Harmonic suppression network, power amplifier and radio frequency power supply

Abstract

The utility model discloses a harmonic suppression network, a power amplifier and a radio frequency power supply, relates to the technical field of all-solid-state radio frequency power supplies, is used for bringing higher output efficiency to a load on the premise of ensuring waveform quality, and provides the harmonic suppression network aiming at the problem of poor waveform quality of a traditional power amplifier. Resonance adjustment is achieved through the first LC resonance circuit and the second LC resonance circuit which are arranged at the drain electrode of the power amplifier MOS tube so as to control harmonic impedance of the corresponding order. Wherein the first LC resonance circuit is used for realizing even harmonic open circuit, and the second LC resonance circuit is used for realizing odd harmonic open circuit, so that the power amplifier obtains ideal voltage and current output, and higher output efficiency is brought while the output waveform quality is ensured.

Description

Technical Field

[0001] The utility model relates to the technical field of all-solid-state radio frequency power supplies, in particular to a harmonic suppression network, a power amplifier and a radio frequency power supply. Background Art

[0002] With the continuous advancement of industry and semiconductor technology, high-frequency power supplies are widely used in various fields. For example, the generation of plasma, the application of aerospace technology, the extraction of special materials and other fields are inseparable from high-frequency power supplies. In addition, with the development of science and technology, the requirements for the working frequency of power supplies are gradually increasing, and power supplies are showing a trend towards high frequency and high power. RF power supplies can meet the above requirements, and their application prospects are becoming more and more broad.

[0003] Traditional RF power supplies are usually designed based on vacuum tubes, which are large in size and low in performance. All-solid-state RF power supplies have the advantages of long life, high reliability, small size, and easy debugging. In addition, with the development of power amplifiers, switching power amplifiers such as Class D and Class E have gradually emerged. These power amplifiers have simple structures and high efficiency, which can meet the high efficiency requirements of RF power supplies in practical applications. But on the other hand, they also have disadvantages such as high drain peak voltage, large influence of operating frequency, and low power output capacity. Due to the limitation of switching frequency and the nonlinearity of transistors, the current and voltage waveforms of the power amplifier often have large overlaps, resulting in a decrease in waveform quality. It can be seen that although the Class E power amplifier can achieve high efficiency, because its output waveform contains a large number of high-order harmonic components, all this high efficiency is achieved by sacrificing waveform quality.

[0004] Therefore, technicians in this field are in urgent need of a harmonic suppression network to bring higher output efficiency to the load while ensuring the waveform quality. Utility Model Content

[0005] The utility model aims to provide a harmonic suppression network, a power amplifier and a radio frequency power supply, which are used to bring high efficiency under the premise of ensuring waveform quality.

[0006] In order to solve the above technical problems, the utility model provides a harmonic suppression network, comprising: a first LC resonant circuit and a second LC resonant circuit;

[0007] The first LC resonant circuit and the second LC resonant circuit are arranged between the drain of the MOS tube in the power amplifier and the output end of the power amplifier;

[0008] Wherein, the even harmonic impedance of the first LC resonant circuit is infinite;

[0009] The odd harmonic impedance of the second LC resonant circuit is zero.

[0010] In a possible embodiment, the first LC resonant circuit includes: a first LC network and a second LC network;

[0011] Wherein, the first end of the first LC network is connected to the drain of the MOS tube, and the second end of the LC network is correspondingly connected to the output end of the power amplifier;

[0012] A first end of the second LC network is connected to a direct current power supply of the power amplifier, and a second end of the second LC network is connected to a second end of the first LC network.

[0013] In a possible embodiment, the second LC resonant circuit includes: the first LC network, a third LC network and a fourth LC network;

[0014] Wherein, the third LC network is arranged between the second end of the first LC network and the output end of the power amplifier;

[0015] A first end of the fourth LC network is connected to a common end of the third LC network and an output end of the power amplifier, and a second end of the fourth LC network is grounded.

[0016] In a possible embodiment, the first LC network, the third LC network, and the fourth LC network are parallel LC networks;

[0017] The second LC network is a series LC network.

