Broadband high-efficiency power amplifier based on open-circuit branch coupler

Abstract

According to the broadband high-efficiency power amplifier based on the open-circuit branch coupler, good fundamental wave impedance matching is achieved, and meanwhile second harmonic suppression is achieved. The coupler adopts a three-branch-line structure to realize the broadband characteristic. After the three-branch broadband coupler is designed, the main line and the branch lines on the two sides are converted into T-shaped junctions with open-circuit branches, so that the converted coupler has the characteristic of suppressing second harmonics. And then a T-shaped matching network is loaded behind the three-branch open-circuit branch coupler so as to realize better fundamental wave impedance matching. According to the open-circuit branch branch line coupler structure, the functions of second harmonic suppression and good fundamental wave impedance matching can be achieved at the same time. The power amplifier designed based on the coupler has broadband and high-efficiency performance, and has better output power, efficiency and gain in the whole working frequency band.

Description

Technical Field

[0001] The present invention belongs to the technical field of radio frequency and microwave, and particularly relates to a broadband and high-efficiency power amplifier based on an open stub coupler. Background Art

[0002] With the rapid development of wireless communication systems, the use of communication frequency bands is becoming increasingly crowded, and the requirements for radio frequency front-end circuits are getting higher and higher. As the core module of a transmitter, radio frequency power amplifiers are also urgently required to develop towards broadband and high efficiency. After decades of development, there have been many types of power amplifiers. Among them, harmonic control power amplifiers such as Class F, Class J, and F-1 have relatively high output efficiency. At the same time, using the continuous mode theory method to design power amplifiers can obtain a larger bandwidth.

[0003] In the existing technology, harmonic control technology is a commonly used power amplifier efficiency improvement technology. Conditionally controlling the harmonic impedance at the drain terminal can reduce the coincidence degree of the voltage and current waveforms at the drain terminal, thereby reducing the energy consumption of harmonics and increasing the fundamental wave power transmitted to the output port. Harmonic control technology can usually enable a power amplifier to obtain relatively high efficiency. However, although the designed power amplifier has relatively high efficiency, its bandwidth is generally narrow. For some power amplifiers without harmonic processing, even though they have a relatively wide bandwidth, their efficiency is usually relatively low.

[0004] In the existing designs, the output structure of a broadband and high-efficiency power amplifier usually includes a fundamental wave impedance matching network and a harmonic suppression network. These two networks are usually designed separately. After the harmonic suppression network is designed, the fundamental wave impedance after passing through the harmonic suppression network is obtained through load-pull technology, and then the fundamental wave impedance matching network is designed. After the design is completed, each network is combined, and finally each part is optimized to achieve a broadband and high-efficiency power amplifier. The complexity and length of the fundamental wave impedance matching network and the harmonic control network directly lead to an increase in the overall size and cost of the power amplifier. At the same time, the joint optimization of the harmonic suppression network and the fundamental wave impedance matching network also increases the workload. This traditional design method not only makes the design cycle of the power amplifier longer, but also makes the tuning more complex during joint simulation due to the complex structure, and it is easy to make mistakes when optimizing the structural parameters, resulting in a deterioration of the overall performance of the power amplifier.

[0005] In addition, algorithms are sometimes also applied to the design of the output structure of power amplifiers. However, most algorithms can only be used for the optimization of the fundamental wave impedance matching network and cannot be used for the optimization design of the harmonic suppression network. Harmonics will consume the input energy, reduce the fundamental wave energy, and affect the output efficiency of the power amplifier. Therefore, even if the broadband performance of the power amplifier is achieved by using optimization algorithms, due to the existence of harmonics, the efficiency of the power amplifier is often not high. In addition, it is not easy to optimize the structure using algorithms, and it is necessary to iterate repeatedly many times to obtain the appropriate parameter values of the components in the fundamental wave impedance matching network to achieve excellent performance.

[0006] Therefore, it is of great significance to develop a broadband high-efficiency power amplifier with excellent performance, simple structure, and easy design. Summary of the Invention

[0007] In view of this, the purpose of the present invention is to provide a design of a broadband high-efficiency power amplifier based on an open stub coupler, which solves the problems in the prior art such as narrow bandwidth, low output efficiency, complex output structure, easy impedance mismatch, and too large circuit size of the power amplifier.

[0008] To achieve the above purpose, the present invention provides the following technical solutions:

[0009] A broadband high-efficiency power amplifier based on an open stub coupler includes an input matching circuit 1, a gate bias circuit 2, a crystal amplifier 3, an output matching and harmonic suppression circuit 4, a drain bias circuit 5, and a dielectric substrate 6. The input matching circuit 1, the gate bias circuit 2, the crystal amplifier 3, the output matching and harmonic suppression circuit 4, and the drain bias circuit 5 are located on one surface of the dielectric substrate 6, and a metal ground is provided on the other surface of the dielectric substrate 6.

