Analog filter design method for power amplifier nonlinear phase error optimization

Abstract

The application discloses a method for designing an analog filter for optimizing nonlinear phase error of a power amplifier, and relates to the field of microwave and millimeter wave technologies, which comprises the following steps: constructing a main coupling structure of an analog filter; designing a source load coupling loop; obtaining a nonlinear phase distortion curve of a target power amplifier and calculating a target hat-shaped phase compensation curve; setting a transmission zero point and initializing; determining a normalized coupling matrix; then configuring coupling parameters of the analog filter; testing, through simulation, whether the hat-shaped phase compensation curve generated by the current analog filter is consistent with the target hat-shaped phase compensation curve; if not, adjusting the transmission zero point and redetermining the normalized coupling matrix; if yes, completing the design of the analog filter. The application can offset the nonlinear phase distortion of the target power amplifier under a large signal condition by accurately designing the phase characteristics of the analog filter, so that an ideal system-level phase response is obtained.

Description

Technical Field

[0001] This invention discloses an analog filter design method for optimizing the nonlinear phase error of power amplifiers, relating to the fields of microwave and millimeter-wave technology. Background Technology

[0002] Currently, digital predistortion technology is mainly used to improve nonlinear phase error in power amplifiers. However, digital predistortion requires complex digital signal processing algorithms and high-speed ADC / DAC converters, which increases system complexity and cost, and makes it inconvenient to carry. Secondly, digital predistortion has processing delay issues, which affect the real-time response performance of the system. Furthermore, digital predistortion is quite sensitive to temperature changes and device aging, and it is difficult to maintain stable compensation accuracy over a long period of time.

[0003] In summary, existing digital predistortion technologies increase system complexity, are not portable, require large amounts of storage resources, have poor real-time performance, and make it difficult to guarantee compensation accuracy.

[0004] Therefore, there is an urgent need for a device with a simple structure, fast response speed, and stable and reliable phase compensation to optimize the nonlinear phase error of power amplifiers. Summary of the Invention

[0005] The purpose of this invention is to propose an analog filter design method for optimizing the nonlinear phase error of power amplifiers. By precisely designing the phase characteristics of the analog filter, the nonlinear phase distortion of the target power amplifier under large signal conditions can be offset, thereby obtaining an ideal system-level phase response.

[0006] In a first aspect, this invention discloses an analog filter design method for optimizing the nonlinear phase error of a power amplifier, comprising:

[0007] S1: Construct the main coupling structure of the analog filter, including setting up the resonant cavity array and inter-cavity coupling loop;

[0008] S2: Design source load coupling loop, including multiple additional coupling loops;

[0009] S3: Obtain the nonlinear phase distortion curve of the target power amplifier in the operating frequency band, and calculate the target cap-shaped phase compensation curve;

[0010] S4: Set a transmission zero on each side of the passband of the target cap-shaped phase compensation curve and initialize it;

[0011] S5: Based on the normalized transmission zeros, the preset filter passband return loss and the target cap-shaped phase compensation curve, combined with the generalized Chebyshev function, determine the normalized coupling matrix.

[0012] S6: Based on the normalized coupling matrix, configure the coupling parameters of the analog filter, including: the cavity conductor length of each resonant cavity, the cavity window size of each cavity coupling loop, and the design parameters of each additional coupling loop in the source load coupling loop;

[0013] S7: Simulate and test whether the hat-shaped phase compensation curve generated by the analog filter under the current coupling parameters is consistent with the target hat-shaped phase compensation curve. If they are inconsistent, adjust the transmission zero and jump to S5; if they are consistent, the design of the analog filter is completed.

[0014] Furthermore, the main coupling structure of the analog filter adopts a third-order asymmetric coupling cavity, including: a first resonant cavity, a second resonant cavity, and a third resonant cavity with different resonant frequencies, which are respectively used to generate initial compensation phases in different operating frequency bands of the target power amplifier; a first coupling loop, disposed between the first resonant cavity and the second resonant cavity, for coupling and superimposing the initial compensation phases of the first resonant cavity and the second resonant cavity; and a second coupling loop, disposed between the second resonant cavity and the third resonant cavity, for coupling and superimposing the initial compensation phases of the second resonant cavity and the third resonant cavity.

