Dual-band filter

Abstract

The invention discloses a dual-frequency filter, and relates to the technical field of filters. The dual-frequency filter comprises a substrate, wherein a plurality of through holes are arranged on the substrate, and the substrate comprises a first conductor layer, a first dielectric layer, a second conductor layer, a second dielectric layer, and a third conductor layer which are stacked in sequence; a plurality of through holes enclose a plurality of substrate integrated waveguide cavities located between the first conductor layer and the third conductor layer on the substrate, and the plurality of substrate integrated waveguide cavities are arranged side by side along a first direction of the substrate, and constitute a substrate integrated waveguide filter; a plurality of planar bandgap units are etched on the second conductor layer, and the plurality of planar bandgap units are arranged side by side along the first direction of the substrate, and constitute a coplanar waveguide filter, and the coplanar waveguide filter is located in the substrate integrated waveguide cavity; the problems that the existing dual-frequency band filter has large size, close dual-frequency band frequencies, and coupling between different frequency bands is difficult to independently adjust are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of filters, and in particular to a dual-frequency filter. Background Art

[0002] With the continuous advancement of wireless communication technology, especially the rapid development of 5G technology, the field of wireless communication is ushering in a revolutionary change. This change has not only promoted a significant increase in data transmission rate, but also promoted the trend of miniaturization and integration of communication equipment. However, in this process, the design of dual-band filters has become one of the key factors restricting the performance improvement of wireless communication equipment.

[0003] In current wireless communication systems, dual-band filters play a vital role. They are widely used in various communication devices to achieve simultaneous processing of signals in multiple frequency bands. However, there are some common problems with dual-band filters in the prior art. The size of existing dual-band filters is generally large, which limits their application in miniaturized communication devices. When the dual passband frequencies of the dual-band filters are close, different resonant modes inside the filters are prone to mutual interference, resulting in a decrease in filtering performance. At the same time, the coupling between different frequency bands in the existing dual-band filters is also difficult to adjust independently, which increases the difficulty of design.

[0004] In summary, in the prior art, the dual-band filter is large in size, the dual-band frequencies are close, and coupling between different frequency bands makes it difficult to adjust them independently, which is a problem that needs to be solved urgently. Summary of the invention

[0005] The main purpose of the present invention is to provide a dual-band filter, aiming to solve the problems of existing dual-band filters, such as large size, close dual-band frequencies, coupling between different frequency bands, and difficulty in independent adjustment.

[0006] To achieve the above object, the dual-frequency filter proposed in the present invention comprises a substrate, a plurality of through holes are arranged on the substrate, and the substrate comprises a first conductor layer, a first dielectric layer, a second conductor layer, a second dielectric layer, and a third conductor layer which are stacked in sequence;

[0007] The plurality of through holes enclose a plurality of substrate integrated waveguide cavities located between the first conductor layer and the third conductor layer on the substrate, and the plurality of substrate integrated waveguide cavities are arranged side by side along the first direction of the substrate to form a substrate integrated waveguide filter;

[0008] A plurality of planar bandgap units are etched on the second conductor layer. The plurality of planar bandgap units are arranged side by side along the first direction of the substrate and constitute a coplanar waveguide filter. The coplanar waveguide filter is located in the substrate integrated waveguide cavity.

[0009] In one embodiment, the plurality of through holes are all circular through holes, and the plurality of through holes include:

[0010] A first through hole array, the first through hole array comprising two rows of transverse through hole grids arranged side by side along a second direction of the substrate, the second direction being orthogonal to the first direction;

[0011] A second through hole array, the second through hole array includes a plurality of longitudinal through hole grids arranged side by side along the first direction of the substrate, the plurality of longitudinal through hole grids are spaced apart in the first direction to enclose a plurality of substrate integrated waveguide cavities with the two transverse through hole grids.