[0010] Optionally, the input matching circuit 1 includes nine microstrip lines, namely a first microstrip transmission line TL1, a second microstrip transmission line TL2, a third microstrip transmission line TL3, a fourth microstrip transmission line TL4, a fifth microstrip transmission line TL5, a sixth microstrip transmission line TL6, a seventh microstrip transmission line TL7, an eighth microstrip transmission line TL8, and a ninth microstrip transmission line TL9. The input matching circuit 1 further includes three electronic components, namely a first DC-blocking capacitor C1, a stabilizing capacitor C2, and a first stabilizing resistor R1. Among them, the left end of the first microstrip transmission line TL1 is connected to the input port, and the first DC-blocking capacitor C1 is connected across the first microstrip transmission line TL1 and the second microstrip transmission line TL2. The left end of the double-T matching network formed by the third microstrip transmission line TL3, the fourth microstrip transmission line TL4, the fifth microstrip transmission line TL5, the sixth microstrip transmission line TL6, the seventh microstrip transmission line TL7, and the eighth microstrip transmission line TL8 is connected to the second microstrip transmission line TL2, and the right end is connected to the stabilizing capacitor C2, the first stabilizing resistor R1, and the gate bias circuit 2. The left end of the ninth microstrip transmission line TL9 is connected to the first stabilizing resistor R1 and the stabilizing capacitor C2, and the right end is connected to the gate of the crystal amplifier 3.

[0011] Optionally, the gate bias circuit 2 includes two transmission lines, namely a tenth microstrip transmission line TL10 and a first microstrip fan-shaped transmission line Stub1. The gate bias circuit 2 further includes a first bypass capacitor C X 1 and a second stabilizing resistor R2. One end of the second stabilizing resistor R2 is connected to the tenth microstrip transmission line TL10, and the other end is connected to the left ends of the stabilizing capacitor C2 and the first stabilizing resistor R1. The first microstrip fan-shaped transmission line Stub1 and the first bypass capacitor C X 1 are connected between the gate voltage V GS and the tenth microstrip transmission line TL10.

[0012] Optionally, the output matching and harmonic suppression circuit 4 includes an eleventh microstrip transmission line TL11, a twelfth microstrip transmission line TL12, two thirteenth microstrip transmission lines TL13, eight fourteenth microstrip transmission lines TL14, four fifteenth microstrip transmission lines TL15, two sixteenth microstrip transmission lines TL16, four seventeenth microstrip transmission lines TL17, two eighteenth microstrip transmission lines TL18, a nineteenth microstrip transmission line TL19, a twentieth microstrip transmission line TL20, a twenty-first microstrip transmission line TL21, a twenty-second microstrip transmission line TL22, and a twenty-third microstrip transmission line TL23, and further includes a second DC-blocking capacitor C3.

[0013] Optionally, the open stub three-way line coupler 7 is composed of 2 thirteenth microstrip transmission lines TL13, 8 fourteenth microstrip transmission lines TL14, 4 fifteenth microstrip transmission lines TL15, 2 sixteenth microstrip transmission lines TL16, 4 seventeenth microstrip transmission lines TL17, 2 eighteenth microstrip transmission lines TL18, and 1 nineteenth microstrip transmission line TL19.

[0014] Optionally, the T-type matching network 8 is composed of 1 twentieth microstrip transmission line TL20, 1 twenty-first microstrip transmission line TL21, and 1 twenty-second microstrip transmission line TL22.

[0015] The left end of the eleventh microstrip transmission line TL11 is connected to the drain of the crystal amplifier tube 3, and the other end is connected to the twelfth microstrip transmission line TL12. One end of the open stub three-way line coupler 7 is connected to the twelfth microstrip transmission line TL12, and the other end is connected to the T-type matching network 8.

[0016] Optionally, in the output matching and harmonic suppression circuit 4, the second DC-blocking capacitor C3 is connected across the T-type matching network 8 and the twenty-third microstrip transmission line TL23, and the other end of the twenty-third microstrip transmission line TL23 is connected to the output port.

[0017] Optionally, the drain bias circuit 5 includes the 1 twenty-fourth microstrip transmission line TL24, 1 second sector-shaped microstrip stub Stub2, and also includes 1 second bypass capacitor C X 2. One end of the twenty-fourth microstrip transmission line TL24 is connected between the eleventh microstrip transmission line TL11 and the twelfth microstrip transmission line TL12, and the other end is connected to the second sector-shaped microstrip stub Stub2, the second bypass capacitor C X 2, and the drain voltage V DS connection.

