Radio frequency power amplifier based on Balun-like annular resonant structure and design method thereof

Abstract

The invention provides a radio frequency power amplifier based on a Balun-like ring resonance structure and a design method thereof, the radio frequency power amplifier comprises an input matching network, a transistor circuit, a bias circuit and an output matching network, the bias circuit comprises a gate bias circuit and a drain bias circuit; the output matching network comprises a harmonic control network and a fundamental wave matching network, the harmonic control network adopts a Balun-like four-port annular resonant structure, and the fundamental wave matching network adopts a T-shaped microstrip line network and comprises a first T-shaped microstrip line fundamental wave matching network and a second T-shaped microstrip line fundamental wave matching network. According to the technology, a novel Balun-like annular resonance structure is used, the filtering characteristic of the structure is utilized, a reactance component is added to an isolation port, through setting of port impedance, a fundamental wave frequency band is made to be a pass band, a second harmonic frequency band is made to be a stop band, second harmonics at the output end are restrained, and the efficiency of a drain electrode of the power amplifier is improved.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency communication technologies, and particularly to a radio frequency power amplifier based on a balun-like ring resonator structure and a design method thereof. Background Art

[0002] With the rapid development of wireless communication technologies and Internet of Things technologies, radio frequency communication systems are required to have higher performance. As a key unit in the radio frequency front end, the power amplifier is used to amplify a signal into a radio frequency large signal with a certain power, and has wide applications in fields such as base station communication, short-distance high-speed wireless communication, and radar communication. The performance of the radio frequency power amplifier directly affects the transmission distance and transmission quality of signals in a wireless communication system; the output power of a radio frequency power amplifier determines the transmission distance of wireless signals; in addition, the power consumption of the radio frequency power amplifier accounts for a large proportion in the wireless communication system, so its efficiency determines the energy utilization problem of the wireless transmission system.

[0003] In a wireless communication system, in order to achieve long-distance transmission of signals and ensure that the signals can be stably received, whether it is long-distance wireless transmission in the base station or short-distance signal coverage indoors, a radio frequency power amplifier is required to reliably amplify the signals. This may require large-scale deployment of power amplifiers, resulting in a continuous increase in power consumption, which does not conform to the concept of green and sustainable development. Therefore, improving the efficiency of radio frequency power amplifiers has become one of the urgent problems.

[0004] Therefore, in view of the technical problems existing in the prior art, it is necessary to provide a solution to improve the efficiency of the power amplifier. Summary of the Invention

[0005] In order to solve the difficulties in the prior art problems, the present invention proposes a radio frequency power amplifier based on a balun-like ring resonator structure and a design method thereof. A novel balun-like ring resonator structure is used, and its filtering characteristics are utilized to complete harmonic control. At the same time, a T-shaped microstrip line structure is used as the fundamental wave matching network at the output end to achieve an improvement in the efficiency of the power amplifier.

[0006] In order to overcome the defects of the prior art, the present invention adopts the following technical solutions:

[0007] A radio frequency power amplifier based on a balun-like ring resonator structure includes an input matching network, a transistor circuit, a bias circuit, and an output matching network. Among them, the bias circuit includes a gate bias circuit and a drain bias circuit; the output matching network includes a harmonic control network and a fundamental wave matching network. The harmonic control network adopts a balun-like four-port ring resonator structure, and the fundamental wave matching network adopts a T-shaped microstrip line network, including a first T-shaped microstrip line fundamental wave matching network and a second T-shaped microstrip line fundamental wave matching network;

[0008] The balun-like four-port ring resonator structure is provided with four ports, which are divided into an input port, a through port, a coupling port, and an isolation port. Among them, the input port is connected to the output end of the first T-shaped microstrip fundamental matching network, the through port is connected to the drain bias circuit, the coupling port is connected to the input end of the second T-shaped microstrip fundamental matching network, and the isolation port is connected to a section of open-circuit tuning line;

[0009] The gate bias circuit is connected to the input matching network; the output end of the second T-shaped microstrip fundamental matching network serves as the output end of the RF power amplifier; the drain of the transistor circuit is connected to the input end of the first T-shaped microstrip fundamental matching network; the gate of the transistor circuit is connected to the output end of the input matching network, and the input end of the input matching network serves as the input end of the RF power amplifier.

