Power amplifier

Abstract

The embodiment of the invention discloses a power amplifier which comprises a Doherty power amplification unit and a resonance unit, and the resonance unit, the output end of a main power amplification branch and the output end of an auxiliary power amplification branch are connected at a combining point; the resonant frequency of the resonant unit is close to the center frequency of the power amplifier, and the resonant unit presents an open-circuit high-resistance characteristic at the center frequency. According to the Doherty power amplifier, the resonance unit compensates the frequency response of the first 1 / 4 wavelength transmission line, and the effective working bandwidth of the Doherty power amplifier is improved.

Description

Technical Field

[0001] The present invention relates to the design field of radio frequency microwave devices, and more particularly to a power amplifier based on a resonance unit. Background Art

[0002] The RF power amplifier is a very critical component in the communication system. The output power of the amplifier determines the communication distance of the system, and the working bandwidth also largely determines the data transmission rate and communication capacity of the system. Due to the properties of the power amplifier itself, it is the most energy-consuming component in the entire communication system. Therefore, improving efficiency is one of the most important goals in designing a power amplifier.

[0003] Doherty power amplifiers are widely used in various communication systems due to their simple architecture and high back-off efficiency. Especially in the transmission links of the radio access network (RAN) base station RRU / AAU and repeater stations, Doherty power amplifiers dominate due to their high output power back-off efficiency and low complexity. However, since the bandwidth of the transmission line that performs load modulation conversion and phase compensation in the Doherty power amplifier is limited, the operating bandwidth of conventional Doherty power amplifiers is relatively narrow, that is, the efficiency of conventional Doherty power amplifiers at their back-off points will seriously decrease as the operating frequency band expands. Summary of the invention

[0004] In view of this, the present invention proposes a power amplifier to solve the problem of a relatively narrow operating bandwidth of a Doherty power amplifier in the prior art.

[0005] An embodiment of the present invention provides a power amplifier, including a Doherty power amplifier unit and a resonance unit, wherein the Doherty power amplifier unit includes at least one main power amplifier branch and at least one auxiliary power amplifier branch, and the resonance unit is electrically connected to the output end of the main power amplifier branch and the output end of the auxiliary power amplifier branch at a junction; the resonance unit resonates near the center frequency of the power amplifier and is configured to compensate for the frequency characteristics of the first 1 / 4 wavelength transmission line impedance in the main power amplifier branch.

[0006] Preferably, at the center frequency, the resonance unit presents an open-circuit high-impedance characteristic.

[0007] Preferably, the impedance of the resonance unit at other frequency points centered on the central frequency is approximately distributed along a high reflection coefficient circle.

[0008] Preferably, the resonance unit presents capacitive impedance at a frequency point higher than the center frequency, and presents inductive impedance at a frequency point lower than the center frequency.

[0009] Preferably, the main power amplifier branch comprises a main power amplifying unit, and the frequency response of the output load impedance of the main power amplifying unit at the back-off point is approximately distributed along an equal resistance circle.

[0010] Preferably, the resonance unit comprises an impedance transformation network consisting of a transmission line and a capacitor.

[0011] Preferably, the resonance unit comprises an impedance transformation network consisting of a capacitor and an inductor.

[0012] Preferably, the resonance unit includes a fourth 1 / 4 wavelength transmission line and a first capacitor coupled in series between the combining point and the reference ground, and a first 1 / 2 wavelength transmission line with one end connected to the common output port and the other end open, wherein the frequencies corresponding to the fourth 1 / 4 wavelength transmission line and the first 1 / 2 wavelength transmission line are both the center frequency.

[0013] Preferably, the resonant frequency of the first capacitor is the center frequency.

[0014] Preferably, the resonant unit includes a first inductor, a second capacitor and a third capacitor, wherein the first inductor is first coupled in parallel with the second capacitor, and then coupled in series with the third capacitor between the junction point and the reference ground, wherein the values ​​of the capacitor and the inductor are determined according to the center frequency.

[0015] Preferably, a resonant frequency of the first inductor and the second capacitor in parallel is near the center frequency.

[0016] Preferably, the resonant frequency of the third capacitor is near the center frequency.

[0017] Preferably, the resonance unit further includes a fourth capacitor connected between the combining point and the reference ground.