[0015] Furthermore, the additional coupling ring includes: a third coupling ring disposed between the input port and the first resonant cavity; a fourth coupling ring disposed between the third resonant cavity and the output port; a fifth coupling ring disposed between the input port and the output port; and a sixth coupling ring disposed between the first resonant cavity and the output port; wherein the coupling strength of the fifth coupling ring and the sixth coupling ring is used to control the positions of the two transmission zeros.

[0016] Furthermore, the target hat-shaped phase compensation curve The calculation formula is:

[0017] ;

[0018] in,

[0019] ;

[0020] In the formula, The target power amplifier exhibits a bowl-shaped nonlinear phase distortion curve within its operating frequency band. For coefficients, Operating frequency band Frequency point variables within, Center frequency, For any constant term.

[0021] Furthermore, the normalized coupling matrix is ​​a fifth-order coupling matrix, specifically:

[0022] ;

[0023] In the formula, The coupling strength of the third coupling loop between the input port and the first resonant cavity. The coupling strength of the fifth coupling loop between the input port and the output port. The coupling strength inside the first resonant cavity. The coupling strength of the first coupling loop between the first resonant cavity and the second resonant cavity. The coupling strength of the sixth coupling loop between the first resonant cavity and the output port is given. The coupling strength inside the second resonant cavity. The coupling strength of the second coupling loop between the second and third resonant cavities is given. The coupling strength inside the third resonant cavity. The coupling strength is the fourth coupling ring between the third resonant cavity and the output port.

[0024] Furthermore, the configuration of the cavity conductor lengths of the first, second, and third resonant cavities includes: determining the fractional bandwidth (FBW) based on the passband bandwidth and center frequency.

[0025] FBW = BW / f0;

[0026] In the formula, BW is the passband bandwidth; Center frequency;

[0027] The center frequency is used as the resonant frequency of the second resonant cavity;

[0028] Based on the center frequency, fractional bandwidth, and coupling strength inside the first resonant cavity, the resonant frequency of the first resonant cavity is calculated. The formula is:

[0029] ;

[0030] Based on the center frequency, fractional bandwidth, and coupling strength within the third resonant cavity, the resonant frequency of the third resonant cavity is calculated. The formula is:

[0031] ;

[0032] For any resonant cavity, the corresponding wavelength is calculated based on the resonant frequency of the cavity, the speed of light, the relative permittivity between the cavity material and vacuum, and 1 / 4 of the corresponding wavelength is taken as the length of the cavity conductor.

[0033] Furthermore, the configuration method for the intercavity window size of the first coupling ring and the second coupling ring includes: calculating the coupling coefficient of the first coupling ring based on the fractional bandwidth and the coupling strength between the first resonant cavity and the second resonant cavity; calculating the coupling coefficient of the second coupling ring based on the fractional bandwidth and the coupling strength between the second resonant cavity and the third resonant cavity; and determining the intercavity window size of the first coupling ring and the second coupling ring based on the pre-obtained relationship curve between the coupling coefficient and the intercavity window size, according to the coupling coefficient of the first coupling ring and the second coupling ring.

[0034] Furthermore, the third and fourth coupling rings are microstrip lines or probes; the design parameter of the microstrip line is the length of the microstrip line, and the design parameter of the probe is the position of the probe.

[0035] The configuration method for the design parameters of the third coupling ring is as follows: based on the fractional bandwidth and the coupling strength of the third coupling ring, the first external quality factor is calculated, and based on the relationship curve between the pre-obtained external quality factor and the design parameters, the design parameters of the third coupling ring are determined.

[0036] The configuration method for the design parameters of the fourth coupling ring is as follows: based on the fractional bandwidth and the coupling strength of the fourth coupling ring, the second external quality factor is calculated, and based on the relationship curve between the pre-obtained external quality factor and the design parameters, the design parameters of the fourth coupling ring are determined.

[0037] The fifth coupling loop is a microstrip line, and its length is based on the coupling strength of the fifth coupling loop. Sure.

