Resonant cavity, filter based on multi-mode folded substrate integrated waveguide and design method

Abstract

The application provides a resonant cavity, a filter and a design method based on a multi-mode folded substrate integrated waveguide. The design method of the resonant cavity comprises: sequentially stacking five layers of structures of a first metal layer, a first dielectric substrate, a second metal layer, a second dielectric substrate and a third metal layer; forming a metal via array which is distributed in a square shape as a whole, the metal via array penetrating the five layers of structures, thereby forming a SIW resonant cavity between the five layers of structures; folding the second metal layer, the folded second metal layer being a folded layer, and a plurality of metal vias on at least one side of the square being reserved on the folded layer, thereby forming a FSIW resonant cavity between the five layers of structures; and forming a perturbation structure, the perturbation structure being used to perturb degenerate double modes existing in the FSIW resonant cavity, so that the degenerate double modes become non-degenerate modes; wherein the perturbation structure comprises two metal vias penetrating the five layers of structures, the two metal vias being located on one diagonal of the square and being symmetric about the center of the square.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electromagnetic field and microwave technology, in particular to a high-frequency filter, especially to a resonant cavity, a filter and a design method based on a multi-mode folded substrate integrated waveguide. BACKGROUND

[0002] The high-speed development of wireless communication systems cannot be separated from the support of high-performance filters. In the face of the upcoming E5G and 6G era, a bandpass filter (BPF) with low insertion loss (high Q value), high frequency selectivity and miniaturization is one of the current research hotspots.

[0003] In the prior art, the microstrip structure cannot be universally used in the frequency band above 8GHz because it can cause excessive loss at high frequencies. At high frequencies, the substrate integrated waveguide (SIW) structure is generally used to realize the design of the BPF. For the SIW structure of the BPF, single-mode design is mostly used. The single-mode SIW filter is realized by using multiple SIW cavities, and the number of cavities used is consistent with the order of the filter, so there is a problem of excessive size, which is not conducive to the miniaturization of the device. In recent years, although the use of incomplete mode SIW cavities (such as half-mode cavities, quarter-mode cavities, and even eighth-mode cavities) has realized the design of miniaturized BPF, it has also sacrificed the unloaded quality factor (Qu) of the filter and worsened the insertion loss. Worse still, they also have a large radiation loss, which will also lead to poor electromagnetic compatibility, which is not conducive to the development of high-performance wireless communication systems.

[0004] In order to further realize the miniaturization of the device, the prior art has proposed a method of designing a multi-mode SIW BPF. Compared with the single-mode SIW structure, the multi-mode SIW can support multiple resonant modes in one cavity, which is equivalent to multiple single-mode resonators, so it can greatly realize the miniaturization of the device. However, the structure of designing and constructing a multi-mode SIW resonant cavity is a technical difficulty. Therefore, the design of a multi-mode SIW filter is generally common in dual-mode. Compared with the dual-mode SIW, the three-mode and four-mode SIW resonant cavity structure is more in line with the development trend of miniaturization. In the prior art, there are few BPFs that can realize three-mode, four-mode and other SIW structures. Even if the design of a multi-mode structure is realized, it is generally realized by using the traditional mode of the SIW and has the technical problems of being unable to flexibly adjust the transmission pole, poor passband selectivity, poor controllability of the bandwidth, etc. SUMMARY

[0005] The existing multi-mode SIW filter design has the technical problems of non-flexible transmission pole adjustment, poor passband selectivity, poor controllability of bandwidth, and further miniaturization application requirements, and the application provides a resonant cavity, a filter and a design method based on a multi-mode folded substrate integrated waveguide (Folded SIW, FSIW).

