Optimization method for impedance matching and surface acoustic wave filter

Abstract

The present invention provides an optimization method for impedance matching and a surface acoustic wave filter. The optimization method comprises the following steps: step S1, obtaining corresponding scattering parameter information, and screening the scattering parameter information on the basis of a set frequency range; step S2, determining an impedance matching circuit that needs to be added for each port; step S3, by taking the reflection circle radius of a scattering parameter of each port as a first optimization objective, performing optimization to obtain a first optimization result of each port; step S4, by taking the first optimization result of each port as an initial value and taking maximum insertion within the set frequency range and the reflection circle radius of the scattering parameter of each port as second optimization objectives, performing optimization again to obtain a second optimization result; and step S5, evaluating the second optimization result. The optimization method of the present invention can improve the optimization speed, reduce the likelihood of optimization falling into a local optimum, and accelerate the convergence speed.

Description

Optimization method of impedance matching and surface acoustic wave filter TECHNICAL FIELD

[0001] The present application relates to the technical field of filter, and in particular to an optimization method of impedance matching of a port network and a surface acoustic wave filter. BACKGROUND

[0002] In the design and production of a surface acoustic wave filter (also referred to as a SAW filter), parasitic inductance and parasitic capacitance are inevitably encountered, which can cause the performance of insertion loss, echo and ripple in the passband to deteriorate, and the performance deterioration caused by the parasitic inductance and parasitic capacitance can be offset by constructing a suitable impedance matching at each port of the surface acoustic wave filter. The specific value of the impedance matching is obtained by an optimization method.

[0003] The optimization method in the related art is to optimize the electrical performance indicators such as the standing wave ratio (also referred to as VSWR), echo and insertion loss (also referred to as IL), and when the design tool optimizes a fixed impedance matching circuit structure, the electrical performance indicators such as the standing wave ratio, echo and insertion loss are used as the optimization target.

[0004] The calculation formula of the standing wave ratio is relatively complex and time-consuming, so it will affect the speed of optimization, and when the standing wave ratio is used as the optimization target, the maximum value in a certain frequency interval needs to be taken, which will cause the value of the optimization target to be not smooth and continuous, thus increasing the possibility of the optimization falling into a local optimal solution, in addition, the impedance matching does not support the function of providing an initial value, and when the number of ports of the port network is large, the number of optimization variables will increase, thus causing the convergence speed of the optimization to be slow. The calculation formula of the standing wave ratio is as follows:

[0005] Wherein, Γ is S ii . SUMMARY

[0006] In view of the above problems of the related art, the present application provides a new optimization method of impedance matching and a surface acoustic wave filter to solve the problems that the optimization method of impedance matching in the related art affects the optimization speed, increases the possibility of the optimization falling into a local optimal solution, and causes the convergence speed of the optimization method to be slow.

[0007] To solve the above technical problems, the present application adopts the following technical solutions:

[0008] In a first aspect, the present application provides an optimization method of impedance matching, comprising the following steps:

[0009] Step S1, load the scattering parameter matrix file of the port network to obtain the corresponding scattering parameter information, and filter the scattering parameter information according to the set frequency range; wherein the port network is composed of multiple ports;

[0010] Step S2, determine the impedance matching circuit to be added for each port according to the Smith chart of the port network;

[0011] Step S3, select each port in turn and obtain the scattering parameter of each port, take the reflection circle radius of the scattering parameter of each port as the first optimization target, and use the quasi-Newton method for optimization to obtain the first optimization result of each port;

[0012] Step S4, take the first optimization result of each port as the initial value, and take the maximum insertion and the reflection circle radius of the scattering parameter of each port in the set frequency range as the second optimization target, and use the quasi-Newton method for optimization again to obtain the second optimization result;

[0013] Step S5, determine the second optimization result: if the determination result meets the performance index of the port network, end the optimization.

[0014] Preferably, in step S5, if the determination result does not meet the performance index of the port network, the following steps are performed;

[0015] Step S6, adjust the impedance matching circuit of the port network according to the second optimization result, and repeat steps S3 to S5 after the adjustment is completed until the determination result meets the performance index of the port network; wherein the impedance matching circuit of the port network is composed of the impedance matching circuit to be added for each port.

[0016] Preferably, in step S2, the impedance matching circuit to be added for each port includes:

[0017] a capacitor or / and an inductor in series, or / and,

[0018] a capacitor or / and an inductor in parallel.

[0019] Preferably, in step S3, the second optimization target satisfies the following condition:

[0020] obj=logi*IL_max+c*R;

[0021] Wherein, obj is the function value of the second optimization target, log is the logarithm operation, i is the iteration number of the optimization algorithm, IL_max is the maximum insertion rate, c is a specified constant, and R is the reflection circle radius.

[0022] Preferably, the reflection circle radius satisfies the following condition:

[0023] R = |S ii |;

[0024] wherein S ii is the scattering parameter of the port.

[0025] In a second aspect, the present application provides a surface acoustic wave filter, whose impedance matching value is obtained by the impedance matching optimization method as described above.