[0012] In one embodiment, the second through hole array includes a first longitudinal through hole grid, a second longitudinal through hole grid, a third longitudinal through hole grid, a fourth longitudinal through hole grid and a fifth longitudinal through hole grid, and the five columns of the longitudinal through hole grids and the two columns of the transverse through hole grids enclose four substrate integrated waveguide cavities;

[0013] The coplanar waveguide filter comprises two planar bandgap units, and the four substrate integrated waveguide cavities are respectively a first substrate integrated waveguide cavity, a second substrate integrated waveguide cavity, a third substrate integrated waveguide cavity, and a fourth substrate integrated waveguide cavity along the first direction; one of the two planar bandgap units is distributed in the first substrate integrated waveguide cavity and the second substrate integrated waveguide cavity, and the other is distributed in the third substrate integrated waveguide cavity and the fourth substrate integrated waveguide cavity.

[0014] In one embodiment, the four substrate integrated waveguide cavities are divided into two groups along a central cross section passing through the center of a through hole in the third longitudinal through hole grid, and the two groups of substrate integrated waveguide cavities are symmetrically arranged about a central cross section passing through the center of a through hole in the third longitudinal through hole grid;

[0015] The two planar bandgap units are symmetrically arranged about a central cross section passing through the center of a through hole in the third longitudinal through hole grid.

[0016] In one embodiment, the length of the first substrate integrated waveguide cavity and the fourth substrate integrated waveguide cavity along the first direction is a first cavity length, and the length of the second substrate integrated waveguide cavity and the third substrate integrated waveguide cavity along the first direction is a second cavity length.

[0017] In one embodiment, each of the planar bandgap units includes a pair of planar electromagnetic bandgaps, a pair of long branches and a pair of short branches, the planar electromagnetic bandgap is arranged between the long branches and the short branches, the pair of long branches of one of the two planar bandgap units is arranged in the first substrate integrated waveguide cavity, the pair of planar electromagnetic bandgaps is arranged in the second substrate integrated waveguide cavity, and the pair of short branches is arranged in the center of the second conductor layer, the pair of long branches of the other planar bandgap unit is arranged in the fourth substrate integrated waveguide cavity, the pair of planar electromagnetic bandgaps is arranged in the third substrate integrated waveguide cavity, and the pair of short branches is arranged in the center of the second conductor layer, and the long branches and short branches are used to enhance the electromagnetic coupling of the planar electromagnetic bandgap.

[0018] In one embodiment, the length of the planar electromagnetic band gap along the first direction is the first band gap length, the length of the planar electromagnetic band gap along the second direction is the first band gap width, the gap width of the planar electromagnetic band gap is the third slot width, and the line distance between the planar electromagnetic band gap and the inner conductor is the first line distance.

[0019] In one embodiment, the length of the long branch along the second direction of the substrate is the first branch length, the groove width of the long branch is the first groove width, the line width between the two grooves of the long branch is the first line width, the width of the short branch along the second direction is the second branch length, the groove width of the short branch is the second groove width, and the line width between the two grooves of the short branch is the first line width. The line length between the long branch and the short branch is the first line length, and the line width between the long branch and the short branch is the second line width.

[0020] In one embodiment, the materials of the first conductor layer, the second conductor layer and the third conductor layer are metal materials; the materials of the first dielectric layer and the second dielectric layer are FerroA6M materials.

[0021] In one embodiment, the thicknesses of the first conductor layer, the second conductor layer and the third conductor layer are all the first thickness, the thicknesses of the first dielectric layer and the second dielectric layer are all the second thickness, and the lengths from the first conductor layer to the third conductor layer are all the first length.

[0022] In one embodiment, the plurality of planar bandgap units and the plurality of through holes are arranged independently of each other.

[0023] In one embodiment, the dual-frequency filter comprises a first port, a second port, a third port and a fourth port, wherein the first port is connected to the second port through the coplanar waveguide filter to adopt the TEM mode for transmission and frequency selection filtering and to operate at the low frequency in the dual-frequency filter; the third port is connected to the fourth port through the substrate integrated waveguide filter to adopt the TE mode for transmission and frequency selection filtering. 10mode for transmission and frequency-selective filtering, and operates at the high frequency in the dual-band filter.