[0018] In a possible embodiment, the second LC network includes: a radio frequency choke and a first capacitor;

[0019] The first end of the RF choke is connected to the DC power supply; the second end of the RF choke is connected to the second end of the first LC network, and is connected to the first end of the third LC network through the first capacitor.

[0020] In order to solve the above technical problems, the utility model also provides a power amplifier, comprising: the harmonic suppression network and MOS tube as described above.

[0021] In a possible embodiment, there are two MOS tubes, and a push-pull structure is formed between the two MOS tubes;

[0022] Correspondingly, there are two harmonic suppression networks, which are respectively arranged between the drains of two MOS tubes and the output end of the power amplifier.

[0023] In order to solve the above technical problems, the utility model further provides a radio frequency power supply, comprising: the power amplifier as described above, a first transformer coupling unit and a second transformer coupling unit;

[0024] The front stage of the first transformer coupling unit is connected to the input signal; the center tap end of the first transformer coupling unit is grounded; the rear stage of the first transformer coupling unit is connected to the input end of the power amplifier;

[0025] The front stage of the second transformer coupling unit is connected to the output end of the power amplifier; the center tap end of the first transformer coupling unit is grounded; and the output end of the second transformer coupling unit is connected to the rear stage load.

[0026] In a possible embodiment, it further includes: a filtering, shaping and impedance matching unit;

[0027] The filtering, shaping and impedance matching unit is arranged between the rear stage of the second transformer coupling unit and the rear stage load.

[0028] In a possible embodiment, the filtering, shaping and impedance matching unit includes: a first inductor and a second capacitor;

[0029] The second capacitor is connected in parallel to both ends of the rear stage of the second transformer coupling unit and both ends of the rear stage load;

[0030] The first inductor is connected in series between the same-name terminal of the rear stage of the second transformer coupling unit and the second capacitor.

[0031] The utility model provides a harmonic suppression network, which realizes the even-order impedance open circuit at the drain of the MOS tube in the power amplifier through the first LC resonant circuit with infinite even-order harmonic impedance, and realizes the odd-order impedance short circuit at the drain of the MOS tube in the power amplifier through the second LC resonant circuit with zero odd-order harmonic impedance; and the voltage spectrum components at the drain of the MOS tube are mainly composed of fundamental waves and even-order harmonics, and the current spectrum components are mainly composed of fundamental waves and odd-order harmonics; therefore, through the harmonic suppression network, the current waveform formed at the drain of the MOS tube is in the form of a square wave, the voltage waveform formed is a half-wave rectified sine wave, and the voltage and current waveforms do not overlap in the time domain, and the power amplifier can theoretically achieve 100% drain efficiency. It can be known that the harmonic suppression network provided by the utility model can realize the transmission of the output power of the RF power supply to the load with maximum efficiency, and the output can maintain a relatively flat waveform, while ensuring high efficiency, it can also ensure the output waveform quality, and better adapt to the needs of RF power supply in actual production and life. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present utility model, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 A structural diagram of a power amplifier provided by an embodiment of the utility model;

[0034] Figure 2 A time domain waveform diagram of an ideal current output of a power amplifier provided by an embodiment of the utility model;

[0035] Figure 3 A time domain waveform diagram of an ideal voltage output of a power amplifier provided in an embodiment of the utility model;

[0036] Figure 4 A structural diagram of a radio frequency power supply provided by the utility model;

[0037] Among them, 10 is a harmonic suppression network, 11 is a first LC resonant circuit, 12 is a second LC resonant circuit, 20 is a MOS tube, and 30 is a filtering, shaping and impedance matching unit. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of them. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the utility model.

[0039] The core of the utility model is to provide a harmonic suppression network, a power amplifier and a radio frequency power supply.

[0040] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0041] At present, the high-efficiency Class E power amplifier commonly used in RF power supplies will produce high harmonic distortion during operation, and its output waveform will contain a large number of high-order harmonic components. Therefore, although the Class E power amplifier can achieve high efficiency, this efficiency is achieved at the expense of waveform quality and still cannot meet the needs of RF power supplies well.