[0026] Compared with the related art, the impedance matching optimization method in the present application optimizes the impedance matching of the port network by taking the reflection circle radius of the scattering parameter of the port as the optimization target, so that the smaller the reflection circle radius, the better the indicators such as the insertion loss, the return loss and the standing wave ratio of the port network, and the calculation method of the reflection circle radius is simple, thereby reducing the calculation complexity of the optimization, making the optimization faster, and since the calculation process will not appear the maximum or minimum value, the value of the optimization target will be smoother and more continuous, which can reduce the possibility of the optimization falling into a local optimal solution, in addition, the impedance matching optimization method in the present application first determines the impedance matching circuit that needs to be added in all ports in the port network, so that when optimizing a single port, the variables participating in the optimization will be reduced, which can improve the optimization speed to quickly obtain the result, and after the optimization of all ports is completed, the optimization results of all ports are recorded as the initial values of the optimization variables of all ports to participate in the secondary optimization, thereby accelerating the convergence speed of the optimization method. BRIEF DESCRIPTION OF DRAWINGS

[0027] The present application will be described in detail below with reference to the accompanying drawings. The above and other aspects of the present application will become more apparent and more readily appreciated by referring to the following detailed description, taken in conjunction with the accompanying drawings, in which:

[0028] Fig. 1 is a step flow diagram of an impedance matching optimization method provided by an embodiment of the present application.

[0029] Fig. 2 is a simple flow diagram of an impedance matching optimization method provided by an embodiment of the present application. DETAILED DESCRIPTION

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application; the use herein of terms such as "comprise", "comprising", "comprises", "including", "includes" or "have" or "has" are used generically and are intended to encompass the presence of stated features, integers, steps, processes, actions, objects, components, devices or the like, but do not exclude the presence of one or more additional features, integers, steps, processes, actions, objects, components, devices or the like; the use herein of terms such as "first", "second" and the like do not denote any order, quantity, combination or arrangement, but are used for the purpose of nomenclature only.

[0031] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase that in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. As will be apparent to those of ordinary skill in the art, embodiments described herein can be combined with other embodiments.

[0032] The technical solutions in the embodiments of the application will be apparently and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without any creative effort belong to the protection scope of the application.

[0033] The impedance matching optimization method provided by the embodiments of the application comprises the following steps:

[0034] Step S1: loading a scattering parameter matrix file of a port network to obtain corresponding scattering parameter information, and screening the scattering parameter information according to a set frequency range.

[0035] The scattering parameter matrix file is abbreviated as an snp file; the scattering parameter information is abbreviated as S parameter information; the S parameter is continuously distributed according to frequency, but the impedance matching optimization method in the embodiment only needs the S parameter in the set frequency range, and therefore the S parameter information needs to be screened according to the set frequency range to obtain the required S parameter.

[0036] The port network is composed of multiple ports.

[0037] Step S2: determining an impedance matching circuit to be added for each port according to a Smith chart of the port network.

[0038] The Smith chart is abbreviated as a Smith chart; the impedance matching circuit to be added for each port is determined by an experienced radio frequency engineer, which is equivalent to preliminary determination.

[0039] The impedance matching circuit to be added to each port comprises a capacitor or / and an inductor in series, or / and a capacitor or / and an inductor in parallel. That is, the impedance matching circuit to be added to each port is one capacitor or multiple capacitors, one inductor or multiple inductors, a combination of capacitors and inductors, and can be arranged in series or in parallel, or arranged in series and in parallel.

[0040] In step S3, each port is selected in turn and the scattering parameter of each port is obtained, the reflection circle radius of the scattering parameter of each port is taken as a first optimization target, and a quasi-Newton method is used for optimization to obtain a first optimization result of each port.

[0041] For example, for multiple ports, after port i is selected, the scattering parameter S ii of the corresponding port can be obtained, the reflection circle radius of S ii is taken as an optimization target, and a quasi-Newton method is used for optimization to obtain an optimization result of port i as an initial value for the next optimization; after the optimization of port i is completed, the remaining ports are repeatedly selected in turn until all ports are optimized, and the optimization results of all ports are recorded as initial values for the next optimization.

[0042] In step S4, the first optimization result of each port is taken as an initial value, the maximum insertion and the reflection circle radius of the scattering parameter of each port in a set frequency range are taken as a second optimization target, and a quasi-Newton method is used for re-optimization to obtain a second optimization result.

[0043] The second optimization target satisfies the following condition:

[0044] obj = logi*IL_max + c*R;

[0045] Wherein, obj is the function value of the second optimization target, log is a logarithmic operation, i is the iteration number of the optimization algorithm, IL_max is the maximum insertion rate, c is a specified constant, and R is the reflection circle radius.

[0046] The reflection circle radius satisfies the following condition:

[0047] R = |S ii |;

[0048] Wherein, S ii is the scattering parameter of the port.

[0049] In step S5, the second optimization result is determined.

[0050] If the determination result meets the performance index of the port network, the optimization is ended.

[0051] If the determination result does not satisfy the performance index of the port network, the following step is performed.

[0052] In step S6, the impedance matching circuit of the port network is adjusted according to the second optimization result, and after the adjustment is completed, steps S3 to S5 are repeated until the determination result satisfies the performance index of the port network.