[0024] The present invention uses the first conductor layer, the third conductor layer and a plurality of through holes of the substrate as the outer conductor of the dual-frequency filter to set up an ultra-large-size substrate integrated waveguide cavity to form a TE 10 The high-frequency filter of the TE mode is formed by using the second conductor layer as the coplanar waveguide surface to form the inner conductor of the dual-band filter and the ridges on both sides, and a low-frequency filter of the TEM mode is formed by etching a planar electromagnetic band gap on the ridge substrate. The TEM filter is nested in the TE 10 The two frequency bands in the filter are independent and work simultaneously, thus achieving a small size, high isolation between the two frequency bands, which can be designed independently of each other, and a large ratio of the center frequencies of the two working frequency bands, making the dual-frequency filter more widely used, and the connection is simple and easy to integrate and design. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0026] Figure 1 is a schematic diagram of the structure of a dual-frequency filter in one embodiment of the present invention;

[0027] Figure 2 for Figure 1 A schematic diagram of the stacked structure of the substrate of the dual-band filter;

[0028] Figure 3 is a schematic diagram of the position structure of the through holes in one embodiment of the present invention;

[0029] Figure 4 is a schematic structural diagram of a second conductor layer in one embodiment of the present invention;

[0030] Figure 5 is a schematic diagram of structural parameters of a dual-frequency filter in one embodiment of the present invention;

[0031] Figure 6 It is a schematic diagram of the measured S parameters of the dual-frequency filter of the present invention;

[0032] Figure 7 It is a dual-channel electric field distribution diagram when the dual-frequency filter of the present invention works at a low frequency;

[0033] Figure 8 This is a dual-channel electric field distribution diagram of the dual-frequency filter of the present invention when it works at high frequency.

[0034] Description of Figure Numbers:

[0035] 1. substrate; 11. first conductor layer; 12. first dielectric layer; 13. second conductor layer; 14. second dielectric layer; 15. third conductor layer; 2. through hole; 21. first through hole array; 22. second through hole array; 3. planar bandgap unit; 31. planar electromagnetic bandgap; 32. long branch; 33. short branch; 4. substrate integrated waveguide cavity;

[0036] L, first length; L1, first cavity length; L2, second cavity length; e1, first bandgap length; e2, first bandgap width; Ls1, first branch length; Ls2, second branch length; Ls3, first line spacing; s1, first slot width; s2, second slot width; s3, third slot width; W, first interval width; W1, first window width; W2, second window width; W3, third window width; Ws1, first line width; Ws0, second line width; t, first thickness; h, second thickness; p, spacing between adjacent through holes; d, diameter of through hole; port1, first port; port2, second port; port3, third port; port4, fourth port; S11, coplanar waveguide filter return loss; S21, coplanar waveguide filter insertion loss; S33, substrate integrated waveguide filter return loss; S43, substrate integrated waveguide filter insertion loss; S31, near-end crosstalk; S41, far-end crosstalk.

[0037] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] It should be noted that all directional indications in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between various components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0040] In addition, the descriptions of "first", "second", etc. in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0041] With the continuous advancement of wireless communication technology, especially the rapid development of 5G technology, the field of wireless communication is ushering in a revolutionary change. This change has not only promoted a significant increase in data transmission rate, but also promoted the trend of miniaturization and integration of communication equipment. However, in this process, the design of dual-band filters has become one of the key factors restricting the performance improvement of wireless communication equipment.

[0042] In current wireless communication systems, dual-band filters play a vital role. They are widely used in various communication devices to achieve simultaneous processing of signals in multiple frequency bands. However, there are some common problems with dual-band filters in the prior art. The size of existing dual-band filters is generally large, which limits their application in miniaturized communication devices. When the dual passband frequencies of the dual-band filters are close, different resonant modes inside the filters are prone to mutual interference, resulting in a decrease in filtering performance. At the same time, the coupling between different frequency bands in the existing dual-band filters is also difficult to adjust independently, which increases the difficulty of design.

[0043] In summary, in the prior art, the dual-band filter is large in size, the dual-band frequencies are close, and coupling between different frequency bands makes it difficult to adjust them independently, which is a problem that needs to be solved urgently.

[0044] In order to solve the above problems, the present invention proposes a dual-frequency filter.

