amplifier, the power splitter is a three-equal power splitter, used to divide the external input radio frequency signal RFin into three equal parts and then input them respectively to the main branch, the auxiliary branch and the compensation branch, the auxiliary branch and the compensation branch are respectively used to amplify the signal input thereto and then output it to the power synthesis network, the power synthesis network It is used to synthesize the signal output by the compensation branch and the signal output by the auxiliary branch in phase, and output them to the post-matching network after matching them to the auxiliary branch and the compensation branch junction. The post-matching network is used to match the impedance of the power synthesis network and the main branch junction to 50 ohms of the wireless communication system standard so as to output the signal output thereto. The auxiliary branch, the compensation branch and the power synthesis network constitute a new auxiliary branch. The compensation branch uses the power synthesis 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, so that the combined current of the auxiliary branch and the compensation branch and the output current of the main branch reach the effect of synchronous saturation.

[0009] Compared with the prior art, the advantage of the present invention is that a new auxiliary branch is formed with the auxiliary branch by adding a compensation branch and a power synthesis network, and 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, so that the combined current of the auxiliary branch and the compensation branch and the output current of the main branch reach the effect of synchronous saturation, avoiding the main power amplifier from entering the oversaturation area. Therefore, the present invention itself can eliminate the adverse effects of the auxiliary power amplifier's weak current output capability and small output current caused by Class C bias, and does not require the introduction of an additional voltage control module for correction, which can reduce the difficulty of integrating 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 outputted therefrom by the three-way power splitter, and the obtained signal after impedance matching is outputted to the main power amplifier, the main power amplifier is used to amplify the signal outputted therefrom by the main input matching network, and the obtained signal after amplification is outputted to the main output matching network, the main output matching network is used to match the signal outputted therefrom by the main power amplifier and then 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 outputted therefrom by the three-way power splitter, and at the same time control the start-up point of the auxiliary power amplifier in the passband, and obtain the signal after impedance matching and start-up control is outputted to the auxiliary power amplifier, the auxiliary power amplifier is used to The signal outputted from the network is amplified, and the amplified signal is outputted to the auxiliary output matching network, and the auxiliary output matching network is used to match the signal outputted from the auxiliary power amplifier and then output it to the power synthesis network; the compensation branch also includes a compensation input matching network and a compensation output matching network, and the compensation input matching network is used to impedance match the signal outputted from the three-way power divider, and at the same time control the start-up point of the compensation power amplifier in the passband to be consistent with the start-up point of the auxiliary power amplifier, so as to output the signal after impedance matching and start-up control to the compensation power amplifier, and the compensation power amplifier is used to amplify the signal outputted from the compensation input matching network, and the amplified signal is outputted to the compensation output matching network, and the compensation output matching network is used to match the signal outputted from the compensation power amplifier and then output it to the power synthesis network.

[0011] Furthermore, the three-way power splitter has an input end and three output ends, 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 ends and output ends, the power synthesis network has two input ends and one output end, the input end of the three-way power splitter serves as the input end of the Doherty power amplifier, and is used to access the external input radio frequency signal RFin, the three output ends of the three-way power splitter are connected to the input ends of the main input matching network, the auxiliary input matching network and the compensation input matching network in a one-to-one correspondence, the output end of the main input matching network is connected to the gate of the main power amplifier, the source of the main power amplifier is grounded, and the output end of the auxiliary input matching network is connected to the auxiliary The gate of the power amplifier is connected, the source of the auxiliary power amplifier is grounded, the output end 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 end of the main output matching network, the drain of the auxiliary power amplifier is connected to the input end of the auxiliary output matching network, the drain of the compensation power amplifier is connected to the input end of the compensation output matching network, the output end of the main output matching network is connected to the input end of the post-matching network, the output end of the auxiliary output matching network and the output end of the compensation output matching network are connected one-to-one with the two input ends of the power synthesis network, the output end of the power synthesis network is connected to the input end of the post-matching network, and the output end of the post-matching network is the output end of the Doherty power amplifier, which is used to output the power-amplified RF signal RFout.