[0018] The beneficial effects of the present invention are as follows: The broadband and high-efficiency power amplifier based on the open stub coupler can achieve fundamental wave impedance matching while suppressing the second harmonic. The proposed three-branch line coupler has the performance of broadband and strong coupling. For a branch line coupler, generally, the more branch lines, the wider the bandwidth. Therefore, a three-branch line structure is adopted to achieve the broadband characteristic. By adjusting the characteristic impedance of the main line and each branch line, a three-branch line coupler with a coupling degree of about 0.5 dB is designed and implemented. After the three-branch broadband coupler is designed, the main line and the two side branch lines are transformed into a T-junction with open stubs, so that the deformed open stub three-branch line coupler has the characteristics of suppressing the second harmonic and fundamental wave impedance matching. At the same time, in order to achieve better matching, a T-type matching network is loaded after the open stub three-branch line coupler to achieve better fundamental wave matching. Compared with the traditional method of separately designing the fundamental wave impedance matching circuit and the harmonic suppression circuit, the open stub three-branch line coupler structure in the present invention can integrally realize the functions of second harmonic suppression and fundamental wave impedance matching. In the case of having a relatively wide operating frequency band, this design method and the designed structure are relatively simple. At the same time, the power amplifier has broadband characteristics, and has a large output power, high efficiency and gain throughout the operating frequency band.

[0019] Other advantages, objectives and features of the present invention will be described to some extent in the subsequent specification, and to some extent, will be obvious to those skilled in the art based on the study of the following text, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following specification. Brief Description of the Drawings

[0020] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail preferably with reference to the accompanying drawings, where:

[0021] Figure 1 Schematic diagram of the overall structure of the broadband and high-efficiency power amplifier based on the open stub coupler.

[0022] Figure 2 Schematic diagram of the structure of the three-branch line coupler.

[0023] Figure 3 Schematic diagram of the structure of the even-odd mode equivalent circuit of the three-branch line coupler. (a) Even mode (b) Odd mode

[0024] Figure 4 Schematic diagram of the simulation results of the three-branch line coupler.

[0025] Figure 5 Schematic diagram of the structure of the transmission line converted into a T-junction with open stubs.

[0026] Figure 6 Structural schematic diagram of an open - stub three - branch line coupler.

[0027] Figure 7 Schematic diagram of the simulation results of an open - stub three - branch line coupler.

[0028] Figure 8 Structural schematic diagram of an open - stub three - branch line coupler loaded with a T - type matching network.

[0029] Figure 9 Schematic diagram of the simulation results of an open - stub three - branch line coupler loaded with a T - type matching network.

[0030] Figure 10 Sample size of the specific embodiment of the broadband high - efficiency power amplifier based on the open - stub coupler of the present invention.

[0031] Figure 11 Voltage and current waveforms of the sample of the specific embodiment of the broadband high - efficiency power amplifier based on the open - stub coupler of the present invention at different frequencies. (a) 2.5 GHz. (b) 2.7 GHz. (c) 3 GHz. (d) 3.3 GHz. (e) 3.6 GHz

[0032] Figure 12 S - parameter diagram of the broadband high - efficiency power amplifier based on the open - stub coupler of the present invention.

[0033] Figure 13 Curves of drain efficiency, output power, and gain varying with frequency in the simulation of the sample of the specific embodiment of the broadband high - efficiency power amplifier based on the open - stub coupler of the present invention.

[0034] Reference numerals: 1 - input matching circuit; 2 - gate bias circuit; 3 - crystal amplifier tube; 4 - output matching and harmonic suppression circuit; 5 - drain bias circuit; 6 - dielectric substrate; 7 - open - stub three - branch line coupler; 8 - T - type matching network; Detailed implementation manners

[0035] The following uses specific specific examples to illustrate the implementation manners of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the diagrams provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0036] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; among them, the drawings are only for illustrative purposes, showing only schematic diagrams, rather than physical diagrams, and should not be construed as a limitation to the present invention; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, and do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0037] As Figure 1 shown is a schematic diagram of the overall structure of a broadband high-efficiency power amplifier based on an open stub coupler. It includes an input matching circuit 1, a gate bias circuit 2, a crystal amplifier 3, an output matching and harmonic suppression circuit 4, a drain bias circuit 5, and a dielectric substrate 6. The input matching circuit 1, the gate bias circuit 2, the crystal amplifier 3, the output matching and harmonic suppression circuit 4, and the drain bias circuit 5 are located on one surface of the dielectric substrate 6, and a metal ground is provided on the other surface of the dielectric substrate 6.