[0018] Preferably, the capacitance of the fourth capacitor is the same as that of the second capacitor.

[0019] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0020] By connecting a resonant unit of a specific structure at the combining point of the Doherty power amplifier unit and compensating the frequency response of the first 1 / 4 wavelength transmission line, the effective operating bandwidth of the Doherty power amplifier is significantly improved, so that the drain efficiency of the back-off point can be maintained at a higher value in a wider frequency band, or within a specific bandwidth, the decrease in the drain efficiency of the back-off point corresponding to the edge frequency of the band relative to the center frequency is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other objects, features and advantages of the present invention will become more apparent through the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

[0022] Figure 1 A schematic diagram of a circuit structure of a power amplifier according to an embodiment of the present invention;

[0023] Figure 2 A schematic diagram of output power back-off points and drain efficiency responses corresponding to different frequencies in the prior art;

[0024] Figure 3 A schematic diagram of the frequency response of the impedance of the resonance unit according to an embodiment of the present invention;

[0025] Figure 4 It is a frequency response diagram of the real part of the output load impedance of the main power amplifying unit at the back-off point according to an embodiment of the present invention;

[0026] Figure 5 A schematic diagram of the frequency response of the back-off point of the imaginary part of the output load impedance of the main power amplifying unit according to an embodiment of the present invention;

[0027] Figure 6 A schematic diagram of the frequency response of the back-off point output load impedance of the main power amplifying unit according to an embodiment of the present invention;

[0028] Figure 7 is a schematic diagram of a first resonance unit according to an embodiment of the present invention;

[0029] Figure 8 It is a response schematic diagram of the output power back-off point and the drain efficiency at different frequencies corresponding to the first resonance unit of an embodiment of the present invention;

[0030] Fig. 9 is a schematic diagram of a second resonance unit according to an embodiment of the present invention;

[0031] Fig.10 Schematic diagram of the response of the output power back-off point and the drain efficiency at different frequencies corresponding to the second resonant unit of an embodiment of the present invention;

[0032] Fig.11 is a schematic diagram of a third resonance unit according to an embodiment of the present invention;

[0033] Fig.12 It is a response schematic diagram of the output power back-off point and drain efficiency at different frequencies corresponding to the third resonance unit of an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The present invention is described below based on embodiments, but the present invention is not limited to these embodiments. In the detailed description of the present invention below, some specific details are described in detail. It is possible for a person skilled in the art to fully understand the present invention without the description of these details. In order to avoid confusing the essence of the present invention, known methods, processes, flows, components and circuits are not described in detail.

[0035] In addition, persons of ordinary skill in the art will appreciate that the drawings provided herein are for illustration purposes and are not necessarily drawn to scale.

[0036] At the same time, it should be understood that in the following description, "circuit" refers to a conductive loop composed of at least one element or subcircuit through electrical connection or electromagnetic connection. When an element or circuit is said to be "connected to" another element or an element / circuit is said to be "connected between" two nodes, it can be directly coupled or connected to another element or there can be an intermediate element, and the connection between the elements can be physical, logical, or a combination thereof. On the contrary, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0037] An embodiment of the present invention discloses a power amplifier, including a Doherty power amplifier unit and a resonance unit, wherein the Doherty power amplifier unit includes a main power amplifier branch and at least one auxiliary power amplifier branch, the resonance unit is connected to the output ends of the main power amplifier branch and the auxiliary power amplifier branch at a junction, the resonance unit resonates near the center frequency of the power amplifier, and the resonance unit exhibits an open circuit high impedance characteristic at the center frequency.

