W-band filter design method and system based on parallel coupling microstrip structure

Abstract

The invention provides a W-band filter design method and system based on a parallel coupling micro-strip structure, and the method comprises the steps: designing a filter through employing the parallel coupling micro-strip structure, and carrying out the analysis and calculation of the filter through employing odd-even mode excitation; the characteristic admittance of each parallel microstrip line is obtained by using the relationship between the odd-even mode characteristic impedance of the coupled microstrip line and the characteristic admittance of the equivalent admittance converter, and then the characteristic impedance of the input / output end open circuit 1 / 4 wavelength microstrip line is calculated according to the characteristic admittance; and performing modeling and performance parameter simulation on the filter in the HFSS software, and adjusting the initial physical size until the performance index meets the requirement. According to the invention, the parallel coupling structure of the microstrip line is optimized, the efficient filtering performance in the W wave band is realized, the size and insertion loss of the filter are effectively reduced, and the frequency selectivity and the out-of-band rejection capability are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of high-frequency wireless communication and radar systems, and in particular to a W-band filter design method and system based on a parallel coupled microstrip structure. Background Art

[0002] With the rapid development of wireless communication and radar technology, low-frequency spectrum resources are almost exhausted, and the development of high-frequency bands has become a new direction of technological development. Among them, the W band is widely used in high-frequency wireless communication and radar systems due to its large working bandwidth, large information carrying capacity and high precision, and has received extensive attention from scholars at home and abroad.

[0003] In order to ensure the quality of W-band radiation signals, W-band filters are required to filter out stray signals in the signal. Traditional W-band filters are large in size, have high insertion loss, and poor frequency selectivity, and cannot be directly applied. In response to the current problems, a parallel coupled microstrip structure is proposed. By adjusting the width, spacing, length and other parameters of the microstrip line, filtering in a specific frequency range can be achieved. However, the performance of the W-band filter directly designed using this method is poor and needs further improvement and optimization.

[0004] Patent application document CN119029514A discloses a WLAN frequency band channel selection narrowband high-order filter, design method and electronic device, the filter includes: an input port, an output port and a resonator composed of more than five microstrip lines; the first end microstrip line of the resonator is connected to the input port, the microstrip lines in the resonator are connected in series in sequence, and the end microstrip line of the resonator is connected to the output port; the resonator is used to perform out-of-band suppression processing on the original signal received by the input port to generate a filtered signal, and output the filtered signal through the output port; the out-of-band frequency band signal outside the preset working frequency band of the original signal is suppressed by the out-of-band suppression processing to obtain a filtered signal with out-of-band suppression exceeding a preset attenuation threshold. However, this patent cannot completely solve the existing technical problems, nor can it meet the needs of the present invention. Summary of the invention

[0005] In view of the defects in the prior art, the object of the present invention is to provide a W-band filter design method and system based on a parallel coupled microstrip structure.

[0006] The W-band filter design method based on the parallel coupled microstrip structure provided by the present invention comprises:

[0007] Step 1: Determine the center frequency, relative bandwidth, order, in-band ripple, and out-of-band suppression of the filter according to the requirements of the communication system or radar system;

[0008] Step 2: Design the filter using a parallel coupled microstrip structure and analyze and calculate the filter using odd and even mode excitation;

[0009] Step 3: Using the relationship between the odd-mode and even-mode characteristic impedances of the coupled microstrip lines and the characteristic admittance of their equivalent admittance converters, the characteristic admittances of each parallel microstrip line are obtained, and then the characteristic impedances of the open-circuit 1 / 4 wavelength microstrip lines at the input and output ends are calculated based on the characteristic admittances;

[0010] Step 4: Use ADS software to input the microstrip line dielectric material parameters, center frequency, and odd-even characteristic impedance, and comprehensively obtain the physical dimensions of each parallel microstrip line and the open-circuit 1 / 4 wavelength microstrip line at the input and output ends. Model the filter and simulate the performance parameters in HFSS software, and adjust the initial physical dimensions until the performance indicators meet the requirements;

[0011] Step 5: Use the adjusted physical dimensions to make a filter, use high-frequency materials as the filter substrate, and introduce capacitors and inductors into the circuit to optimize the filter performance. Use instruments to test the filter performance.