[0006] In a first aspect, the application provides a design method of a resonant cavity based on a multi-mode folded substrate integrated waveguide, comprising:

[0007] Stacking the first metal layer, the first dielectric substrate, the second metal layer, the second dielectric substrate and the third metal layer in sequence to form a 5-layer structure;

[0008] Forming a metal via array with a square distribution as a whole, the metal via array penetrating the 5-layer structure to form an SIW resonant cavity between the 5-layer structure;

[0009] Folding the second metal layer, and the folded second metal layer is denoted as a folded layer, and a plurality of metal vias on at least one side of the square are retained on the folded layer, thereby forming an FSIW resonant cavity between the 5-layer structure; it should be noted that the purpose of retaining a plurality of metal vias on at least one side of the square on the folded layer is to ensure that the folded layer and the other four layers can form an SIW resonant cavity, which is a prerequisite for realizing an FSIW resonant cavity.

[0010] Forming a perturbation structure to perturb the degenerate double mode existing in the FSIW resonant cavity to make it a non-degenerate mode; wherein the perturbation structure includes two metal vias penetrating the 5-layer structure, and the two metal vias are located on one diagonal of the square and symmetric about the center of the square. It should be noted that the degenerate double mode existing in the FSIW resonant cavity is changed to a non-degenerate mode by the perturbation structure, which is a preparation for forming a multi-mode BPF later.

[0011] The design method is based on the fact that the folded layer and the other layers can realize an SIW resonant cavity, and different shape structures of the folded layer can be designed as needed to realize an FSIW resonant cavity with multiple modes, which has better design flexibility and freedom.

[0012] Further, a plurality of metal vias on two sides of the square are retained on the folded layer, and the folded layer as a whole has a stepped shape.

[0013] Further, a plurality of metal vias on two sides of the square are retained on the folded layer, and the folded layer as a whole also has a square shape; the perturbation structure further includes a groove line etched on the surface of the folded layer.

[0014] In a second aspect, the present application provides a resonant cavity based on a multi-mode folded substrate integrated waveguide, which is obtained by using any of the design methods provided in the first aspect.

[0015] In a third aspect, the present application provides a design method of a miniaturized filter based on a multi-mode folded substrate integrated waveguide, which forms a resonant cavity based on a multi-mode folded substrate integrated waveguide by using the design method in the first aspect.

[0016] An input port feed line is arranged on the first metal layer along a first reference line direction, and an output port feed line is arranged on the first metal layer along a second reference line direction; wherein the input port feed line and the output port feed line have the same structure, and each include a microstrip line and two coupling slots symmetrical about the microstrip line; and the distance between the microstrip line of the input port feed line and the first reference line and the distance between the microstrip line of the output port feed line and the second reference line are both D in , D in is a number not less than 0; wherein a virtual line segment passing through the center of the square and parallel to two vertical edges thereof respectively serves as the first reference line and the second reference line.

[0017] Further, the coupling slots are L-shaped as a whole.

[0018] Further, the folded layer is three-level stepped as a whole.

[0019] In a fourth aspect, the present application provides a design method of a miniaturized filter based on a multi-mode folded substrate integrated waveguide, which forms a resonant cavity based on a multi-mode folded substrate integrated waveguide by using another design method in the first aspect; an input port feed line is arranged on the first metal layer along a first reference line direction, and an output port feed line is arranged on the first metal layer along a second reference line direction; wherein the input port feed line and the output port feed line have the same structure, and each include a microstrip line and two coupling slots symmetrical about the microstrip line; and the distance between the microstrip line of the input port feed line and the first reference line and the distance between the microstrip line of the output port feed line and the second reference line are both D in , D in is a number not less than 0; wherein a virtual line segment passing through the center of the square and parallel to two vertical edges thereof respectively serves as the first reference line and the second reference line.

[0020] Further, the coupling slots are L-shaped as a whole.

[0021] In a fifth aspect, the present application provides a miniaturized filter based on a multi-mode folded substrate integrated waveguide, which is obtained by using the design methods provided in the third aspect and the fourth aspect.

[0022] The beneficial effects of the present application are as follows:

[0023] (1) The design method provided by the present application can construct a multi-mode FSIW resonant cavity structure. In the case of using a single-cavity SIW, the multi-mode FSIW resonant cavity can excite multiple modes to resonate at similar frequencies, thereby constructing a high-order BPF. Compared with the commonly used single-mode cascading method to construct a high-order BPF in the prior art, while maintaining the high quality factor of the traditional SIW resonant cavity, the overall size of the device is greatly reduced, making it more suitable for the increasingly miniaturized high-speed wireless communication system.

