BIC-based sensitivity-adjustable waveguide resonant cavity complex dielectric constant measuring device and application thereof

Abstract

The invention discloses a BIC-based sensitivity-adjustable waveguide resonant cavity complex dielectric constant measuring device and application thereof, and belongs to the technical field of microwave device engineering. The method solves the problem that an existing measurement method is difficult to effectively characterize a medium of which the loss tangent crosses multiple orders of magnitude. Based on the waveguide resonant cavity structure, the system symmetry is broken through controlling the offset of the resonant cavity, so that the BIC is degraded into the quasi-BIC. And by utilizing the characteristic of high quality factor of the quasi-BIC, the variation range of the quality factor of the quasi-BIC stretches across a plurality of orders of magnitude by controlling the degradation degree of the quasi-BIC, so that the flexible regulation and control of the complex dielectric constant measurement sensitivity are realized, a medium of which the loss tangent stretches across a plurality of orders of magnitude can be effectively represented, and the application value is relatively high.

Description

Technical Field

[0001] The invention relates to a BIC-based sensitivity-adjustable waveguide resonant cavity complex dielectric constant measuring device and application thereof, belonging to the technical field of microwave device engineering. Background Art

[0002] The dielectric constant is a key parameter that characterizes the electromagnetic properties of materials. Its accurate measurement is crucial to fields such as materials science, electronic engineering, biomedicine, and chemical engineering. Accurate measurement of the loss tangent is particularly critical when evaluating the insulation and dielectric properties of materials and their stability in high-frequency applications. The loss tangent not only affects the dielectric loss of the material, but is also directly related to the operating frequency of electronic equipment, signal transmission quality, and the energy efficiency ratio of the system. Therefore, dielectric constant measurement technology that can accurately measure the loss tangent is crucial to promoting the advancement of materials science and improving equipment performance.

[0003] At present, dielectric constant measurement technology has made certain progress, including capacitance method, free space method, resonant cavity method and transmission reflection method. These technologies can provide relatively accurate measurement results under specific conditions. However, with the rapid development of materials science and electronic engineering, the requirements for measurement technology are getting higher and higher. Existing measurement technologies often have certain limitations when facing many media with loss tangents spanning multiple orders of magnitude. A single method performs well when measuring high loss tangent media, but is not sensitive or accurate enough when measuring low loss tangent media. In short, when measuring dielectric loss, it is difficult for existing technologies to take into account the sensitivity, accuracy and measurement range of the measurement, which makes it difficult to meet diverse measurement needs in practical applications.

[0004] These limitations not only restrict the in-depth study of material properties, but also affect the optimization of electronic device design and the improvement of performance. Therefore, developing a measurement technology that can effectively characterize a wide range of loss tangents has important scientific significance and application value. This can not only promote technological progress in related fields, but also provide strong technical support for the research and development of new materials and the improvement of existing material performance.

[0005] As a special resonance, bound states in the continuum (BIC) have an infinite quality factor in theory, thus achieving perfect energy localization. Due to the high localization of the electromagnetic field of BIC, the interaction between electromagnetic waves and matter is greatly enhanced, making it have important application potential in sensor design, quantum computing and photonics.

[0006] In practical applications, pure BIC is difficult to achieve, but through perturbation means, such as changing the geometry of the resonant cavity or the material properties, BIC can be degenerated into quasi-BIC. Although quasi-BIC is not a completely localized mode, it still has an extremely high quality factor, which makes them more practical and flexible in practical systems and provides a new way for the design of high-performance electromagnetic devices. Summary of the invention

[0007] The present invention aims to solve the problem that the single dielectric constant measuring device currently cannot effectively characterize the medium whose loss tangent spans multiple orders of magnitude, and provides a BIC-based sensitivity adjustable waveguide resonant cavity complex dielectric constant measuring device and its application.

[0008] The technical method of the present invention:

[0009] One of the purposes of the present invention is to provide a BIC-based sensitivity adjustable waveguide resonant cavity complex dielectric constant measurement device, the device comprises a rectangular waveguide 1, a rectangular parallelepiped resonant cavity 2, a coupling slit 3, a transition waveguide 4 and a wave-to-wave converter 5; the coupling slit 3 is located above the center of the rectangular waveguide 1; the rectangular waveguide 1 and the rectangular parallelepiped resonant cavity 2 are coupled through the coupling slit 3; the rectangular parallelepiped resonant cavity 2 can move longitudinally along the rectangular waveguide 1; the transition waveguide 4 is used to connect the rectangular waveguide 1 and the wave-to-wave converter 5.