[0042] To solve the above problems, the present application provides a harmonic suppression network 10, which is applied to a power amplifier, such as Figure 1As shown, it includes: a first LC resonant circuit 11 and a second LC resonant circuit 12;

[0043] The first LC resonant circuit 11 and the second LC resonant circuit 12 are arranged between the drain of the MOS tube 20 in the power amplifier and the output end of the power amplifier;

[0044] Wherein, the even harmonic impedance of the first LC resonant circuit 11 is infinite;

[0045] The odd harmonic impedance of the second LC resonance circuit 12 is zero.

[0046] First, the working principle of the harmonic suppression network 10 provided in this application is described:

[0047] The purpose of this application is to provide a power amplifier with high output efficiency and guaranteed waveform quality. In the implementation of the amplifier, the power amplifier can be designed by an optimal flat waveform. For example, in the current part, a Figure 2 The square wave signal shown in the figure forms a voltage section as shown in the figure. Figure 3 The half-sine wave signal shown can obtain a standard stable sine wave output through resonance after filtering and shaping, meeting the waveform output requirements of the power amplifier. In addition, if the square wave of the current part and the half-sine wave of the voltage part do not overlap in the time domain, theoretically, it can bring 100% output efficiency, which can be achieved by adjusting the phase difference of the two signals.

[0048] Based on the above, the key to solving the problem of how to simultaneously ensure the output waveform quality and efficiency of the power amplifier is to make the current part of the power amplifier output a square wave approximately, and the voltage part output a half-sine wave approximately (the closer the waveform, the better the waveform quality and the higher the efficiency), and make the two waveforms have no overlap in the time domain.

[0049] Based on this, according to the Fourier transform principle, a square wave can be approximated by the superposition of odd harmonics of a sine signal, and a half-sine wave can be approximated by the superposition of even harmonics of a sine signal. Then, in order to obtain the above-mentioned current square wave and voltage half-sine wave at the output end of the power amplifier (i.e., the drain of the power tube), it is required that the even current harmonics are superimposed as a square wave, and the odd voltage harmonics are superimposed as a half-sine wave. Then the voltage output of the power amplifier is and current output The expression is as follows:

[0050] ;

[0051] in, , is the fundamental angular frequency, t is the time parameter; , is the fundamental frequency; is the DC voltage applied to the drain, is the drain current.

[0052] The above harmonic superposition can be achieved by impedance matching. In order to obtain the above harmonic waveform, the circuit impedance of the field effect transistor (MOSFET, referred to as MOS tube) at the drain of the power amplifier as a power tube needs to satisfy the following formula:

[0053] ;

[0054] Among them, Z i represents the i-th impedance; R1 is the optimal fundamental wave load impedance.

[0055] It is not difficult to see from the above formula that the above circuit impedance requires that the drain needs to achieve infinite impedance at even harmonics, that is, to achieve an open circuit, and achieve zero impedance at odd harmonics, that is, to achieve a short circuit.

[0056] In summary, by realizing open circuit of even harmonics and short circuit of odd harmonics at the drain of MOS tube 20 in the power amplifier, a waveform output close to a standard stable sine wave and an output efficiency close to 100% can be achieved, thereby solving the problems existing in traditional power amplifiers.

[0057] Therefore, a harmonic suppression network 10 provided in the present application utilizes an inductor-capacitor (LC) resonant circuit to form resonance at a desired frequency point in a series or parallel manner. According to the theory of series resonance and parallel resonance, the short-circuit and open-circuit effects of impedance can be achieved at this frequency point to control the harmonic impedance of the corresponding order.

[0058] Specifically, a harmonic suppression network 10 provided in the present application includes a first LC resonant circuit 11 and a second LC resonant circuit 12 arranged at the drain of a power amplifier MOS tube 20 to achieve resonance adjustment to control the harmonic impedance of the corresponding order. The first LC resonant circuit 11 is used to realize an even harmonic open circuit, and the second LC resonant circuit 12 is used to realize an odd harmonic open circuit to meet the above-mentioned harmonic output requirements, while ensuring the output waveform quality, bringing higher output efficiency.