[0038] Furthermore, the third-order asymmetric coupled cavity is configured as a ring, and the fourth and sixth coupled rings are configured as the same probe. The distance between this probe and the third resonant cavity is designed based on the second external quality factor, and the coupling strength is based on the sixth coupled ring. Design the distance between the probe and the first resonant cavity.

[0039] In a second aspect, the present invention discloses a power amplifier system, comprising: a power amplifier and an analog filter; the analog filter is designed using the analog filter design method for optimizing the nonlinear phase error of the power amplifier as described in the first aspect; the input port of the analog filter is connected to an input pin, and the output port is connected to the power amplifier; the other end of the power amplifier is connected to an output pin.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] This invention employs an analog filter to directly compensate for the nonlinear phase error of a target power amplifier. By constructing a coupling structure, setting transmission zeros on both sides of the passband, and setting the coupling parameters of the components in the coupling structure, a hat-shaped phase compensation curve is simulated to cancel the nonlinear phase distortion curve. This invention uses an analog filter that can accurately compensate for the phase deviation generated by the power amplifier at different frequency points, significantly improving the overall phase response characteristics of the system. It has a simple structure, low power consumption, fast response speed, and can provide a stable and reliable phase compensation effect. Attached Figure Description

[0042] Figure 1 This is a flowchart of the analog filter design method for optimizing the nonlinear phase error of a power amplifier provided in Embodiment 1 of the present invention;

[0043] Figure 2 This is a schematic diagram of the main coupling structure of the analog filter for optimizing the nonlinear phase error of a power amplifier provided in Embodiment 1 of the present invention;

[0044] Figure 3 This is a schematic diagram of the cancellation compensation between the nonlinear phase distortion curve and the cap-shaped phase compensation curve of the target power amplifier provided in Embodiment 1 of the present invention.

[0045] Figure 4 This is a schematic diagram of the power amplifier system provided in Embodiment 2 of the present invention. Detailed Implementation

[0046] To better understand the present invention, the following description, in conjunction with the accompanying drawings of the embodiments of the present invention, will further illustrate the present invention, but this is not intended to limit the present invention; various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the design concept of the present invention should fall within the protection scope of the present invention.

[0047] Example 1

[0048] refer to Figure 1 This embodiment discloses an analog filter design method for optimizing the nonlinear phase error of a power amplifier, including the following steps:

[0049] Step 1: Construct the main coupling structure of the analog filter, including setting up the resonant cavity array and inter-cavity coupling loop.

[0050] Specifically, the main coupling structure refers to the energy transfer structure between adjacent resonant cavities, which determines the inter-cavity coupling strength, filter bandwidth, and passband characteristics. In this embodiment, a structure is adopted in which multiple independent resonant cavities are separated by inter-cavity coupling rings. An inter-cavity window is opened in the middle of the inter-cavity coupling ring. The signal is transmitted between adjacent cavities through electromagnetic field coupling of the window. The larger the window, the stronger the coupling and the wider the filter bandwidth.

[0051] refer to Figure 2 , in one embodiment, the main coupling structure adopts a third-order asymmetric coupled cavity, comprising: a first resonant cavity R1, a second resonant cavity R2, a third resonant cavity R3, a first coupling ring C1 and a second coupling ring C2; wherein the first coupling ring C1 is arranged between the first resonant cavity R1 and the second resonant cavity R2, and the second coupling ring C2 is arranged between the second resonant cavity R2 and the third resonant cavity R3.

[0052] as Figure 2 shown, each resonant cavity has different resonant frequencies f1, f2, f3, which satisfy the increasing relationship of f1<f2<f3. The first resonant cavity R1 and the third resonant cavity R3 serve as end cavities, and the second resonant cavity R2 serves as a central cavity, all of which are used to generate initial compensation phases within the working frequency band of the target power amplifier; within the passband frequency range of the working frequency band, the three resonant cavities operate simultaneously and each generates an independent phase response. The phase response of the R1 cavity mainly affects the low-frequency band characteristics, R2 as the central cavity produces the main phase change and mainly affects the mid-frequency band characteristics, and the R3 cavity affects the high-frequency band response.