[0010] It is further defined that the internal rectangular cross-section size of the rectangular metal waveguide 1 is a1×b1, and the internal length is c1, which is used to generate an eigenmode with the electric field direction along the z direction.

[0011] It is further defined that the inner cavity size of the rectangular parallelepiped resonant cavity 2 is a2×b2×c2, which is used to generate an eigenmode with an electric field intensity along the y or z direction.

[0012] It is further defined that the coupling slit 3 is located above the rectangular waveguide 1 and is used to introduce coupling between the eigenmodes of the rectangular waveguide 1 and the cuboid resonant cavity 2 to form a BIC.

[0013] It is further defined that the offset distance of the center of the rectangular parallelepiped resonant cavity 2 relative to the coupling slit 3 is d.

[0014] The second object of the present invention is to provide a method for using the above-mentioned BIC-based sensitivity adjustable waveguide resonant cavity complex dielectric constant measurement device, specifically using the resonant cavity method to test and obtain the dielectric constant and loss tangent of the filling medium.

[0015] It is further defined that the above-mentioned BIC-based sensitivity adjustable waveguide resonant cavity complex dielectric constant measurement device can be applied to material dielectric constant measurement, radio frequency circuit, antenna or wireless communication system panel complex dielectric constant measurement.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The present invention is based on a waveguide resonant cavity structure. By adjusting the offset distance of the center of the rectangular resonant cavity relative to the coupling slit and adjusting the degree of BIC degeneration to quasi-BIC, the sensitivity of the sensor can be adjusted to achieve effective characterization of the complex dielectric constant of the medium whose loss tangent spans multiple orders of magnitude.

[0018] (2) The present invention measures the relative dielectric constant and loss tangent of the material to be measured based on the electromagnetic resonance in the rectangular parallelepiped resonant cavity, thereby avoiding background signal interference and improving measurement accuracy.

[0019] (3) The present invention utilizes the high quality factor characteristic of quasi-BIC to further improve the measurement accuracy. In theory, according to the physical property that the quality factor of quasi-BIC can be infinite, the loss tangent of the material to be measured can achieve arbitrarily high measurement accuracy.

[0020] (4) The present invention uses a rectangular waveguide and a rectangular parallelepiped resonant cavity as a measurement system, which has the advantages of simple design, low preparation difficulty and low manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] in:

[0023] Figure 1 A schematic diagram of the structure of a BIC-based sensitivity-adjustable waveguide resonant cavity complex dielectric constant measurement device provided by the present invention;

[0024] Figure 2 Schematic diagram of rectangular waveguide structure;

[0025] Figure 3 It is a schematic diagram of the rectangular resonant cavity structure;

[0026] Figure 4 It is a schematic diagram of the combination of rectangular waveguide and rectangular parallelepiped resonant cavity;

[0027] Figure 5 The transmission spectrum of an embodiment of the present invention when there is no material to be tested;

[0028] Figure 6 This is an internal electric field diagram of an embodiment of the present invention when d=0 mm and there is no material to be tested;

[0029] Figure 7 This is an internal electric field diagram of an embodiment of the present invention when d=20 mm and there is no material to be tested;

[0030] Figure 8 The transmission spectrum corresponding to the test of the material to be tested with lossless media of different relative dielectric constants when d=5 mm is shown in one embodiment of the present invention;

[0031] Fig. 9 A kinetic diagram of an embodiment of the present invention;

[0032] Fig.10 is a schematic diagram of an equivalent circuit of an embodiment of the present invention;

[0033] Fig.11 The corresponding transmission spectra for the medium with relative permittivity equal to 2 and different loss tangents at d = 13 mm;

[0034] Fig.12 The corresponding transmission spectra for the dielectric constant equal to 2 and different loss tangents when d = 16 mm;

[0035] Fig.13 The figure shows the comparison between the measurement results of this method and the transmission reflection method.

[0036] In the figure, 1- rectangular waveguide, 2- rectangular parallelepiped resonant cavity, 3- coupling slit, 4- transition waveguide, 5- wave converter. DETAILED DESCRIPTION

[0037] The technical solution of the present invention will be described below in conjunction with the accompanying drawings. 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.