[0045] See also Figures 1 to 5 The dual-frequency filter comprises a substrate 1, on which a plurality of through holes 2 are arranged, and the substrate 1 comprises a first conductor layer 11, a first dielectric layer 12, a second conductor layer 13, a second dielectric layer 14, and a third conductor layer 15 which are stacked in sequence;

[0046] The plurality of through holes 2 enclose a plurality of substrate integrated waveguide cavities 4 located between the first conductor layer 11 and the third conductor layer 15 on the substrate 1. The plurality of substrate integrated waveguide cavities 4 are arranged side by side along the first direction of the substrate 1 to form a substrate integrated waveguide filter.

[0047] A plurality of planar bandgap units 3 are etched on the second conductor layer 13 . The plurality of planar bandgap units 3 are arranged side by side along the first direction of the substrate 1 and constitute a coplanar waveguide filter. The coplanar waveguide filter is located in the substrate integrated waveguide cavity 4 .

[0048] It should be noted that in recent years, the concept of substrate integrated waveguide has been proposed. It has the advantages of rectangular waveguide and is easy to integrate in planar, and has broad application prospects in integrated circuits. People have conducted extensive research on the propagation characteristics of substrate integrated waveguides, and have developed many high-performance planar devices based on substrate integrated waveguide structures. 10 In order to solve the serious problem of mode dispersion, people proposed the concept of substrate integrated coaxial line. By integrating the coaxial line plane to propagate TEM mode, the dispersion problem is largely solved while retaining the closed structure. In order to further reduce the size of substrate integrated coaxial line, people proposed ridge substrate integrated coaxial line. By adding ridges on both sides of the substrate integrated coaxial line, not only the size is reduced but also the bandwidth is wider, the leakage is smaller, and there is more room for design. The present invention designs a dual-frequency filter based on the MCRSICL (mode composite ridge substrate integrated coaxial line) structure. This structure combines mode composite and orthogonal mode theory to transmit TEM and TE in parallel. 10 Two modes achieve more compact use of space.

[0049] like Figures 1 to 5 As shown in, in this embodiment, the physical structure of the dual-frequency filter is composed of a substrate 1 and a through hole 2 penetrating the substrate 1. The substrate 1 is composed of a first conductor layer 11, a first dielectric layer 12, a second conductor layer 13, a second dielectric layer 14, and a third conductor layer 15 stacked in sequence from top to bottom. The materials of the first conductor layer 11, the second conductor layer 13, and the third conductor layer 15 can be metal, conductive polymer, or graphene and other materials with conductivity that meets the design requirements. This embodiment does not specifically limit this. Among them, the three metal layers and the through hole 2 constitute the conductor of the dual-frequency filter, the first dielectric layer 12 is a dielectric filled between the first conductor layer 11 and the second conductor layer 13, and the second dielectric layer 14 is a dielectric filled between the second conductor layer 13 and the third conductor layer 15.

[0050] The plurality of through holes 2 all penetrate the substrate 1, wherein the first conductor layer 11 and the third conductor layer 15 and the through holes 2 form an outer conductor of a dual-frequency filter, and the plurality of through holes 2 on the outer conductor enclose a plurality of ultra-large substrate integrated waveguide cavities 4 thereon, thereby introducing a substrate integrated waveguide filter, and the substrate integrated waveguide filter is a Chebyshev-type integrated waveguide bandpass filter whose order corresponds to the number of substrate integrated waveguide cavities 4; the second conductor layer 13 can be regarded as a coplanar waveguide surface, constituting the inner conductor of the dual-frequency filter and the ridge substrate on both sides, and is etched with a plurality of planar bandgap units 3, and the planar bandgap unit 3 is a combination of a planar electromagnetic bandgap and a branch, thereby introducing a coplanar waveguide filter, and the coplanar waveguide filter is a coplanar waveguide bandpass filter whose order corresponds to the number of planar bandgap units 3.