[0010] As a further improvement, the balun-like ring resonator structure has a filtering characteristic. An inductive or capacitive component is added to its isolation port, and the S-parameter response is adjusted by setting the impedance of the four ports of the balun-like ring resonator structure to achieve a fundamental passband and a second harmonic stopband, so as to achieve the function of harmonic control. At the same time, it has good conduction characteristics within the fundamental frequency range.

[0011] As a further improvement, in the balun-like ring resonator structure, the electrical length between its input port and coupling port is three-quarter wavelength of the center frequency of the operating frequency band; the electrical lengths between the input port and the through port, the through port and the isolation port, and the isolation port and the coupling port are all one-quarter wavelength of the center frequency of the operating frequency band.

[0012] As a further improvement, the input matching network is composed of four sections of series microstrip lines and one section of parallel microstrip line, and within the frequency range of 7.1 - 7.7 GHz, the matching between the 50Ω source impedance and the optimal input impedance of the transistor is achieved.

[0013] As a further improvement, the first T-shaped microstrip fundamental matching network is used to achieve the matching between the optimal output impedance of the transistor and the input impedance of the harmonic control network, and the second T-shaped microstrip fundamental matching network is used to achieve the matching between the output impedance of the harmonic control network and the 50Ω load, so as to achieve the best performance of the power amplifier within the frequency range of 7.1 - 7.7 GHz.

[0014] As a further improvement, the gate bias circuit and the drain bias circuit adopt microstrip lines with a length of one-quarter wavelength of the center frequency of the operating frequency band, and are shunted with a bias capacitor and three filtering capacitors. On the one hand, it provides a bias voltage for the transistor, and on the other hand, it prevents the leakage of RF signals and the influence of power supply clutter on the main circuit.

[0015] As a further improvement, the transistor circuit uses GaN HEMT CG2H40010F; a DC-blocking capacitor is connected to its input terminal and output terminal respectively. Among them, an RC parallel stabilization circuit is also included in the input matching network.

[0016] The present invention also proposes a design method for a radio frequency power amplifier based on a balun-like ring resonator structure, including the following steps:

[0017] Step S1: Determine the operating frequency of the power amplifier to select the transistor, as well as the DC-blocking capacitor and the bias capacitor.

[0018] Step S2: Use the load-pull technique to obtain the load impedance and source impedance of the transistor at the corresponding bias voltage and operating frequency.

[0019] Step S3: According to the transistor source impedance obtained in Step S2, use four sections of series microstrip lines and one section of parallel microstrip line, and add an RC stabilization circuit at the same time to design the input matching network.

[0020] Step S4: Based on the balun-like ring resonator structure, design the harmonic control network; among them, first, according to the operating frequency range, adjust the size of the ring resonator structure, and at the same time adjust the open-circuit tuning line at the isolation end of the ring resonator structure, so that the S-parameter response of the ring resonator structure is a passband in the fundamental frequency band and a stopband in the second harmonic frequency band.

[0021] Step S5: Design the fundamental matching network. According to the transistor load impedance obtained in Step S2, add a T-shaped microstrip line structure at the input terminal and output terminal of the harmonic control network respectively for impedance conversion, and adjust the size of the T-shaped microstrip line to match the optimal load impedance of the transistor drain to the input impedance of the harmonic control network, and match the output impedance of the harmonic control network to a 50Ω load.

[0022] Step S6: Connect the transistor to the input matching network, output matching network and bias circuit, and perform simulation optimization tuning to form the radio frequency power amplifier.

[0023] As a further improvement, the radio frequency power amplifier includes an input matching network, a transistor circuit, a bias circuit and an output matching network. Among them, the bias circuit includes a gate bias circuit and a drain bias circuit; the output matching network includes a harmonic control network and a fundamental matching network. The harmonic control network uses a balun-like four-port ring resonator structure, and the fundamental matching network uses a T-shaped microstrip line network, including a first T-shaped microstrip line fundamental matching network and a second T-shaped microstrip line fundamental matching network.