[0024] (2) In the design of the multi-mode FSIW resonant cavity structure, the structure design is used to excite the folded modes TE 1 / 2、0、1 / 2 , TE 1 / 2、0、3 / 2 and TE 3 / 2、0 . At the same operating frequency, the structure size required by such modes is smaller than that required by normal modes. Compared with the structure design in the traditional operating mode, such structure design further realizes the miniaturization of the device.

[0025] (3) In the present application, different structure designs of the folded layer can flexibly excite different operating modes to resonate at similar frequencies, realizing three-mode and four-mode BPF designs. Compared with the multi-mode structure in the prior art, the flexible structure design of the folded layer has more design freedom. Different shapes of the folded layer have multiple size parameters, which can realize the BPF designed by multiple parameter control, and further realize the purposes of controllable bandwidth and adjustable frequency position of the finite frequency transmission zero point. Such design improves the high selectivity of the BPF to a certain extent, and solves the problem that the multi-mode BPF is not easy to control in the prior art.

[0026] (4) In the present application, the metal layer that excites the folded resonant mode is located in the middle of the dielectric substrate, and the top layer and the bottom layer both have metal layers, and the four sides have closed metal vias, forming a self-shielding structure. This structure design can effectively reduce the energy radiation loss under the incomplete operating mode, and makes up for the large energy radiation loss of the SIW band-pass filter operating in the incomplete mode in the prior art. At the same time, such structure has good electromagnetic shielding effect, stronger anti-interference ability and higher power capacity characteristics, and has universality in the microwave and millimeter wave frequency bands, and has strong application value and prospect in the 5G and even future B5G and 6G era.

[0027] (5) The design of the top metal layer of the present application is used to set the feed structure. The feed structure is set in the top metal layer, and the SIW resonator is combined with the 50 Ω microstrip line in the form of the coplanar waveguide, which can make up for the problem that the three-dimensional structure is not easy to integrate with other devices. At the same time, the feed structure can also use the stepped impedance microstrip line to connect the resonant cavity, which is more convenient for impedance matching, so that the overall structure design has more flexibility.

[0028] (6) Based on the design method of the present application, the multi-mode BPF retains the high performance of the SIW structure, and further has the advantages of high selectivity, compact size, limited frequency transmission zero point, and flexible and controllable bandwidth.

[0029] (7) The filter designed in the present application does not need a special dielectric substrate to realize, and can be universally used in the millimeter wave working frequency band, so it can meet the needs of miniaturization, low cost, high frequency wireless radio frequency system, and further improve the market application prospect and value. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The structure diagram of the multi-mode FSIW resonant cavity proposed in the present application is shown in the figure;

[0031] Figure 2 The side structure diagram of the multi-mode FSIW resonant cavity proposed in the present application is shown in the figure;

[0032] Figure 3 The first metal layer plane diagram of the multi-mode FSIW resonant cavity proposed in the present application is shown in the figure;

[0033] Figure 4 The second metal layer plane diagram of the multi-mode FSIW resonant cavity proposed in the present application is shown in the figure;

[0034] Figure 5 The folding layer plane diagram of the multi-mode FSIW resonant cavity proposed in the present application is shown in the figure;

[0035] Figure 6 The second folding layer plane diagram of the multi-mode FSIW resonant cavity proposed in the present application is shown in the figure;

[0036] Figure 7 The simulation and test frequency response curve of example 3 proposed in the present application is shown in the figure;

[0037] Figure 8 The simulation adjustable example of example 3 proposed in the present application is shown in the figure;

[0038] Figure 9 The simulation and fitting frequency response curve and adjustable example of example 4 proposed in the present application are shown in the figure;

[0039] Figure 10Simulation and test frequency response curves for the embodiment 5 proposed by the present application;

[0040] Figure 11 Simulation controllable examples for the embodiment 5 proposed by the present application;

[0041] Figure 12 Simulation and test frequency response curves for the embodiment 6 proposed by the present application;