[0012] Furthermore, the main input matching network, the auxiliary input matching network and the compensation input matching network all adopt high-order impedance matching networks to achieve impedance conversion, thereby effectively controlling the second harmonic and improving the efficiency of the Doherty power amplifier. At the same time, the start-up points of the auxiliary power amplifier and the compensation power amplifier can be accurately controlled to ensure that the auxiliary power amplifier and the compensation power amplifier are turned 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 respectively referred to as the first impedance tuning line to the ninth impedance tuning line, the three capacitors are respectively referred to as the first capacitor to the third capacitor, and the two resistors are respectively referred to as the first resistor and the second resistor. One end of the first impedance tuning line is the input end 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 respectively connected to one end of the fifth impedance tuning line and one end of the seventh impedance tuning line, 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, and the other end of the sixth impedance tuning line is connected to one end of the second capacitor, and the connection ends thereof are connected to a gate bias voltage V for causing the main power amplifier to 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 respectively 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 substantially the same as those of the main input matching network, except that the auxiliary input matching network is connected to a gate bias voltage V for making the auxiliary power amplifier operate in class C mode. g2 The compensation input matching network is connected to the gate bias voltage V for making the compensation amplifier operate in the 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 the connection end thereof is the input end 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 the connection end thereof is connected to the drain bias voltage V for 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 end 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 the connection end thereof is the input end 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 the connection end thereof is connected to the drain bias voltage V for 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, and the other end of the seventeenth impedance tuning line is the output end 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 for normal operation of the compensation power amplifier. d3 .

[0017] Furthermore, the power synthesis 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 end of the power synthesis network, the other end of the eighteenth impedance tuning line is respectively connected to one end of the nineteenth impedance tuning line and one end of the twentieth impedance tuning line, 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 end between the other end of the nineteenth impedance tuning line and one end of the third resistor and the connection end between the other end of the third resistor and the other end of the twentieth impedance tuning line are the two input ends of the power synthesis network.

[0018] Furthermore, the post-matching network includes a twenty-first impedance tuning line, a twenty-second impedance tuning line, a twenty-third impedance tuning line, a twenty-fourth impedance tuning line, a twenty-fifth impedance tuning line and a seventh capacitor, one end of the twenty-first impedance tuning line is the input end of the post-matching network, the other end of the twenty-first impedance tuning line is connected to one end of the twenty-second impedance tuning line, the other end of the twenty-second impedance tuning line is connected to one end of the twenty-third impedance tuning line, the other end of the twenty-third impedance tuning line is connected to one end of the twenty-fourth impedance tuning line, the other end of the twenty-fourth impedance tuning line is connected to one end of the seventh capacitor, the other end of the seventh capacitor is connected to one end of the twenty-fifth impedance tuning line, and the other end of the twenty-fifth impedance tuning line is the output end of the post-matching network. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A structural diagram of a load modulation enhanced Doherty power amplifier according to the present invention; Figure 2 A circuit diagram of a main input matching network of a load modulation enhanced Doherty power amplifier according to the present invention; Figure 3 A circuit diagram of a main output matching network of a load modulation enhanced Doherty power amplifier according to the present invention; Figure 4 A circuit diagram of an auxiliary output matching network of a load modulation enhanced Doherty power amplifier according to the present invention; Figure 5 A circuit diagram of a power combining network of a load modulation enhanced Doherty power amplifier according to the present invention; Figure 6 A circuit diagram of a post-matching network of a load modulation enhanced Doherty power amplifier according to the present invention; Figure 7 A graph showing the efficiency and gain of the load modulation enhanced Doherty power amplifier of the present invention as a function of output power; Figure 8 FIG. 1 is a graph showing how the saturation efficiency and back-off efficiency of the load modulation enhanced Doherty power amplifier of the present invention vary with frequency. DETAILED DESCRIPTION

[0020] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0021] Example 1: Figure 1As shown, a load modulation enhanced Doherty power amplifier includes a power splitter, a main branch, an auxiliary branch and a post-matching network, the main branch includes a main power amplifier, the auxiliary branch includes an auxiliary power amplifier, the main branch is used to amplify the signal input thereto and then output it to the post-matching network, the Doherty power amplifier also includes a compensation branch and a power synthesis network, the compensation branch includes a compensation power amplifier, the power splitter is a three-way power splitter, used to divide the external input radio frequency signal RFin into three equal parts and then input them into the main branch, the auxiliary branch and the compensation branch respectively, the auxiliary branch and the compensation branch are used to amplify the signal input thereto and then output it to the power synthesis network, the power synthesis network is used to The signal output by the compensation branch and the signal output by the auxiliary branch are synthesized in phase, matched to the junction of the auxiliary branch and the compensation branch, and then output to the post-matching network. The post-matching network is used to match the impedance of the power synthesis network and the junction of the main branch to the wireless communication system standard of 50 ohms, thereby outputting the signal output thereto. The auxiliary branch, the compensation branch and the power synthesis network constitute a new auxiliary branch. The compensation branch uses the power synthesis 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, so that the combined current of the auxiliary branch and the compensation branch and the output current of the main branch reach the effect of synchronous saturation.