[0059] Furthermore, since there are many mature technical solutions for achieving the corresponding harmonic target through the LC resonant circuit when the harmonic impedance target is known (even harmonics open circuit, odd harmonics open circuit), the present application does not limit the specific circuit implementation of the first LC resonant circuit 11 and the second LC resonant circuit 12. However, this embodiment provides a possible implementation scheme, in which the first LC resonant circuit 11 is as follows: Figure 4 As shown, it includes: a first LC network (corresponding to Figure 4 LC network 1) and a second LC network (corresponding to Figure 4 LC network in 2);

[0060] The first end of the first LC network is connected to the drain of the MOS tube 20, and the second end of the LC network is correspondingly connected to the output end of the power amplifier;

[0061] A first end of the second LC network is connected to a direct current power supply of the power amplifier, and a second end of the second LC network is connected to a second end of the first LC network.

[0062] In addition, this embodiment also provides a possible implementation scheme of a second LC resonant circuit 12, such as Figure 4 As shown, the second LC resonant circuit 12 includes: a first LC network, a third LC network (corresponding to Figure 4 LC network 3) and the fourth LC network (corresponding to Figure 4 LC network in 4);

[0063] Wherein, the third LC network is arranged between the second end of the first LC network and the output end of the power amplifier;

[0064] A first end of the fourth LC network is connected to a common end of the third LC network and an output end of the power amplifier, and a second end of the fourth LC network is grounded.

[0065] It should be noted that the first LC network in the first LC resonant circuit 11 and the first LC network in the second LC resonant circuit 12 may be the same LC network.

[0066] The first LC resonant circuit 11 and the second LC resonant circuit 12 provided in the above embodiment are resonant circuits for realizing the second harmonic impedance open circuit and the third harmonic impedance short circuit. Figure 4 As shown:

[0067] For the second harmonic impedance, the second LC network introduces a short-circuit point at point B; after passing through the first LC network and the parasitic parameter network of the MOS tube 20, the drain current source A is approximately an open circuit.

[0068] For the third harmonic impedance, a short circuit point is introduced at point C by the fourth LC network (also called microstrip line LC network); the parasitic parameter network passing through the first LC network, the third LC network and the MOS tube 20 is approximately short-circuited at the drain current source A.

[0069] That is, this embodiment provides an LC resonant circuit solution corresponding to the second and third harmonic impedance adjustment that meets the above-mentioned harmonic impedance control requirements. It should be noted that in the design of actual circuits, increasing the control order of multiple harmonics too much will greatly increase the complexity of circuit design, and even reduce the efficiency of the power amplifier due to the complex circuit structure. Therefore, in actual circuit design, generally only controlling the second and third harmonic frequency impedances can obtain more ideal working conditions, thereby achieving higher power amplifier efficiency and better waveform quality.

[0070] Furthermore, it can be seen from the above embodiments that the LC network can be implemented by connecting inductors and capacitors in series or in parallel. Therefore, this embodiment further provides a corresponding implementation scheme based on the above embodiments:

[0071] The first LC network, the third LC network, and the fourth LC network are parallel LC networks; and the second LC network is a series LC network.

[0072] Furthermore, based on the second LC network provided in the above embodiment, this embodiment also provides a possible implementation scheme for the specific structure of the second LC network, wherein the second LC network includes: a radio frequency choke and a first capacitor;

[0073] The first end of the radio frequency choke is connected to a DC power supply; the second end of the radio frequency choke is connected to the second end of the first LC network, and is connected to the first end of the third LC network through the first capacitor.

[0074] It is easy to understand that the RF choke is a large inductor. In this embodiment, in addition to resonance adjustment, the RF choke is also used to prevent the RF signal on the drain of the MOS tube 20 from being superimposed on the DC power supply to eliminate the coupling between the AC signal and the DC source and the ground.

[0075] In the above embodiment, a harmonic suppression network 10 is described in detail. The present application also provides a corresponding embodiment of a power amplifier.

