Method and system for realizing bound state on quasi-continuous domain on SIW

Abstract

The invention discloses a method and a system for realizing a bound state on a quasi-continuous domain on a substrate integrated waveguide (SIW), and belongs to the technical field of substrate integrated waveguides. The method comprises the following steps: S1, calculating the cut-off frequency of an SIW and the resonant frequency of an SIW resonant cavity according to design requirements; s2, gradually constructing an SIW resonant cavity laminated structure model and an SIW-SIW resonant cavity laminated structure model in simulation software; s3, setting simulation frequency, boundary conditions and a field monitor; s4, scanning a plurality of parameters to obtain an S curve, and selecting different parameters according to the required bandwidth and amplitude; if the S curve meeting the preset condition does not exist, more parameters are scanned again until the S curve meeting the preset condition is obtained; and S5, adjusting parameters according to the ratio of the required transmission resonance frequency to the maximum resonance half width to realize a bound state on the quasi-continuous domain on the SIW. The quasi-BIC is realized on the SIW, the processing difficulty and the process complexity are reduced, and device miniaturization is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of substrate integrated waveguide, and in particular to a method and system for realizing bound states on a quasi-continuous domain on a SIW. Background Art

[0002] As the front-end design basis of communication systems, microwave filters play a vital role in modern communication systems. Due to its low insertion loss and easy integration, substrate integrated waveguide (SIW) has become the best choice for RF filters. Therefore, the Q value of SIW is one of the important indicators affecting the performance of modern communication systems.

[0003] In recent years, bound states in the continuum (BIC) have attracted much attention due to their infinite lifetime, extending from quantum physics to photonics. It is different from traditional bound states whose frequencies are outside the continuum. It is located in the continuum and maintains the characteristics of perfectly localized electromagnetic waves in the absence of radiation. It coexists with the continuous radiation spectrum without leaking energy. Therefore, ideally, BIC is invisible in the spectrum, that is, the resonance bandwidth is zero and the Q value is infinite.

[0004] Completely ideal BIC is difficult to achieve in experiments. With current experimental technology, people's application research on BIC tends to focus on the field of bound states (quasi-BIC) on the quasi-continuum domain. Quasi-BIC is a collapsed form of BIC, which refers to approximately bound states. Although they are coupled to the radiation mode, the leakage is very small, thus showing a limited but very high Q value. Therefore, introducing quasi-BIC into SIW can greatly improve the Q value of SIW structure and be applied to narrowband filtering, etc.

[0005] In previous research, the realization of BIC on SIW required air as a medium to be filled in the substrate layer of the SIW structure. Although simulation, experiment and theory have perfectly demonstrated the existence of BIC in the SIW-SIW resonant cavity system, the processing and design of the sample is relatively complicated, and the experimental test results are quite different from the simulation results, resulting in the design method being limited to theoretical verification and unable to generate application value. Using air as a lossless medium is difficult to process and the process is complex, which is not conducive to miniaturization. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a method, system and storage medium for realizing bound states on a quasi-continuous domain on a SIW.

[0007] The objective of the present invention is achieved through the following technical solutions: The first aspect of the present invention provides: a method for realizing bound states on a quasi-continuous domain on an SIW, comprising the following steps: S1: Calculate the cutoff frequency of SIW and the resonant frequency of SIW resonant cavity according to design requirements; S2: gradually construct SIW and SIW-SIW resonant cavity stacked structure models in the simulation software; S3: Set simulation frequency, boundary conditions and field monitor; S4: Scan multiple parameters to obtain an S curve, and select different parameters according to the required bandwidth and amplitude; if there is no S curve that meets the preset conditions, rescan more parameters until an S curve that meets the preset conditions is obtained; S5: Adjust the parameters according to the ratio of the required transmission resonance frequency to the maximum half-width of the resonance to realize the bound state on the quasi-continuous domain on the SIW.