[0012] Preferably, step 2 includes: according to the design indicators of the bandpass filter, a parallel coupled microstrip structure is adopted to divide the arbitrarily excited coupled microstrip line into two symmetrical excitation calculations, one is equal-amplitude in-phase voltage excitation, called even-mode excitation; the other is equal-amplitude reverse voltage excitation, called odd-mode excitation; through the Green's function method, the conformal transformation method, or using the tools in the microwave circuit design software ADS and HFSS, the even-mode and odd-mode characteristic impedances are calculated to analyze the transmission characteristics of the coupled microstrip line.

[0013] Preferably, under symmetrical excitation, the characteristics of the coupled microstrip line are obtained through even-mode and odd-mode parameters. The specific process is: first determine the structural parameters of the coupled line: including the width of the conduction strip, the spacing between the two conduction strips, the distance between the two ground plates, and the dielectric constant of the filling medium; secondly calculate the even-mode and odd-mode characteristic impedances; solve according to the excitation conditions: under even-mode excitation, the electric field distribution of the coupled line is symmetrical, and the even-mode characteristic impedance is used to describe its transmission characteristics; under odd-mode excitation, the electric field distribution of the coupled line is antisymmetrical, and the odd-mode characteristic impedance is used to describe its transmission characteristics; according to specific excitation conditions, including voltage amplitude and phase, solve the transmission parameters of the coupled line, including attenuation and phase delay.

[0014] Preferably, step 3 comprises: using the relationship between the odd-mode characteristic impedance Z0 of the coupled microstrip line and the characteristic admittance Y0 of its equivalent admittance converter, analyzing the odd-mode characteristic impedance of two open-circuit 1 / 4 wavelength coupled microstrip lines at the input and output ends of the filter, and the relationship between the two is:

[0015]

[0016] Among them, Z 0e is the odd-mode characteristic impedance; Z 0o is the even-mode characteristic impedance; J0 is the inverter constant.

[0017] Preferably, step 4 includes: establishing a corresponding mathematical model according to the structure and excitation conditions of the coupled microstrip line; setting boundary conditions according to the actual situation of the problem; solving the mathematical model using finite element method, boundary element method or analytical method to obtain the distribution of electric and magnetic fields and corresponding transmission parameters; and verifying the correctness and accuracy of the results by comparing the calculated results with the experimental results or theoretical expected values.

[0018] The W-band filter design system based on the parallel coupled microstrip structure provided by the present invention comprises:

[0019] Module M1: Determine the center frequency, relative bandwidth, order, in-band ripple, and out-of-band suppression of the filter according to the requirements of the communication system or radar system;

[0020] Module M2: Design filters using parallel coupled microstrip structures and analyze and calculate filters using odd and even mode excitation;

[0021] Module M3: Utilize the relationship between the odd-even mode characteristic impedance of the coupled microstrip line and the characteristic admittance of its equivalent admittance converter to obtain the characteristic admittance of each parallel microstrip line, and then calculate the characteristic impedance of the open-circuit 1 / 4 wavelength microstrip line at the input and output ends based on the characteristic admittance;

[0022] Module M4: Using ADS software, input the microstrip line dielectric material parameters, center frequency, and odd-even characteristic impedance, and comprehensively obtain the physical dimensions of each parallel microstrip line and the open-circuit 1 / 4 wavelength microstrip line at the input and output ends. Model the filter and simulate the performance parameters in HFSS software, and adjust the initial physical dimensions until the performance indicators meet the requirements;

[0023] Module M5: Use the adjusted physical dimensions to make the filter, use high-frequency materials as the filter substrate, and introduce capacitors and inductors into the circuit to optimize the filter performance. Use instruments to test the filter performance.

[0024] Preferably, the module M2 includes: according to the design indicators of the bandpass filter, a parallel coupled microstrip structure is adopted to divide the coupled microstrip line of any excitation into two symmetrical excitation calculations, one is equal-amplitude in-phase voltage excitation, called even-mode excitation; the other is equal-amplitude reverse voltage excitation, called odd-mode excitation; through the Green's function method, the conformal transformation method, or using the tools in the microwave circuit design software ADS and HFSS, the even-mode and odd-mode characteristic impedances are calculated to analyze the transmission characteristics of the coupled microstrip line.