[0076] This embodiment provides a power amplifier such as Figure 1 As shown, it includes: the harmonic suppression network 10 and the MOS tube 20 as described in the above embodiment.

[0077] Since the connection relationship between the MOS tube 20 and the harmonic suppression network 10 has been described in detail in the embodiment of the harmonic suppression network 10, this embodiment will not be repeated here. Similarly, for various possible implementation schemes of the harmonic suppression network 10, please refer to the description of the embodiment of the harmonic suppression network 10, which will not be repeated here.

[0078] In particular, for the MOS tube 20 in the power amplifier, such as Figure 4As shown, this embodiment provides a preferred implementation scheme:

[0079] There are two MOS transistors 20 (MSOFET1 and MSOFET2), and a push-pull structure is formed between the two MOS transistors 20.

[0080] Accordingly, there are two harmonic suppression networks 10, which are respectively arranged between the drains of the two MOS tubes 20 and the output terminals of the power amplifier. Figure 4 In the embodiment, one group of harmonic suppression networks 10 corresponds to LC networks 1-4, and another group of harmonic suppression networks 10 corresponds to LC networks 5-8. The two groups of harmonic suppression networks 10 have the same structure and are symmetrically arranged.

[0081] Specifically, Figure 4 As shown, the sources of the two MOS transistors 20 are connected to the ground, the gates are coupled and controlled by the transformer T1 in the RF power supply, and the drains are coupled and output by the transformer T2 in the RF power supply, forming a push-pull structure. The MOS transistors 20 in the push-pull structure are responsible for the waveform amplification tasks of the positive and negative half cycles respectively. When the circuit is working, only one of the two symmetrical MOS transistors 20 is turned on at a time, so the conduction loss is small and the efficiency is high.

[0082] The power amplifier network composed of the push-pull structure provided in this embodiment can reduce the working pressure of each MOS tube 20 device. In the push-pull structure, two MOS tubes 20 devices are configured as a pair and work alternately to amplify the input signal. The design of this structure helps to share the workload of each MOS tube 20, thereby reducing the power and heat borne by a single device, which is beneficial to reducing the pressure of the device and improving the reliability and stability of the overall system. In addition, this embodiment also has the advantage that if a problem occurs in one MOS tube 20, it will not cause the entire RF module to completely fail to work.

[0083] On the other hand, this embodiment also provides an embodiment corresponding to a radio frequency power supply, such as Figure 4 As shown, a radio frequency power supply includes: the power amplifier as described in the above embodiment, a first transformer coupling unit T1 and a second transformer coupling unit T2;

[0084] The front stage of the first transformer coupling unit T1 is connected to the input signal; the center tap end of the first transformer coupling unit T1 is grounded; the rear stage of the first transformer coupling unit T1 is connected to the input end of the power amplifier;

[0085] The front stage of the second transformer coupling unit T2 is connected to the output end of the power amplifier; the center tap end of the first transformer coupling unit T1 is grounded; and the output end of the second transformer coupling unit T2 is connected to the rear stage load RL.

[0086] It should be noted that, since the embodiments of the RF power supply part correspond to the embodiments of the resonance suppression network and the power amplifier part, please refer to the above embodiments for the embodiments of the resonance suppression network and the power amplifier part, which will not be repeated here.

[0087] However, on this basis, this embodiment also provides a preferred implementation scheme, such as Figure 4 As shown, the above-mentioned radio frequency power supply further includes: a filtering shaping and impedance matching unit 30;

[0088] The filtering, shaping and impedance matching unit 30 is disposed between the rear stage of the second transformer coupling unit T2 and the rear stage load RL.

[0089] Furthermore, this embodiment does not limit the specific circuit composition of the filter shaping and impedance matching unit 30. From the perspective of functional implementation, it can be implemented by a combination of a filter circuit and an impedance matching circuit. However, this embodiment also provides a specific circuit implementation scheme of the filter shaping and impedance matching unit 30, such as Figure 4 As shown, the filtering, shaping and impedance matching unit 30 includes: a first inductor L and a second capacitor C;

[0090] The second capacitor C is connected in parallel between the two ends of the second transformer coupling unit T2 and the two ends of the load RL;

[0091] The first inductor L is connected in series between the same-name terminal of the rear stage of the second transformer coupling unit T2 and the second capacitor C.