[0008] Preferably, the cutoff frequency of the SIW is lower than the resonant frequency of the SIW resonant cavity. The resonant frequency of the SIW resonant cavity is calculated as follows: ; in c is the speed of light in a vacuum; m is the first resonance mode number; n is the second resonance mode number; is the dielectric constant; and is the equivalent width and length of the SIW resonant cavity, calculated using the equivalent formula of the full-wave finite element method: , in L 1. W 1 is the length and width of the SIW resonant cavity; d is the metal via diameter; p is the distance between two adjacent through holes; The cutoff frequency calculation formula of SIW is as follows: , in h is the thickness of the SIW dielectric substrate.

[0009] Preferably, the S2 further comprises the following steps: A SIW structural model is established in the simulation software, and a coplanar waveguide transition structure is added at both ends of the SIW to match the impedance; A coupling gap is opened at the center of the metal layer on the upper surface of the SIW to cut the surface current so that the energy is coupled into the SIW resonant cavity; Build a SIW resonant cavity model above the SIW and set the tunable parametersy , so that the SIW resonant cavity y The value changes along y Axis translation.

[0010] Preferably, the S4 further comprises the following steps: For tunable parameters y Perform a sweep and simulate using a frequency domain solver; Adjust the center offset of the SIW resonant cavity about the symmetry axis of the coupling slot y , to destroy the symmetry protection state in the resonant mode, thereby adjusting the ratio of the transmission resonance frequency to the maximum half-width of the resonance, so that the coupling between the bound state in the SIW resonant cavity and the continuous state in the SIW below is enhanced, and the ability of the SIW resonant cavity to bind energy is weakened.

[0011] Preferably, spectrum analysis and coupled mode theory are used to determine whether a resonance conforms to the quasi-BIC phenomenon.

[0012] Preferably, the simulation software is CST Microwave Studio software.

[0013] The second aspect of the present invention provides: a system for realizing bound states on a quasi-continuous domain on an SIW, which is used to realize any of the above methods for realizing bound states on a quasi-continuous domain on an SIW, comprising: A calculation module, used to calculate the cutoff frequency of the SIW and the resonant frequency of the SIW resonant cavity according to design requirements; Simulation module, used to gradually build SIW and SIW-SIW resonant cavity stack structure models in the simulation software; set simulation frequency, boundary conditions and field monitors; The curve generation module is used to scan multiple parameters to obtain an S curve, and select different parameters according to the required bandwidth and amplitude; if there is no S curve that meets the preset conditions, more parameters are rescanned until an S curve that meets the preset conditions is obtained; The adjustment module is used to adjust the parameters according to the ratio of the required transmission resonance frequency to the maximum half-width of the resonance to realize the bound state on the quasi-continuous domain on the SIW.

[0014] The third aspect of the present invention provides: a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are loaded and executed by a processor, any of the above-mentioned methods for realizing bound states on a quasi-continuous domain on an SIW is implemented.

[0015] The beneficial effects of the present invention are: 1) Quasi-BIC is realized on SIW, and the internal coupling topology of the system is established and deduced using CMT. The resonance characteristics of the coupling slot width can be controlled to select the appropriate quasi-BIC state according to the bandwidth and Q value requirements, which can be applied to narrowband filters or high-Q value sensors, reducing the processing difficulty and process complexity and facilitating the miniaturization of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Flowchart of the method for realizing bound states on quasi-continuous domains on SIW; Figure 2 It is a schematic diagram of SIW structural model; Figure 3 For parameters y Schematic diagram of S parameters after change; Figure 4 Q value varies with parameter y Schematic diagram of the changes; Figure 5 For different y Contour plot of the transmission spectrum at ; Figure 6 is a schematic diagram of electric field distribution; Figure 7 It is a schematic diagram of the topological structure of the stacked SIW; Figure 8 Schematic diagram of reflection curves for different slot widths. DETAILED DESCRIPTION