[0053] The impedance matching circuit of the port network is composed of the impedance matching circuit required to be added to each port.

[0054] Fig. 2 is a simple flowchart of the impedance matching optimization method in the embodiment. The first step is to load the snp file to obtain the S parameter information of the port network, and then to filter according to the frequency range. The second step is to preliminarily determine the impedance matching circuit (capacitance, inductance) required to be added to each port according to the Smith chart without adding any matching. The third step is to traverse each port: taking the reflection circle radius corresponding to each port as the optimization target, the BFGS algorithm is used for optimization, and the optimization result is recorded. The fourth step is to participate in optimization of all ports: taking the optimization result of each port as the initial value, taking the insertion and reflection circle radius in the passband as the optimization target, and using the BFGS algorithm to obtain the final optimization result. The fifth step is to judge whether the requirement is met: if yes, the optimization is ended; if no, the impedance matching circuit of the port is adjusted according to the optimization result, and the third step, the fourth step and the fifth step are repeated until it is judged that the requirement is met.

[0055] Compared with the related art, the impedance matching optimization method in the embodiment optimizes the impedance matching of the port network by taking the reflection circle radius of the scattering parameter of the port as the optimization target, so that the smaller the reflection circle radius, the better the insertion loss, return loss and VSWR of the port network, and the calculation method of the reflection circle radius is simple, which can reduce the calculation complexity of the optimization, speed up the optimization, and because the calculation process does not involve taking the maximum or minimum value, the value of the optimization target is smoother and more continuous, which can reduce the possibility of the optimization falling into a local optimal solution. In addition, the impedance matching optimization method of the present application first determines the impedance matching circuit required to be added to all ports in the port network, so that when a single port is optimized, the number of variables participating in the optimization is reduced, which can improve the optimization speed and quickly obtain the result. After the individual optimization of all ports is completed, the optimization results of all ports are recorded as the optimization variables of all ports to participate in the initial value of the secondary optimization, so as to accelerate the convergence speed of the optimization method.

[0056] The application further provides another embodiment, a surface acoustic wave filter, whose impedance matching values are obtained by the optimization method of impedance matching in the above embodiment. Since the impedance matching values of the surface acoustic wave filter in this embodiment are obtained by the optimization method of impedance matching in the above embodiment, the technical effects achieved by the optimization method of impedance matching in the above embodiment can also be achieved, which will not be described here.

[0057] It should be noted that the various embodiments described above with reference to the drawings are merely intended to illustrate the present application but not to limit the scope of the present application, and those of ordinary skill in the art should understand that modifications or equivalent replacements made to the present application without departing from the spirit and scope of the present application should be covered within the scope of the present application. In addition, unless otherwise indicated by the context, the word in singular form includes the word in plural form, and vice versa. In addition, unless otherwise specified, all or part of any embodiment can be used in combination with all or part of any other embodiment.

Claims

1. A method of optimizing impedance matching, characterized by, The impedance matching optimization method comprises the following steps: Step S1, load the scattering parameter matrix file of the port network to obtain the corresponding scattering parameter information, and filter the scattering parameter information according to the set frequency range; wherein the port network is composed of multiple ports; Step S2, according to the Smith chart of the port network, determine the impedance matching circuit to be added for each port; Step S3, select each port in turn and obtain the scattering parameter of each port, take the reflection circle radius of the scattering parameter of each port as the first optimization target, and use the quasi-Newton method for optimization to obtain the first optimization result of each port; Step S4, take the first optimization result of each port as the initial value, and take the maximum insertion and the reflection circle radius of the scattering parameter of each port in the set frequency range as the second optimization target, and use the quasi-Newton method for optimization again to obtain the second optimization result; Step S5, determine the second optimization result: if the determination result meets the performance index of the port network, end the optimization.

2. The method of impedance matching optimization of claim 1, wherein, In step S5, if the determination result does not meet the performance index of the port network, the following steps are performed; Step S6, adjust the impedance matching circuit of the port network according to the second optimization result, and repeat steps S3 to S5 after the adjustment is completed until the determination result meets the performance index of the port network; wherein the impedance matching circuit of the port network is composed of the impedance matching circuit to be added for each port.

3. The method of optimization of impedance matching according to claim 2, characterized in that, In step S2, the impedance matching circuit to be added for each port comprises: series capacitor or / and inductor, or / and, parallel capacitor or / and inductor.

4. The method of impedance matching optimization of claim 1, wherein, In step S3, the second optimization target satisfies the following condition: obj=logi*IL_max+c*R; Wherein, obj is the function value of the second optimization target, log is the logarithm operation, i is the iteration number of the optimization algorithm, IL_max is the maximum insertion rate, c is a specified constant, and R is the reflection circle radius.

5. The method of impedance matching optimization of claim 4, wherein, The reflection circle radius satisfies the following condition: R = |S ii |; where S ii is the scattering parameter of the port.

6. A surface acoustic wave filter, characterized by, The impedance matching value of the surface acoustic wave filter is obtained by the impedance matching optimization method according to any one of claims 1 to 5.

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