[0092] The filtering, shaping and impedance matching unit 30 provided in this embodiment is used to filter and shape the output of the second transformer coupling unit T2 of the subsequent stage and perform impedance matching, obtain a standard stable sine wave through resonance, and achieve the maximum efficient transmission of the output power of the RF power supply to the load.

[0093] The above is a detailed introduction to a harmonic suppression network, a power amplifier and a radio frequency power supply provided by the utility model. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referenced to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can be referred to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the utility model, the utility model can also be improved and modified in a number of ways, and these improvements and modifications also fall within the scope of protection of the utility model.

[0094] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

Claims

1. A harmonic suppression network, characterized in that: include: A first LC resonant circuit (11) and a second LC resonant circuit (12); The first LC resonant circuit (11) and the second LC resonant circuit (12) are arranged between the drain of the MOS tube (20) in the power amplifier and the output end of the power amplifier; Wherein, the even harmonic impedance of the first LC resonant circuit (11) is infinite; The odd harmonic impedance of the second LC resonant circuit (12) is zero.

2. The harmonic suppression network according to claim 1, characterized in that: The first LC resonant circuit (11) comprises: a first LC network and a second LC network; Wherein, the first end of the first LC network is connected to the drain of the MOS tube (20), and the second end of the LC network is correspondingly connected to the output end of the power amplifier; A first end of the second LC network is connected to a direct current power supply of the power amplifier, and a second end of the second LC network is connected to a second end of the first LC network.

3. The harmonic suppression network according to claim 2, characterized in that: The second LC resonant circuit (12) comprises: the first LC network, a third LC network and a fourth LC network; Wherein, the third LC network is arranged between the second end of the first LC network and the output end of the power amplifier; A first end of the fourth LC network is connected to a common end of the third LC network and an output end of the power amplifier, and a second end of the fourth LC network is grounded.

4. The harmonic suppression network according to claim 3, characterized in that: The first LC network, the third LC network, and the fourth LC network are parallel LC networks; The second LC network is a series LC network.

5. The harmonic suppression network according to claim 4, characterized in that: The second LC network includes: a radio frequency choke and a first capacitor; The first end of the RF choke is connected to the DC power supply; the second end of the RF choke is connected to the second end of the first LC network, and is connected to the first end of the third LC network through the first capacitor.

6. A power amplifier, characterized in that: include: A harmonic suppression network (10) and a MOS tube (20) as claimed in any one of claims 1 to 5.

7. The power amplifier according to claim 6, characterized in that: There are two MOS tubes (20), and a push-pull structure is formed between the two MOS tubes (20); Correspondingly, there are two harmonic suppression networks (10), which are respectively arranged between the drains of two MOS tubes (20) and the output end of the power amplifier.

8. A radio frequency power supply, characterized in that: include: The power amplifier, the first transformer coupling unit and the second transformer coupling unit as claimed in claim 6; The front stage of the first transformer coupling unit is connected to the input signal; the center tap end of the first transformer coupling unit is grounded; the rear stage of the first transformer coupling unit is connected to the input end of the power amplifier; The front stage of the second transformer coupling unit is connected to the output end of the power amplifier; the center tap end of the first transformer coupling unit is grounded; and the output end of the second transformer coupling unit is connected to the rear stage load.

9. The radio frequency power supply according to claim 8, characterized in that: Also includes: Filter shaping and impedance matching unit (30); The filtering, shaping and impedance matching unit (30) is arranged between the rear stage of the second transformer coupling unit and the rear stage load.

10. The radio frequency power supply according to claim 9, characterized in that: The filtering, shaping and impedance matching unit (30) comprises: a first inductor and a second capacitor; The second capacitor is connected in parallel to both ends of the rear stage of the second transformer coupling unit and both ends of the rear stage load; The first inductor is connected in series between the same-name terminal of the rear stage of the second transformer coupling unit and the second capacitor.

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