A design method of a three-band power amplifier and an impedance matching network thereof

Abstract

The application discloses a three-frequency-band power amplifier which is composed of an input matching network, a transistor and an output matching network; a three-frequency-band impedance matching network in the input matching network and the output matching network is a key part of the application and is composed of a tuning transmission line, a T-shaped transmission line network, a transmission line with a characteristic impedance of Z0 and a three-frequency-band susceptor branch network; the application can increase the range of the matchable impedance and reduce the possibility of using a transmission line with extremely high or extremely low characteristic impedance; the three-frequency-band susceptor branch network also serves as a power supply bias network of a gate or a drain, and effectively simplifies the complexity of the design of the transistor matching network; the application can realize the matching between the complex impedance of three frequency bands and the system impedance at the same time, and solves the matching problem of the three-frequency-band power amplifier.

Description

Technical Field

[0001] This invention belongs to the field of power amplifier technology, and in particular relates to a power amplifier that can operate simultaneously in three frequency bands. Background Technology

[0002] The rapid development of wireless communication technology requires wireless transmitters to operate in multiple modes and according to multiple standards. As a key module in wireless transmitters, power amplifiers, if capable of multi-band operation, can effectively replace multiple single-band power amplifiers in multi-band transmitters, thereby significantly reducing system complexity, energy consumption, and cost. Therefore, research on multi-band power amplifiers is of great significance to the development of multi-mode, multi-frequency communication. Especially when frequency bands are widely separated, ultra-wideband power amplifiers struggle to maintain high efficiency across the entire bandwidth, making multi-band power amplifiers the preferred solution for high efficiency.

[0003] Reconfigurable multi-band power amplifiers can cover multiple frequency bands, but they typically require switching circuits for switching and cannot operate in multiple bands simultaneously. Impedance matching is an essential part of realizing multi-band concurrent power amplifiers and is extremely important for energy transfer. It, along with transistors, determines the frequency characteristics and output performance of the power amplifier. The optimal source impedance / load impedance of a power amplifier is usually a complex number, and due to the parasitic effects of transistors, it varies with frequency, meaning that the optimal impedances for the three frequency bands are not equal. This increases the design difficulty of the impedance matching circuit. Most current three-band concurrent power amplifiers are solved using optimization algorithms, which require time-consuming numerical optimization calculations and are prone to getting trapped in local optima.

[0004] Therefore, to address the aforementioned problems, it is necessary to provide an analytical solution for a three-band complex impedance matching circuit, enabling the power amplifier to operate concurrently in three frequency bands, which will have broad application prospects. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention proposes a transmission line network matching method for three-band complex impedance and system impedance Z0. All transmission line parameters can be solved analytically and applied to the input and output matching network of a power amplifier, enabling the power amplifier to operate simultaneously in three frequency bands.

[0006] This invention relates to a design method for a three-band power amplifier and its impedance matching network. The center operating frequencies of the three bands are f1, f2, and f3. The amplifier is characterized by being composed of an input matching network, a transistor, and an output matching network.

[0007] The power amplifier transistor presents three optimal source impedances and three optimal load impedances at three operating frequency bands. The input matching circuit simultaneously achieves the matching function of the three optimal source impedances with the system impedance Z0, and the output matching circuit simultaneously achieves the matching function of the three optimal load impedances with the system impedance Z0.

[0008] The input matching network consists of a transmission line with a characteristic impedance of Z0, an input DC blocking capacitor, a three-band impedance matching network, an RC stabilization circuit, and a gate transmission line connected in series. The RC stabilization circuit is located between the gate transmission line and the three-band impedance matching network to ensure that the transistor remains stable within the operating frequency band.

[0009] The output matching network consists of a drain transmission line, a three-band impedance matching network, an output DC blocking capacitor, and a transmission line with a characteristic impedance of Z0 connected in series.