[0024] The balun-like four-port ring resonator structure has four ports, namely an input port, a through port, a coupling port, and an isolation port. Among them, the input port is connected to the output end of the first T-shaped microstrip fundamental matching network, the through port is connected to the drain bias circuit, the coupling port is connected to the input end of the second T-shaped microstrip fundamental matching network, and the isolation port is connected to a section of open-circuit tuning line;

[0025] The gate bias circuit is connected to the input matching network; the output end of the second T-shaped microstrip fundamental matching network serves as the output end of the RF power amplifier; the drain of the transistor circuit is connected to the input end of the first T-shaped microstrip fundamental matching network; the gate of the transistor circuit is connected to the output end of the input matching network, and the input end of the input matching network serves as the input end of the RF power amplifier.

[0026] As a further improvement, the balun-like ring resonator structure has filtering characteristics. Reactance components are added to its isolation port, and the S-parameter response is adjusted by setting the impedances of the four ports of the balun-like ring resonator structure to achieve a fundamental passband and a second-harmonic stopband, so as to achieve the effect of harmonic control. At the same time, it has good conduction characteristics within the fundamental frequency range.

[0027] Compared with the prior art, the present invention has the following technical effects:

[0028] Based on the excellent filtering characteristics of the balun-like ring resonator structure, in the design of a single-transistor power amplifier, the drain of the transistor circuit is connected to the input port of the four-port ring resonator structure, and the bias circuit is connected to the through port to provide a bias voltage for the transistor; the coupling port serves as the output port of the power amplifier; reactance components are added to the isolation port, and the fundamental impedance matching and second-harmonic component suppression are simultaneously achieved through the impedance settings of the four ports, so as to improve the efficiency of the power amplifier. This balun-like ring resonator structure serves as a harmonic control network, with a simple circuit design and can be applied to the design of power amplifiers in different frequency bands. At the same time, four sections of series microstrip lines and one section of parallel microstrip line are used in the input matching network to complete impedance transformation within a specific operating frequency range. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a structural block diagram of an RF power amplifier based on a balun-like ring resonator structure in the present invention;

[0030] Figure 2 is a structural schematic diagram of the balun-like ring resonator structure adopted by the harmonic control network in the present invention;

[0031] Figure 3 are the S-parameters of the harmonic control network based on the balun-like ring resonator structure in the present invention;

[0032] Figure 4 It is the impedance space diagram of the output matching network at the fundamental frequency and the second harmonic frequency of the RF power amplifier based on the balun-like ring resonator structure in the present invention;

[0033] Figure 5 It is the simulation result diagram of the drain efficiency and output power varying with frequency of the RF power amplifier based on the balun-like ring resonator structure in the saturation state of the present invention;

[0034] Figure 6 It is the simulation result diagram of the drain efficiency and gain of the RF power amplifier based on the balun-like ring resonator structure varying with the output power in the present invention. Specific Embodiments

[0035] The following are specific embodiments of the present invention and, in conjunction with the accompanying drawings, further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0036] Refer to Figure 1 , which shows the structural block diagram of an RF power amplifier based on the balun-like ring resonator structure in the present invention, including an input matching network, a transistor circuit, a bias circuit, and an output matching network. Among them, the bias circuit includes a gate bias circuit and a drain bias circuit; the output matching network includes a harmonic control network and a fundamental wave matching network. The harmonic control network adopts a balun-like four-port ring resonator structure, and the fundamental wave matching network adopts a T-shaped microstrip line network, including a first T-shaped microstrip line fundamental wave matching network and a second T-shaped microstrip line fundamental wave matching network. The first T-shaped microstrip line fundamental wave matching network includes microstrip lines TL7, TL8, and TL9; the second T-shaped microstrip line fundamental wave matching network includes microstrip lines TL12, TL13, and TL14. For the specific circuit connection relationship, refer to Figure 1 shown. The gate of the transistor is connected to the input matching network, and a gate bias circuit is added to the input matching network; the drain of the transistor is connected to the output matching network, and a drain bias circuit is added to the output matching network. The efficiency of the power amplifier is improved by means of harmonic control.

[0037] Refer to Figure 2 , which shows the structural schematic diagram of the balun-like ring resonator structure adopted by the harmonic control network in the present invention. As a four-port network, there are differences in electrical length between ports, which are divided into four ports: input, through, coupled, and isolated. In the present invention, this four-port network works as a harmonic control network, where the input port is connected to the first T-shaped microstrip line fundamental wave matching network at the drain output end of the transistor circuit, the through end is connected to the drain bias circuit, and the coupled output end is connected to the second T-shaped microstrip line fundamental wave matching network.