[0025] Preferably, under symmetrical excitation, the characteristics of the coupled microstrip line are obtained through even-mode and odd-mode parameters. The specific process is: first determine the structural parameters of the coupled line: including the width of the conduction strip, the spacing between the two conduction strips, the distance between the two ground plates, and the dielectric constant of the filling medium; secondly calculate the even-mode and odd-mode characteristic impedances; solve according to the excitation conditions: under even-mode excitation, the electric field distribution of the coupled line is symmetrical, and the even-mode characteristic impedance is used to describe its transmission characteristics; under odd-mode excitation, the electric field distribution of the coupled line is antisymmetrical, and the odd-mode characteristic impedance is used to describe its transmission characteristics; according to specific excitation conditions, including voltage amplitude and phase, solve the transmission parameters of the coupled line, including attenuation and phase delay.

[0026] Preferably, the module M3 comprises: using the relationship between the odd-mode characteristic impedance Z0 of the coupled microstrip line and the characteristic admittance Y0 of its equivalent admittance converter, analyzing the odd-mode characteristic impedance of two open-circuit 1 / 4 wavelength coupled microstrip lines at the input and output ends of the filter, and the relationship between the two is:

[0027] Z 0e =Z0[1+J0 / Y0+(J0 / Y0) 2 ]

[0028] Z 0o =Z0[1-J0 / Y0+(J0 / Y0) 2 ]

[0029] Among them, Z 0e is the odd-mode characteristic impedance; Z 0o is the even-mode characteristic impedance; J0 is the inverter constant.

[0030] Preferably, the module M4 includes: establishing a corresponding mathematical model according to the structure and excitation conditions of the coupled microstrip line; setting boundary conditions according to the actual situation of the problem; solving the mathematical model using the finite element method, boundary element method or analytical method to obtain the distribution of electric and magnetic fields and corresponding transmission parameters; and verifying the correctness and accuracy of the results by comparing the calculated results with the experimental results or theoretical expected values.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention designs a W-band filter design method based on a parallel coupled microstrip structure, realizes the size parameter design and performance index verification of the parallel coupled microstrip structure. The filter designed using this method has the advantages of small size, low insertion loss, high frequency selectivity and strong out-of-band suppression capability, and can effectively filter out stray signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0034] Figure 1 A schematic diagram of the size parameters of the parallel coupled microstrip structure filter described in the present invention;

[0035] Figure 2 This is a HFSS simulation model diagram of the parallel coupled microstrip structure filter described in the present invention;

[0036] Figure 3 This is a diagram of HFSS performance index simulation results of the parallel coupled microstrip structure filter described in the present invention;

[0037] Figure 4 This is a diagram showing actual test results of the parallel coupled microstrip structure filter described in the present invention. DETAILED DESCRIPTION

[0038] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0039] Embodiment 1:

[0040] The present invention provides a W-band filter design method based on a parallel coupled microstrip structure, comprising the following steps:

[0041] Step S1: According to the requirements of high-frequency wireless communication or radar systems, when analyzing whether the filter meets the system requirements, it is necessary to clarify the design indicators of the filter, such as center frequency, bandwidth, passband attenuation, out-of-band suppression, and input and output impedance. These indicators will directly guide the subsequent design steps. The requirements for various performance indicators, the symbols of various parameters and their physical meanings are as follows:

[0042] f1, f2: cut-off frequency, indicating the upper and lower cut-off frequencies of the bandpass filter with a loss of 3dB on both sides of the passband;

[0043] f0: filter center frequency, which is the middle value of the passband range of the bandpass filter and can be expressed as the cutoff frequency f0 = (f1 + f2) / 2;

[0044] L Ar : In-band ripple, which describes the flatness of the insertion loss in the passband and can be expressed as the difference between the maximum and minimum values;

[0045] L: Out-of-band suppression, which indicates the attenuation degree of the filter on out-of-band interference signals;

[0046] Z0: input and output transmission line characteristic impedance;

[0047] FBW: Relative bandwidth, which is the ratio of the filter bandwidth to the center frequency, FBW = (f2-f1) / f0.