[0038] like Figure 1 The above is a schematic diagram of a power amplifier of the present invention, wherein the Doherty power amplifier unit 11 includes a power divider 114 and two power amplifier branches, the power divider 114 is configured to receive a radio frequency signal at the input end RF_IN of the Doherty power amplifier unit 11 and divide the radio frequency signal into input signals of two power amplifier branches, one of which is a main power amplifier branch 111, and the other is an auxiliary power amplifier branch 112, and the output ends of the main power amplifier branch 111 and the auxiliary power amplifier branch 112 are connected to a combining point P C The main power amplifier branch 111 includes a first 1 / 4 wavelength transmission line 1112 and a main power amplifier unit 1111, wherein the input end of the main power amplifier unit 1111 is connected to the first output end of the power divider 114, the output end is connected to the first end of the first 1 / 4 wavelength transmission line 1112, and the second end of the first 1 / 4 wavelength transmission line 1112 is connected to the junction point P CThe auxiliary power amplifier branch 112 includes a second 1 / 4 wavelength transmission line 1121 and an auxiliary power amplification unit 1122, wherein one end of the second 1 / 4 wavelength transmission line 1121 is connected to the second output port of the power divider 114, and the other end is connected to the input end of the auxiliary power amplification unit 1122, and the output end of the auxiliary power amplification unit 1122 is connected to the combining point P C The second 1 / 4 wavelength transmission line 1121 is used to compensate for the phase difference caused by the first 1 / 4 wavelength transmission line 1112. Preferably, in this example, the Doherty power amplifier unit 11 may also include a third 1 / 4 wavelength transmission line 113, which is connected between the combining point and the output terminal RF_OUT of the Doherty power amplifier unit 11, and is used to convert the combining point P C wherein the frequencies corresponding to the first 1 / 4 wavelength transmission line 1112, the second 1 / 4 wavelength transmission line 1121 and the third 1 / 4 wavelength transmission line 113 are all the center frequency Fc of the power amplifier.

[0039] The power amplifier in this embodiment also includes a power amplifier connected to the combining point P C The resonant unit 12 connected thereto has a resonant frequency that is the center frequency Fc of the power amplifier (taking into account factors such as errors, it can also be approximated to the center frequency Fc, that is, near the center frequency Fc), and the resonant unit 12 exhibits an open circuit high impedance characteristic at the center frequency Fc. In this embodiment, the resonant unit 12 compensates for the frequency characteristic of the impedance of the first wavelength transmission line 1112, changes the frequency response curve of the output load impedance Zmod of the main power amplifier unit 1111 at the back-off point, and reduces the real and imaginary parts of the output load impedance Zmod of the main power amplifier unit 1111 at the back-off point with the frequency variation range, that is, the main power amplifier unit 1111 achieves high-efficiency load impedance matching in a wider frequency band, thereby improving the drain efficiency of the power amplifier at the back-off point. Among them, the output load impedance Zmod of the main power amplification unit 1111 at the back-off point represents the impedance from the drain output end of the RF power amplifier tube in the main power amplification unit 1111 looking toward the output load end when the auxiliary power amplification unit 1122 is not turned on and hardly participates in power amplification at the power back-off point, which is referred to as the load impedance Zmod hereinafter.

[0040] In the prior art, a conventional Doherty power amplifier only includes Figure 1The Doherty power amplifier unit 11 in the embodiment does not include the resonance unit 12. Since the first 1 / 4 wavelength transmission line 1112, the second 1 / 4 wavelength transmission line 1121 and the third 1 / 4 wavelength transmission line 113 are bandwidth-limited, especially the first 1 / 4 wavelength transmission line 1112, which bears the load impedance modulation function of the main power amplifier unit 1111 and plays a decisive role in the working bandwidth of the Doherty power amplifier unit, the working bandwidth of conventional Doherty power amplifiers is relatively narrow. Figure 2 Schematic diagram of the output power back-off point and drain efficiency response of a Doherty power amplifier at different frequencies in the prior art. Taking a symmetrical two-way Doherty PA as an example, the center frequency of the Doherty power amplifier is fc. Figure 2 As shown, it is a schematic diagram of the output power back-off point and drain efficiency response corresponding to different frequencies in the prior art. In the figure, the frequencies corresponding to the curves from top to bottom are successively away from the center frequency fc, wherein the frequency corresponding to the first curve from top to bottom is the center frequency fc, and the frequencies corresponding to the last curve from top to bottom are 0.9fc and 1.1fc, with a corresponding back-off point of -6dB, and the relative bandwidth in which the drain efficiency (Drain Efficiency, DE) decreases by 3% is only about 7%; at a relative bandwidth of 20%, the drain efficiency of the highest frequency 1.1fc and the lowest frequency 0.9fc in the corresponding band edge frequencies decreases by 19% relative to the center frequency Fc, wherein the relative bandwidth = 2*(highest frequency - lowest frequency) / (highest frequency + lowest frequency).