[0042] Figure 13 Simulation controllable examples for the embodiment 6 proposed by the present application. DETAILED DESCRIPTION

[0043] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0044] Embodiment 1

[0045] The embodiment of the present application provides a resonant cavity based on a multi-mode folded substrate integrated waveguide, and the design process is as follows: in combination with the drawings shown in Figure 1 , Figure 2 and Figure 5 , five layers of layer structures of a first metal layer, a first dielectric substrate, a second metal layer, a second dielectric substrate and a third metal layer are stacked in sequence; a metal via array in a square distribution is formed, the metal via array penetrates the five layers of layer structures, so that a SIW resonant cavity is formed between the five layers of layer structures; the second metal layer is folded, and the folded second metal layer is marked as a folded layer, a plurality of metal vias on two edges of the square are reserved on the folded layer, and the folded layer is in a stepped shape as a whole, as shown in Figure 5 , so that a FSIW resonant cavity is formed between the five layers of layer structures; a perturbation structure is formed, so that the degenerate double mode existing in the FSIW resonant cavity is disturbed by the perturbation structure to become a non-degenerate mode; wherein the perturbation structure includes two metal vias penetrating the five layers of layer structures, and the two metal vias are located on one diagonal of the square and are symmetric about the center of the square.

[0046] Specifically, the folded layer is designed to be in a stepped shape, which can excite a TE 1 / 2、0、1 / 2 mode in the FSIW cavity, and the metal via can split the degenerate modes TE 102 and TE 201 , the FSIW resonant cavity provided by the embodiment can excite TE 102 and TE201 and TE 1 / 2、0、1 / 2 Three modes.

[0047] Embodiment 2

[0048] The embodiment of the present invention provides a resonator based on a multi-mode folded substrate integrated waveguide, and its design process is as follows: Combining Figure 1 , Figure 2 and Figure 6 as shown, stack a total of 5-layer structures including the first metal layer, the first dielectric substrate, the second metal layer, the second dielectric substrate, and the third metal layer in sequence; form a metal through-hole array distributed in a square shape, and the metal through-hole array penetrates through the 5-layer structure, thereby forming a SIW resonator between the 5-layer structures; fold the second metal layer, and denote the folded second metal layer as the folded layer. A number of metal through-holes on two sides of the square are reserved on the folded layer, and the folded layer is also square as a whole, thereby forming a FSIW resonator between the 5-layer structures; form a perturbation structure, thereby using the perturbation structure to perturb the degenerate dual modes existing in the FSIW resonator to make it a non-degenerate mode; wherein, the perturbation structure includes two metal through-holes penetrating through the five-layer structure and a slot line etched on the surface of the folded layer, and the two metal through-holes are located on one diagonal of the square and are symmetric about the center of the square.

[0049] Specifically, designing the overall shape of the folded layer as a square can excite the incomplete mode. The first metal layer and the third metal layer can be regarded as electric walls with respect to the second metal layer, which can effectively reduce the energy radiation loss in the incomplete mode. The FSIW resonator provided in this embodiment can excite TE 1 / 2、0、1 / 2 , TE 1 / 2、0、3 / 2 , TE 3 / 2、0、1 / 2 , TE 102 and TE 201 (or TE 101 ) five modes. Among them, TE 1 / 2、0、3 / 2 , TE 3 / 2、0、1 / 2 and TE 102 [[ID=�6]], TE 201 are respectively a pair of degenerate dual modes. The slot line is used to perturb the TE 1 / 2、0、3 / 2 and TE 3 / 2、0、1 / 2 modes, and the two metal through-holes are used to perturb the TE 102 and TE 201 modes. Among them, as Figure 4 shown, denote the distance between two opposite sides of the square metal through-hole array as L1, and denote the side length of the folded layer as L2. When L2 < L1 / 2, TE 101 replaces TE 201 [[ID=۵2]]as the fundamental mode.

[0050] Preferably, as shown in Figure 6 , the slot line is in the shape of a rectangle as a whole, the length of the rectangular slot line is denoted as L S , and the width is denoted as W S .

