Optimization method of impedance matching and surface acoustic wave filter
By taking the radius of the scattering parameter of the port as the optimization goal, combined with the quasi-Newtonian method and impedance matching circuit adjustment, the problems of slow impedance matching optimization speed and local optimal solution in the existing technology are solved, and faster optimization speed and Better performance metrics.
Patent Information
- Application Number
- CN202411168164.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-08-23
- Publication Date
- 2024-12-27
- Estimated Expiration
- 2044-08-23
AI Technical Summary
The impedance matching optimization method in the prior art affects the optimization speed, resulting in an increase in the possibility of optimization falling into a local optimal solution, and the optimization convergence speed is slow, especially when the number of ports and network ports is large.
The reflection circle radius of the scattering parameters of the port is used as the optimization goal, and the quasi-Newtonian method is optimized, and the impedance matching circuit is adjusted according to the optimization results, so as to gradually improve the smooth continuity and convergence speed of the optimization results.
By reducing the calculation complexity and value discontinuity of optimization targets, reducing optimization variables, improving optimization speed and convergence speed, reducing the possibility of local optimal solutions, and achieving better interpolation loss, echo and standing wave Compare indicators.
Smart Images
Figure CN118677394B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of filters, and in particular to an optimization method for impedance matching of a port network and a surface acoustic wave filter. Background Art
[0002] In the design and production of surface acoustic wave filters (also known as SAW filters), parasitic inductance and capacitance are inevitably encountered, which will lead to poor performance such as insertion loss, echo and ripple in the passband. By constructing appropriate impedance matching at each port of the surface acoustic wave filter, the performance degradation caused by parasitic inductance and capacitance can be offset. The specific value of impedance matching is obtained through optimization methods.
[0003] The optimization method in related technologies is to optimize based on electrical performance indicators such as standing wave ratio (also known as VSWR), echo and insertion loss (also known as IL). For example, when design tools optimize fixed impedance matching circuit structures, they use electrical performance indicators such as standing wave ratio, echo and insertion loss as optimization targets.
[0004] Among them, the calculation formula of the standing wave ratio is relatively complex and time-consuming, so it will affect the speed of optimization. At the same time, when the standing wave ratio is used as the optimization target, it is also necessary to take the maximum value in a certain frequency range. This method will cause the value of the optimization target to be not smooth and continuous, so it will increase the possibility of the optimization falling into the local optimal solution. In addition, the impedance matching does not support the function of providing initial values. When the number of ports in the port network is large, the number of optimization variables will increase, which will lead to a slower convergence speed of the optimization. Among them, the calculation formula of the standing wave ratio is as follows:
[0005] ;
[0006] in, is the S parameter matrix . Summary of the invention
[0007] In view of the deficiencies of the above-mentioned related technologies, the present invention proposes a new impedance matching optimization method and a surface acoustic wave filter to solve the problem that the impedance matching optimization method in the related technology will affect the optimization speed, increase the possibility of the optimization falling into a local optimal solution, and cause the optimization method to converge slowly.
[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions:
[0009] In a first aspect, the present invention provides a method for optimizing impedance matching, which comprises the following steps:
[0010] Step S1, loading a scattering parameter matrix file of a port network, obtaining corresponding scattering parameter information, and screening the scattering parameter information according to a set frequency range; wherein the port network is composed of a plurality of ports;
[0011] Step S2: Determine the impedance matching circuit to be added to each port according to the Smith chart of the port network;
[0012] Step S3, selecting each of the ports in turn and obtaining the scattering parameters of each port, taking the reflection circle radius of the scattering parameters of each port as the first optimization target, and optimizing using the quasi-Newton method to obtain a first optimization result for each port;
[0013] Step S4, taking the first optimization result of each port as an initial value, and taking the maximum insertion loss within a set frequency range and the reflection circle radius of the scattering parameter of each port as a second optimization target, and performing optimization again using the quasi-Newton method to obtain a second optimization result;
[0014] Step S5: Determine the second optimization result: if the determination result meets the performance index of the port network, end the optimization.
[0015] Preferably, in step S5, if the determination result does not meet the performance index of the port network, the following steps are performed;
[0016] Step S6, adjusting the impedance matching circuit of the port network according to the second optimization result, and repeating 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 that needs to be added to each port.
[0017] Preferably, in step S2, the impedance matching circuit to be added to each port includes: a capacitor or / and an inductor connected in series, or / and,
[0018] Capacitors and / or inductors connected in parallel.
[0019] Preferably, in step S3, the second optimization objective satisfies the following conditions:
[0020] ；
[0021] in, is the function value of the second optimization objective, is the logarithmic operation, is the number of iterations of the optimization algorithm, is the maximum insertion loss, is the specified constant, is the reflection circle radius.