[0051] The present invention uses the first conductor layer 11, the third conductor layer 15 and the plurality of through holes 2 of the substrate 1 as the outer conductor of the dual-frequency filter to set up an ultra-large-size substrate integrated waveguide cavity 4 to form a TE 10 The high-frequency filter of the mode is formed by using the second conductor layer 13 as the coplanar waveguide surface to form the inner conductor of the dual-frequency filter and the ridges on both sides thereof, and a low-frequency filter of the TEM mode is formed by etching a planar electromagnetic band gap on the ridge substrate. The low-frequency filter is nested in the high-frequency filter and works independently and simultaneously. The MCRSICL dual-frequency filter provided by the present invention adopts a dual-channel dual-mode transmission filter, which shares the same cavity compared with the traditional multiple cavity cascade type, greatly reducing the size; compared with the multi-mode resonator using the degenerate mode or other adjacent resonant modes as the working mode, a larger center frequency ratio can be achieved; compared with other mode composite filters, the ultra-large substrate integrated waveguide cavity 4 structure is combined with the coplanar waveguide bandpass filter for the first time. Although the two filters share the cavity, the filtering structure does not overlap and can realize the separate adjustment and design of different mode filtering, greatly reducing the design complexity and improving the design freedom. Thus, the small size, high isolation between the dual bands, independent design, and large ratio of the center frequencies of the two working frequency bands are achieved, so that the dual-frequency filter has a wider application range, and the switching is simple and easy to integrate and design.

[0052] See also Figure 1 and Figure 3 In one embodiment, the plurality of through holes 2 are all circular through holes, and the plurality of through holes 2 include:

[0053] A first through hole array 21, wherein the first through hole array 21 comprises two rows of transverse through hole grids arranged side by side along a second direction of the substrate 1, wherein the second direction is orthogonal to the first direction;

[0054] The second through hole array 22 includes a plurality of longitudinal through hole grids arranged side by side along the first direction of the substrate 1, and the plurality of longitudinal through hole grids are arranged at intervals in the first direction to enclose a plurality of substrate integrated waveguide cavities 4 with the two transverse through hole grids.

[0055] It should be noted that the substrate 1 is rectangular, and the first direction is along the length direction of the substrate 1, that is, Figure 1 The second direction is the x-axis direction of the substrate 1, and the second direction is the width direction of the substrate 1. Figure 1 In the y-axis direction, the first direction is orthogonal to the second direction. Then, a plurality of substrate integrated waveguide cavities 4 can be enclosed by the first through hole array 21 and the second through hole array 22. If the second through hole array 22 includes N columns of longitudinal through hole grids, N-1 substrate integrated waveguide cavities 4 can be enclosed. And a gap is left in the middle of each longitudinal through hole grid in the second through hole array 22 as a coupling window for coupling conduction of electromagnetic waves.

[0056] In this embodiment, a plurality of ultra-large-size substrate integrated waveguide cavities 4 are enclosed on the outer conductor formed by the first conductor layer 11 and the third conductor layer 15 by the first through hole array 21 and the second through hole array 22, thereby introducing a substrate integrated waveguide bandpass filter, that is, being able to use TE 10 A high-frequency filter that transmits high-frequency electromagnetic waves.

[0057] As an example, Figure 5 As shown, the first spacing width W between the two rows of transverse through-hole grids is 4.9 mm, the diameter d of the through-holes is 0.1 mm, and the spacing p between adjacent through-holes in the through-hole array is 0.4 mm.

[0058] See also Figure 4 and Figure 5 In one embodiment, the second through hole array 22 includes a first longitudinal through hole grid, a second longitudinal through hole grid, a third longitudinal through hole grid, a fourth longitudinal through hole grid and a fifth longitudinal through hole grid, and the five columns of the longitudinal through hole grids and the two columns of the transverse through hole grids enclose four substrate integrated waveguide cavities 4;

[0059] The coplanar waveguide filter comprises two planar bandgap units 3, and the four substrate integrated waveguide cavities 4 are respectively a first substrate integrated waveguide cavity, a second substrate integrated waveguide cavity, a third substrate integrated waveguide cavity, and a fourth substrate integrated waveguide cavity along the first direction; one of the two planar bandgap units 3 is distributed in the first substrate integrated waveguide cavity and the second substrate integrated waveguide cavity, and the other is distributed in the third substrate integrated waveguide cavity and the fourth substrate integrated waveguide cavity.