[0051] The result achieved by the overall resonant cavity structure is that the resonant frequencies of different modes in the FSIW resonant cavity can be regulated by regulating the relevant size parameters, so that the resonant frequencies are far away from or close to each other, and the order and working frequency required in actual engineering applications are achieved. The application of the resonant cavity can be specifically referred to the following embodiments 4, 5 and 6.

[0052] Embodiment 3

[0053] Based on the FSIW resonant cavity provided in the above embodiment 1, the embodiment of the present application provides a three-mode FSIW cavity structure using TE 102 , TE 201 and TE 1 / 2、0、1 / 2 modes, which realizes a design example of a single-band triplexer filter with three finite frequency transmission zeros, and the design process is as follows: combining Figure 3 and Figure 5 , the resonant cavity based on the multi-mode folded substrate integrated waveguide described in the above embodiment 1 is formed; an input port feed line is arranged on the first metal layer along a first reference line direction, and an output port feed line is arranged on the first metal layer along a second reference line direction; wherein the input port feed line and the output port feed line have the same structure and both include a microstrip line and two coupling slots symmetrical about the microstrip line; and the distance between the microstrip line of the input port feed line and the first reference line and the distance between the microstrip line of the output port feed line and the second reference line are both D in , D in is a number not less than 0; wherein the virtual line segments passing through the center of the square and parallel to two vertical edges thereof respectively serve as the first reference line and the second reference line.

[0054] Specifically, in the present embodiment, as shown in Figure 3 , the coupling slots are in the shape of L as a whole, the width of the coupling slots is denoted as g0, the length of the shorter end of the coupling slots is denoted as g1, the length of the longer end of the coupling slots is denoted as g2, and the width of the microstrip line is denoted as W0. As shown in Figure 5 , the folded layer is in the shape of a three-level ladder as a whole, and the widths of the three levels are denoted as L3, L2 and L4 respectively. By adjusting the size parameters of L2, L3 and L4, the resonant frequency of the TE 1 / 2、0、1 / 2 mode can be changed. By selecting appropriate size parameters, the TE 1 / 2、0、1 / 2 mode can be made to be close to the perturbed TE 102 and TE 201With similar resonant frequencies, an effective passband can be formed. The distance between two opposite sides of the square metal via array is denoted as L1.

[0055] Using g1, g2, and D in And L4 to change the external quality factor to control the passband bandwidth and FTZ S The location.

[0056] Preferably, W0=1.53, g0=0.25, g1=1.3, g2=2.6, D in =1.55, P d =2.4, L1=21.93, L2=7.61, L3=3.8, L4=4.6, all units: mm.

[0057] The dielectric substrate used has the following parameters: relative permittivity 2.2, thickness 0.254 mm, loss tangent 0.0009, and all metal layers are 17 μm thick.

[0058] Figure 7 The results are simulation and actual measurement of the frequency scattering parameters of the bandpass filter under the aforementioned optimized parameter design. Simulation was performed using HFSS software according to the optimized dimensions, and a physical prototype was fabricated and measured using a vector network analyzer. Finally, the S-parameter plot of the bandpass filter is shown below. Figure 7 As shown, the measured results agree well with the simulation results. The measured center frequency... f The in-band insertion loss (IL), loop loss (RL), and 3-dB bandwidth (BW) are 10.18 GHz, 2.33 dB, 16.13 dB, and 327 MHz, respectively. The frequency locations of the finite frequency transmission zeros are 9.77 GHz, 10.39 GHz, and 10.99 GHz, respectively.

[0059] To demonstrate the controllability of the three FTZs positions, the frequency response to changes in dimensional parameters was simulated using software, such as... Figure 8 As shown. Combined with Figure 3 and Figure 8 When D in When the frequency positions of the first and third FTZs change, the second FTZ remains unchanged. (Combined) Figure 5 and Figure 8 When L4 changes, the frequency position of the first FTZ changes slightly, the frequency position of the third FTZ changes more significantly, and the second FTZ remains unchanged; when P d When the frequency positions of the three FTZs are changed, the frequency positions of the three FTZs change slightly. From the above experiments, it is clear that the three FTZs have a certain degree of adjustability. The data also directly demonstrate that the BPF designed using this method has highly selective filtering characteristics.