[0041] It should be noted that the structure of the Doherty power amplifier unit 11 includes but is not limited to Figure 1 The power amplifier type shown includes two branches, and may also include multiple branches, which may be symmetrical, asymmetrical, positive, negative, parallel, series, switch, etc.; as long as the output load impedance Zmod of the back-off point of the main power amplifier unit 1111 of the Doherty power amplifier unit 11 satisfies Figure 6 The left curve trend diagram in FIG. 1 satisfies the requirements of this embodiment and is not limited here. Figure 1 In the example, the input ends of the main power amplification unit 1111 and the auxiliary power amplification unit 1122 can be connected to an input impedance matching circuit, and the output ends can be connected to an output matching circuit. For the convenience of example, Figure 1 On the other hand, in this embodiment, a dual-path symmetrical Doherty power amplifier unit is used as an example for explanation, that is, the back-off point is -6dB; in other examples, the back-off point is determined according to the specific structure of the Doherty power amplifier unit 11 and is not necessarily -6dB.

[0042] Figure 3 The figure shows a frequency response diagram of the resonance unit impedance of the present embodiment. At the center frequency Fc, the port of the resonance unit 12 presents an open circuit high impedance characteristic, and the impedance of the remaining frequency points centered on the center frequency Fc is distributed along the total reflection coefficient circle of the Smith chart. Furthermore, the resonance unit 12 presents a capacitive impedance at a frequency point higher than the center frequency Fc, and presents an inductive impedance at a frequency point lower than the center frequency.

[0043] It should be noted that Figure 3 As a preferred example, the impedance of the remaining frequency points centered on the center frequency Fc is distributed along the total reflection circle of the Smith chart. In other examples, as long as the frequency response curves of the impedance of the remaining frequency points centered on the center frequency Fc are approximately distributed along the high reflection coefficient circle of the Smith chart, such as distributed along the equal reflection coefficient circle with a reflection coefficient greater than 0.9, at the center frequency Fc, a higher impedance is presented, and at frequencies higher than the center frequency Fc, capacitive impedance is presented; at frequencies lower than the center frequency Fc, the structural composition of the resonant unit presents inductive impedance, all meet the requirements of the invention and are not limited herein.

[0044] like Figure 4 , which is a frequency response diagram of the real part Real (Zmod) of the output load impedance Zmod of the main power amplifier unit 1111 of the embodiment of the present invention at the back-off point, wherein the solid line represents the real part change curve of the load impedance Zmod at the back-off point when the resonance unit 12 is included, and the dotted line represents the real part change curve of the load impedance Zmod when the resonance unit 12 is not included. This diagram takes the power amplifier back-off point of -6dB as an example for explanation, and the center frequency of the power amplifier is Fc. Figure 4 It can be seen that within the frequency range of 0.75Fc to 1.25Fc, the variation range of the solid line is smaller than that of the dotted line, that is, when the power amplifier includes the resonant unit 12, the range of variation of the real part Real (Zmod) of the load impedance Zmod at the back-off point with frequency becomes smaller, thereby making the real part Real (Zmod) fit the equal resistance circle better.

[0045] like Figure 5 , which is a frequency response diagram of the imaginary part Imag(Zmod) of the output load impedance Zmod of the main power amplifier unit 1111 of the embodiment of the present invention at the back-off point, wherein the solid line represents the change curve of the imaginary part of the load impedance Zmod at the back-off point when the resonance unit 12 is included, and the dotted line represents the change curve of the imaginary part of the load impedance Zmod at the back-off point when the resonance unit 12 is not included. This diagram also takes the back-off point of -6dB as an example for explanation, and the center frequency of the power amplifier is Fc; Figure 5It can be seen that in the frequency range of 0.75Fc to 1.25Fc, the solid line is closer to the horizontal axis than the dotted line, that is, when the power amplifier includes the resonant unit 12, the amplitude of the imaginary part of the load impedance Zmod at the back-off point is closer to the horizontal axis, so that the range of change of the imaginary part of the load impedance Zmod with the frequency at the back-off point also becomes smaller.