[0038] The input matching circuit 1 is as Figure 1 shown by the dotted box in the figure. The input matching circuit 1 includes 9 microstrip lines, the first microstrip transmission line TL1, the second microstrip transmission line TL2, the third microstrip transmission line TL3, the fourth microstrip transmission line TL4, the fifth microstrip transmission line TL5, the sixth microstrip transmission line TL6, the seventh microstrip transmission line TL7, the eighth microstrip transmission line TL8, and the ninth microstrip transmission line TL9. The input matching circuit 1 also includes three electronic components, the first DC blocking capacitor C1, the stabilizing capacitor C2, and the first stabilizing resistor R1. Among them, the left end of the first microstrip transmission line TL1 is connected to the input port, and the first DC blocking capacitor C1 is connected across the first microstrip transmission line TL1 and the second microstrip transmission line TL2. The left end of the double-T matching network formed by the third microstrip transmission line TL3, the fourth microstrip transmission line TL4, the fifth microstrip transmission line TL5, the sixth microstrip transmission line TL6, the seventh microstrip transmission line TL7, and the eighth microstrip transmission line TL8 is connected to the second microstrip transmission line TL2, and the right end is connected to the stabilizing capacitor C2, the first stabilizing resistor R1, and the gate bias circuit 2. The left end of the ninth microstrip transmission line TL9 is connected to the first stabilizing resistor R1 and the stabilizing capacitor C2, and the right end is connected to the gate of the crystal amplifier 3.

[0039] The gate bias circuit 2 is as Figure 1 shown by the dotted box in the figure. The gate bias circuit 2 includes 2 transmission lines, the tenth microstrip transmission line TL10 and the first microstrip fan-shaped transmission line Stub1. The gate bias circuit 2 also includes a bypass capacitor C X 1 and the second stabilizing resistor R2. One end of the second stabilizing resistor R2 is connected to the tenth microstrip transmission line TL10, and the other end is connected to the left ends of the stabilizing capacitor C2 and the first stabilizing resistor R1. The first microstrip fan-shaped transmission line Stub1 and the first bypass capacitor CX 1 is connected between the gate voltage VGS and the tenth microstrip transmission line TL10.

[0040] The output matching and harmonic suppression circuit 4 is as Figure 1 shown by the dashed box in the figure. The output matching and harmonic suppression circuit 4 includes one eleventh microstrip transmission line TL11, one twelfth microstrip transmission line TL12, two thirteenth microstrip transmission lines TL13, eight fourteenth microstrip transmission lines TL14, four fifteenth microstrip transmission lines TL15, two sixteenth microstrip transmission lines TL16, four seventeenth TL17, two eighteenth microstrip transmission lines TL18, one nineteenth microstrip transmission line TL19, one twentieth microstrip transmission line TL20, one twenty - first microstrip transmission line TL21, one twenty - second microstrip transmission line TL22, one twenty - third microstrip transmission line TL23, and also includes a second DC - blocking capacitor C3.

[0041] Among them, the three - branch T - type branch - line coupler 7 is composed of two thirteenth microstrip transmission lines TL13, eight fourteenth microstrip transmission lines TL14, four fifteenth microstrip transmission lines TL15, two sixteenth microstrip transmission lines TL16, four seventeenth microstrip transmission lines TL17, two eighteenth microstrip transmission lines TL18, and one nineteenth microstrip transmission line TL19. The T - type matching network 8 is composed of one twentieth microstrip transmission line TL20, one twenty - first microstrip transmission line TL21, and one twenty - second microstrip transmission line TL22.

[0042] The left end of the eleventh microstrip transmission line TL11 is connected to the drain of the crystal amplifier 3, and the other end is connected to the twelfth microstrip transmission line TL12. One end of the open - stub three - branch line coupler 7 is connected to the twelfth microstrip transmission line TL12, and the other end is connected to the T - type matching network 8.

[0043] As Figure 1 shown, the output matching and harmonic suppression circuit 4 also has the second DC - blocking capacitor C3 connected across the T - type matching network 8 and the twenty - third microstrip transmission line TL23, and the other end of the twenty - third microstrip transmission line TL23 is connected to the output port.

[0044] The drain bias circuit 5 is as Figure 1 shown by the dashed box in the figure, and includes one twenty - fourth microstrip transmission line TL24, one second fan - shaped microstrip stub Stub2, and also includes one second bypass capacitor C X 2. One end of the twenty - fourth microstrip transmission line TL24 is connected between the eleventh microstrip transmission line TL11 and the twelfth microstrip transmission line TL12, and the other end is connected to the second fan - shaped microstrip stub Stub2, the bypass capacitor C X 2, and the drain voltage V DS is connected.