[0060] Example 4

[0061] Based on the FSIW resonant cavity provided in Embodiment 2 above, this embodiment of the invention provides a method using TE 102 TE 201 and TE 1 / 2、0、3 / 2 A design example of a single-band tripolar filter with three finite-frequency transmission zeros is implemented using a tri-mode FSIW cavity structure. The design process is as follows: [The text then repeats the description of the design process, which is not translated here.] Figure 4 and Figure 6 This forms the resonant cavity based on a multimode folded substrate integrated waveguide as described in Embodiment 2 above; an input port feed line is disposed on the first metal layer along the direction of the first reference line, and an output port feed line is disposed on the first metal layer along the direction of the second reference line; wherein, the input port feed line and the output port feed line have the same structure, both including a microstrip line and two coupling slots symmetrical about the microstrip line; and the distance between the microstrip line of the input port feed line and the first reference line, and the distance between the microstrip line of the output port feed line and the second reference line are both D. in D in The number is not less than 0; wherein, the virtual line segments passing through the center of the square and parallel to the two vertical sides therein are respectively used as the first reference line and the second reference line.

[0062] Specifically, such as Figure 4 As shown, the microstrip lines in the input and output feed lines are connected to the tri-mode SIW cavity using stepped impedance microstrip lines. This structural design is for better impedance matching. The perturbation structure metal vias are located on the diagonal of the proposed FSIW resonant cavity. In this embodiment, as... Figure 4 As shown, the coupling groove is generally L-shaped, and the width of the coupling groove is denoted as g0 ( Figure 4 Not shown in the image, this parameter can be referenced. Figure 3 Let g1 be the length of the shorter end of the coupling slot and g2 be the length of the longer end. Let W0 be the width of the narrower end of the stepped impedance microstrip line and W1 be the width of the wider end.

[0063] Using g1, g2, and D in This is used to change the external quality factor in order to control the passband bandwidth and finite frequency transmission zeros (FTZ). S The location of the FSIW cavity. Specifically, when W1 < 2 mm or W1 > 3.2 mm, the FSIW cavity has a resonant mode TE. 102 TE 201 and TE 1 / 2、0、3 / 2 The three-cavity design.

[0064] Preferably, W0=1.53, W1=1.5, g0=0.25, g1=0.65, g2=2.55, D in =0.55, P d =1.7, L1=21.87, L2=15.1, L S =2.95, W S =0.25, all units: mm.

[0065] The dielectric substrate used has the following parameters: relative permittivity 2.2, thickness 0.254 mm, loss tangent 0.0009, and all metal layers are 17 μm thick.

[0066] Figure 9 (a) shows the simulation and matrix fitting results of the bandpass filter frequency scattering parameters under the above-mentioned optimized parameter design. As shown in the figure, the center frequency... f The values ​​are: 0 = 10 GHz, BW = 360 MHz, RL = 20 dB, and the frequency positions of the three FTZs are 9.34 GHz, 10.25 GHz, and 10.91 GHz. The final fitting results agree well with the simulation results.

[0067] To demonstrate the controllability of the three FTZs positions, the frequency response with varying dimensional parameters was simulated using simulation software (HFSS). Figure 9 As shown in (b), when D in When the value changes, the frequency positions of the first and third FTZs will change, while the frequency position of the second FTZ will remain unchanged. For example... Figure 9 As shown in (c), the frequency position of the third FTZ changes as g2 increases. Figure 9 As shown in (d), when W1 changes, due to TE 3 / 2、0、1 / 2 The periodic excitation results in an additional FTZ. Therefore, when W1 = 1.75 mm, TE 3 / 2、0、1 / 2 Completely suppressed. When W1 selects an appropriate width, TE 3 / 2、0、1 / 2 It will be stimulated. The experimental data above clearly demonstrate that FTZs have high selectivity.

