An ultra-wideband power amplifier based on reactive harmonic network and its design method

Abstract

The present invention discloses an ultra-wideband power amplifier based on a reactive harmonic network and a design method thereof, comprising an input matching circuit, a low-order harmonic control network, a high-order harmonic reactance control network, and a fundamental wave output matching circuit, wherein the low-order harmonic control network is used to short-circuit the second harmonic and open the third harmonic; the high-order reactive harmonic network is composed of a series-parallel short stub and an impedance converter, so that the high-order harmonic impedance is equivalent to the fundamental wave impedance. Compared with the prior art, the present invention adopts a reactive harmonic network to transform the reactance value of the high-order harmonic, compensate its resistance value, and make its impedance equivalent to the fundamental wave impedance, so as to better control the high-order harmonics at the output end, and can achieve matching within a wide frequency band, overcoming the problem that the power amplifier spans an octave and the fundamental wave and the harmonic have different impedances at the same frequency; the low-order harmonic control network not only ensures the efficiency of the power amplifier, but also avoids the overlap of the second and third harmonics with the high-order harmonics.

Description

Technical Field

[0001] The present invention relates to the field of radio frequency communication technology, and in particular to an ultra-wideband power amplifier based on a reactive harmonic network and a design method thereof. Background Art

[0002] As the complexity of wireless infrastructure, communication standards and frequency segmentation increase, this will place higher demands on efficient broadband power amplifiers. Wide-bandgap GaN HEMT transistors are considered to be an important enabling technology in this development. This is mainly due to the greatly improved transistor impedance size, which simplifies the design of broadband matching and amplifiers.

[0003] The impedance of the power amplifier affects the bandwidth, power and efficiency of the final amplifier. For high-efficiency power amplifiers, it is difficult to maintain a suitable size for high-order harmonic impedance outside the octave. Although the design of balanced efficiency and bandwidth can extend the range to a certain extent, it is inevitable that the highest fundamental frequency will overlap the lowest second harmonic frequency, resulting in inconsistency between the fundamental and harmonic impedances at the same frequency, and it is impossible to achieve ultra-wideband matching across the octave.

[0004] Therefore, it is necessary to conduct research to provide a solution to solve the defects in the prior art. Summary of the invention

[0005] In view of this, the purpose of the present invention is to provide an ultra-wideband power amplifier based on a reactive harmonic network and a design method thereof, which uses a load with resistance transformation at higher-order harmonics to make its impedance equivalent to the fundamental impedance, thereby better controlling the higher-order (higher than the second and third) harmonics at the output end, overcoming the problem of different impedances across octaves of the power amplifier and difficulty in matching, and expanding the working bandwidth of the power amplifier.

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

[0007] An ultra-wideband power amplifier based on a reactive harmonic network includes an input matching circuit, a transistor, a low-order harmonic control network, a high-order reactive harmonic network, and a fundamental wave output matching circuit, wherein:

[0008] The low-order harmonic control network comprises a first transmission line TL1 with a length of one-twelfth wavelength, a second transmission line TL2 with a length of one-twelfth wavelength, a third transmission line TL3 with a length of one-sixth wavelength, and a fourth transmission line TL4 with a length of one-quarter wavelength, wherein one end of the first transmission line TL1 is connected to the output end of the transistor, the other end of the first transmission line TL1 is connected to one end of the second transmission line TL2 and one end of the third transmission line TL3, and the other end of the second transmission line TL2 is open; the other end of the third transmission line TL3 is connected to one end of the fourth transmission line TL4, and the other end of the fourth transmission line TL4 is grounded;

[0009] The high-order reactive harmonic network includes a fifth transmission line TL5 connected in series with 50Ω, a sixth transmission line TL6 connected in parallel with 50Ω, and an impedance transformation resistor R, wherein the fifth transmission line TL5 is connected to the low-order harmonic control network, the other end of the fifth transmission line TL5 is connected to one end of the sixth transmission line TL6 and one end of the impedance transformation resistor R, and the other end of the sixth transmission line TL6 is open; the other end of the impedance transformation resistor R is connected to one end of the fundamental output matching circuit;

[0010] The input matching circuit is used to match the optimal impedance obtained by transistor source pulling to an input load port of 50 ohms;

[0011] The fundamental wave output matching circuit is used to match the optimal impedance obtained by transistor load pulling to an output load port of 50 ohms.