[0038] The gate bias circuit is connected to the input matching network; the output end of the second T-shaped microstrip fundamental matching network serves as the output end of the RF power amplifier; the drain of the transistor circuit is connected to the input end of the first T-shaped microstrip fundamental matching network; the gate of the transistor circuit is connected to the output end of the input matching network, and the input end of the input matching network serves as the input end of the RF power amplifier. For the specific circuit connection relationship, please refer to Figure 1 as shown.

[0039] In the class balun ring resonator structure, its isolation port is connected to an open-circuit tuning line (i.e., microstrip line TL11) for tuning the passband and stopband of the harmonic control network. The connection relationships of the input, through, and coupling ports with the transistor circuit, bias circuit, and output matching network can be adjusted. In an ideal situation, there is no power leakage at the isolation port, and reactive components are added for tuning the port impedance; the core design idea is to enable the S-parameter response based on this class of balun ring resonator structure to achieve a fundamental passband and a second-harmonic stopband to achieve harmonic suppression. The electrical length between the input port and the coupled output port of the class balun four-port ring resonator structure is three-quarter wavelengths of the center frequency of the operating frequency band; the electrical lengths between the input port and the through port, between the through port and the isolation port, and between the isolation port and the coupled output port are all one-quarter wavelengths of the center frequency of the operating frequency band. Denote the port impedance as Z0, then the impedance of the microstrip line of the ring resonator structure is √2Z0, and the line width and line length of the microstrip line of the ring resonator structure are obtained according to the impedance and electrical length, and the parameters are tuned according to the design of the actual harmonic control network.

[0040] Please refer to Figure 3 , as shown in the S-parameter simulation results of the harmonic control network based on the class balun ring resonator structure in the present invention. The designed power amplifier in this example operates in the frequency band of 7.1 - 7.7 GHz, and the corresponding second-harmonic frequency band is 14.2 - 15.4 GHz. It can be seen from Figure 3 that the fundamental frequency band is a passband, and the second-harmonic frequency band is a stopband, realizing the control of the second harmonic at the output end, and at the same time having good conduction characteristics within the fundamental frequency range.

[0041] Please refer to Figure 4 , as shown in the impedance space diagram of the output matching network at the fundamental frequency and the second-harmonic frequency of the RF power amplifier based on the class balun ring resonator structure in the present invention. The output matching network is matched to a low-resistance area near the short-circuit point within the second-harmonic frequency range and is matched to an area near the center of the Smith chart within the fundamental frequency range, which conforms to the characteristics of a high-efficiency RF power amplifier.

[0042] Please refer to Figure 5, which shows the simulation result diagram of the drain efficiency and output power varying with frequency of the RF power amplifier based on the balun-like ring resonator structure in the saturation state of the present invention. For the power amplifier designed in the embodiment of the present invention, in the frequency range of 7.1 - 7.7 GHz, the drain efficiency is higher than 50%, and the output power is higher than 38 dBm.

[0043] See Figure 6 , which shows the simulation result diagram of the drain efficiency and gain of the RF power amplifier based on the balun-like ring resonator structure varying with the output power in the present invention. For the designed power amplifier, in the frequency range of 7.1 - 7.7 GHz, the gain is 8 - 9.8 dB, and the drain efficiency is 50.4 - 58.1%. It shows good efficiency and gain performance in the whole frequency range.

[0044] The present invention also provides a design method for an RF power amplifier based on the balun-like ring resonator structure, which is realized through the following steps:

[0045] Step S1: Determine the operating frequency of the power amplifier, and select the transistors, as well as the DC blocking capacitors and bias capacitors.