[0045] In the present invention, the output matching and harmonic suppression circuit is the core of the power amplifier design. First, a three-branch line coupler with broadband strong coupling is designed, and then the two side branch lines of the three-branch line coupler are transformed into a T-junction with open stubs, so that the finally designed three-branch line coupler has the effects of second harmonic suppression and fundamental wave impedance matching. To further illustrate the working principle of the three-branch coupler, the odd-even mode analysis method is used to analyze it. The structural schematic diagram of the three-branch line coupler is as shown in Figure 2 the figure, where θ = 90°, and the equivalent circuits under odd-mode and even-mode excitations are as shown in Figure 3 the figure. The transmission matrix under even-mode excitation is:

[0046]

[0047] The transmission matrix under odd-mode excitation is:

[0048]

[0049] where

[0050]

[0051] where Z A , Z B , Z C , Z D are the characteristic impedances of each transmission line respectively, and its normalized transmission parameters are given by the following formula:

[0052]

[0053]

[0054] Using the transformation relationship from the normalized transmission matrix to the scattering parameter matrix, the scattering parameters are given by the following formula:

[0055]

[0056] where Γ e and Γ o are the reflection coefficients of the even mode and the odd mode, and Τ o and Τ e are the transmission coefficients of the odd mode and the even mode. When there is no reflection at the input port of the coupler, the following conditions should be satisfied:

[0057]

[0058] Similarly, when port 1 and port 4 are isolated, the following conditions should be satisfied:

[0059]

[0060] Therefore, equations (15) and (16) can be simplified to:

[0061] Γ e = Γ o = 0 (17)

[0062] Then, substituting equation (17) into equations (11) and (12), the expressions can be obtained as follows

[0063] d = a (18)

[0064] b = c (19)

[0065] Using equations (18) and (19), the expressions can be derived as follows:

[0066]

[0067] Where Equation (12) is the first equation of Z B and Z D . At the same time, equations (13) and (14) can be simplified to

[0068]

[0069] The power ratio k of output ports 2 and 3 2 is set to

[0070]

[0071] while S 21 and S 31 can be obtained by the following method

[0072]

[0073] Since C is imaginary and A is real, the following relationship can be obtained from equation (23):

[0074] c 2 = -k 2 a 2 (26)

[0075] Since port 4 is an isolated port, there is |S 21 | 2 + |S 31 |[[]] 2 = 1. Combining with equation (23), the following can be obtained:

[0076]

[0077] Combining equation (24) and equations (26)-(27), the following results can be obtained by the following method​

[0078]

[0079] Combining Equation (26) with Equations (18) and (19), Z B and Z D The second equation of can be obtained as

[0080]

[0081] Combining Equation (29) with Equation (20), the following expression can be obtained:

[0082]

[0083] In order to make more energy output from Port 3, set k = 3, that is, the power output from Port 3 is 9 times that of Port 2. Port 2 is the through port and Port 3 is the coupled port. The calculated coupling degree of the coupler is 0.5 dB. The real part of the output impedance at the drain terminal of the transistor is around 18 Ω, and it is matched from 18 Ω to 50 Ω. Set the impedance transformation ratio r = 2.7. At this time, Z A = Z C When, the coupler can obtain a relatively large relative bandwidth. When k = 3 and r = 2.7, the impedances of the main line, branch lines and port transmission lines of the three-branch coupler can be calculated as Z A = 29 Ω, Z C = 29 Ω, Z B = Z D = 102 Ω, Z 1b = 18 Ω, Z 2b = 50 Ω, where Port 1 is used as the input end, the coupled Port 3 is used as the output end, and the through Port 2 and the isolation Port 4 are set to open circuit. After the design is completed, simulate and optimize the relevant structural parameters. The simulation results are as shown in Figure 4 As shown, from Figure 4 It can be seen that in the working frequency band of 2.5 GHz - 3.6 GHz, |S 11 | is lower than -20 dB, having good fundamental wave impedance matching performance, and |S 31 | is close to 0.3 dB. It can be seen that within the working frequency band, there is basically no energy loss, and most of the energy can be transmitted from the input Port 1 to Port 3.

[0084] On the basis of the broadband branch-line coupler structure with specific parameters already obtained, open stubs are added to the main line and the two branch lines on both sides, that is, the main line with a characteristic impedance of Z A = 29 Ω and Z B = Z DThe branch line with a characteristic impedance of 102 Ω is transformed into the form of a T-junction with an open stub. By utilizing the bandgap effect of the open stub to suppress the second harmonic, it is essentially equivalent to a filter that generates a transmission zero at the second harmonic frequency. The transmission line can be equivalently transformed into a T-junction with an open stub, as shown in Figure 5 where the transmission matrix of the transmission line is:

[0085]

[0086] The transmission matrix of the equivalent T-junction with an open stub is:

[0087] M T = M 14 M 15 M 14 (34)

[0088] where:

[0089]

[0090] Let the T-junction be equivalently replaced by the branch lines and the main line on both sides, that is, let their transmission matrices be equal, i.e., M L = M T , and the following results can be obtained:

[0091] Z 14 = Z A cotθ 14 (37)

[0092]