[0012] As a further improvement, a gate bias circuit is provided between the input matching circuit and the transistor, and the bias voltage thereof is -2.7V.

[0013] As a further improvement, a drain bias circuit is provided between the low-order harmonic control network and the high-order reactive harmonic network, and its bias voltage is 28V.

[0014] As a further improvement, the transistor adopts a GaN HEMT CGH40010F transistor.

[0015] The present invention also discloses a design method of an ultra-wideband power amplifier based on a reactive harmonic network, which specifically comprises the following steps:

[0016] Step S1: designing an input matching circuit to achieve conjugate matching from the input port to the transistor gate impedance;

[0017] Step S2: performing load pulling on the drain of the transistor to obtain the optimal impedance at the second, third and higher harmonic frequencies respectively;

[0018] Step S3: Design a low-order harmonic control network, using series-parallel short stubs to short-circuit the second harmonic and open the third harmonic;

[0019] Step S4: designing a high-order reactive harmonic network, transforming the reactance and resistance of the high-order harmonics respectively through a parallel short stub and an impedance transformer, and transforming the impedance of the high-order harmonics to be close to the fundamental impedance;

[0020] Step S5: designing a transition lossless network to enable the signal to be transmitted between the two harmonic networks without loss;

[0021] Step S6: Design fundamental wave output matching to match the fundamental wave impedance and the impedance of higher harmonics to the load port simultaneously within a wide frequency band to achieve broadband matching.

[0022] As a further improvement, in step S1, source pulling is performed on the gate of the transistor at the center frequency to obtain an optimal impedance, and an input matching circuit is designed on a Smith chart.

[0023] Compared with the prior art, the ultra-wideband power amplifier based on a reactive harmonic network provided by the present invention uses a resistive load for higher-order harmonics, making the higher-order impedance equivalent to the fundamental impedance, better controlling the higher-order (higher than the second and third) harmonics at the output end, avoiding the phenomenon that the impedance of the power amplifier across the octave is different and difficult to match, and expanding the working bandwidth of the power amplifier. However, in-depth research has found that the method of controlling harmonics using a reactive harmonic network causes the efficiency of the power amplifier to be lower than that of other high-efficiency power amplifiers. Therefore, on this basis, the control of the second and third harmonics is added, the second harmonic is short-circuited, and the third harmonic is open-circuited, so that the overlapping part of the current and voltage waveforms is minimized, thereby improving the efficiency of the power amplifier. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the overlap problem of the fundamental wave and each harmonic in the target frequency band of the present invention.

[0025] Figure 2 It is a structural block diagram of an ultra-wideband power amplifier based on a reactive harmonic network of the present invention.

[0026] Figure 3 It is a structural schematic diagram of the low-order harmonic control network in the present invention.

[0027] Figure 4 It is a structural schematic diagram of the high-order harmonic resistance load harmonic control network in the present invention.

[0028] Figure 5 This is a diagram of the output power simulation results in ADS under the condition that the input power of the present invention is 30dBm.

[0029] Figure 6It is a simulation result diagram of the drain efficiency of the present invention in ADS.

[0030] Figure 7 The present invention is a flowchart of a method for designing an ultra-wideband power amplifier based on a reactive harmonic network. DETAILED DESCRIPTION

[0031] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0032] In view of the defects of the prior art, the applicant has conducted in-depth research on the structure of ultra-wideband power amplifiers across octaves in the prior art. The applicant found that most broadband power amplifiers in the prior art cannot achieve good performance within the bandwidth outside the octave, and even the continuous B / J amplifier cannot ignore the problem of different fundamental impedance and higher harmonic impedance values. In order to overcome the defects of the prior art, the present application provides an ultra-wideband power amplifier based on a reactive harmonic network, which realizes waveform shaping of low-order harmonics and improves work efficiency. The use of a reactive harmonic control network at higher harmonics makes the higher harmonic impedance equivalent to the fundamental impedance, better controls the higher harmonics at the output end, avoids the phenomenon of different harmonic impedances of the power amplifier across octaves, and expands the working bandwidth of the power amplifier.