[0046] Step S2: Use the load-pull technique to obtain the load impedance and source impedance of the transistor at the corresponding bias voltage and operating frequency;

[0047] Step S3: According to the transistor source impedance obtained in Step S2, adopt a four-section series microstrip line and a one-section parallel microstrip line, and add an RC stabilization circuit at the same time to design the input matching network;

[0048] Step S4: Design the harmonic control network based on the balun-like ring resonator structure; first, according to the operating frequency range, adjust the size of the ring resonator structure, and at the same time adjust the open-circuit tuning line at the isolation end of the ring resonator structure, so that the S-parameter response of the ring resonator structure is a passband in the fundamental frequency band and a stopband in the second harmonic frequency band;

[0049] Step S5: Design the fundamental wave matching network. According to the transistor load impedance obtained in Step S2, add a T-shaped microstrip line structure at the input end and output end of the harmonic control network respectively for impedance conversion, adjust the size of the T-shaped microstrip line, match the optimal load impedance of the transistor drain to the input impedance of the harmonic control network, and match the output impedance of the harmonic control network to a 50Ω load;

[0050] Step S6: Connect the transistor with the input matching network, output matching network and bias circuit to form the overall circuit of the power amplifier, and perform simulation optimization tuning to further improve the performance of the designed power amplifier.

[0051] The simulation result of the final overall circuit is as Figure 5 andFigure 6 As shown, the designed radio frequency power amplifier based on the balun-like ring resonator structure has a drain efficiency of 50.4 - 58.1% in the frequency range of 7.1 - 7.7 GHz, an output power of 38 - 39.8 dBm, and a gain of 8 - 9.8 dB, showing good performance throughout the frequency range. In the current development trend of spectrum fragmentation and increasingly high wireless signal frequencies, the balun-like ring resonator structure of the present invention, as a harmonic control network, has a simple circuit design and can be applied to the design of power amplifiers in different wireless communication frequency bands to achieve efficiency improvement.

[0052] The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. Various modifications to these embodiments are obvious to those skilled in the art, and the general principles defined in this application can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to these embodiments shown in this application, but will conform to the widest scope consistent with the principles and novel features disclosed in this application.

Claims

1. A radio frequency power amplifier based on a balun-like ring resonator structure, characterized in that It includes an input matching network, a transistor circuit, a bias circuit, and an output matching network. Among them, the bias circuit includes a gate bias circuit and a drain bias circuit; the output matching network includes a harmonic control network and a fundamental wave matching network. The harmonic control network adopts a balun-like four-port ring resonator structure, and the fundamental wave matching network adopts a T-shaped microstrip line network, including a first T-shaped microstrip line fundamental wave matching network and a second T-shaped microstrip line fundamental wave matching network; The balun-like four-port ring resonator structure is provided with four ports, which are divided into an input port, a through port, a coupling port, and an isolation port. Among them, the input port is connected to the output end of the first T-shaped microstrip line fundamental wave matching network, the through port is connected to the drain bias circuit, the coupling port is connected to the input end of the second T-shaped microstrip line fundamental wave matching network, and the isolation port is connected to an open-circuit tuning line; The gate bias circuit is connected to the input matching network; the output end of the second T-shaped microstrip line fundamental wave matching network serves as the output end of the RF power amplifier; the drain of the transistor circuit is connected to the input end of the first T-shaped microstrip line fundamental wave matching network; the gate of the transistor circuit is connected to the output end of the input matching network, and the input end of the input matching network serves as the input end of the RF power amplifier.

2. The RF power amplifier based on a balun-like ring resonator structure according to claim 1, wherein The balun-like ring resonator structure has a filtering characteristic. By adding a reactance component to its isolation port and adjusting its S-parameter response by setting the impedances of the four ports of the balun-like ring resonator structure, a fundamental wave passband and a second harmonic stopband are realized to achieve the function of harmonic control, and at the same time, it has good conduction characteristics within the fundamental wave frequency range.

3. The RF power amplifier based on a balun-like ring resonator structure according to claim 2, characterized in that, In the balun-like ring resonator structure, the electrical length between its input port and coupling port is three-quarter wavelength of the center frequency of the operating frequency band; the electrical lengths between the input port and the through port, the through port and the isolation port, and the isolation port and the coupling port are all one-quarter wavelength of the center frequency of the operating frequency band.

4. A radio frequency power amplifier based on a balun-like ring resonator structure according to claim 1, characterized in that The input matching network is composed of four series microstrip lines and one parallel microstrip line, and realizes the matching of a 50Ω source impedance to the optimal input impedance of the transistor within the frequency range of 7.1 - 7.7GHz.