[0068] Example 5

[0069] Based on the FSIW resonant cavity provided in Embodiment 2 above, this embodiment of the invention provides a method using TE 102 TE 201、 TE 1 / 2、0、3 / 2 and TE 3 / 2、0、1 / 2The four-mode FSIW cavity structure of the mode realizes a single-band four-pole filter design example with four finite frequency transmission zero points. Different from the embodiment 4, the mode TE 1 / 2、0、3 / 2 and TE 3 / 2、0、1 / 2 modes are used to design a double-band four-pole filter in the embodiment of the present application. The rest of the design process is the same as that of the embodiment 4, which will not be described here.

[0070] Specifically, the resonances of TE 1 / 2、0、3 / 2 , TE 3 / 2、0、1 / 2 , TE 201 and TE 102 are represented by f1, f2, f3 and f4 respectively. The modes TE 1 / 2、0、3 / 2 and TE 3 / 2、0、1 / 2 are excited to form the first passband, represented by passband 1; the modes TE 201 and TE 10 2 are excited to form the second passband, represented by passband 2. By adjusting the corresponding size parameters, the frequency responses of f1, f2, f3 and f4 can be adjusted to form different double-passband responses, so that three different filters can be designed. The A type is a response with one FTZ below the passband 1, one FTZ above the passband 2, and two FTZs between the passband 1 and the passband 2; the B type is a response with one FTZ below the passband 1, two FTZs above the passband 2, and one FTZ between the passband 1 and the passband 2; the C type is a response with one FTZ below the passband 1, no FTZ above the passband 2, and three FTZs between the passband 1 and the passband 2.

[0071] Preferably, W0=1.53, W1=1.53, g0=0.25, g1=1, g2=3, Din=0.15, P d =3.35, L1=22.33, L2=17.6, L S =2.75, W S =0.25, all in units of mm.

[0072] The medium substrate parameters used are: relative dielectric constant 2.2, thickness 0.254 mm, loss tangent 0.0009, and all metal layer thickness 17 μm.

[0073] Figure 10 is the frequency scattering parameter simulation and measurement results of the bandpass filter under the preferred parameter design described above. According to the preferred size described above, simulation is performed using simulation software (HFSS), and physical processing is performed. A vector network analyzer is used for physical testing. For the passband 1, the measured f BW1, the in-band IL, RL and 3-dB BW1 are 8.705 GHz, 2.8 dB, 17.1 dB and 0.169 MHz, respectively; f BW1 , where f1 represents the center frequency of passband 1, and BW1 represents the bandwidth of passband 1. For passband 2, the measured f BW2 , the in-band IL, RL and 3-dB BW2 are 10.104 GHz, 1.98 dB, 12.64 dB and 276 MHz, respectively; f BW2 , where f2 represents the center frequency of passband 2, and BW2 represents the bandwidth of passband 2. In addition, four FTZs are observed at 8.19 GHz, 8.98 GHz, 9.63 GHz and 10.67 GHz. As can be seen from the figure, under the method of the application, the designed BPF realizes high selectivity of the two passbands and good isolation between the two passbands. As can be seen from the figure, the final measurement results are in good agreement with the simulation results.

[0074] In combination with Figure 6 and Figure 11 , when L2 changes, the center frequency of passband 2 can be kept unchanged, and the center frequency of passband 1 can be freely adjustable. When Ls changes, the bandwidth of passband 1 changes, and the bandwidth of passband 2 remains unchanged. When P d changes, the bandwidths of passband 1 and passband 2 both change. The above experimental data directly show that the proposed dual-band filter has free adjustability in the positions, bandwidths and center frequencies of FTZs. This further shows that the proposed BPF has high selectivity.

[0075] Embodiment 6

[0076] Based on the FSIW resonant cavity provided in Embodiment 2 above, the embodiment of the application provides a single-band four-pole filter design example with four finite frequency transmission zeros using TE 102 , TE 201、 TE 1 / 2、0、3 / 2 and TE 3 / 2、0、1 / 2 modes. Different from Embodiment 5 above, the embodiment of the application uses the folding layer size parameter and the feed line structure parameter to excite f1, f2, f3 and f4 into a passband, forming a single-passband four-pole filter frequency response. The rest of the design process is the same as that of Embodiment 5 above, which will not be repeated here.