[0010] The tri-band impedance matching network includes a tuned transmission line TLx, a T-type transmission line network, a transmission line TLc with a characteristic impedance of Z0, and a tri-band charged nano-stub network. The T-type transmission line network includes a transmission line TLa, a parallel stub S1, and a transmission line TLb. The tri-band charged nano-stub network includes two series transmission lines TL1 and TL2 with the same characteristic impedance and electrical length, and a terminal open-circuit stub S2 connected in parallel in the middle. One end of the tuned transmission line TLx is connected to the gate or drain transmission line, and the other end is connected to the transmission line TLa of the T-type transmission line network. One end of the transmission line TLc of the T-type transmission line network is connected to the series transmission line TL1 of the tri-band charged nano-stub network, and the other end of TLc is connected to the series transmission line TL1 of the tri-band charged nano-stub network. The end of the series transmission line TL2 is short-circuited to ground through a capacitor. The tuned transmission line TLx in the tri-band impedance matching network is used to increase the matched impedance range, and the tri-band charged nano-stub network also serves as a power supply bias network for the gate or drain.

[0011] The tuned transmission line TLx and the T-type transmission line network can achieve the matching of complex impedances at frequencies f1 and f3 to the system impedance Z0; the transmission line TLc and the three-frequency charged nano-stub network can achieve the matching of complex impedances at frequency f2 to the system impedance Z0 without changing the already matched impedances at frequencies f1 and f3.

[0012] The parameters of the three-band impedance matching network are obtained according to the following design formulas (1) to (14), assuming that the complex impedance to be matched is Z at the three specific operating frequencies f1, f2 and f3 respectively. L , f1 =R L1 +jB L1 Z L , f2 =R L2 +jB L2 ZL , f3 =R L3 +jB L3 The characteristic impedance Z of the tuned transmission line TLx x and electric length θ x All are free variables;

[0013] Given the load impedance Z L Given a series transmission line with characteristic impedance Z and electrical length θ, its input impedance Z can be calculated using the classical transmission line impedance equation (1). in ;

[0014] (1)

[0015] The input impedance Z through the transmission line TLx can be calculated using the transmission line impedance equation. in1 , fi i=1, 2, 3, as described in (2), at frequencies f1 and f3 respectively Z in1 , f1 =R 1x +jX 1x Z in1 , f3 = R 3x +jX 3x ;

[0016] (2)

[0017] The characteristic impedance of transmission line TLa is:

[0018] (3)

[0019] The electrical length θ of the transmission line TLa at frequency f1 a for:

[0020] (4)

[0021] Where r is the frequency ratio f3 / f1, and n=0 or 1 is to ensure θ a It is a positive number;

[0022] Using the transmission line impedance equation, the input admittance through the transmission line TLa at frequencies f1 and f3 are respectively Y in2 , f1 =G2+jB2, Y in2 , f3 =G2-jB2, the electrical length θ of the transmission line TLb at frequency f1 b for:

[0023] (5)

[0024] The characteristic impedance Z of transmission line TLb b for:

[0025] (6)

[0026] The electric length θ of the parallel stub S1 at frequency f1 s1 From the following formula, we can obtain

[0027] (7)

[0028] Where m = 0 or 1 is to ensure that θ s1 It is a positive number;

[0029] The characteristic impedance Z of the parallel stub S1 s1 From the following formula, we can obtain

[0030] (8)

[0031] The parameters of the tuned transmission line TLx and the T-type transmission line network have now been determined, and the matching work for frequencies f1 and f3 has been completed. The input admittance Y of the transmission line TLc looking to the left, obtained from the transmission line impedance equation, is now calculated. in3 , f1 =G0,Y in3 , f2 =G3+jB3,Y in3 , f3 =G0, the electrical length θ of the transmission line TLc at frequency f1 c for:

[0032] (9)

[0033] Where q = 0 or 1 is to ensure that θ c It is a positive number;

[0034] The electrical lengths θ1 and θ2 of transmission lines TL1 and TL2 and the parallel open stub S2 at frequency f1 and θ s2 They are respectively:

[0035] (10)

[0036] (11)

[0037] The characteristic impedances Z1 and Z2 of transmission lines TL1 and TL2 and the parallel open stub S2, as well as Z s2 They are respectively:

[0038] (12)

[0039] (13)

[0040] in

[0041] (14)

[0042] Thus, the parameters of all transmission lines in the three-band impedance matching network have been calculated.