[0060] In this embodiment, the number of the substrate integrated waveguide cavities 4 is four, and a fourth-order Chebyshev-type substrate integrated waveguide bandpass filter is introduced, using TE 10 The planar bandgap unit 3 is used for transmission and frequency-selective filtering in the TEM mode, and works at the high frequency in the dual-frequency filter; the number of the planar bandgap units 3 is two, and a second-order coplanar waveguide bandpass filter is introduced, which uses the TEM mode for transmission and frequency-selective filtering, and works at the low frequency in the dual-frequency filter. The two filter structures are nested, and although they share the same cavity, they still retain a certain design space, and the size of the dual-frequency filter is effectively reduced through spatial multiplexing. And a larger dual-frequency frequency ratio can be achieved. Different from the partial mode composite waveguide that uses a physical structure to achieve shielding between modes, the dual-frequency filter of the present invention achieves a high degree of isolation based on mode orthogonality, which is conducive to integration with other planar circuits and is suitable for circuit board and chip-level application scenarios.

[0061] As an example, Figure 5 As shown, the coupling window widths of the first to fifth longitudinal through-hole grids are respectively the first window width W1, the second window width W2, the third window width W3, the second window width W2, and the first window width W1. Figure 4 As shown, the first window width W1 is 2.1 mm, the second window width W2 is 1.48 mm, and the third window width W3 is 1.34 mm.

[0062] See also Figure 4 and Figure 5 In one embodiment, the four substrate integrated waveguide cavities 4 are divided into two groups along the central cross section passing through the center of the through hole in the third longitudinal through hole grid, and the two groups of substrate integrated waveguide cavities 4 are symmetrically arranged about the central cross section passing through the center of the through hole in the third longitudinal through hole grid;

[0063] The two planar bandgap units 3 are symmetrically arranged about a central cross section passing through the center of the through hole in the third longitudinal through hole grid.

[0064] In this embodiment, two groups of substrate integrated waveguide cavities 4 are symmetrically arranged about the central cross section passing through the center of the through hole in the third longitudinal through hole grid; the two planar bandgap units 3 are symmetrically arranged about the central cross section passing through the center of the through hole in the third longitudinal through hole grid, so that the fourth-order substrate integrated waveguide bandpass filter and the second-order coplanar waveguide filter are both symmetrical along the central cross section of the filter. This layout can make the filter more balanced and stable in processing high-frequency and low-frequency signals. At the same time, since the transmission path of the signal in the filter is more symmetrical and consistent, the reflection and loss of the signal can be reduced, thereby improving the performance of the filter.

[0065] See also Figure 5In one embodiment, the length of the first substrate integrated waveguide cavity and the fourth substrate integrated waveguide cavity along the first direction is a first cavity length L1, and the length of the second substrate integrated waveguide cavity and the third substrate integrated waveguide cavity along the first direction is a second cavity length L2.

[0066] It should be noted that the length of the cavity is one of the key factors affecting the performance of the filter. It determines the path length of the signal transmitted in the cavity of the substrate integrated waveguide cavity 4, thereby affecting the key indicators of the filter such as frequency response, bandwidth, and insertion loss. By adjusting the length of different cavities, the designer can control the performance of the filter to a certain extent. For example, increasing the cavity length can reduce the bandwidth of the filter, while reducing the cavity length can increase the bandwidth. This design flexibility enables the filter to meet the needs of different application scenarios. The first substrate integrated waveguide cavity and the fourth substrate integrated waveguide cavity have the same length (first cavity length L1), and the second substrate integrated waveguide cavity and the third substrate integrated waveguide cavity also have the same length (second cavity length L2). This symmetrical design helps to maintain the balance and consistency of the filter in high-frequency and low-frequency signal processing, thereby improving the overall performance of the filter.

[0067] In this embodiment, as an example, Figure 5 As shown, Figure 5 The left side is a top view of the first conductor layer 11 , the first cavity length L1 is 1.87 mm, and the second cavity length L2 is 2.11 mm.