[0053] This embodiment implements asymmetric coupling through the first coupling ring C1 and the second coupling ring C2. The first coupling ring C1 is configured to generate a first coupling coefficient, so as to couple and superimpose the initial compensation phases of the first resonant cavity and the second resonant cavity; the second coupling ring C2 is configured to generate a second coupling coefficient, so as to couple and superimpose the initial compensation phases of the second resonant cavity and the third resonant cavity; the coupling coefficients are respectively and , the coupling coefficient is related to the size of the inter-cavity window of the corresponding coupling ring, and the design of the coupling coefficient will be described in the subsequent content.

[0054] By arranging two transmission zeros of the third-order asymmetric coupled cavity, a hat-shaped phase compensation curve can be generated, which is used to cancel the nonlinear phase distortion curve of the target power amplifier in the working frequency band.

[0055] Step 2: Design the source-load coupling ring.

[0056] In this embodiment, an independent electromagnetic path is constructed between the input port and the output port; the coupling strength and polarity are changed through the size, gap, shape and placement position of the coupling ring, and full-domain asymmetric frequency response is realized in cooperation with the third-order asymmetric main coupling structure.

[0057] In one embodiment, the source-load coupling ring comprises a plurality of additional coupling rings, specifically comprising: a third coupling ring between the input port and the first resonant cavity R1, a fourth coupling ring between the third resonant cavity R3 and the output port, a fifth coupling ring between the input port and the output port, and a sixth coupling ring between the first resonant cavity R1 and the output port.

[0058] Source-load coupling is achieved by adding microstrip lines or probes to the input and output ports. The coupling strength is controlled by adjusting the microstrip line length and probe position. Non-adjacent coupling is also achieved by controlling the position. Since a cap-shaped phase compensation curve is needed to match the bowl-shaped nonlinear phase distortion curve of the target power amplifier in the operating frequency band, transmission zeros need to be set on both sides of the passband. The coupling strengths of the fifth and sixth coupling loops are used to control the positions of the two transmission zeros.

[0059] Step 3: Obtain the nonlinear phase distortion curve of the target power amplifier in the operating frequency band, and calculate the target cap-shaped phase compensation curve.

[0060] refer to Figure 3 , Figure 3 The bowl-shaped curve in the figure represents the nonlinear phase distortion curve of the target power amplifier within its operating frequency band. It can be either a symmetrical or asymmetrical curve. Figure 3 The cap-shaped curve in the figure is the cap-shaped phase compensation curve generated by the analog filter provided in this embodiment. The superposition of two opposite curves achieves the cancellation of the nonlinear phase distortion curve of the target power amplifier.

[0061] In one embodiment, the center frequency is calculated based on the operating frequency band, and the target cap-shaped phase compensation curve is calculated by combining the nonlinear phase distortion curve. Specifically, this includes: obtaining the bowl-shaped nonlinear phase distortion curve of the target power amplifier within the operating frequency band through measurement. Calculate the required target cap-shaped phase compensation curve :

[0062] ;

[0063] in,

[0064] ;

[0065] In the formula, For coefficients, Operating frequency band Frequency point variables within, Center frequency, For any constant term.

[0066] Step 4: Set a transmission zero on each side of the passband of the target cap-shaped phase compensation curve and initialize it.

[0067] To obtain a cap-shaped phase, a zero needs to be set on each side of the passband. Specifically, the normalized frequency ω=(f−f0) / BW is set, where BW is the passband bandwidth. The normalized transmission zeros are initially set, and the return loss within the filter passband is set.

[0068] Step 5: Based on the normalized transmission zeros, filter passband return loss, and target cap-shaped phase compensation curve, and combined with the generalized Chebyshev function, determine the normalized coupling matrix.

[0069] In this embodiment, the coupling matrix is ​​a fifth-order coupling matrix, which contains at least several elements characterizing the coupling coefficients between the components. The components include an input port, a first resonant cavity R1, a second resonant cavity R2, a third resonant cavity R3, and an output port. The normalized fifth-order coupling matrix is ​​as follows:

[0070] ;

[0071] In the formula, The coupling strength of the third coupling loop between the input port and the first resonant cavity R1. The coupling strength of the fifth coupling loop between the input port and the output port. The coupling strength inside the first resonant cavity R1 is... Let R1 be the coupling strength of the first coupling loop between the first resonant cavity R1 and the second resonant cavity R2. The coupling strength of the sixth coupling loop between the first resonant cavity R1 and the output port is given. The coupling strength inside the second resonant cavity R2. The coupling strength of the second coupling loop between the second resonant cavity R2 and the third resonant cavity R3. The coupling strength inside the third resonant cavity R3. The coupling strength is the fourth coupling ring between the third resonant cavity R3 and the output port.