[0017] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0018] See also Figure 1-Figure 8 The first aspect of the present invention provides: a method for realizing bound states on a quasi-continuous domain on an SIW, comprising the following steps: S1: Calculate the cutoff frequency of SIW and the resonant frequency of SIW resonant cavity according to design requirements; S2: gradually construct SIW and SIW-SIW resonant cavity stacked structure models in the simulation software; S3: Set simulation frequency, boundary conditions and field monitor; S4: Scan multiple parameters to obtain an S curve, and select different parameters according to the required bandwidth and amplitude; if there is no S curve that meets the preset conditions, rescan more parameters until an S curve that meets the preset conditions is obtained; S5: Adjust the parameters according to the ratio of the required transmission resonance frequency to the maximum half-width of the resonance to realize the bound state on the quasi-continuous domain on the SIW.

[0019] In this embodiment, air filling is abandoned, a SIW is printed on the PCB, and a coupling slot is opened on its upper surface to radiate energy to another SIW resonant cavity, forming a SIW-SIW resonant cavity system that produces a quasi-BIC improvement to improve the Q value of the structure.

[0020] In some embodiments, the cutoff frequency of the SIW is lower than the resonant frequency of the SIW resonant cavity. The resonant frequency of the SIW resonant cavity is calculated by the following formula: ; in c is the speed of light in a vacuum; m is the first resonance mode number; n is the second resonance mode number; is the dielectric constant; and is the equivalent width and length of the SIW resonant cavity, calculated using the equivalent formula of the full-wave finite element method: , in L 1. W 1 is the length and width of the SIW resonant cavity; d is the metal via diameter; p is the distance between two adjacent through holes; The cutoff frequency calculation formula of SIW is as follows: , in h is the thickness of the SIW dielectric substrate.

[0021] In this embodiment, the resonant frequency is first determined according to the design requirements. Since SIW is essentially a waveguide structure, its characteristics are equivalent to a high-pass filter, and the SIW resonant cavity is excited by the slot coupling above the SIW. Therefore, it is necessary to ensure that the cutoff frequency of the SIW is lower than the resonant frequency of the SIW resonant cavity. The resonant frequency of the SIW resonant cavity can be calculated by analogy with the rectangular metal resonant cavity.

[0022] Preliminary calculations TE 101 The resonant frequency of the mode is around 4.86 GHz. If you want to get the corresponding resonant frequency, you can substitute any and According to the formula, SIW can be calculated to get the cutoff frequency of the fundamental mode at around 3.62GHz, which is lower than TE 101 The resonant frequency.

[0023] In some embodiments, the S2 further comprises the following steps: A SIW structural model is established in the simulation software, and a coplanar waveguide transition structure is added at both ends of the SIW to match the impedance; A coupling gap is opened at the center of the metal layer on the upper surface of the SIW to cut the surface current so that the energy is coupled into the SIW resonant cavity; Build a SIW resonant cavity model above the SIW and set the tunable parameters y , so that the SIW resonant cavity y The value changes along y Axis translation.

[0024] In this embodiment, the SIW structure model is as follows: Figure 2 As shown, it is composed of two layers of PCB, each layer of dielectric substrate is Rogers 5880 dielectric with a thickness of t = 0.8mm (relative dielectric constant =4.7, loss tangent tanδ=0.022), the metal on both sides is 0.035mm thick copper with a conductivity of 5.8×10 7 The lower layer is a SIW with a coplanar waveguide transition, with a slot opened horizontally in the center of its top to radiate energy to the SIW resonant cavity above it. d is the diameter of the metal via, p is the distance between two adjacent through holes. L 2 and W 2 represent the length and width of SIW respectively. L 1 and W 1 is the length and width of the SIW resonant cavity. The length and width of the coupling slot are L gap and W gap , by adjusting the center offset of the SIW resonant cavity about the symmetry axis of the coupling slot y , in order to achieve the quasi-BIC with maximum Q value, the specific parameters are shown in Table 1.