[0068] See also Figure 4 and Figure 5 In one embodiment, each of the planar bandgap units 3 includes a pair of planar electromagnetic bandgaps 31, a pair of long branches 32 and a pair of short branches 33, the planar electromagnetic bandgap 31 is arranged between the long branches 32 and the short branches 33, the pair of long branches 32 of one of the two planar bandgap units 3 is arranged in the first substrate integrated waveguide cavity, the pair of planar electromagnetic bandgaps 31 is arranged in the second substrate integrated waveguide cavity, and the pair of short branches 33 is arranged in the center of the second conductor layer 13, the pair of long branches 32 of the other planar bandgap unit 3 is arranged in the fourth substrate integrated waveguide cavity, the pair of planar electromagnetic bandgaps 31 is arranged in the third substrate integrated waveguide cavity, and the pair of short branches 33 is arranged in the center of the second conductor layer 13, and the long branches and short branches are used to enhance the electromagnetic coupling of the planar electromagnetic bandgap.

[0069] In this embodiment, two planar bandgap units 3 are symmetrically etched on the second conductor layer 13, that is, a pair of planar electromagnetic band gaps 31, long branches 32 and short branches 33 are symmetrically etched about the central cross section, and the planar electromagnetic band gaps 31, long branches 32 and short branches 33 are nested in the substrate integrated waveguide cavity 4 and do not overlap each other, so that the dual-frequency filter of this embodiment can greatly reduce the size through spatial multiplexing, and can realize the separate adjustment and design of different mode filtering, thereby greatly reducing the design complexity and improving the design freedom. In addition, the setting of the long branches 32 and the short branches 33 enhances the electromagnetic coupling of the planar electromagnetic band gap 31, thereby improving the filtering effect of the filter.

[0070] See also Figure 4 and Figure 5 In one embodiment, the length of the planar electromagnetic band gap 31 along the first direction is a first band gap length e1, the length of the planar electromagnetic band gap 31 along the second direction is a first band gap width e2, the gap width of the planar electromagnetic band gap 31 is a third slot width s3, and the line spacing between the planar electromagnetic band gap 31 and the inner conductor is a first line spacing Ls3.

[0071] It should be noted that the length, width and gap width of the planar electromagnetic band gap 31 jointly determine its filtering performance. By adjusting these parameters, the propagation and suppression of electromagnetic waves within a specific frequency range can be controlled, thereby achieving a filtering function. By adjusting these parameters, designers can control the performance of the filter to a certain extent to meet the needs of different application scenarios. This design flexibility enables the filter to adapt to various complex electromagnetic environments. When designing a filter, it is necessary to clarify its operating frequency range. This will help determine the size and position relationship of the planar electromagnetic band gap 31 to ensure that the filter can work normally within the required frequency range.

[0072] In this embodiment, as an example, Figure 5 As shown, Figure 5 The right side is a top view of the second conductor layer 13 , the first bandgap length e1 is 0.9 mm, the first bandgap width e2 is 1.18 mm, the third slot width s3 is 0.11 mm, and the first line distance Ls3 is 0.43 mm.

[0073] See also Figure 4 and Figure 5In one embodiment, the length of the long branch 32 along the second direction of the substrate 1 is the first branch length Ls1, the groove width of the long branch 32 is the first groove width s1, the line width between the two grooves of the long branch 32 is the first line width Ws1, the width of the short branch 33 along the second direction is the second branch length Ls2, the groove width of the short branch 33 is the second groove width s2, and the line width between the two grooves of the short branch 33 is the first line width Ws1. The line length between the long branch 32 and the short branch 33 is the first line length Ls0, and the line width between the long branch 32 and the short branch 33 is the second line width Ws0.

[0074] It should be noted that the size and shape of the long branch 32 and the short branch 33 have an important influence on the performance of the filter. By reasonably designing these parameters, the required filtering function can be achieved and the performance and stability of the filter can be improved. In the design process, multiple factors such as electromagnetic coupling, manufacturing process and frequency range need to be comprehensively considered.