[0048] Step S2: According to the design index of the bandpass filter, a parallel coupled microstrip structure is adopted to divide the coupled microstrip line of any excitation into two symmetrical excitation calculations, one is equal amplitude in-phase voltage excitation, called even mode excitation, and the other is equal amplitude reverse voltage excitation, called odd mode excitation; in order to analyze the transmission characteristics of the coupled microstrip line, it is necessary to calculate its even mode and odd mode characteristic impedance. This can usually be done by methods such as Green's function method and conformal transformation method. In practical applications, tools in microwave circuit design software (such as ADS, HFSS, etc.) can also be used to calculate these parameters. Under symmetrical excitation, the characteristics of the coupled microstrip line can be obtained by even mode and odd mode parameters. The specific calculation steps are as follows: first determine the structural parameters of the coupled line: including the width of the conduction strip, the spacing between the two conduction strips, the distance between the two ground plates, and the dielectric constant of the filling medium; secondly calculate the even mode and odd mode characteristic impedance: use the above-mentioned Green's function method, conformal transformation method or microwave circuit design software to calculate the even mode and odd mode characteristic impedance. Solve according to the excitation conditions: Under even-mode excitation, the electric field distribution of the coupled line is symmetrical, and the even-mode characteristic impedance can be used to describe its transmission characteristics; under odd-mode excitation, the electric field distribution of the coupled line is antisymmetric, and the odd-mode characteristic impedance can be used to describe its transmission characteristics. According to the specific excitation conditions (such as voltage amplitude, phase, etc.), the transmission parameters of the coupled line (such as attenuation, phase delay, etc.) can be solved;

[0049] Step S3: Using the relationship between the odd-mode and even-mode characteristic impedance Z0 of the coupled microstrip line and the characteristic admittance Y0 of its equivalent admittance converter, the odd-mode and even-mode characteristic impedances of the two open-circuited 1 / 4 wavelength coupled microstrip lines at the input and output ends of the filter are analyzed. The relationship between the two is:

[0050] Z 0e =Z0[1+J0 / Y0+(J0 / Y0) 2 ]

[0051] Z 0o =Z0[1-J0 / Y0+(J0 / Y0) 2 ]

[0052] Among them, Z 0e is the odd-mode characteristic impedance; Z 0o is the even-mode characteristic impedance; J0 is the inverter constant.

[0053] Step S4: To solve the two-dimensional static field boundary value problem, it is necessary to consider factors such as the structural parameters of the coupled microstrip line, the dielectric constant of the filling medium, and the excitation conditions. The specific steps are as follows: 1) Establish a mathematical model: Establish a corresponding mathematical model based on the structure and excitation conditions of the coupled microstrip line. 2) Set boundary conditions: Set appropriate boundary conditions according to the actual situation of the problem. 3) Solve the mathematical model: Use appropriate numerical methods (such as finite element method, boundary element method, etc.) or analytical methods to solve the mathematical model and obtain the distribution of electric and magnetic fields and the corresponding transmission parameters. 4) Verify the results: Verify the correctness and accuracy of the results by comparing the calculated results with the experimental results or theoretical expectations.