[0025] Table 1 Variable values ​​(unit: mm) In some embodiments, the S4 further comprises the following steps: For tunable parameters y Perform a sweep and simulate using a frequency domain solver; Adjust the center offset of the SIW resonant cavity about the symmetry axis of the coupling slot y, to destroy the symmetry protection state in the resonant mode, thereby adjusting the ratio of the transmission resonance frequency to the maximum half-width of the resonance, so that the coupling between the bound state in the SIW resonant cavity and the continuous state in the SIW below is enhanced, and the ability of the SIW resonant cavity to bind energy is weakened.

[0026] In this embodiment, y Perform parameter sweep and use frequency domain solver to simulate. When the center of the coupling slot is offset y = 0, the system structure is symmetrical, but its dielectric substrate is not lossless, which causes its internal energy to dissipate in the form of absorption loss. At this time, the resonant cavity mode is a quasi-BIC mode, and its transmission spectrum does not have a peak or depression like the symmetric protection BIC mode, but shows a slight convexity like the Fano resonance. y When the value increases, the amplitude of the resonant cavity increases, the convex phenomenon becomes more obvious, and the Q value decreases. This is due to the adjustment of the center offset of the coupling slot. y The SIW resonant cavity can be made along y The symmetry of the axis is broken, but along x The symmetry of the axis is maintained. However, this perturbation behavior that destroys the inversion symmetry in the structure plane causes the BIC, which was originally protected by symmetry, to produce radiation loss, increase the resonance line width, and transform into a quasi-BIC with high Q, such as Figure 3 As shown in the figure, from the S parameters of the system, it can be seen that the transmission spectrum peak of the system is relatively sharp, and it will have a broad application in high-Q value narrowband filters and sensors in the future.

[0027] The Q mentioned above is the ratio of the transmission resonance frequency ω0 to the maximum half-width of the resonance ∆ω, that is: .according to Figure 3 The Q value of the system can be obtained from the transmission spectrum in (a). Figure 4 As shown, the horizontal axis is different y Value (unit: mm), the vertical axis is Q value. y As the value decreases, Q tends to infinity. k Presentation The attenuation relationship of the function, both BIC and quasi-BIC have this feature.

[0028] The system adjusts the center offset of the SIW resonant cavity about the symmetry axis of the coupling slot. y This operation is to destroy the symmetric protection state in the resonant mode. Therefore, this quasi-BIC belongs to the symmetric protection type BIC. The symmetric protection characteristics are not only shown in the structure and resonant mode, but also in the resonant cavity. y The direction of axis movement also shows symmetry. Figure 5 It shows that when the resonant cavity is yThe axis center zero point, moving in any direction (positive or negative), shows an increase in the resonance line width (the 4.9GHz dark blue area is the bandwidth), and the resonance is the smallest at the center zero point, which is the quasi-BIC point with the maximum Q. When the system structure protection symmetry is broken, the coupling between the bound state in the SIW resonant cavity and the continuous state in the SIW below is enhanced, which weakens the ability of the SIW resonant cavity to bind energy.

[0029] The electric field pattern distribution of the system of the present invention is as follows Figure 6 As shown, y =0.4, the structural symmetry collapses, and different degrees of strong coupling effects induce rapid changes in the electric field in the SIW resonant cavity, that is, y The smaller the value, the larger the amplitude of the electric field tends to be, which also implies that the ability of this system to confine electromagnetic waves is enhanced, that is, the Q value increases.

[0030] In some embodiments, spectrum analysis and coupled mode theory are used to determine whether a resonance conforms to the quasi-BIC phenomenon.

[0031] In this embodiment, judging whether a resonance conforms to the quasi-BIC phenomenon requires not only spectrum analysis but also the use of the coupled mode theory (CMT) as a theoretical tool for discussion. The present invention establishes a CMT topology structure according to the working principle of the stacked SIW. Figure 7 Energy The energy flowing into the SIW resonant cavity from Port 1 is coupled to the resonant cavity through the coupling slot, and the other part flows to Port 2. The energy flowing into the SIW resonant cavity will also flow back to the SIW below, which are recorded as and ,and is the total output of Port2.