[0022] For a traditional Doherty power amplifier, if you want to achieve an ideal active load modulation trajectory, the current change rate of the auxiliary amplifier should be twice that of the main amplifier, so as to ensure the synchronous saturation of the auxiliary amplifier and the main amplifier. This current change rate is the transconductance gm The concept of is expressed by formula (1): (1) △Ic Indicates the slope of the drain current of the transistor (power amplifier tube), △V in Indicates the slope of the input voltage of the transistor (power amplifier tube).

[0023] Due to the late start-up of the auxiliary power amplifier and the influence of Class C bias, for traditional Doherty power amplifiers, it is impossible for the main power amplifier and auxiliary power amplifier to reach synchronous saturation to achieve ideal active load modulation without oversaturating the main power amplifier, thus restricting the performance of the Doherty power amplifier.

[0024] The present invention injects a compensation current by setting a compensation branch, thereby achieving correction of the weak current output capability and small output current of the auxiliary branch caused by the Class C bias, so that the output current of the newly constructed auxiliary branch reaches the effect of synchronous saturation with the output current of the main branch. The compensation branch, the auxiliary branch and the power synthesis network are combined to form a new auxiliary branch. At this time, the transconductance of the new auxiliary branch is still the derivative of the overall output current with respect to the input voltage in a physical sense. The transconductance of the main power amplifier is denoted as gm,m, the transconductance of the auxiliary power amplifier is denoted as gm,a, and the transconductance of the compensation power amplifier is denoted as gm,c. The load modulation enhanced Doherty power amplifier of the present invention essentially compensates and corrects the gm,a of the auxiliary power amplifier, that is, theoretically realizes the effect of gm,m=gm,c+gm,a, fundamentally corrects the current output capability of the auxiliary power amplifier, and eliminates the adverse effects caused by the weak current output capability of the auxiliary power amplifier.

[0025] Embodiment 2: This embodiment is basically the same as embodiment 1, except that: in this embodiment, the main branch further 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 outputted therefrom by the three-way power splitter, and output the obtained impedance-matched signal to the main power amplifier. The main power amplifier is used to amplify the signal outputted therefrom by the main input matching network, and output the amplified signal to the main output matching network. The main output matching network is used to match the signal outputted therefrom by the main power amplifier and output 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 is used to perform impedance matching on the signal outputted therefrom by the three-way power splitter, and at the same time control the start-up point of the auxiliary power amplifier in the passband, and output the obtained impedance-matched and start-up controlled signal to the auxiliary power amplifier. The auxiliary power amplifier is used to amplify the signal outputted from the auxiliary input matching network, and output the amplified signal to the auxiliary output matching network. The auxiliary output matching network is used to match the signal outputted from the auxiliary power amplifier and then output it to the power synthesis 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 impedance match the signal outputted from the three-way power divider, and at the same time control the start-up point of the compensation power amplifier in the passband to be consistent with the start-up point of the auxiliary power amplifier, so that the signal after impedance matching and start-up control is outputted to the compensation power amplifier. The compensation power amplifier is used to amplify the signal outputted from the compensation input matching network, and output the amplified signal to the compensation output matching network. The compensation output matching network is used to match the signal outputted from the compensation power amplifier and then output it to the power synthesis network.

[0026] In this embodiment, the three-way power divider has an input end and three output ends, 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 ends and output ends, the power synthesis network has two input ends and one output end, the input end of the three-way power divider serves as the input end of the Doherty power amplifier, and is used to receive the external input radio frequency signal RFin, the three output ends of the three-way power divider are connected to the input ends of the main input matching network, the auxiliary input matching network and the compensation input matching network in a one-to-one correspondence, the output end of the main input matching network is connected to the gate of the main power amplifier, the source of the main power amplifier is grounded, and the output end of the auxiliary input matching network The main power amplifier is connected to the gate of the auxiliary power amplifier, the source of the auxiliary power amplifier is grounded, the output end 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 end of the main output matching network, the drain of the auxiliary power amplifier is connected to the input end of the auxiliary output matching network, the drain of the compensation power amplifier is connected to the input end of the compensation output matching network, the output end of the main output matching network is connected to the input end of the post-matching network, the output end of the auxiliary output matching network and the output end of the compensation output matching network are connected one-to-one with the two input ends of the power synthesis network, the output end of the power synthesis network is connected to the input end of the post-matching network, and the output end of the post-matching network is the output end of the Doherty power amplifier, which is used to output the power-amplified RF signal.