[0046] Figure 6 FIG. 1 is a frequency response diagram of the back-off point output load impedance Zmod of the main power amplifier unit of the embodiment of the present invention. The thinner curve on the left is the load impedance Z when the power amplifier does not include the resonant unit 12. mod The frequency response curve at the back-off point, the thicker curve on the right is the load impedance Z when the power amplifier includes the resonant unit 12 mod The frequency response curve at the back-off point. Figure 6 As shown, when the power amplifier does not include the resonant unit 12, the load impedance Z mod The phenomenon of cutting the equal resistance circle appears at the back-off point. When the power amplifier includes the resonant unit 12, the frequency response curve of the load impedance Zmod at the back-off point fits the equal resistance circle, and is represented by Figure 4 and Figure 5 It can be seen that when the resonant unit 12 is included, the real part Real (Zmod) and the imaginary part Imag (Zmod) of the load impedance Zmod both become smaller in the range of variation with frequency at the back-off point. Therefore, the load impedance Zmod also becomes smaller in the range of variation with frequency at the back-off point, that is, it becomes more convergent, so that the main power amplifier unit 1111 achieves high-efficiency load impedance matching within a wider frequency band.

[0047] Combine the following Figure 6The compensation effect of the resonance unit 12 on the first 1 / 4 wavelength transmission line 1112 is explained. Among them, the frequencies corresponding to points 1 and 2 are both 0.75*Fc, the frequency corresponding to point 3 is the center frequency Fc, and the frequencies corresponding to points 4 and 5 are both 1.25*Fc. When the frequency is less than the center frequency Fc, the resonance unit 12 presents an inductive impedance. At this time, the resonance unit 12 is equivalent to an inductor. Compared with the conventional 1 / 4 wavelength impedance converter, the resonance unit 12 transfers the load impedance Zmod of the main power amplifier unit 1111 that is less than the center frequency Fc from the curve between points 3 and 1 on the left curve to between points 3 and 2 on the right curve; when the frequency is equal to the center frequency Fc, the resonance unit 12 is equivalent to an open circuit with infinite impedance. At this time, the 1 / 4 wavelength impedance converter is connected in parallel to an open circuit branch with infinite impedance. , relative to the conventional 1 / 4 wavelength impedance converter, the resonant unit 12 maintains the load impedance Zmod of the main power amplifier unit 1111 whose frequency is equal to the center frequency Fc at point 3; when the frequency is greater than the center frequency Fc, the resonant unit 12 presents a capacitive impedance, and the resonant unit 12 is equivalent to a capacitor. Relative to the conventional 1 / 4 wavelength impedance converter, the resonant unit 12 compensates and transfers the output load impedance Zmod of the main power amplifier unit 1111 whose frequency is greater than the center frequency Fc from the curve between points 3 and 4 on the left curve to between points 3 and 5 on the right curve. Therefore, since the resonant unit 12 compensates for the load impedance Zmod of the first 1 / 4 wavelength transmission line 1112 at the frequency point that is not at the center frequency Fc, the load impedance Z is changed. mod The frequency response curve at the back-off point makes the load impedance Zmod of the main power amplifier unit 1111 fit the equal resistance circle more closely and converge more, thereby improving the dispersion phenomenon and achieving high-efficiency load impedance matching of the main power amplifier unit 1111 in a wider frequency band.

[0048] Specifically, the resonance unit 12 may include an impedance transformation network composed of a transmission line and a capacitor, or may include an impedance transformation network composed of a capacitor and an inductor.

[0049] like Figure 7 As shown, it is an example diagram of the first type of resonance unit 12, the resonance unit 12 includes a fourth 1 / 4 wavelength transmission line and a first capacitor C1 connected in series between the junction point Pc and the reference ground, and a first 1 / 2 wavelength transmission line connected to the junction point Pc at one end, wherein the first capacitor C1 is connected between the fourth 1 / 4 wavelength transmission line and the reference ground, the other end of the first 1 / 2 wavelength transmission line is open, the frequencies corresponding to the fourth 1 / 4 wavelength transmission line and the first 1 / 2 wavelength transmission line are both the center frequency Fc, the resonance frequency of the first capacitor C1 is near the center frequency Fc, that is, the equivalent impedance of the first capacitor C1 presents low resistance near the center frequency Fc. Figure 8As shown in FIG. 1 , the power amplifier includes the first resonant unit 12 at the back-off point corresponding to the drain efficiency. It can be seen that when the first resonant unit 12 is included, the relative bandwidth corresponding to the drain efficiency of the Doherty power amplifier unit 11 at the output power -6dB back-off point drops to 3% is about 26%; at a relative bandwidth of 20%, the corresponding drain efficiency of the highest frequency 1.1fc and the lowest frequency 0.9fc drops relative to the center frequency Fc efficiency from Figure 2 The 19% of the prior art is reduced to 0.9%.