[0072] Step 6: Configure the coupling parameters of the analog filter based on the normalized coupling matrix.

[0073] In this embodiment, the coupling parameters of the analog filter include: the cavity conductor lengths of the first resonant cavity R1, the second resonant cavity R2 and the third resonant cavity R3, the size of the intercavity window of the first coupling ring C1 and the second coupling ring C2, and the design parameters of the third coupling ring, the fourth coupling ring, the fifth coupling ring and the sixth coupling ring in the source-load coupling ring.

[0074] In one embodiment, the configuration of the cavity conductor lengths of the first resonant cavity R1, the second resonant cavity R2, and the third resonant cavity R3 includes:

[0075] Determine the fractional bandwidth (FBW) based on the passband bandwidth and center frequency:

[0076] FBW = BW / f0;

[0077] In the formula, BW is the passband bandwidth; Center frequency;

[0078] The center frequency is taken as the resonant frequency of the second resonant cavity R2;

[0079] Based on the center frequency, fractional bandwidth, and coupling strength inside the first resonant cavity R1, the resonant frequency of the first resonant cavity R1 is calculated. The formula is:

[0080] ;

[0081] Based on the center frequency, fractional bandwidth, and coupling strength inside the third resonant cavity R3, calculate the resonant frequency of the third resonant cavity R3. The formula is:

[0082] ;

[0083] For any resonant cavity, based on its resonant frequency, the speed of light, and the relative permittivity between the cavity material and vacuum, calculate the corresponding wavelength. The wavelength calculation formula is as follows:

[0084] ;

[0085] In the formula, For wavelength, At the speed of light, Let be the relative permittivity between the cavity material of the resonant cavity and the vacuum. Let be the resonant frequency of the i-th resonant cavity.

[0086] corresponding wavelength One-quarter of the length is taken as the length of the cavity conductor of the resonant cavity.

[0087] In some embodiments, the cavity window sizes of the first coupling ring and the second coupling ring are configured as follows: the coupling coefficient of the first coupling ring C1 is calculated using the fractional bandwidth and the coupling strength of the first coupling ring C1; the coupling coefficient of the second coupling ring C2 is calculated using the fractional bandwidth and the coupling strength of the first coupling ring C2; the calculation formula is: Then, based on the relationship curve between the coupling coefficient and the cavity window size obtained from the pre-simulation, the cavity window size of the first coupling ring C1 and the second coupling ring C2 is determined.

[0088] In a source-load coupling loop, the fifth coupling loop located between the input and output ports can only be a microstrip line, and its length is based on the coupling strength. design.

[0089] The third, fourth, and sixth coupling rings can be microstrip lines or probes. The design parameter for the microstrip line is its length, and the design parameter for the probe is its position.

[0090] In some implementations, the design parameters of the third coupling ring are configured as follows: the first external quality factor is calculated based on the fractional bandwidth and the coupling strength of the third coupling ring, and then the design parameters of the third coupling ring are determined based on the relationship curve between the design parameters and the external quality factor obtained from pre-simulation.

[0091] The configuration method for the design parameters of the fourth coupling ring is as follows: calculate the second external quality factor based on the fractional bandwidth and the coupling strength of the fourth coupling ring, and then determine the design parameters of the fourth coupling ring based on the relationship curve between the design parameters and the external quality factor obtained from the pre-simulation.

[0092] Specifically, the first external quality factor Second external quality factor They are respectively:

[0093] ;

[0094] ;

[0095] In the formula, FBW is the fractional bandwidth. The coupling strength of the third coupling ring. The coupling strength of the fourth coupling ring.

[0096] When the third and fourth coupling loops are microstrip lines, based on the first external quality factor Second external quality factor Determine the lengths of the two microstrip lines respectively.