[0043] The design method for the three-band impedance matching network includes the following steps:

[0044] Step 1: Determine the complex impedance to be matched at three specific operating frequencies f1, f2, and f3, where Z is respectively Z L , f1 =R L1 +jB L1 Z L , f2 =R L2 +jB L2 Z L , f3 =R L3 +jB L3 ;

[0045] Step 2: Select the electrical length θ of the tuned transmission line TLx x Gradually increase the characteristic impedance Z x In order to ensure that the characteristic impedance value meets the achievable range of microstrip lines and to reduce the discontinuity of series microstrip lines, its characteristic impedance is generally between 20Ω and 50Ω. The parameters of the T-type transmission line network (TLa, S1, TLb) are calculated sequentially according to formulas (2) to (8).

[0046] Step 3: Given B4 obtained from formula (9), calculate and select the parameters of the three-frequency charged nano-stub network sequentially using formulas (9) to (14);

[0047] Step 4: Check that the characteristic impedance of all transmission lines is within the range of 20Ω to 120Ω; otherwise, return to step 2.

[0048] Step 5: If Step 4 is satisfied, select a three-band impedance matching network scheme with similar characteristic impedance values ​​for all transmission lines and a shorter overall electrical length.

[0049] This invention proposes a solution method for a three-band power amplifier and its impedance matching network. The beneficial effects are: (1) It proposes an analytical solution method for the matching network of a three-band complex impedance to the system impedance Z0, which allows for flexible selection of Z0. xThe value of can reduce the possibility of using extremely high / low characteristic impedance transmission lines; (2) The tri-frequency charged nano stub network can be used as a power supply bias line, which effectively simplifies the complexity of transistor matching network design; (3) The tri-frequency charged nano stub network introduces a fixed transmission zero (f1+f3) / 2 located at the center of frequency f1 and frequency f3, which makes it have a certain out-of-band suppression function. Attached Figure Description

[0050] Figure 1 This is the overall functional block diagram of a three-band power amplifier.

[0051] Figure 2 This is the circuit structure diagram of a three-band impedance matching network.

[0052] Figure 3 Flowchart for the design of a three-band impedance matching network.

[0053] Figure 4 The remaining transmission line parameters of the three-band impedance matching network in this embodiment vary with the characteristic impedance Z. x A diagram illustrating the changes.

[0054] Figure 5 The diagram shows the three-band impedance matching circuit structure of the output matching network in the example and its S-parameter simulation results.

[0055] Figure 6 This is a schematic diagram of the overall circuit structure of an embodiment.

[0056] Figure 7 The following are simulation results of drain efficiency and output power for an example. Detailed Implementation

[0057] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings and embodiments. For those skilled in the art, all other embodiments obtained based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0058] like Figure 1 As shown, the present invention is a design method for a three-band power amplifier and its impedance matching network, which consists of an input matching network, a transistor, and an output matching network. The power amplifier transistor presents three optimal source impedances and three optimal load impedances at three operating frequency bands. The input matching circuit simultaneously achieves the matching function of the three optimal source impedances with the system impedance of 50Ω, and the output impedance matching circuit simultaneously achieves the matching function of the three optimal load impedances with the system impedance of 50Ω.

[0059] The input matching network consists of a transmission line with a characteristic impedance of Z0, an input DC blocking capacitor, a three-band impedance matching network, an RC stabilization circuit, and a gate transmission line connected in series. The RC stabilization circuit is located between the gate transmission line and the three-band impedance matching network to ensure that the transistor remains stable within the operating frequency band.

[0060] The output matching network consists of a drain transmission line, a three-band impedance matching network, an output DC blocking capacitor, and a transmission line with a characteristic impedance of Z0 connected in series.

[0061] Figure 2 The circuit topology of a three-band impedance matching network includes a tuned transmission line TLx connected at one end to the gate or drain transmission line, and at the other end to a T-type transmission line network (transmission line TLa, parallel stub S1, and transmission line TLb). One end of transmission line TLb is connected to a transmission line TLc with a characteristic impedance of Z0, and the other end of transmission line TLc is connected to a three-band charged nano-stub network. The function of the tuned transmission line is to increase the matched impedance range. The three-band charged nano-stub network consists of two transmission lines TL1 and TL2 with the same characteristic impedance and electrical length connected in series, and a parallel open-circuit stub S2 located in the middle. One end of transmission line TL1 is connected to transmission line TLc, and the other end is connected to transmission line TL2, while the other end of transmission line TL2 is short-circuited to ground through a capacitor. This three-band charged nano-stub network also serves as the power supply bias network for the gate or drain.