[0033] See also Figure 1 , which is a schematic diagram of the problem of overlapping fundamental and harmonic waves in the target frequency band of 0.5-2.5 GHz of the present invention. The drain of the selected transistor CGH40010F is load-pulled at the frequencies of 0.5, 1, 1.5, 2, and 2.5 GHz, and the respective optimal impedances are 26.9+j*23.6, 26.1+j*11.1, 21.2+j*7.9, 19.6+j*16.8, and 13.8+j*7.2. The subsequent harmonic control circuit structure needs to transform the fundamental impedance and each harmonic impedance at the five frequencies.

[0034] See also Figure 2 , shown is a structural diagram of an ultra-wideband power amplifier based on a reactive harmonic network of the present invention, including an input matching circuit, a low-order harmonic control network, a high-order harmonic resistance load control network, and a fundamental output matching circuit, wherein the input matching circuit matches the optimal impedance obtained by transistor source pulling to a 50-ohm input load port; the low-order harmonic control network utilizes the impedance transformation characteristics of a quarter-wavelength line to short-circuit the second harmonic and open-circuit the third harmonic through a quarter-wavelength line at each harmonic frequency, thereby improving the efficiency of the power amplifier; the high-order reactive harmonic control network utilizes a parallel short-circuit line and a resistor R to transform the reactance value of the high-order harmonic and compensate for its resistance value; the fundamental output matching circuit matches the optimal impedance obtained by transistor load pulling to a 50-ohm output load port.

[0035] See also Figure 3 , shown is a schematic structural diagram of a low-order harmonic control network of the present invention, the low-order harmonic control network comprises two first transmission lines TL1 and TL2 of one-twelfth wavelength, a third transmission line TL3 of one-sixth wavelength, and a fourth transmission line TL4 of one-quarter wavelength, one end of the first transmission line TL1 is connected to the output end of the power amplifier, the other end of the first transmission line TL1 is connected to one end of the second transmission line TL2 and one end of the third transmission line TL3, the other end of the second transmission line TL2 is open; the other end of the third transmission line TL3 is connected to one end of the fourth transmission line TL4, and the other end of the fourth transmission line TL4 is grounded.

[0036] The harmonic control network mainly utilizes the impedance transformation characteristics of a quarter-wavelength line (90°) from short circuit to open circuit. At the respective harmonic frequencies, the second harmonic short circuit and the third harmonic open circuit waveform of the transistor output are achieved through series-parallel transmission lines. The output current waveform is a half-sine wave, while the output voltage waveform is a square wave. The voltage and current waveforms differ in phase by 180°, and the overlapping part is minimal, thereby reducing power loss and improving the drain efficiency of the power amplifier.

[0037] The second transmission line TL2 is a twelfth wavelength of the fundamental wave, which is equivalent to a quarter-wavelength line under the third harmonic. One end of the line is an open circuit for the third harmonic, and the other end A of TL2 is short-circuited after impedance transformation. Similarly, the fourth transmission line TL4 is a quarter-wavelength line of the fundamental wave, which is equivalent to two quarter-wavelength lines under the second harmonic. One end of the line is a short circuit for the second harmonic, and the other end B of TL4 is short-circuited after secondary impedance transformation. After passing through the first transmission line TL1 and the third transmission line TL3, the second harmonic is short-circuited and the third harmonic is open-circuited, completing the control of the low-order harmonics of the fundamental wave. Specifically, the transmission line impedance calculation formula is as follows:

[0038]

[0039]

[0040]

[0041]

[0042]

[0043] See also Figure 4, shown is a schematic diagram of the structure of the high-order reactive harmonic network of the present invention, the high-order reactive harmonic network includes a fifth transmission line TL5 connected in series, a sixth transmission line TL6 connected in parallel and an impedance transformation resistor R, the fifth transmission line TL5 is connected to the low-order harmonic control network, the other end of the fifth transmission line TL5 is connected to one end of the sixth transmission line TL6 and one end of the impedance transformation resistor R, the other end of the sixth transmission line TL6 is open; the other end of the impedance transformation resistor R is connected to one end of the fundamental output matching circuit.