[0027] Embodiment 3: This embodiment is basically the same as Embodiment 2, except that: in this embodiment, 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 conversion.

[0028] 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 respectively referred to as the first impedance tuning line TL1 to the ninth impedance tuning line TL9, the three capacitors are respectively referred to as the first capacitor C1 to the third capacitor C3, and the two resistors are respectively referred to as the first resistor R1 and the second resistor R2. One end of the first impedance tuning line TL1 is the input end 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, the other end of the first capacitor C1 is connected to one end of the second impedance tuning line TL2, and the second impedance tuning line TL 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 the connection ends thereof are connected to the gate bias voltage V for making the main power amplifier operate in the 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 respectively 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, and the other end of the ninth impedance tuning line TL9 is the output end of the main input matching network; 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 the gate bias voltage V for making the auxiliary power amplifier operate in the Class C mode g2 The compensation input matching network is connected to the gate bias voltage V used to make the compensation amplifier operate in Class C mode. g3 .

[0029] In this embodiment, when the main input matching network, the auxiliary input matching network and the compensation input matching network realize impedance conversion, the second harmonic can be effectively controlled, thereby improving the efficiency of the Doherty power amplifier. At the same time, the auxiliary input matching network and the compensation input matching network can also accurately control the start-up 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.

[0030] 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 the connection end thereof serves as the input end 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 the connection end thereof is connected to a drain bias voltage V for 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, and the other end of the thirteenth impedance tuning line TL13 is the output end of the main output matching network.

[0031] In this embodiment, the main power amplifier output matching network is implemented using a streamlined 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 overall high efficiency and high output power characteristics of the Doherty power amplifier under saturated power operating conditions and back-off power operation. At the same time, the second harmonic of the main power amplifier is further regulated to further improve efficiency.

[0032] 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 the connection end thereof serves as the input end 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 the connection end thereof is connected to a drain bias voltage V for normal operation of the auxiliary power amplifier. 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, and the other end of the seventeenth impedance tuning line TL17 is the output end 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, the only difference is that the compensation output matching network is connected to the drain bias voltage V for normal operation of the compensation power amplifier d3 . Normally, V d1 = Vd2 = V d3 .

[0033] In this embodiment, the auxiliary output matching network and the compensation output matching network both adjust the output impedance of the corresponding power amplifier to a high-efficiency, high-power operating region within the passband, ensuring that the auxiliary power amplifier and the compensation power amplifier operate in a high-efficiency, high-output power mode, thereby improving the efficiency and output power of the overall Doherty power amplifier.

[0034] 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 end of the power combining network, the other end of the eighteenth impedance tuning line TL18 is respectively connected to one end of the nineteenth impedance tuning line TL19 and one end of the twentieth impedance tuning line TL20, the other end of the nineteenth impedance tuning line TL19 is connected to one end of the third resistor R3, the other end of the third resistor R3 is connected to the other end of the twentieth impedance tuning line TL20, and the connection end of the other end of the nineteenth impedance tuning line TL19 and one end of the third resistor R3 and the connection end of the other end of the third resistor R3 and the other end of the twentieth impedance tuning line TL20 are two input ends of the power combining network.

[0035] In this embodiment, the power combining network further fine-tunes the phase of the signals outputted from the auxiliary power amplifier and the compensation power amplifier to achieve a state where two paths are combined in phase, thereby reducing the loss caused by power combining and thereby improving the output power and operating efficiency of the overall Doherty power amplifier.

[0036] Example 7: This example is basically the same as Example 2, except that: Figure 6As shown, the post-matching network includes a twenty-first impedance tuning line TL21, a twenty-second impedance tuning line TL22, a twenty-third impedance tuning line TL23, a twenty-fourth impedance tuning line TL24, a twenty-fifth impedance tuning line TL25 and a seventh capacitor C7. One end of the twenty-first impedance tuning line TL21 is the input end 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, and the other end of the twenty-fifth impedance tuning line TL25 is the output end of the post-matching network.