[0062] The tuned transmission line TLx and the T-type transmission line network (TLa, S1, TLb) can achieve the matching of complex impedances at frequencies f1 and f3 to the system impedance Z0; the transmission line TLc and the three-frequency charged nano-stub network can achieve the matching of complex impedances at frequency f2 to the system impedance Z0 without changing the already matched impedances at frequencies f1 and f3.

[0063] This invention uses the CG2H40010F power amplifier manufactured by CREE for designing a three-band power amplifier. The operating frequency bands selected are the commonly used 5G communication bands f1=2.6GHz, f2=3.4GHz, and f3=4.9GHz. Load-pull and source-pull simulations were performed on the amplifier to determine the optimal load impedance and optimal source impedance for the three frequency bands as follows:

[0064] <![CDATA[Z Source ]]> 7.5-j9.7 27.8-j14.7 48.5-j69.3 <![CDATA[Z Load ]]> 15-j0.1 12.4-j6.2 12.9-j21.8

[0065] Figure 3 The flowchart for designing a three-band impedance matching network is provided. Based on this flowchart, taking the three-band impedance matching network in the output impedance matching network as an example, the following can be derived: Figure 4 The curve shown represents the remaining transmission line parameters of the three-band impedance matching network as a function of the characteristic impedance Z. xThe characteristic impedance of the transmission line is set to range from 20Ω to 120Ω, i.e. Figure 4 Considering the overall electrical length and minimizing discontinuities between microstrip lines, Z is selected from the available range. x =23Ω, θ x =30°.

[0066] Figure 5 The simulation results of the three-band impedance matching circuit structure and its S-parameters for the output matching network show that the S11 values ​​of the low-frequency band (2.6GHz), mid-frequency band (3.4GHz), and high-frequency band (4.9GHz) are all below -40dB, and the S11 value at 3.75GHz is close to 0dB. This circuit can achieve good matching of the three frequency bands and introduce a transmission zero (f1+f3) / 2=3.75GHz.

[0067] Similarly, a three-band impedance matching network can be designed in the input matching network, and then the two parts can be cascaded together to form a network such as... Figure 6 The diagram shows the overall circuit structure of the three-band power amplifier. Figure 7 The figure shows the simulation results of the drain efficiency and output power of the three-band power amplifier in this embodiment. As can be seen from the figure, the embodiment has a zero at 3.75GHz, which can effectively suppress spurious signals in the vicinity. It achieves good three-band characteristics in the typical operating frequency bands of 5G communication in China, namely 2.6GHz, 3.4GHz, and 4.9GHz, meeting the requirements of multi-band power amplifiers in current wireless communication frequency bands. The drain efficiency at 2.6GHz is 74.9%, with a corresponding output power of 42.5dBm; the drain efficiency at 3.4GHz is 73.9%, with a corresponding output power of 41.8dBm; and the drain efficiency at 4.9GHz is 67.5%, with a corresponding output power of 41.5dBm.