[0093] In the above formula, Z A is known, so it is necessary to determine θ 14 and θ 15 in order to calculate the parameters Z 14 and Z 15 . Since θ is 90°, θ 14 needs to be less than 45°. In order to effectively reduce the size of the coupler, θ 14 is set to 30°. In order to suppress the second harmonic and generate a transmission zero at the second harmonic frequency, the length of the open stub with a characteristic impedance of Z 15 should be a quarter wavelength corresponding to the second harmonic frequency. Therefore, θ 15 is set to 45°. Substituting the values of θ 14 and θ 15 into the above formula, the corresponding values of Z 14 and Z 15 can be obtained, where Z 14 = 50 Ω and Z 15= 48 Ω. Similarly, the other two side branch lines can be converted into T-junctions with open stubs according to the above method, so that the transmission zeros of these six T-junctions are all at the second harmonic. The schematic diagram of the transformed open-stub three-branch line coupler is as shown in Figure 6 shown. After the design is completed, the relevant structural parameters are simulated and optimized. The simulation results are as shown in Figure 7 shown. It can be seen from Figure 7 that in the frequency range of 2.5 GHz - 3.6 GHz, |S 11 | remains below -15 dB, and |S 31 | is close to 0 dB. In addition, in the second harmonic frequency range of 5 GHz - 7.2 GHz, which is outside the passband, |S 11 | is close to 0 dB, while |S 31 | remains below -20 dB. Therefore, the open-stub three-branch line coupler has good filtering performance to suppress the second harmonic, but the performance of fundamental wave impedance matching has decreased.

[0094] In order to better match the impedance of the transistor output port to the port impedance of 50 Ω, a T-type matching network is loaded after the design of the open-stub three-branch line coupler is completed. The overall structure is as shown in Figure 8 shown. And the open-stub three-branch line coupler with the loaded T-type matching network is simulated. The results after the simulation are as shown in Figure 9 shown. It can be seen that in the frequency band of 2.5 GHz - 3.6 GHz, |S 11 | can still be less than -20 dB, |S 31 | is close to 0 dB. In the out-of-band frequency range of 5 GHz - 7.2 GHz, |S 11 | is close to 0 dB, and |S 31 | is less than -20 dB. It can be seen that the designed structure can not only achieve good fundamental wave impedance matching within the working frequency band, but also achieve second harmonic suppression outside the band.

[0095] As shown in Figure 10 is the sample size of the specific embodiment of the broadband high-efficiency power amplifier based on the open-stub coupler of the present invention. Figure 11 Shows the drain current and voltage waveforms of the transistor during large-signal simulation using ADS software. It can be observed that the overlap between the drain output voltage and current waveforms is very small, indicating potential high efficiency.

[0096] As shown in Figure 12 shown, in the second harmonic frequency band of 5 GHz - 7.2 GHz, the second harmonic suppression reaches 44 dBc, and the working bandwidth range is 2.5 GHz - 3.6 GHz, |S 11|Both are less than -20 dB, which verifies good fundamental wave impedance matching performance and validates that the output matching and harmonic suppression circuit can achieve second harmonic suppression and good fundamental wave impedance matching. From Figure 13 It can be seen that in the working frequency range of 2.5 GHz to 3.6 GHz, the drain efficiency is 66.10% - 77.20%. The highest drain efficiency of 77.20% occurs at a frequency of 2.95 GHz. In the frequency band of 2.65 GHz to 3.50 GHz, the drain efficiency exceeds 70%. Between 2.5 GHz and 3.6 GHz, the output power is between 40.55 dBm and 42.35 dBm. From Figure 13 It can be seen that in the frequency range of 2.5 GHz to 3.6 GHz, the gain is between 10.55 dB and 13.35 dB. Through the analysis of the simulation results, it is shown that the sample of this embodiment has high drain efficiency and output power throughout the working frequency band. The above simulation results indicate that the sample of this embodiment has characteristics such as high efficiency, high output power, and wideband in the working frequency band.

[0097] In this embodiment, a preferred structure of the present invention is proposed. The sample of this embodiment is a broadband high-efficiency power amplifier based on an open stub coupler with a working frequency of 2.5 GHz - 3.6 GHz. The entire power amplifier structure is fabricated on a Rogers 4350B dielectric substrate with a relative dielectric constant of 3.66, a dielectric substrate loss tangent of 0.0037, and a substrate thickness of 0.508 mm. The DC blocking capacitors and stabilization capacitors used in the sample of this embodiment are all Murata GRM series capacitors with a capacitor package parameter of 1.0 mm × 0.5 mm. The resistor in the stabilization circuit is a 0805 type surface mount resistor with a resistor package size of 2.0 mm × 1.2 mm. The circuit size of the power amplifier of the sample of this embodiment is 113.1 mm × 62.6 mm. The crystal amplifier tube uses the CGH40010F model produced by CREE Company. According to the data sheet, the static operating point gate voltage V gs =-2.7 V, and the drain voltage V ds =28 V. The drain current at this operating point state is 190 mA.