[0037] In this embodiment, the post-matching network uses a high-order impedance transformation network to match the fundamental impedance of the junction point of the main output matching network and the power combining network to the wireless communication system standard of 50 ohms. At the same time, it also strictly suppresses the second harmonic and tunes the second harmonic to a high-efficiency region. The signal input thereto is output to the output end of the Doherty power amplifier with the highest efficiency and maximum power, ensuring the high-performance operation of the entire Doherty power amplifier.

[0038] In order to verify the performance of the load modulation enhanced Doherty power amplifier of the present invention, the load modulation enhanced Doherty power amplifier of the present invention was actually manufactured and tested. When testing the manufactured Doherty power amplifier, the corresponding copper block was tightly fixed underneath it with screws to ensure good grounding and heat dissipation. At the same time, a fan was used to assist in heat dissipation during the test. The temperature and humidity of the laboratory during the test were 25°C and about 50%, respectively. A 40dB attenuator was added between the Doherty power amplifier and the spectrum analyzer to avoid damage to the spectrum analyzer.

[0039] The Doherty power amplifier was tested by single-tone continuous wave. The signal frequency was set at five specific frequency points: 1.3GHz, 1.4GHz, 1.5GHz, 1.6GHz, 1.7GHz and 1.8GHz. The power was linearly scanned at these frequency points. The following results were obtained: Figure 7 The efficiency and gain of the Doherty power amplifier enhanced by load modulation of the present invention vary with the output power. Figure 7It can be seen that in the frequency range of the working frequency band of 1.3-1.8 GHz, the saturated drain efficiency of the load modulation enhanced Doherty power amplifier of the present invention is 69.1%-71.9%, the 6dB back-off efficiency is 62.9%-69.4%, and the output power is 43.7-44.5dBm. These performance indicators show that the load modulation enhanced Doherty power amplifier of the present invention exhibits good efficiency and power output capability within a wide bandwidth. Thanks to the three-way Doherty architecture adopted by the load modulation enhanced Doherty power amplifier of the present invention, which can compensate for the current output capability of the auxiliary power amplifier, the saturated output efficiency of more than 69.1% and the 6dB back-off efficiency of more than 62.9% in the passband show excellent energy conversion efficiency, which is at the leading level in the industry today. In addition, the output power range of 43.7-44.5dBm also fully meets the demand for high power output of modern wireless communication systems.

[0040] At the same time, under the same test conditions, the saturation efficiency and back-off efficiency of the Doherty power amplifier with enhanced load modulation of the present invention are tested and the graph of the change with frequency is obtained, as shown in FIG. Figure 8 As shown. Figure 8 It can be seen from the figures that the load modulation enhanced Doherty power amplifier of the present invention shows consistency and stability of performance within the frequency band, can maintain efficient operation within the passband, and shows great application potential.

Claims

1. A Doherty power amplifier with enhanced load modulation, comprising a power splitter, a main branch, an auxiliary branch, and a post-matching network, wherein the main branch comprises a main power amplifier, the auxiliary branch comprises an auxiliary power amplifier, the main branch is used to amplify a signal input thereto and then output it to the post-matching network, characterized in that The Doherty power amplifier also includes a compensation branch and a power synthesis network. The compensation branch includes a compensation power amplifier. The power divider is a three-way power divider for dividing the external input radio frequency signal RFin into three equal parts and inputting them into the main branch, the auxiliary branch and the compensation branch respectively. The auxiliary branch and the compensation branch are respectively used to amplify the signals input thereto and then output them to the power synthesis network. The power synthesis network is used to synthesize the signal output by the compensation branch and the signal output by the auxiliary branch in phase, and then match them to the junction point of the auxiliary branch and the compensation branch and output them to the post-matching The post-matching network is used to match the impedance of the power synthesis network and the main branch junction to the wireless communication system standard of 50 ohms so as to output the signal output thereto. The auxiliary branch, the compensation branch and the power synthesis network constitute a new auxiliary branch. The compensation branch uses the power synthesis 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, so that the combined current of the auxiliary branch and the compensation branch and the output current of the main branch achieve synchronous saturation.