5. A radio frequency power amplifier based on a balun-like ring resonator structure according to claim 1, characterized in that, The first T-shaped microstrip line fundamental wave matching network is used to realize the matching of the optimal output impedance of the transistor to the input impedance of the harmonic control network, and the second T-shaped microstrip line fundamental wave matching network is used to realize the matching of the output impedance of the harmonic control network to a 50Ω load, so as to achieve the best performance of the power amplifier within the frequency range of 7.1 - 7.7GHz.

6. The RF power amplifier based on a balun-like ring resonator structure according to claim 1, wherein The gate bias circuit and the drain bias circuit adopt microstrip lines with an electrical length of one-quarter wavelength of the center frequency of the operating frequency band, and are shunted with a bias capacitor and three filtering capacitors. On the one hand, it provides a bias voltage for the transistor, and on the other hand, it prevents the leakage of RF signals and the influence of power supply clutter on the main circuit.

7. The RF power amplifier based on a balun-like ring resonator structure according to claim 1, characterized in that The transistor circuit adopts GaN HEMT CG2H40010F; a DC blocking capacitor is connected to its input end and output end respectively. Among them, an RC parallel stabilization circuit is also included in the input matching network.

8. A design method of a radio frequency power amplifier based on a balun-like ring resonator structure, characterized in that, It includes the following steps: Step S1: Determine the operating frequency of the power amplifier to select transistors, DC-blocking capacitors, and bias capacitors. Step S2: Use load-pull technology to obtain the load impedance and source impedance of the transistor at the corresponding bias voltage and operating frequency. Step S3: According to the transistor source impedance obtained in Step S2, use four-section series microstrip lines and one-section parallel microstrip line, and add an RC stabilization circuit to design the input matching network. Step S4: Design the harmonic control network based on a balun-like ring resonator structure. Specifically, first, adjust the size of the ring resonator structure according to the operating frequency range, and at the same time, adjust the open-circuit tuning line at the isolation end of the ring resonator structure so that the S-parameter response of the ring resonator structure is a passband in the fundamental frequency band and a stopband in the second harmonic frequency band. Step S5: Design the fundamental matching network. According to the transistor load impedance obtained in Step S2, add a T-shaped microstrip line structure at the input and output ends of the harmonic control network for impedance conversion. Adjust the size of the T-shaped microstrip line to match the optimal load impedance of the transistor drain to the input impedance of the harmonic control network and match the output impedance of the harmonic control network to a 50Ω load. Step S6: Connect the transistor to the input matching network, output matching network, and bias circuit, and perform simulation optimization tuning to form the RF power amplifier.

9. The design method of the radio frequency power amplifier based on the balun-like ring resonator structure according to claim 8, characterized in that, The RF power amplifier includes an input matching network, a transistor circuit, a bias circuit, and an output matching network. Among them, the bias circuit includes a gate bias circuit and a drain bias circuit; the output matching network includes a harmonic control network and a fundamental matching network. The harmonic control network uses a balun-like four-port ring resonator structure, and the fundamental matching network uses a T-shaped microstrip line network, including a first T-shaped microstrip line fundamental matching network and a second T-shaped microstrip line fundamental matching network. The balun-like four-port ring resonator structure has four ports, which are divided into an input port, a through port, a coupling port, and an isolation port. Among them, the input port is connected to the output end of the first T-shaped microstrip line fundamental matching network, the through port is connected to the drain bias circuit, the coupling port is connected to the input end of the second T-shaped microstrip line fundamental matching network, and the isolation port is connected to an open-circuit tuning line. The gate bias circuit is connected to the input matching network; the output end of the second T-shaped microstrip line fundamental matching network serves as the output end of the RF power amplifier; the drain of the transistor circuit is connected to the input end of the first T-shaped microstrip line fundamental matching network; the gate of the transistor circuit is connected to the output end of the input matching network, and the input end of the input matching network serves as the input end of the RF power amplifier.

10. A design method of a radio frequency power amplifier based on a balun-like ring resonator structure according to claim 9, characterized in that, The balun-like ring resonator structure has filtering characteristics. Add a reactance component at its isolation port. By setting the impedance of the four ports of the balun-like ring resonator structure, adjust its S-parameter response to achieve a fundamental passband and a second harmonic stopband, so as to achieve the function of harmonic control and have good conduction characteristics in the fundamental frequency range.

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