[0098] The electromagnetic simulation software ADS of Keysight Technologies is used to simulate and optimize the three-branch line coupler and the three-branch line T-type coupler with a loaded T-type matching network in the present invention, where Figure 2 the characteristic impedance value of the transmission line of the three-branch coupler, Figure 8 the specific parameter dimensions of the final output matching and harmonic suppression circuit are shown in Table 1 and Table 2:

[0099] Table 1 Specific parameter values of each part of the three-branch line coupler

[0100]

[0101]

[0102] Table 2 Specific parameter values of each part of the output matching and harmonic suppression circuit

[0103] Parameter Value Parameter Value <![CDATA[Z 13 (Ω)]]> 14.3 <![CDATA[Z 16 (Ω)]]> 16.6 <![CDATA[Z 14 (Ω)]]> 49.2 <![CDATA[Z 15 (Ω)]]> 52.5 <![CDATA[Z 17 (Ω)]]> 19.4 <![CDATA[Z 18 (Ω)]]> 9.3 <![CDATA[Z 19 (Ω)]]> 52.2 <![CDATA[Z 20 (Ω)]]> 24.8 <![CDATA[Z 21 (Ω)]]> 15.0 <![CDATA[Z 22 (Ω)]]> 39.9 <![CDATA[Z 23 (Ω)]]> 19.5 <![CDATA[θ 13 (°)]]> 20.8 <![CDATA[θ 14 (°)]]> 41.7 <![CDATA[θ 15 (°)]]> 45.1 <![CDATA[θ 17 (°)]]> 33.9 <![CDATA[θ 18 (°)]]> 7.2 <![CDATA[θ 19 (°)]]> 63.6 <![CDATA[θ 20 (°)]]> 14.1 <![CDATA[θ 21 (°)]]> 11.7 <![CDATA[θ 22 (°)]]> 36.3 <![CDATA[θ 23 (°)]]> 15.6

[0104] Specific parameter values of the sample of the specific embodiment of the broadband high-efficiency power amplifier based on an open stub coupler of the present invention are shown in Table 3 as follows:

[0105] Table 3 Specific parameter values of the embodiment sample (width / length mm)

[0106] Parameter Value Parameter Value Parameter Value Parameter Value TL1 1.7 / 2 TL2 2.9 / 5 TL3 1 / 5.1 TL4 3.5 / 7.1 TL5 3.9 / 2.9 TL6 3.9 / 5 TL7 1.5 / 1.8 TL8 11.5 / 1 TL9 11.5 / 2.4 TL10 1 / 15.7 TL11 1 / 1 TL12 6.2 / 1.2 TL13 7 / 1.4 TL14 1.7 / 6.6 TL15 3 / 2.8 TL16 7 / 1.4 TL17 5.5 / 7.3 TL18 3.5 / 4.1 TL19 1.6 / 14.6 TL20 2.8 / 4.3 TL21 5.1 / 1.2 TL22 1.6 / 4 TL23 2.2 / 2.5 TL24 1 / 13.7 Stub1 6 / 99° Stub2 8 / 99°

[0107] From Figure 13 As shown, for the broadband high-efficiency power amplifier based on an open stub coupler of the present invention, within the operating frequency range of 2.5 GHz to 3.6 GHz, the drain efficiency is 66.10% to 77.20%. The highest drain efficiency of 77.20% is at a frequency of 2.95 GHz. In the frequency band of 2.65 GHz to 3.50 GHz, the drain efficiency exceeds 70%. Between 2.5 GHz and 3.6 GHz, the output power is between 40.55 dBm and 42.35 dBm. At a frequency of 2.5 GHz to 3.6 GHz, the gain is between 10.55 dB and 13.35 dB. Through the analysis of the simulation results, it is shown that the sample of this embodiment has a relatively high drain efficiency and output power throughout the operating frequency band. The above simulation results show that the sample of this embodiment has characteristics such as high efficiency, high output power, and wideband in the operating frequency band.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the present technical solution, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A broadband and high-efficiency power amplifier based on an open-circuit stub coupler, which is composed of an input matching circuit 1, a gate bias circuit 2, a crystal amplifier 3, an output matching and harmonic suppression circuit 4, a drain bias circuit 5, and a dielectric substrate 6. The input matching circuit 1, the gate bias circuit 2, the crystal amplifier 3, the output matching and harmonic suppression circuit 4, and the drain bias circuit 5 are located on one surface of the dielectric substrate 6, and a metal ground is provided on the other surface of the dielectric substrate 6.