[0054] To complete the transmission characteristics analysis of parallel coupled lines, 1) First, it is necessary to clarify the goal of the analysis, that is, to understand the transmission characteristics of parallel coupled lines, including their frequency response, attenuation characteristics, phase characteristics, etc. 2) In order to analyze the transmission characteristics of parallel coupled lines, it is necessary to establish a corresponding mathematical model. This usually involves the distribution of electric and magnetic fields and their interactions. In the case of parallel coupled lines, it can be regarded as a symmetrical two-port network, and the odd-even mode analysis method is used to simplify the analysis process. 3) Perform odd-even mode analysis. Under odd-mode excitation, the electric field distribution of the coupled line is antisymmetric. At this time, the coupled line can be regarded as two independent transmission lines, but their voltages and currents are in antiphase. By solving the odd-mode characteristic impedance, the transmission characteristics of the coupled line under odd-mode excitation can be understood; under even-mode excitation, the electric field distribution of the coupled line is symmetrical. At this time, the coupled line can be regarded as a single transmission line, and its voltage and current are in phase. By solving the even-mode characteristic impedance, the transmission characteristics of the coupled line under even-mode excitation can be understood. 4) Characteristic impedance is an important parameter to describe the transmission characteristics of transmission lines. For parallel coupled lines, it is necessary to calculate their odd-mode and even-mode characteristic impedances separately. This usually involves complex electromagnetic field calculations, but tools in microwave circuit design software (such as ADS, HFSS, etc.) can be used to assist in the calculation. 5) Frequency response is an important indicator to describe the transmission characteristics of transmission lines at different frequencies. For parallel coupled lines, it is necessary to analyze their attenuation, phase and other characteristics at different frequencies. This can be achieved through measurement or simulation. 6) Finally, it is necessary to verify the correctness and accuracy of the analysis results. This can be achieved by comparing with experimental results or with other theoretical expected values. If there is a large difference between the analysis results and the experimental results or theoretical expected values, it may be necessary to review factors such as mathematical models, calculation methods or experimental conditions.

[0055] Step S5: Use simulation software such as ADS and HFSS to simulate and calculate the filter microstrip size parameters and the main performance indicators of the filter. The symbols and physical meanings of the filter parallel coupled microstrip size parameters are as follows:

[0056] Y0: open circuit 1 / 4 wavelength microstrip line characteristic impedance;

[0057] W n : The right width of the n-1th parallel microstrip line and the left width of the nth parallel microstrip line;

[0058] s n : The distance between the n-1th parallel microstrip line and the nth parallel microstrip line;

[0059] l n : The length of the right side of the n-1th parallel microstrip line and the left side of the nth parallel microstrip line.

[0060] Embodiment 2:

[0061] The technical problem to be solved by the present invention is to provide a W-band filter design method based on a parallel coupled microstrip structure, which uses the parallel coupled microstrip structure to reduce the volume of the filter and improve the frequency selectivity of the filter. By reasonably designing the microstrip line parameters and introducing suitable components, the insertion loss of the filter is reduced and the out-of-band suppression of the filter is improved. The specific implementation of the method is achieved by the following steps:

[0062] Step 1: Determine the filter’s center frequency f0, relative bandwidth FBW, order n, and in-band ripple L according to the requirements of the communication system or radar system. Ar and out-of-band suppression L;

[0063] Step 2: Design the filter using a parallel coupled microstrip structure, and analyze and calculate the filter using odd and even mode excitation;

[0064] Step 3: Using the relationship between the odd-even mode characteristic impedance of the coupled microstrip line and the characteristic admittance Y0 of its equivalent admittance converter, the characteristic admittance of each parallel microstrip line is obtained. Then, the characteristic impedance of the open-circuit 1 / 4 wavelength microstrip line at the input and output ends is calculated based on the characteristic admittance to obtain J j,j+1 / Y0、(Z0e)j,j +1 、(Z0o)j,j +1 (j=0, 1, 2, 3, ...);

[0065] Step 4: Use ADS software to input the microstrip line dielectric material parameters, center frequency, and odd-even characteristic impedance, and synthesize the physical dimensions W of each parallel microstrip line and the open-circuit 1 / 4 wavelength microstrip line at the input and output ends. n 、s n , l n ;

[0066] Step 5: Use the physical dimensions calculated in step 4 to model the filter and simulate the performance parameters in HFSS software, and adjust the initial physical dimensions according to the insufficient performance parameters until the performance indicators meet the requirements;

[0067] Step 6. Use the adjusted physical dimensions to make a filter, use low-loss high-frequency materials as the filter substrate, and introduce appropriate capacitors, inductors and other components into the circuit to optimize the filter performance, and use instruments to test the filter performance.

[0068] Those skilled in the art know that, in addition to implementing the system, device and its various modules provided by the present invention in a purely computer-readable program code, it is entirely possible to implement the same program in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers and embedded microcontrollers by logically programming the method steps. Therefore, the system, device and its various modules provided by the present invention can be considered as a hardware component, and the modules included therein for implementing various programs can also be considered as structures within the hardware component; the modules for implementing various functions can also be considered as both software programs for implementing the method and structures within the hardware component.