[0022] Preferably, the reflection circle radius satisfies the following conditions:
[0023] ;
[0024] in, is the scattering parameter of the port.
[0025] In a second aspect, the present invention provides a surface acoustic wave filter, the impedance matching value of which 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 invention 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. In this way, the smaller the reflection circle radius, the better the indicators such as insertion loss, echo and standing wave ratio of the port network, and the simple calculation method of the reflection circle radius can be used to reduce the calculation complexity of the optimization and make the optimization speed faster. Since the calculation process will not take the maximum or minimum value, the value of the optimization target will be smoother and 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 invention first determines the impedance matching circuits that need to be added to all ports in the port network. In this way, when optimizing a single port, the variables involved in the optimization will be reduced, which can improve the optimization speed and quickly obtain results. After completing the individual optimization of all ports, the optimization results of all ports are recorded as the initial values of the optimization variables of all ports participating in the secondary optimization, thereby accelerating the convergence speed of the optimization method. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The present invention will be described in detail below in conjunction with the accompanying drawings. The above and other aspects of the present invention will become clearer and easier to understand through the detailed description made in conjunction with the following drawings. In the accompanying drawings:
[0028] Figure 1 A schematic flow chart of the steps of an impedance matching optimization method provided by an embodiment of the present invention.
[0029] Figure 2 A simplified flowchart of an impedance matching optimization method provided by an embodiment of the present invention. DETAILED DESCRIPTION
[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present application; the terms used in the specification of the application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "including" and "having" and any variations thereof in the specification and claims of the present application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of the present application or the above-mentioned drawings are used to distinguish different objects, not to describe a specific order.
[0031] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.
[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0033] An embodiment of the present invention provides an impedance matching optimization method, which includes the following steps:
[0034] Step S1, loading a scattering parameter matrix file of a port network, obtaining corresponding scattering parameter information, and screening the scattering parameter information according to a set frequency range.
[0035] Among them, the scattering parameter matrix file is referred to as the snp file; the scattering parameter information is referred to as the S parameter information. The S parameters are continuously distributed according to the frequency, but the impedance matching optimization method in this embodiment only needs the S parameters within the set frequency range. Therefore, it is necessary to screen the scattering parameter information according to the set frequency range to obtain the required S parameters.
[0036] The port network consists of a plurality of ports.
[0037] Step S2: Determine the impedance matching circuit that needs to be added to each port according to the Smith chart of the port network.
[0038] Among them, the Smith chart is referred to as the Smith chart; the impedance matching circuit that needs to be added to each port is determined by an experienced RF engineer, which is equivalent to a preliminary determination.
[0039] The impedance matching circuit that needs to be added to each port includes: a capacitor or / and an inductor connected in series, or / and, a capacitor or / and an inductor connected in parallel. That is, the impedance matching circuit that needs to be added to each port is a capacitor or multiple capacitors, an inductor or multiple inductors, or a combination of capacitors and inductors, and can be set in series or in parallel, or in a series plus parallel setting.
[0040] Step S3, selecting each of the ports in turn and obtaining the scattering parameters of each port, taking the reflection circle radius of the scattering parameters of each port as the first optimization target, and optimizing using the quasi-Newton method to obtain the first optimization result of each port.
[0041] Among them, taking multiple ports as an example, after selecting port i, the scattering parameters of the corresponding port can be obtained ;by The reflection circle radius is taken as the optimization target, and the quasi-Newton method is used for optimization, then the optimization result of port i can be obtained, which is used as the initial value for the next optimization. After the optimization of port i is completed, the remaining ports are repeated in sequence until all ports are optimized, and the optimization results of all ports are recorded as the initial value for the next optimization.
[0042] Step S4, taking the first optimization result of each port as the initial value, and taking the maximum insertion loss within the set frequency range and the reflection circle radius of the scattering parameter of each port as the second optimization target, and using the quasi-Newton method to perform optimization again to obtain the second optimization result.
[0043] Wherein, the second optimization objective satisfies the following conditions:
[0044] ；
[0045] in, is the function value of the second optimization objective, is the logarithmic operation, is the number of iterations of the optimization algorithm, is the maximum insertion loss, is the specified constant, is the reflection circle radius.
[0046] The reflection circle radius meets the following conditions:
[0047] ;
[0048] in, is the scattering parameter of the port.
[0049] Step S5: Determine the second optimization result.
[0050] If the determination result satisfies the performance index of the port network, the optimization is terminated.
[0051] If the determination result does not meet the performance index of the port network, the following steps are performed;
[0052] Step S6: adjusting the impedance matching circuit of the port network according to the second optimization result, and repeating steps S3 to S5 after the adjustment is completed, until the determination result meets the performance index of the port network.