2. A Doherty power amplifier with enhanced load modulation according to claim 1, characterized in that 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 thereto and then output it to the main power amplifier. The main power amplifier is used to amplify the signal output thereto and then output it to the main output matching network. The main output matching network is used to match the signal output thereto and then 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 thereto and simultaneously control the start-up point of the auxiliary power amplifier in the passband and then output it to the auxiliary power amplifier. The auxiliary power amplifier is used to amplify the signal output thereto and then output it to the main output matching network. The signal is amplified and then output to the auxiliary output matching network, and the auxiliary output matching network is used to match the signal output thereto and then output it to the power synthesis network; the compensation branch also includes a compensation input matching network and a compensation output matching network, and the compensation input matching network is used to impedance match the signal output thereto, and at the same time control the start-up point of the compensation power amplifier in the passband to be consistent with the start-up point of the auxiliary power amplifier and then output it to the compensation power amplifier, the compensation power amplifier is used to amplify the signal output thereto and then output it to the compensation output matching network, and the compensation output matching network is used to match the signal output thereto and then output it to the power synthesis network.

3. A Doherty power amplifier with enhanced load modulation according to claim 2, characterized in that The three-way power splitter has an input end and three output ends. 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 ends and output ends. The power synthesis network has two input ends and one output end. The three output ends of the three-way power splitter are connected to the input ends of the main input matching network, the auxiliary input matching network and the compensation input matching network in a one-to-one correspondence. The output end of the main input matching network is connected to the gate of the main power amplifier, and the output end of the auxiliary input matching network is connected to the gate of the auxiliary power amplifier. The output end 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 end of the main output matching network, the drain of the auxiliary power amplifier is connected to the input end of the auxiliary output matching network, the drain of the compensation power amplifier is connected to the input end of the compensation output matching network, the output end of the main output matching network is connected to the input end of the post-matching network, the output end of the auxiliary output matching network and the output end of the compensation output matching network are connected one-to-one to the two input ends of the power synthesis network, and the output end of the power synthesis network is connected to the input end of the post-matching network.

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

5. The Doherty power amplifier with enhanced load modulation according to claim 4, characterized in that The main input matching network includes first to ninth impedance tuning lines, first to third capacitors, a first resistor and a second resistor. One end of the first impedance tuning line is the input end 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. The connection ends of the first impedance tuning line are connected to a gate bias voltage V for making 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 respectively 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. A Doherty power amplifier with enhanced load modulation according to claim 5, characterized in that 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, except that the auxiliary input matching network is connected to the gate bias voltage V for making the auxiliary power amplifier operate in Class C mode. g2 The compensation input matching network is connected to the gate bias voltage V for making the compensation amplifier operate in the Class C mode. g3 .

7. The Doherty power amplifier with enhanced load modulation 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 the connection end thereof is the input end 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 the connection end thereof is connected to a drain bias voltage V for 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 end of the main output matching network.

8. The Doherty power amplifier with enhanced load modulation 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 its connection end is the input end 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 end is connected to the drain bias voltage V for 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, and the other end of the seventeenth impedance tuning line is the output end 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 for normal operation of the compensation power amplifier. d3 .

9. The Doherty power amplifier with enhanced load modulation according to claim 3, characterized in that The power synthesis 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 end of the power synthesis network, the other end of the eighteenth impedance tuning line is respectively connected to one end of the nineteenth impedance tuning line and one end of the twentieth impedance tuning line, the other end of the nineteenth impedance tuning line is connected to one end of the third resistor, and the other end of the third resistor is connected to the other end of the twentieth impedance tuning line. The connection end between the other end of the nineteenth impedance tuning line and one end of the third resistor and the connection end between the other end of the third resistor and the other end of the twentieth impedance tuning line are the two input ends of the power synthesis network.

10. The load modulation enhanced Doherty power amplifier according to claim 3, characterized in that The post-matching network includes a twenty-first impedance tuning line, a twenty-second impedance tuning line, a twenty-third impedance tuning line, a twenty-fourth impedance tuning line, a twenty-fifth impedance tuning line and a seventh capacitor. One end of the twenty-first impedance tuning line is the input end of the post-matching network, the other end of the twenty-first impedance tuning line is connected to one end of the twenty-second impedance tuning line, the other end of the twenty-second impedance tuning line is connected to one end of the twenty-third impedance tuning line, the other end of the twenty-third impedance tuning line is connected to one end of the twenty-fourth impedance tuning line, the other end of the twenty-fourth impedance tuning line is connected to one end of the seventh capacitor, the other end of the seventh capacitor is connected to one end of the twenty-fifth impedance tuning line, and the other end of the twenty-fifth impedance tuning line is the output end of the post-matching network.

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