[0069] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A W-band filter design method based on a parallel coupled microstrip structure, characterized in that: include: Step 1: Determine the center frequency, relative bandwidth, order, in-band ripple, and out-of-band suppression of the filter according to the requirements of the communication system or radar system; Step 2: Design the filter using a parallel coupled microstrip structure and analyze and calculate the filter using odd and even mode excitation; Step 3: Using the relationship between the odd-mode and even-mode characteristic impedances of the coupled microstrip lines and the characteristic admittance of their equivalent admittance converters, the characteristic admittances of each parallel microstrip line are obtained, and then the characteristic impedances of the open-circuit 1 / 4 wavelength microstrip lines at the input and output ends are calculated based on the characteristic admittances; Step 4: Use ADS software to input the microstrip line dielectric material parameters, center frequency, and odd-even characteristic impedance, and comprehensively obtain the physical dimensions of each parallel microstrip line and the open-circuit 1 / 4 wavelength microstrip line at the input and output ends. Model the filter and simulate the performance parameters in HFSS software, and adjust the initial physical dimensions until the performance indicators meet the requirements; Step 5: Use the adjusted physical dimensions to make a filter, use high-frequency materials as the filter substrate, and introduce capacitors and inductors into the circuit to optimize the filter performance. Use instruments to test the filter performance.

2. The W-band filter design method based on parallel coupled microstrip structure according to claim 1, characterized in that: The step 2 comprises: according to the design index of the bandpass filter, a parallel coupled microstrip structure is adopted to divide the coupled microstrip line of any excitation into two symmetrical excitation calculations, one is equal amplitude and same phase voltage excitation, called even mode excitation; the other is equal amplitude and reverse voltage excitation, called odd mode excitation; through the Green's function method, the conformal transformation method, or using the tools in the microwave circuit design software ADS and HFSS, the even mode and odd mode characteristic impedances are calculated to analyze the transmission characteristics of the coupled microstrip line.

3. The W-band filter design method based on parallel coupled microstrip structure according to claim 2, characterized in that: Under symmetrical excitation, the characteristics of the coupled microstrip line are obtained through even-mode and odd-mode parameters. The specific process is: first determine the structural parameters of the coupled line: including the width of the conduction strip, the spacing between the two conduction strips, the distance between the two ground plates, and the dielectric constant of the filling medium; secondly calculate the even-mode and odd-mode characteristic impedances; solve according to the excitation conditions: under even-mode excitation, the electric field distribution of the coupled line is symmetrical, and the even-mode characteristic impedance is used to describe its transmission characteristics; under odd-mode excitation, the electric field distribution of the coupled line is antisymmetric, and the odd-mode characteristic impedance is used to describe its transmission characteristics; according to the specific excitation conditions, including voltage amplitude and phase, solve the transmission parameters of the coupled line, including attenuation and phase delay.

4. The W-band filter design method based on parallel coupled microstrip structure according to claim 1, characterized in that: The step 3 includes: using the relationship between the odd-mode and even-mode characteristic impedance Z0 of the coupled microstrip line and the characteristic admittance Y0 of its equivalent admittance converter, analyzing the odd-mode and even-mode characteristic impedances of two open-circuited 1 / 4 wavelength coupled microstrip lines at the input and output ends of the filter, and the relationship between the two is: Z 0e =Z0[1+J0 / Y0+(J0 / Y0) 2 ] Z 0o =Z0[1-J0 / Y0+(J0 / Y0) 2 ] Among them, Z 0e is the odd-mode characteristic impedance; Z 0o is the even-mode characteristic impedance; J0 is the inverter constant.

5. The W-band filter design method based on parallel coupled microstrip structure according to claim 1, characterized in that: The step 4 includes: establishing a corresponding mathematical model according to the structure and excitation conditions of the coupled microstrip line; setting boundary conditions according to the actual situation of the problem; solving the mathematical model using the finite element method, boundary element method or analytical method to obtain the distribution of electric and magnetic fields and corresponding transmission parameters; and verifying the correctness and accuracy of the results by comparing the calculated results with the experimental results or theoretical expected values.