[0053] The impedance matching circuit of the port network is composed of the impedance matching circuit that needs to be added to each port.
[0054] Figure 2 The following is a simplified flowchart of the impedance matching optimization method in this embodiment. The first step is to load the snp file to obtain the S parameter information of the port network, and then screen it according to the frequency range; the second step is to preliminarily determine the impedance matching circuit (capacitor, inductor) to be added to each port according to the Smith chart without any matching; the third step is to traverse each port: take the reflection circle radius corresponding to each port as the optimization target, use the quasi-Newton algorithm (BFGS) for optimization, and record the optimization results; the fourth step is for all ports to participate in the optimization: take the optimization result of each port as the initial value, take the insertion loss and reflection circle radius in the passband as the optimization target, and use the quasi-Newton algorithm to optimize to obtain the final optimization result; the fifth step is to determine whether the requirements are met: if yes, the optimization is over; if not, adjust the impedance matching circuit of the port according to the optimization result, and repeat the third, fourth and fifth steps until it is determined that the requirements are met.
[0055] Compared with the related art, the impedance matching optimization method in this 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. In this way, the smaller the reflection circle radius, the better the indicators such as insertion loss, echo and standing wave ratio of the port network, and the simple calculation method of the reflection circle radius can be used to reduce the calculation complexity of the optimization and make the optimization speed faster. Since the calculation process will not take the maximum or minimum value, the value of the optimization target will be smoother and continuous, which can reduce the possibility of the optimization falling into the local optimal solution. In addition, the impedance matching optimization method of the present invention first determines the impedance matching circuits that need to be added to all ports in the port network. In this way, when optimizing a single port, the variables involved in the optimization will be reduced, which can improve the optimization speed and quickly obtain results. After completing the individual optimization of all ports, the optimization results of all ports are recorded as the initial values of the optimization variables of all ports participating in the secondary optimization, thereby accelerating the convergence speed of the optimization method.
[0056] The present invention also provides another embodiment, a surface acoustic wave filter, whose impedance matching value is obtained by the impedance matching optimization method in the above embodiment. Since the impedance matching value of the surface acoustic wave filter in this embodiment is obtained by the impedance matching optimization method in the above embodiment, it can also achieve the technical effect achieved by the impedance matching optimization method in the above embodiment, and will not be described in detail here.
[0057] It should be noted that the various embodiments described above with reference to the accompanying drawings are only used to illustrate the present invention rather than to limit the scope of the present invention. Those skilled in the art should understand that any modification or equivalent substitution of the present invention without departing from the spirit and scope of the present invention should be included within the scope of the present invention. In addition, unless otherwise indicated by the context, words appearing in the singular include the plural form, and vice versa. In addition, unless otherwise specified, all or part of any embodiment may be used in combination with all or part of any other embodiment.
Claims
1. An impedance matching optimization method, characterized in that: The impedance matching optimization method comprises the following steps: Step S1, loading a scattering parameter matrix file of a port network, obtaining corresponding scattering parameter information, and screening the scattering parameter information according to a set frequency range; wherein the port network is composed of a plurality of ports; Step S2: Determine the impedance matching circuit to be added to each port according to the Smith chart of the port network; Step S3, selecting each of the ports in turn and obtaining the scattering parameters of each port, taking the reflection circle radius of the scattering parameters of each port as the first optimization target, and optimizing using the quasi-Newton method to obtain a first optimization result for each port; Step S4, taking the first optimization result of each port as an initial value, and taking the maximum insertion loss within a set frequency range and the reflection circle radius of the scattering parameter of each port as a second optimization target, and performing optimization again using the quasi-Newton method to obtain a 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 impedance matching optimization method according to claim 1, characterized in that: In step S5, if the determination result does not meet the performance index of the port network, the following steps are performed; Step S6, adjusting the impedance matching circuit of the port network according to the second optimization result, and repeating 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 that needs to be added to each port.
3. The impedance matching optimization method according to claim 2, characterized in that: In step S2, the impedance matching circuit to be added to each port includes: a capacitor or / and an inductor connected in series, or / and, Capacitors and / or inductors connected in parallel.
4. The impedance matching optimization method according to claim 1, characterized in that: In step S3, the second optimization objective satisfies the following conditions: ； in, is the function value of the second optimization objective, is the logarithmic operation, is the number of iterations of the optimization algorithm, is the maximum insertion loss, is the specified constant, is the reflection circle radius.
5. The impedance matching optimization method according to claim 4, characterized in that: The reflection circle radius meets the following conditions: ； in, is the scattering parameter of the port.
6. A surface acoustic wave filter, characterized in that: 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.