[0050] like Fig. 9 As shown in FIG. 1 , it is an example diagram of a second type of resonance unit 12, the resonance unit 12 includes a first inductor L1, a second capacitor C2 and a third capacitor C3, wherein the first inductor L1 is first connected in parallel with the second capacitor C2, and then connected in series with the third capacitor C3 between the junction point Pc and the reference ground. Specifically, the resonance frequency of the parallel first inductor L1 and the second capacitor C2 is near the center frequency Fc, and the resonance frequency of the third capacitor is near the center frequency Fc, that is, the equivalent impedance of the third capacitor C3 presents a low resistance near the center frequency Fc. Fig.10 As shown, the drain efficiency of the power amplifier including the second resonant unit 12 at the back-off point corresponds to 9%. It can be seen that the relative bandwidth of the drain efficiency of the power amplifier at the back-off point of the output power -6dB decreases by 3% is 9%; at a relative bandwidth of 20%, the corresponding drain efficiency of the highest frequency 1.1fc and the lowest frequency 0.9fc relative to the efficiency of the center frequency Fc is reduced from Figure 2 The prior art was reduced from 19% to 13.9%.

[0051] like Fig.11 As shown, it is an example diagram of the third type of resonance unit 12, the resonance unit 12 includes a second inductor L2, a fourth capacitor C4, a fifth capacitor C5 and a sixth capacitor C6, wherein the second inductor L2 is first connected in parallel with the fourth capacitor C4, and then connected in series with the fifth capacitor C5 between the junction point Pc and the reference ground, and the sixth capacitor is connected between the junction point Pc and the reference ground. Specifically, the resonance frequency of the parallel second inductor L2 and the fourth capacitor C4 is near the center frequency Fc, the resonance frequency of the fifth capacitor C5 is near the center frequency Fc, and the capacitance values ​​of the fourth capacitor C4 and the sixth capacitor C6 are equal. Fig.12 As shown, the drain efficiency of the power amplifier including the third resonant unit 12 at the back-off point corresponds to 12%. It can be seen that the relative bandwidth corresponding to the 3% decrease in drain efficiency of the Doherty power amplifier unit 11 at the back-off point with an output power of -6dB is 12%. At a relative bandwidth of 20%, the drain efficiency of the highest frequency 1.1fc and the lowest frequency 0.9fc relative to the center frequency Fc is 1.1fc / 0.9 ... Figure 2The prior art was reduced from 19% to 8.8%.

[0052] It should be noted that Figure 7 , Fig. 9 and Fig.11 As an example only, the impedance is shown to satisfy Figure 3 The circuit example of the resonance unit 12, it should be noted that as long as the frequency response of the impedance satisfies Figure 3 The circuit structure can meet the requirements of this embodiment. In actual use, the resonant unit 12 may not be directly connected to the junction point, but may be included in the output matching circuit of the main power amplifier unit 1111 on the side close to the junction point Pc, or included in the output matching circuit of the auxiliary power amplifier unit 1122 on the side close to the junction point, or included in the third 1 / 4 wavelength transmission line 113 on the side close to the junction point, or included in the first 1 / 4 wavelength transmission line 1112, or included in the drain power supply bias network connected through the junction point on the side close to the junction point. As long as the connection mode in which the resonant unit and the output end of the main power amplifier branch and the output end of the auxiliary power amplifier branch are electrically connected to the junction point, the invention is satisfied. In addition, the implementation method of the resonance unit 12 can be PCB board level (microstrip line, microstrip line combined with discrete passive components, etc.), integrated passive device (IPD) process of various semiconductor substrates (CMOS, LDMOS, GaN, GaAs, InP, SiGe, etc.), or a combination of the two connected by direct bonding or Bonding Wire, etc., all of which meet this requirement; they can also be integrated into one circuit, and the specific implementation method of the resonance unit 12 is not limited here.