[0032] According to the classical CMT proposed in optical resonant cavity, the following dynamic equation can be derived: ,in, κ , d and T are the coupling coefficients between the incident wave and the SIW resonant cavity and between the incident wave and the outgoing wave, respectively; ω0 is the transmission resonance frequency; is the amplitude in the SIW resonant cavity About Time t The differential of and They represent the radiation loss and absorption loss of the system respectively; and the total output wave of port 2 can be written as: ; According to the time inversion rule in Maxwell's equations, we can get the existence of , T =1, so the amplitude in the SIW resonant cavity The expression is as follows: , where ω is the operating frequency, so S 21 It can be expressed as: ; The amplitude and bandwidth of the coupling resonance are determined by the radiation loss and absorption loss. positive correlation, so the present invention adjusts the center offset of the coupling slot y To change the coupling relationship and thus affect .

[0033] From the formula derived from the above coupled mode theory, it can be seen that the resonance bandwidth and amplitude of the resonant cavity of the present invention are given by and Decide, is inherent to the system, thus changing the radiation loss The value of is a direct way to control the resonance characteristics. The excitation source of the upper SIW resonant cavity comes from the SIW coupling below. In the previous section, the characteristics of the symmetry-protected BIC have been demonstrated (by adjusting the center offset of the SIW resonant cavity about the symmetry axis of the coupling slot). y ) to adjust the resonance bandwidth and amplitude.

[0034] In this system, the aperture of the coupling slot is also a key factor affecting the radiation loss. Here, the slot width is W gap The influence of different slot widths on the resonance reflection curve in this system is studied. Figure 8 As shown, with the slot width W gap The resonant frequency of the SIW cavity decreases slightly, and the resonant bandwidth becomes narrower and narrower. This is the difference between different slot widths. W gap The impact of different disturbances on the system resonance. W gap The larger the value, the wider the resonance bandwidth, so the slot width is also one of the important parameters affecting the Q value.

[0035] In summary, based on the characteristics of bound states on the quasi-continuum domain and the derivation of coupled modes, it is obvious that the parameter y and W gapBoth can achieve the regulation of resonance, which is conducive to the future expansion of applications in filters, high-Q sensors, etc. When used as a high-Q sensor, the device is placed in different solutions, and the resonance peaks will show different resonance amplitudes, bandwidths, etc., which can be analyzed according to the algorithm to analyze the dielectric constant, temperature, concentration and other information of the solution.

[0036] In some embodiments, the simulation software is CST Microwave Studio software.

[0037] The second aspect of the present invention provides: a system for realizing bound states on a quasi-continuous domain on an SIW, which is used to realize any of the above methods for realizing bound states on a quasi-continuous domain on an SIW, comprising: A calculation module, used to calculate the cutoff frequency of the SIW and the resonant frequency of the SIW resonant cavity according to design requirements; Simulation module, used to gradually build SIW and SIW-SIW resonant cavity stack structure models in the simulation software; set simulation frequency, boundary conditions and field monitors; The curve generation module is used to scan multiple parameters to obtain an S curve, and select different parameters according to the required bandwidth and amplitude; if there is no S curve that meets the preset conditions, more parameters are rescanned until an S curve that meets the preset conditions is obtained; The adjustment module is used to adjust the parameters according to the ratio of the required transmission resonance frequency to the maximum half-width of the resonance to realize the bound state on the quasi-continuous domain on the SIW.

[0038] The third aspect of the present invention provides: a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are loaded and executed by a processor, any of the above-mentioned methods for realizing bound states on a quasi-continuous domain on an SIW is implemented.