[0044] The main purpose of the high-order reactive harmonic network in the present invention is to transform the high-order harmonic impedance value generated by the fundamental wave to an approximate impedance value of the same frequency as the fundamental wave. Therefore, the sixth transmission line TL6 is used to offset the high-order harmonic reactance and make its reactance approach the point reactance value of the fundamental wave. The fifth transmission line TL5 establishes lossless transmission matching of the two harmonic networks. During the design, discrete parallel capacitors are used to adjust the reactance of the high-order harmonics, and converted into the sixth transmission line TL6 in the actual simulation to eliminate parasitic effects.

[0045] The conversion method is to calculate the physical length of the microstrip line as follows:

[0046]

[0047]

[0048] In formula (6) and (7), ω c is the center frequency of the designed matching network, λ is the wavelength at the center frequency, and Z OL and Z OC They are high and low characteristic impedance respectively.

[0049] The higher harmonic impedance at point C needs to be equivalent to the fundamental impedance value through pure reactance transformation. Since the resistor will produce huge losses in the circuit, in order to ensure the characteristics at high frequencies, a six-segment Chebyshev impedance transformer is used in the invention to replace the resistor R.

[0050] The matching between the low-order harmonic network and the high-order harmonic network can be listed using the ABCD matrix, and the transfer matrix K is:

[0051]

[0052] Where θ is the electrical length of the microstrip line TL5, and the impedance values ​​are all normalized to 50Ω.

[0053] In order to make the matching between the two harmonic networks lossless, a lossless relation |A| is established for the K matrix. 2 +|C| 2 =1, the impedance value of microstrip line TL5 and Z B , ZC 、Z5:

[0054]

[0055] Therefore, the transmission of the two harmonic control networks can be realized through the transition microstrip line TL5, thereby completing the matching between them.

[0056] The matching network designed by the present invention uses broadband matching technology, and the simplified real frequency method is to establish a scattering parameter network for the matching circuit and iteratively optimize the transmission power gain. The fundamental impedance of five points is selected within the frequency band to optimize the matching circuit.

[0057] See also Figure 5 , 6 , shown is the simulation result diagram of the ultra-wideband power amplifier based on the reactive harmonic network of the present invention in ADS. The designed power amplifier has an output power of 40-42.8dBm in the 5-fold frequency band of 0.5-2.8GHz and an input power of 30dBm. The drain efficiency is 63.8-70.2%, and the gain is 10-12dB, showing good performance indicators.

[0058] In a preferred embodiment, the power amplifier is implemented using a GaN HEMT CGH40010F transistor from Cree.

[0059] In a preferred embodiment, a gate bias circuit is provided between the input matching circuit and the transistor, and the bias voltage of the gate bias circuit is -2.7V.

[0060] In a preferred embodiment, a drain bias circuit is provided between the low-order harmonic control network and the high-order harmonic resistance load control network, and its bias voltage is 28V.

[0061] See also Figure 7 The present invention also discloses a design method of an ultra-wideband power amplifier based on a reactive harmonic network, which specifically comprises the following steps:

[0062] Step S1: For the gate of the transistor, source pulling is performed at the center frequency to obtain the optimal impedance, and the input matching circuit is designed on the Smith chart to achieve conjugate matching from the input port to the transistor gate impedance;

[0063] Step S2: Load-pull the drain of the transistor to obtain the optimal impedance at the second, third and higher harmonic frequencies respectively;

[0064] Step S3: Using series-parallel short stubs, designing a low-order harmonic control network, short-circuiting the second harmonic and opening the third harmonic, so that the overlap of the voltage and current waveforms becomes smaller, completing the second and third harmonic waveform shaping, which not only reduces the loss and improves the efficiency but also solves the overlap problem with the higher harmonics;

[0065] Step S4: designing a high-order reactive harmonic network, transforming the reactance and resistance of the high-order harmonics respectively through a parallel short stub and an impedance transformer, transforming the impedance of the high-order harmonics to be close to the fundamental impedance, and solving the overlap problem of the cross-octave harmonics and the fundamental of the power amplifier;

[0066] Step S5: Design a transition lossless network to enable the signal to be transmitted losslessly between the two harmonic networks.