Claims

1. A three-band power amplifier, wherein the center operating frequencies of the three bands are: f 1, f 2 and f 3. Characterized by: It consists of an input matching network, a transistor, and an output matching network; The input matching network consists of a single characteristic impedance of Z The transistor consists of a 0-channel transmission line, an input DC blocking capacitor, a three-band impedance matching network, an RC stabilization circuit, and a gate transmission line connected in series. The RC stabilization circuit is located between the gate transmission line and the three-band impedance matching network to ensure that the transistor remains stable within its operating frequency band. The output matching network consists of a drain transmission line, a three-band impedance matching network, an output DC blocking capacitor, and a characteristic impedance of [missing information]. Z The transmission lines for 0 are connected in series. The aforementioned three-band impedance matching network includes a tuned transmission line TL. x A T-type transmission line network, a line with a characteristic impedance of Z 0 transmission line TL c A three-frequency charged nano-stub network; wherein the T-type transmission line network includes transmission lines TL a Parallel stub S1, transmission line TL b The tri-frequency charged nano-stub network includes two series transmission lines TL1 and TL2 with the same characteristic impedance and electrical length, and a terminal open-circuit stub S2 connected in parallel in the middle; the tuned transmission line TL x One end is connected to the gate or drain transmission line, and the other end is connected to the transmission line TL of the T-type transmission line network. a ; Transmission and transmission lines TL in a T-type transmission line network c One end is connected to the transmission line TL. c The other end is connected to the series transmission line TL1 of the three-band electric nano-stub network; the end of the series transmission line TL2 is short-circuited to ground through a capacitor; the tuned transmission line TL in the three-band impedance matching network x To increase the range of matchable impedance, the tri-band charged nano-stub network also serves as a power supply bias network for the gate or drain. The tuned transmission line TL x T-type transmission line networks can achieve frequency f 1 and f Complex impedance to system impedance 3 Z 0 matching; transmission line TL c Three-frequency charged nano-stub networks can achieve frequency f Two complex impedances to system impedance Z While achieving zero matching, the frequency remains unchanged. f 1 and f The impedances at the three locations have already been matched; The parameters of the three-band impedance matching network are obtained according to the following design formulas (1) to (14), assuming that the complex impedance to be matched is at three specific operating frequencies. f 1. f 2 and f 3 are respectively Z L , f1 = R L1 + jB L1 , Z L , f2 = R L2 + jB L2 , Z L , f3 = R L3 + jB L3 ; Tuned transmission line TL x Characteristic impedance Z x and electrical length θ x All are free variables; Given load impedance Z L And the parameters of a series transmission line, where the characteristic impedance is Z The electric length is θ In this case, its input impedance can be obtained using the classic transmission line impedance equation (1). Z in ; （1） Use the transmission line impedance equation to find the TL of the transmission line. x Input impedance Z in1 , fi i=1, 2, 3, as described in (2), at frequency f 1 and f 3 are respectively Z in1 , f1 = R 1x + jX 1x , Z in1 , f3 = R 3x + jX 3x ; （2） Transmission line TL a The characteristic impedance is: （3） Transmission line TL a In frequency f 1 electrical length θ a for: （4） in r Frequency ratio f 3 / f 1, n =0 or 1 is to ensure θ a It is a positive number; Use the transmission line impedance equation to find the TL of the transmission line. a The input admittance at frequency , Transmission line TL b In frequency f 1 electrical length θ b for: （5） Transmission line TL b Characteristic impedance Z b for: （6） Parallel stub S1 at frequency f 1 electrical length θ s1 From the following formula, we can obtain （7） in m =0 or 1 is to ensure θ s1 It is a positive number; Characteristic impedance of parallel stub S1 Z s1 From the following formula, we can obtain （8） This concludes the determination of the tuned transmission line TL. x The parameters of the T-type transmission line network were used to complete the frequency... f 1 and f The matching work of 3 is to determine the transmission line impedance TL using the transmission line impedance equation. c The input admittance for looking to the left is Transmission line TL c In frequency f 1 electrical length θ c for: （9） in q =0 or 1 is to ensure θ c It is a positive number; Transmission lines TL1 and TL2, as well as the parallel open stub S2, at frequency f 1 electrical length θ 1 and θ 2 and θ s2 They are respectively: Characteristic impedances of transmission lines TL1 and TL2 and the parallel open stub S2 Z 1 and Z 2 and Z s2 They are respectively: Thus, the parameters of all transmission lines in the three-band impedance matching network have been calculated.

2. The design method of the three-band impedance matching network in the three-band power amplifier according to claim 1, comprising the following steps: Step 1: Determine the complex impedance to be matched at three specific operating frequencies. f 1. f 2 and f 3 are respectively Step 2: Select the tuned transmission line TL x Electrical length θ x Gradually increase the characteristic impedance Z x In order to ensure that the characteristic impedance value meets the realizable range of the microstrip line and to reduce the discontinuities of the series microstrip line, Its characteristic impedance is between 20Ω and 50Ω. The parameters of the T-type transmission line network are calculated sequentially according to formulas (2) to (8). Step 3: Obtain from formula (9) B In case 4, the parameters of the three-frequency charged nano-stub network are calculated and selected sequentially using formulas (9) to (14); Step 4: Check that the characteristic impedance of all transmission lines is within the range of 20Ω to 120Ω; otherwise, return to step 2. Step 5: If Step 4 is satisfied, select a three-band impedance matching network scheme with similar characteristic impedance values ​​for all transmission lines and a shorter overall electrical length.

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