[0077] Preferably, W0=1.53, W1=2.35, g0=0.25, g1=0.45, g2=2.3, Din=0.15, P d =3.4, L1=21.9, L2=14.8, L S= 3.57, W S = 0.25, all units: mm.

[0078] The medium substrate parameters used are: relative dielectric constant 2.2, thickness 0.254 mm, loss tangent 0.0009, and thickness of all metal layers 17 μm.

[0079] Figure 12 is the frequency scattering parameter simulation and measurement results of the bandpass filter under the preferred parameter design described above. According to the preferred size described above, simulation is performed using simulation software (HFSS), and a physical object is processed and manufactured, and a vector network analyzer is used to test the physical object. The measured f 0, in-band IL, RL and 3-dB BW are 10.08 GHz, 1.82 dB, 11.78 dB and 458 MHz, respectively. The frequency positions of the four FTZs are 9.54 GHz, 10.33 GHz, 10.38 GHz and 11.93 GHz. It can be seen from Figure 12 that the final measurement results are in good agreement with the simulation results.

[0080] In combination with Figure 4 and Figure 13 , when the value of D in is changed, the frequency positions of the four FTZs are changed. In combination with Figure 6 and Figure 13 , when Ls is changed, the frequency position of the first FTZ is changed; when the value of P d is changed, the frequency positions of the three upper stopband FTZs are changed. These experimental data also directly show that the proposed filter has the advantages of high selectivity, controllable FTZs and bandwidth.

[0081] It can be understood that the design idea proposed in the present application is not limited to the three-mode / four-mode, single / dual-passband BPF based on the proposed two-fold FSIW resonant cavity design. Based on the idea of the present application, more multi-mode resonant cavities and BPFs in application scenarios can be designed by changing the structure shape of the folded layer or using the above-mentioned resonant mode combination.

[0082] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A design method for a resonant cavity based on a multimode folded substrate integrated waveguide, characterized in that, include: A five-layer structure consisting of a first metal layer, a first dielectric substrate, a second metal layer, a second dielectric substrate, and a third metal layer is stacked sequentially. A metal via array is formed in a square shape, the metal via array penetrating 5 layers of structure, thereby forming a SIW resonant cavity between the 5 layers of structure; The second metal layer is folded, and the folded second metal layer is referred to as the folded layer. The folded layer retains several metal through holes on the two sides of the square, and the folded layer as a whole is stepped, thereby forming an FSIW resonant cavity between the 5 layers. A perturbation structure is formed to perturb the degenerate dual modes present in the FSIW resonant cavity, thereby transforming them into non-degenerate modes; wherein, the perturbation structure includes two metal vias penetrating the 5-layer structure, the two metal vias being located on one of the diagonals of the square and being symmetrical about the center of the square.

2. A resonant cavity based on a multimode folded substrate integrated waveguide, characterized in that, It is obtained by using the design method described in claim 1.

3. A design method for miniaturized filters based on multimode folded substrate integrated waveguides, characterized in that, include: A resonant cavity based on a multimode folded substrate integrated waveguide is formed using the design method described in claim 1; An input port feed line is disposed on the first metal layer along the direction of a first reference line, and an output port feed line is disposed on the first metal layer along the direction of a second reference line; wherein, the input port feed line and the output port feed line have the same structure, both including a microstrip line and two coupling slots symmetrical about the microstrip line; and the distance between the microstrip line of the input port feed line and the first reference line, and the distance between the microstrip line of the output port feed line and the second reference line are both D. in D in The number is not less than 0; wherein, the virtual line segments passing through the center of the square and parallel to the two vertical sides therein are respectively used as the first reference line and the second reference line.

4. The design method for miniaturized filters based on multimode folded substrate integrated waveguides according to claim 3, characterized in that, The coupling groove is L-shaped overall.

5. The design method for miniaturized filters based on multimode folded substrate integrated waveguides according to claim 4, characterized in that, The folded layer is in the shape of a three-tiered ladder.

6. A miniaturized filter based on a multimode folded substrate integrated waveguide, characterized in that, It is obtained by using the design method described in any one of claims 3 to 5.

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