[0067] Step S6: Design fundamental wave output matching, use simplified real frequency technology, and match the fundamental wave impedance and the impedance of higher harmonics to the load port simultaneously within a wide frequency band to achieve broadband matching.

[0068] The above technical solution is adopted to first control the second and third harmonics through the traditional F-class harmonic control network, improve the efficiency through waveform arrangement, and avoid the problem of overlap between the second and third harmonics and higher harmonics. Then, through the reactive harmonic network, the impedance transformation of higher harmonics is approximated with the fundamental impedance to achieve matching together. This solves the problem of the power amplifier crossing the octave and expands the bandwidth.

[0069] The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for those of ordinary skill in the art, without departing from the principles of the present invention, the present invention 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 claims of the present invention. It is obvious to those skilled in the art that various modifications to these embodiments 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 the present application, but will conform to the widest range consistent with the principles and novel features disclosed in the present application.

Claims

1. An ultra-wideband power amplifier based on a reactive harmonic network, characterized in that: It includes input matching circuit, transistor, low-order harmonic control network, high-order reactive harmonic network, fundamental wave output matching circuit, among which, The low-order harmonic control network comprises a first transmission line TL1 with a length of one-twelfth wavelength, a second transmission line TL2 with a length of one-twelfth wavelength, a third transmission line TL3 with a length of one-sixth wavelength, and a fourth transmission line TL4 with a length of one-quarter wavelength, wherein one end of the first transmission line TL1 is connected to the output end of the transistor, the other end of the first transmission line TL1 is connected to one end of the second transmission line TL2 and one end of the third transmission line TL3, and the other end of the second transmission line TL2 is open; the other end of the third transmission line TL3 is connected to one end of the fourth transmission line TL4, and the other end of the fourth transmission line TL4 is grounded; The high-order reactive harmonic network includes a fifth transmission line TL5 connected in series with 50Ω, a sixth transmission line TL6 connected in parallel with 50Ω, and an impedance transformation resistor R, wherein the fifth transmission line TL5 is connected to the low-order harmonic control network, the other end of the fifth transmission line TL5 is connected to one end of the sixth transmission line TL6 and one end of the impedance transformation resistor R, and the other end of the sixth transmission line TL6 is open; the other end of the impedance transformation resistor R is connected to one end of the fundamental output matching circuit; The input matching circuit is used to match the optimal impedance obtained by transistor source pulling to an input load port of 50 ohms; The fundamental wave output matching circuit is used to match the optimal impedance obtained by transistor load pulling to an output load port of 50 ohms; A gate bias circuit is provided between the input matching circuit and the transistor, and its bias voltage is -2.7V; A drain bias circuit is provided between the low-order harmonic control network and the high-order reactive harmonic network, and its bias voltage is 28V.

2. The ultra-wideband power amplifier based on reactive harmonic network according to claim 1, characterized in that: The transistor adopts a GaN HEMT CGH40010F transistor.

3. The design method of an ultra-wideband power amplifier based on a reactive harmonic network as claimed in claim 1 or 2, characterized in that: The specific steps include: Step S1: designing an input matching circuit to achieve conjugate matching from the input port to the transistor gate impedance; Step S2: performing load pulling on the drain of the transistor to obtain the optimal impedance at the second, third and higher harmonic frequencies respectively; Step S3: Design a low-order harmonic control network, using series-parallel short stubs to short-circuit the second harmonic and open the third harmonic; Step S4: designing a high-order reactive harmonic network, transforming the reactance and resistance of the high-order harmonics respectively through a parallel short stub and an impedance transformer, and transforming the impedance of the high-order harmonics to be close to the fundamental impedance; Step S5: designing a transition lossless network to enable the signal to be transmitted between the two harmonic networks without loss; Step S6: Design fundamental wave output matching to match the fundamental wave impedance and the impedance of higher harmonics to the load port simultaneously within a wide frequency band to achieve broadband matching.

4. The design method of an ultra-wideband power amplifier based on a reactive harmonic network according to claim 3, characterized in that: In step S1, source pulling is performed on the gate of the transistor at the center frequency to obtain the optimal impedance, and the input matching circuit is designed on the Smith chart.

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