6. A W-band filter design system based on a parallel coupled microstrip structure, characterized in that: include: Module M1: Determine the center frequency, relative bandwidth, order, in-band ripple, and out-of-band suppression of the filter according to the requirements of the communication system or radar system; Module M2: Design filters using parallel coupled microstrip structures and analyze and calculate filters using odd and even mode excitation; Module M3: Utilize the relationship between the odd-even mode characteristic impedance of the coupled microstrip line and the characteristic admittance of its equivalent admittance converter to obtain the characteristic admittance of each parallel microstrip line, and then calculate the characteristic impedance of the open-circuit 1 / 4 wavelength microstrip line at the input and output ends based on the characteristic admittance; Module M4: Using ADS software, input the microstrip line dielectric material parameters, center frequency, and odd-even characteristic impedance, and comprehensively obtain the physical dimensions of each parallel microstrip line and the open-circuit 1 / 4 wavelength microstrip line at the input and output ends. Model the filter and simulate the performance parameters in HFSS software, and adjust the initial physical dimensions until the performance indicators meet the requirements; Module M5: Use the adjusted physical dimensions to make the filter, use high-frequency materials as the filter substrate, and introduce capacitors and inductors into the circuit to optimize the filter performance. Use instruments to test the filter performance.

7. The W-band filter design system based on parallel coupled microstrip structure according to claim 6, characterized in that: The module M2 includes: according to the design indicators of the bandpass filter, a parallel coupled microstrip structure is adopted to divide the coupled microstrip line of any excitation into two symmetrical excitation calculations, one is equal-amplitude in-phase voltage excitation, called even-mode excitation; the other is equal-amplitude reverse voltage excitation, called odd-mode excitation; through the Green's function method, the angle-conformal transformation method, or using the tools in the microwave circuit design software ADS and HFSS, the even-mode and odd-mode characteristic impedances are calculated to analyze the transmission characteristics of the coupled microstrip line.

8. The W-band filter design system based on parallel coupled microstrip structure according to claim 7, characterized in that: Under symmetrical excitation, the characteristics of the coupled microstrip line are obtained through even-mode and odd-mode parameters. The specific process is: first determine the structural parameters of the coupled line: including the width of the conduction strip, the spacing between the two conduction strips, the distance between the two ground plates, and the dielectric constant of the filling medium; secondly calculate the even-mode and odd-mode characteristic impedances; solve according to the excitation conditions: under even-mode excitation, the electric field distribution of the coupled line is symmetrical, and the even-mode characteristic impedance is used to describe its transmission characteristics; under odd-mode excitation, the electric field distribution of the coupled line is antisymmetric, and the odd-mode characteristic impedance is used to describe its transmission characteristics; according to the specific excitation conditions, including voltage amplitude and phase, solve the transmission parameters of the coupled line, including attenuation and phase delay.

9. The W-band filter design system based on parallel coupled microstrip structure according to claim 6, characterized in that: The module M3 includes: using the relationship between the odd-even mode characteristic impedance Z0 of the coupled microstrip line and the characteristic admittance Y0 of its equivalent admittance converter, analyzing the odd-even mode characteristic impedance of two open-circuit 1 / 4 wavelength coupled microstrip lines at the input and output ends of the filter, and the relationship between the two is: Z 0e =Z0[1+J0 / Y0+(J0 / Y0) 2 ] Z 0o =Z0[1-J0 / Y0+(J0 / Y0) 2 ] Among them, Z 0e is the odd-mode characteristic impedance; Z 0o is the even-mode characteristic impedance; J0 is the inverter constant.

10. The W-band filter design system based on parallel coupled microstrip structure according to claim 6, characterized in that: The module M4 includes: establishing a corresponding mathematical model according to the structure and excitation conditions of the coupled microstrip line; setting boundary conditions according to the actual situation of the problem; solving the mathematical model using the finite element method, boundary element method or analytical method to obtain the distribution of electric and magnetic fields and corresponding transmission parameters; and verifying the correctness and accuracy of the results by comparing the calculated results with the experimental results or theoretical expected values.

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