[0097] In one embodiment, when the fourth coupling ring is a probe, the third-order asymmetric coupling cavity is configured as a ring. In this case, the sixth coupling ring and the fourth coupling ring are the same probe, and thus based on the second external quality factor... The distance between the probe and the third resonant cavity R3 is determined based on the coupling strength of the sixth coupling ring. Determine the distance between the probe and the first resonant cavity R1.

[0098] Step 7: Simulate and test whether the hat-shaped phase compensation curve generated by the analog filter under the current coupling parameters is consistent with the target hat-shaped phase compensation curve. If the hat-shaped phase compensation curve generated by the third-order asymmetric coupling cavity is insufficient to offset the nonlinear phase distortion curve, adjust the transmission zero and return to step 5, redetermine the normalized coupling matrix, and configure the coupling parameters of the analog filter until the simulation test produces a hat-shaped phase compensation curve that meets the expectations, thus completing the design of the analog filter.

[0099] Example 2

[0100] This embodiment provides a power amplifier system, such as Figure 4 As shown, it includes: a power amplifier and an analog filter; wherein, the analog filter is obtained by the analog filter design method for power amplifier nonlinear phase error optimization as described in Example 1; the input port of the analog filter is connected to the input pin, and the output port is connected to the target power amplifier; the other end of the target power amplifier is connected to the output pin.

[0101] This embodiment and the above method embodiment belong to the same concept. For details of its implementation process, please refer to the method embodiment, which will not be repeated here.

[0102] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for designing an analog filter to optimize the nonlinear phase error of a power amplifier, characterized in that, include: S1: Construct the main coupling structure of the analog filter, including setting up the resonant cavity array and inter-cavity coupling loop; S2: Design source load coupling loop, including multiple additional coupling loops; S3: Obtain the nonlinear phase distortion curve of the target power amplifier in the operating frequency band, and calculate the target cap-shaped phase compensation curve; S4: Set a transmission zero on each side of the passband of the target cap-shaped phase compensation curve and initialize it; S5: Based on the normalized transmission zeros, the preset filter passband return loss and the target cap-shaped phase compensation curve, combined with the generalized Chebyshev function, determine the normalized coupling matrix. S6: Based on the normalized coupling matrix, configure the coupling parameters of the analog filter, including: the cavity conductor length of each resonant cavity, the cavity window size of each cavity coupling loop, and the design parameters of each additional coupling loop in the source load coupling loop; S7: Simulate and test whether the hat-shaped phase compensation curve generated by the analog filter under the current coupling parameters is consistent with the target hat-shaped phase compensation curve. If they are inconsistent, adjust the transmission zero and jump to S5; if they are consistent, the design of the analog filter is completed.

2. The analog filter design method for optimizing the nonlinear phase error of a power amplifier according to claim 1, characterized in that, The main coupling structure of the analog filter adopts a third-order asymmetric coupling cavity, including: a first resonant cavity, a second resonant cavity and a third resonant cavity with different resonant frequencies, which are used to generate the initial compensation phase in different operating frequency bands of the target power amplifier, respectively. A first coupling loop is disposed between the first resonant cavity and the second resonant cavity, and is used to couple and superimpose the initial compensation phases of the first resonant cavity and the second resonant cavity. The second coupling ring is disposed between the second resonant cavity and the third resonant cavity, and is used to couple and superimpose the initial compensation phases of the second resonant cavity and the third resonant cavity.

3. The analog filter design method for optimizing the nonlinear phase error of a power amplifier according to claim 2, characterized in that, The additional coupling loop includes: The third coupling loop is positioned between the input port and the first resonant cavity; The fourth coupling ring is located between the third resonant cavity and the output port; The fifth coupling ring is located between the input port and the output port; The sixth coupling ring is located between the first resonant cavity and the output port; The coupling strengths of the fifth and sixth coupling rings are used to control the positions of the two transmission zeros.

4. The analog filter design method for optimizing the nonlinear phase error of a power amplifier according to claim 1, characterized in that, The target hat-shaped phase compensation curve The calculation formula is: ； in, ； In the formula, The target power amplifier exhibits a bowl-shaped nonlinear phase distortion curve within its operating frequency band. For coefficients, Operating frequency band Frequency point variables within, Center frequency, For any constant term.