2. The broadband high-efficiency power amplifier based on an open stub coupler according to claim 1, wherein: The input matching circuit 1 includes nine microstrip lines, namely, the first microstrip transmission line TL1, the second microstrip transmission line TL2, the third microstrip transmission line TL3, the fourth microstrip transmission line TL4, the fifth microstrip transmission line TL5, the sixth microstrip transmission line TL6, the seventh microstrip transmission line TL7, the eighth microstrip transmission line TL8, and the ninth microstrip transmission line TL9. The input matching circuit 1 also includes three electronic components, namely, the first DC-blocking capacitor C1, the stabilizing capacitor C2, and the first stabilizing resistor R1. Among them, the left end of the first microstrip transmission line TL1 is connected to the input port, and the first DC-blocking capacitor C1 is connected across the first microstrip transmission line TL1 and the second microstrip transmission line TL2. The left end of the double-T matching network formed by the third microstrip transmission line TL3, the fourth microstrip transmission line TL4, the fifth microstrip transmission line TL5, the sixth microstrip transmission line TL6, the seventh microstrip transmission line TL7, and the eighth microstrip transmission line TL8 is connected to the second microstrip transmission line TL2, and the right end is connected to the stabilizing capacitor C2, the first stabilizing resistor R1, and the gate bias circuit 2. The left end of the ninth microstrip transmission line TL9 is connected to the first stabilizing resistor R1 and the stabilizing capacitor C2, and the right end is connected to the gate of the crystal amplifier 3.

3. The broadband high-efficiency power amplifier based on an open stub coupler according to claim 1, wherein: The gate bias circuit 2 includes two transmission lines, namely the tenth microstrip transmission line TL10, the first microstrip fan-shaped transmission line Stub1, the first bypass capacitor C X 1, and the second stabilizing resistor R2. One end of the second stabilizing resistor R2 is connected to the tenth microstrip transmission line TL10, and the other end is connected to the left ends of the stabilizing capacitor C2 and the first stabilizing resistor R1. The first microstrip fan-shaped transmission line Stub1 and the first bypass capacitor C X 1 are connected between the gate voltage V GS and the tenth microstrip transmission line TL10.

4. The broadband high-efficiency power amplifier based on an open stub coupler according to claim 1, wherein: The output matching and harmonic suppression circuit 4 includes one eleventh microstrip transmission line TL11, one twelfth microstrip transmission line TL12, two thirteenth microstrip transmission lines TL13, eight fourteenth microstrip transmission lines TL14, four fifteenth microstrip transmission lines TL15, two sixteenth microstrip transmission lines TL16, four seventeenth microstrip transmission lines TL17, two eighteenth microstrip transmission lines TL18, one nineteenth microstrip transmission line TL19, one twentieth microstrip transmission line TL20, one twenty-first microstrip transmission line TL21, one twenty-second microstrip transmission line TL22, one twenty-third microstrip transmission line TL23, and the second DC-blocking capacitor C3.

5. The output matching and harmonic suppression circuit 4 according to claim 4, wherein: The open-circuit stub three-branch line coupler 7 is composed of two thirteenth microstrip transmission lines TL13, eight fourteenth microstrip transmission lines TL14, four fifteenth microstrip transmission lines TL15, two sixteenth microstrip transmission lines TL16, four seventeenth microstrip transmission lines TL17, two eighteenth microstrip transmission lines TL18, and one nineteenth microstrip transmission line TL19.

6. The output matching and harmonic suppression circuit 4 according to claim 4, wherein: The T-type matching network 8 is composed of a twentieth microstrip transmission line TL20, a twenty-first microstrip transmission line TL21, and a twenty-second microstrip transmission line TL22. The left end of the eleventh microstrip transmission line TL11 is connected to the drain of the crystal amplifier tube 3, and the other end is connected to the twelfth microstrip transmission line TL12. One end of the open stub three-branch line coupler 7 is connected to the twelfth microstrip transmission line TL12, and the other end is connected to the T-type matching network 8.

7. The broadband high-efficiency power amplifier based on an open stub coupler according to claim 1, characterized in that: In the output matching and harmonic suppression circuit 4, the second DC-blocking capacitor C3 is connected across the T-type matching network 8 and the twenty-third microstrip transmission line TL23, and the other end of the twenty-third microstrip transmission line TL23 is connected to the output port.

8. The broadband high-efficiency power amplifier based on an open stub coupler according to claim 1, characterized in that: The drain bias circuit 5 includes a twenty-fourth microstrip transmission line TL24, a second sector-shaped microstrip transmission line Stub2, and a second bypass capacitor C X 2. One end of the twenty-fourth microstrip transmission line TL24 is connected between the eleventh microstrip transmission line TL11 and the twelfth microstrip transmission line TL12, and the other end is connected to the second sector-shaped microstrip transmission line Stub2, the second bypass capacitor C X 2, and the drain voltage V DS are connected.

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