[0039] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A method for realizing bound states on a quasi-continuous domain on an SIW, characterized by: The following steps are involved: S1: Calculate the cutoff frequency of SIW and the resonant frequency of SIW resonant cavity according to design requirements; S2: gradually construct SIW and SIW-SIW resonant cavity stacked structure models in the simulation software; S3: Set simulation frequency, boundary conditions and field monitor; S4: Scan multiple parameters to obtain an S curve, and select different parameters according to the required bandwidth and amplitude; if there is no S curve that meets the preset conditions, rescan more parameters until an S curve that meets the preset conditions is obtained; S5: Adjust the parameters according to the ratio of the required transmission resonance frequency to the maximum half-width of the resonance to realize the bound state on the quasi-continuous domain on the SIW.

2. The method for realizing bound states on a quasi-continuous domain on an SIW according to claim 1, characterized in that: The cutoff frequency of the SIW is lower than the resonant frequency of the SIW resonant cavity. The resonant frequency of the SIW resonant cavity is calculated as follows: ； in c is the speed of light in a vacuum; m is the first resonance mode number; n is the second resonance mode number; is the relative dielectric constant; and is the equivalent width and length of the SIW resonant cavity, calculated using the equivalent formula of the full-wave finite element method: ， in L 1. W 1 is the length and width of the SIW resonant cavity; d is the metal via diameter; p is the distance between two adjacent through holes; The cutoff frequency calculation formula of SIW is as follows: ， in h is the thickness of the SIW dielectric substrate.

3. The method for realizing bound states on a quasi-continuous domain on a SIW according to claim 1, characterized in that: The S2 further comprises the following steps: A SIW structural model is established in the simulation software, and a coplanar waveguide transition structure is added at both ends of the SIW to match the impedance; A coupling gap is opened at the center of the metal layer on the upper surface of the SIW to cut the surface current so that the energy is coupled into the SIW resonant cavity; Build a SIW resonant cavity model above the SIW and set the tunable parameters y , so that the SIW resonant cavity y The value changes along y Axis translation.

4. The method for realizing bound states on a quasi-continuous domain on a SIW according to claim 3, characterized in that: The S4 further comprises the following steps: For tunable parameters y Perform a scan and use the frequency domain solver for simulation; Adjust the center offset of the SIW resonant cavity about the symmetry axis of the coupling slot y , to destroy the symmetry protection state in the resonant mode, thereby adjusting the ratio of the transmission resonance frequency to the maximum half-width of the resonance, so that the coupling between the bound state in the SIW resonant cavity and the continuous state in the SIW below is enhanced, and the ability of the SIW resonant cavity to bind energy is weakened.

5. The method for realizing bound states on a quasi-continuous domain on a SIW according to claim 1, characterized in that: Spectral analysis and coupled mode theory are used to determine whether a resonance conforms to the quasi-BIC phenomenon.

6. The method for realizing bound states on a quasi-continuous domain on a SIW according to any one of claims 1 to 5, characterized in that: The simulation software is CST Microwave Studio software.

7. A system for realizing bound states on a quasi-continuous domain on an SIW, characterized in that: A method for realizing a bound state on a quasi-continuous domain on an SIW as claimed in any one of claims 1 to 6, comprising: A calculation module, used to calculate the cutoff frequency of the SIW and the resonant frequency of the SIW resonant cavity according to design requirements; Simulation module, used to gradually build SIW and SIW-SIW resonant cavity stack structure models in the simulation software; set simulation frequency, boundary conditions and field monitors; The curve generation module is used to scan multiple parameters to obtain an S curve, and select different parameters according to the required bandwidth and amplitude; if there is no S curve that meets the preset conditions, more parameters are rescanned until an S curve that meets the preset conditions is obtained; The adjustment module is used to adjust the parameters according to the ratio of the required transmission resonance frequency to the maximum half-width of the resonance to realize the bound state on the quasi-continuous domain on the SIW.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are loaded and executed by the processor, the method for realizing bound states on a quasi-continuous domain on an SIW as described in any one of claims 1 to 6 is implemented.

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