[0053] In summary, the present invention discloses a power amplifier, which includes a Doherty power amplifier unit and a resonance unit, wherein the Doherty power amplifier unit includes at least one main power amplifier branch and at least one auxiliary power amplifier branch, wherein the resonance unit is connected to the output end of the main power amplifier branch and the output end of the auxiliary power amplifier branch at a junction; the resonance frequency of the resonance unit is near the center frequency of the power amplifier, and the resonance unit exhibits an open circuit high impedance characteristic at the center frequency. The present invention compensates for the frequency response of the first 1 / 4 wavelength transmission line by connecting a resonance unit of a specific structure at the junction of the Doherty amplifier, thereby significantly improving the effective working bandwidth of the Doherty power amplifier, that is, the back-off point efficiency can maintain a higher value in a wider frequency band, or reduce the decrease in the back-off point efficiency at the edge of the band relative to the center frequency efficiency within a specific bandwidth.

[0054] Although the embodiments or implementations are described and explained separately above, some common technologies are involved. It is the opinion of ordinary technicians in this field that the embodiments or implementations can be replaced and integrated between them. If one of the embodiments or implementations is not clearly recorded, reference can be made to another recorded embodiment.

[0055] According to the embodiments of the present invention as described above, these embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made based on the above description. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and the modified use based on the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A power amplifier, characterized in that: It comprises a Doherty power amplifier unit and a resonance unit, wherein the Doherty power amplifier unit comprises at least one main power amplifier branch and at least one auxiliary power amplifier branch, and the resonance unit is electrically connected to the output end of the main power amplifier branch and the output end of the auxiliary power amplifier branch at a combining point; The resonance unit resonates near the center frequency of the power amplifier and is configured to compensate for the frequency characteristics of the first 1 / 4 wavelength transmission line impedance in the main power amplifier branch.

2. The power amplifier according to claim 1, characterized in that: At the center frequency, the resonance unit presents an open-circuit high-impedance characteristic.

3. The power amplifier according to claim 1, characterized in that: The impedance of the resonance unit at other frequency points centered on the central frequency is approximately distributed along a high reflection coefficient circle.

4. The power amplifier according to claim 3, characterized in that: The resonant unit presents capacitive impedance at a frequency point higher than the center frequency, and presents inductive impedance at a frequency point lower than the center frequency.

5. The power amplifier according to claim 1, characterized in that: The main power amplifier branch comprises a main power amplifying unit, and the frequency response of the output load impedance of the main power amplifying unit at the back-off point is approximately distributed along an equal resistance circle.

6. The power amplifier according to claim 1, characterized in that: The resonance unit includes an impedance transformation network composed of a transmission line and a capacitor.

7. The power amplifier according to claim 1, characterized in that: The resonance unit includes an impedance transformation network composed of a capacitor and an inductor.

8. The power amplifier according to claim 6, characterized in that: The resonance unit includes a fourth 1 / 4 wavelength transmission line and a first capacitor coupled in series between the combining point and the reference ground, and a first 1 / 2 wavelength transmission line with one end connected to the common output port and the other end open, wherein the frequencies corresponding to the fourth 1 / 4 wavelength transmission line and the first 1 / 2 wavelength transmission line are both the center frequency.

9. The power amplifier according to claim 8, characterized in that: The resonant frequency of the first capacitor is the center frequency.

10. The power amplifier according to claim 7, characterized in that: The resonant unit includes a first inductor, a second capacitor and a third capacitor, wherein the first inductor is first coupled in parallel with the second capacitor, and then coupled in series with the third capacitor between the junction point and the reference ground, wherein the values ​​of the capacitor and the inductor are determined according to the center frequency.

11. The power amplifier according to claim 10, characterized in that: A resonant frequency of the first inductor and the second capacitor in parallel is near the center frequency.

12. The power amplifier according to claim 10, characterized in that: The resonant frequency of the third capacitor is near the center frequency.

13. The power amplifier according to claim 10, characterized in that: The resonance unit further includes a fourth capacitor connected between the combining point and the reference ground.

14. The power amplifier according to claim 13, characterized in that: The capacitance of the fourth capacitor is the same as that of the second capacitor.

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