[0038] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0039] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0040] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0041] Example:

[0042] Reference Figure 1 , Figure 2 , Figure 3 and Figure 4 The structure of this embodiment is specifically described. This embodiment provides a BIC-based sensitivity-adjustable waveguide resonant cavity complex dielectric constant measurement device operating at a frequency of 2.60 to 3.95 GHz, the device comprising a rectangular waveguide 1, a rectangular resonant cavity 2, a coupling slit 3, a transition waveguide 4 and a wave-to-wave converter 5; wherein the coupling slit 3 is located above the center position of the rectangular metal waveguide 1; the rectangular waveguide 1 and the rectangular resonant cavity 2 are coupled through the coupling slit 3; the rectangular resonant cavity 2 can move longitudinally along the rectangular waveguide 1; and the transition waveguide 3 is used to connect the rectangular waveguide 1 and the wave-to-wave converter 5.

[0043] In this arrangement, due to the coupling effect of the coupling slit 3, the system composed of the rectangular waveguide 1 and the rectangular parallelepiped resonant cavity 2 is used to form a quasi-BIC, forming a resonance valley on the transmission spectrum; the rectangular parallelepiped resonant cavity 2 is filled with the material to be tested, resulting in changes in the frequency and amplitude of the resonance valley, thereby achieving accurate characterization of the dielectric constant and loss tangent of the material to be tested.

[0044] In this embodiment, the specific structural parameters are as follows: a1=72.14mm, b1=8.60mm, c1=200mm, l1=72.14mm, s1=1mm, a2=72.14mm, b2=10mm, c2=70mm.

[0045] In order to facilitate the description of this embodiment, the formation of the BIC in the complex dielectric constant measurement device of the waveguide resonant cavity with adjustable sensitivity based on BIC is described here. Figure 5The transmission spectra of the measuring device in the BIC mode and the quasi-BIC mode without the material to be tested are shown. For the waveguide resonant cavity structure coupled by the coupling slit 3, its transmission spectrum will have a resonance valley near the eigenfrequency of the eigenmode of the rectangular resonant cavity 1. When the offset distance d of the center of the rectangular resonant cavity 2 with respect to the coupling slit 3 changes, the frequency and bandwidth of the resonance valley will change. When d takes a specific value, the bandwidth of the resonance valley is zero, and the quasi-BIC is transformed into BIC.

[0046] Based on the above parameters, the eigenfrequencies of the eigenmodes in the cuboid resonant cavity 2 are named from low to high starting from 1. The offset distance of the cuboid resonant cavity 2 corresponding to the formation of the BIC of the i-th mode is d i , d i =c3*(2N-i-1) / 2i mm, where N is a positive integer ranging from 1 to i. For the BIC of the corresponding eigenmode, d is d i The farther away, the greater the degree to which BIC degenerates into quasi-BIC.

[0047] For mode 1, when d = 0 mm, the resonance valley disappears, such as Figure 5 As shown, at this time, the resonance is transformed into BIC, and the electric field in the resonant cavity is distributed in antiphase with respect to the coupling slit 3, as shown in Figure 6 As shown; when d≠0 mm, the symmetry of the system is broken, resulting in a resonance valley on the transmission spectrum, such as Figure 5 As shown, at this time, BIC degenerates into quasi-BIC, and the electric field in the resonant cavity is distributed in phase, as shown in Figure 7 shown.

[0048] In order to observe more resonance valleys, based on the above structure, when d = 5 mm, modes 1 to 6 are all degenerated into quasi-BIC. Different dielectric constant materials are filled into the rectangular metal resonant cavity 2 to obtain the corresponding transmission spectra as shown in Figure 8 As shown, the frequency of the resonance valley changes with the change of ε1 of the material to be tested, so the sensor is designed based on this.

[0049] The above structure can be abstracted into a two-terminal network, such as Fig. 9 The arrow direction is the transmission direction of electromagnetic energy. The dynamic equation of this system is written as follows

[0050]

[0051] |s - >=C|s + >+D|a>

[0052] Where ω0 represents the natural angular frequency of the resonant cavity. 1 / τ eand 1 / τ0 represent the radiation loss and dielectric loss of electromagnetic energy in the rectangular resonant cavity, respectively. |a> represents the amplitude of the mode in the resonant cavity and is normalized so that<a|a> Represents the energy in the resonant cavity. |S + 〉 and |S - > represent the amplitudes of the modes of the input and output systems, respectively, and they are also normalized so that + |S + > and - |S - > represents the energy flowing into and out of the system from the port. C is the direct scattering matrix between the two ports of the waveguide. In the selected frequency range, the closed resonant cavity supports only one eigenmode, so |a> is a one-dimensional column vector.