5. The analog filter design method for optimizing the nonlinear phase error of a power amplifier according to claim 3, characterized in that, The normalized coupling matrix is ​​a fifth-order coupling matrix, specifically: ； In the formula, The coupling strength of the third coupling loop between the input port and the first resonant cavity. The coupling strength of the fifth coupling loop between the input port and the output port. The coupling strength inside the first resonant cavity. The coupling strength of the first coupling loop between the first resonant cavity and the second resonant cavity. The coupling strength of the sixth coupling loop between the first resonant cavity and the output port is given. The coupling strength inside the second resonant cavity. The coupling strength of the second coupling loop between the second and third resonant cavities is given. The coupling strength inside the third resonant cavity. The coupling strength is the fourth coupling ring between the third resonant cavity and the output port.

6. The analog filter design method for optimizing the nonlinear phase error of a power amplifier according to claim 5, characterized in that, The configuration of the cavity conductor lengths of the first resonant cavity, the second resonant cavity, and the third resonant cavity includes: Determine the fractional bandwidth (FBW) based on the passband bandwidth and center frequency: FBW = BW / f0; In the formula, BW is the passband bandwidth; Center frequency; The center frequency is used as the resonant frequency of the second resonant cavity; Based on the center frequency, fractional bandwidth, and coupling strength inside the first resonant cavity, the resonant frequency of the first resonant cavity is calculated. The formula is: ； Based on the center frequency, fractional bandwidth, and coupling strength within the third resonant cavity, the resonant frequency of the third resonant cavity is calculated. The formula is: ； For any resonant cavity, the corresponding wavelength is calculated based on the resonant frequency of the cavity, the speed of light, the relative permittivity between the cavity material and vacuum, and 1 / 4 of the corresponding wavelength is taken as the length of the cavity conductor.

7. The analog filter design method for optimizing the nonlinear phase error of a power amplifier according to claim 6, characterized in that, The configuration methods for the intercavity window size of the first coupling ring and the second coupling ring include: The coupling coefficient of the first coupling loop is calculated based on the fractional bandwidth and the coupling strength between the first resonant cavity and the second resonant cavity. The coupling coefficient of the second coupling loop is calculated based on the fractional bandwidth and the coupling strength between the second and third resonant cavities. Based on the pre-obtained relationship curve between the coupling coefficient and the cavity window size, the cavity window size of the first coupling ring and the second coupling ring is determined according to the coupling coefficient of the first coupling ring and the second coupling ring.

8. The analog filter design method for optimizing the nonlinear phase error of a power amplifier according to claim 6, characterized in that, The third and fourth coupling rings are microstrip lines or probes; the design parameter of the microstrip line is the length of the microstrip line, and the design parameter of the probe is the position of the probe. The configuration method for the design parameters of the third coupling ring is as follows: based on the fractional bandwidth and the coupling strength of the third coupling ring, the first external quality factor is calculated, and based on the relationship curve between the pre-obtained external quality factor and the design parameters, the design parameters of the third coupling ring are determined. The configuration method for the design parameters of the fourth coupling ring is as follows: based on the fractional bandwidth and the coupling strength of the fourth coupling ring, the second external quality factor is calculated, and based on the relationship curve between the pre-obtained external quality factor and the design parameters, the design parameters of the fourth coupling ring are determined. The fifth coupling loop is a microstrip line, and its length is based on the coupling strength of the fifth coupling loop. Sure.

9. The analog filter design method for optimizing the nonlinear phase error of a power amplifier according to claim 8, characterized in that, The third-order asymmetric coupled cavity is configured as a ring, and the fourth and sixth coupled rings are configured as the same probe. The distance between this probe and the third resonant cavity is designed based on the second external quality factor, and the coupling strength is based on the sixth coupled ring. Design the distance between the probe and the first resonant cavity.

10. A power amplifier system, characterized in that, include: A power amplifier and an analog filter; the analog filter is designed using the analog filter design method for optimizing the nonlinear phase error of a power amplifier as described in any one of claims 1-9; The input port of the analog filter is connected to the input pin, and the output port is connected to the power amplifier; the other end of the power amplifier is connected to the output pin.

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