[0053] By solving the equation, the scattering parameters of the system can be obtained as

[0054]

[0055] Therefore, we can get the transmission coefficient as

[0056]

[0057] By equating the above structure to Fig.10 The resonant circuit shown has a resonant frequency of The material to be tested in the resonant cavity is equivalent to the material filled in the parallel plate capacitor. According to the positive correlation between the capacitance value C1 in the parallel plate capacitor and the relative dielectric constant ε1 of the filling medium, the resonance frequency f and the transmission coefficient amplitude S can be obtained by integrating and simplifying the parameters. 21 The relationship between the relative dielectric constant ε1 and the loss tangent tanδ of the material to be tested

[0058]

[0059] Where ε1 is the relative dielectric constant of the medium, tanδ is the loss tangent of the medium, f is the frequency of the resonance valley (GHz), S 21 is the transmission coefficient, m, n, 1 / τ e are the fitting coefficients.

[0060] According to the formula tanδ=S 21 / τ e πf(1-S 21 ) can be obtained, for the material to be tested with the same ε1, when S 21 When the same, 1 / τ e It is directly proportional to tanδ. Therefore, by adjusting 1 / τ e ​​Thus affecting the sensitivity of S21 to tanδ. According to calculations, mode 2 transforms into BIC at d = 17.5 mm. Filling the rectangular metal resonant cavity 2 with a material with a relative dielectric constant equal to 2, when d = 13 mm, the sensitivity is low. The transmission response can effectively characterize materials with larger loss tangents, such as Fig.11 As shown; when d = 16 mm, the sensitivity is higher, and the transmission response can effectively characterize materials with smaller loss tangent, such as Fig.12 shown.

[0061] The relative dielectric constant and loss tangent of the resin and nylon samples were obtained by the transmission reflection method. The relative dielectric constants of the two samples were in the range of 2 to 3. In this embodiment, when the material to be tested is placed in the resonant cavity, for the medium with a relative dielectric constant in the range of 2 to 3, the resonance frequency of mode 2 falls within the operating frequency range of the wave converter 5. Therefore, mode 2 is used to measure the dielectric constant and loss tangent of the material to be tested. The fitting parameters for mode 2 are m=4.6140, n=0.3075, 1 / τ e =0.2292.

[0062] The relative dielectric constant and loss tangent of 3D printed resin and nylon samples were tested by this method and compared with the measurement results of the transmission reflection method. Fig.13 As shown, the results show that the relative dielectric constant and loss tangent of the samples measured by the two methods are basically consistent, and the error is caused by defects in the manufacturing of the device. The experimental results verify the effectiveness of the above device.

[0063] Finally, it should be noted that:

[0064] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0065] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, a person skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A BIC-based sensitivity adjustable waveguide resonant cavity complex dielectric constant measurement device, characterized in that: It includes a rectangular waveguide, a rectangular parallelepiped resonant cavity, a coupling slit, a transition waveguide and a wave-to-wave converter; wherein the coupling slit is located above the rectangular waveguide; the rectangular waveguide and the rectangular parallelepiped resonant cavity are coupled through the coupling slit; and the transition waveguide is used to connect the rectangular waveguide and the wave-to-wave converter.

2. The measuring device according to claim 1, characterized in that The rectangular waveguide has an internal rectangular cross-section size of a1×b1 and an internal length of c1, and is used to generate an eigenmode with an electric field direction along the z direction; The inner cavity size of the rectangular parallelepiped resonant cavity is a2×b2×c2, and is used to generate an eigenmode with an electric field intensity along the y or z direction; The coupling slit is located above the rectangular waveguide and is used to introduce coupling between the rectangular waveguide and the eigenmode of the cuboid resonant cavity to form a BIC; The rectangular parallelepiped resonant cavity can move along the y direction of the rectangular waveguide, and the offset distance of the center of the rectangular parallelepiped resonant cavity relative to the coupling slit is d.

3. The measuring device according to claim 1, characterized in that The coupling strength between the rectangular waveguide and the eigenmode of the rectangular parallelepiped resonant cavity is controlled by adjusting the offset distance d of the center of the rectangular parallelepiped resonant cavity with respect to the coupling slit, thereby controlling the degree of BIC degeneration into quasi-BIC and further controlling the measurement sensitivity.

4. A method for measuring the complex dielectric constant of a waveguide resonant cavity with adjustable sensitivity based on BIC, characterized in that: Using the device described in any one of claims 1 to 3, the dielectric constant and loss tangent of the medium are obtained by adopting the resonant cavity method.

5. An application of the BIC-based sensitivity adjustable waveguide resonant cavity complex dielectric constant measurement device according to any one of claims 1 to 3, characterized in that: The device is used for measuring the complex dielectric constant of radio frequency circuits, antennas or wireless communication system panels.

Images