[0075] In this embodiment, as an example, Figure 5 As shown in the right part, the first branch length Ls1 is 1.93mm, the second branch length Ls2 is 0.29mm, the first groove width s1 is 0.17mm, the second groove width s2 is 0.11mm, the first line width Ws1 is 0.11mm, the second line width Ws0 is 0.12mm, and the first line length Ls0 is 2.32mm.

[0076] In one embodiment, the materials of the first conductor layer 11 , the second conductor layer 13 and the third conductor layer 15 are metal materials; the materials of the first dielectric layer 12 and the second dielectric layer 14 are FerroA6M materials.

[0077] In this embodiment, the material of the conductor layer is metallic silver, the through hole is a metallized through hole, and the material of the dielectric layer is FerroA6M material, which is a low-temperature co-fired ceramic material with a dielectric constant of 5.84 and a dielectric loss tangent of 0.0019.

[0078] See also Figure 1 and Figure 2 In one embodiment, the thicknesses of the first conductor layer 11, the second conductor layer 13 and the third conductor layer 15 are all the first thickness t, the thicknesses of the first dielectric layer 12 and the second dielectric layer 14 are all the second thickness h, and the lengths from the first conductor layer 11 to the third conductor layer 15 are all the first length L.

[0079] In this embodiment, as an example, Figure 1As shown, the thicknesses of the first conductor layer 11, the second conductor layer 13 and the third conductor layer 15 are all the first thickness t of 0.01 mm, the thicknesses of the first dielectric layer 12 and the second dielectric layer 14 are all the second thickness h of 0.288 mm, and the length from the first conductor layer 11 to the third conductor layer 15, that is, the length of the substrate 1, is the first length L of 8 mm.

[0080] It is understandable that in another embodiment, the dielectric constant and thickness of the corresponding dielectric layer and the thickness and length of the corresponding conductor layer can be selected according to actual needs.

[0081] See also Figures 1 to 5 In one embodiment, the plurality of planar bandgap units 3 and the plurality of through holes are arranged independently of each other.

[0082] It should be noted that the plurality of through holes are arranged to penetrate the first conductor layer 11 to the third conductor layer 15 , wherein the plurality of through holes and the plurality of planar bandgap units 3 etched on the second conductor layer 13 are independent of each other and do not overlap with each other.

[0083] In this embodiment, a substrate integrated waveguide bandpass filter formed by a substrate integrated waveguide cavity 4 structure surrounded by a plurality of through holes is combined with a coplanar waveguide bandpass filter formed by etching a planar bandgap unit 3 on the second conductor layer 13, but the structure etched on the second conductor layer 13 does not conflict with the cavity formed by the through holes and has a certain adjustment design space, which can realize TEM or TE 10 The two filtering mode structures are designed separately without interfering with each other, which greatly reduces the design complexity and improves the design freedom.

[0084] In one embodiment, see Figures 6 to 8 The dual-frequency filter comprises a first port port1, a second port port2, a third port port3 and a fourth port port4, wherein the first port and the second port port2 are connected through the coplanar waveguide filter to adopt the TEM mode for transmission and frequency selection filtering and work at the low frequency in the dual-frequency filter; the third port port3 and the fourth port port4 are connected through the substrate integrated waveguide filter to adopt the TE mode for transmission and frequency selection filtering. 10 mode for transmission and frequency-selective filtering, and operates at the high frequency in the dual-band filter.

[0085] like Figure 6 As shown, it should be noted that Figure 6The S-parameter performance diagram of the dual-frequency filter provided by the present invention when it is working. The horizontal axis represents the frequency (Frequency), the unit is GHz. The vertical axis represents the transmission performance (S-parameters) of each channel, the unit is dB. The insertion loss and return loss of the coplanar waveguide filter in TEM mode are represented by S21 and S11, and the TE mode is used to represent the insertion loss and return loss of the coplanar waveguide filter in TEM mode. 10 The insertion loss and return loss of the substrate integrated waveguide filter of the mode are represented by S43 and S33. Crosstalk is the crosstalk between channels, while S31 and S41 represent the crosstalk from the TEM channel to the TE channel, respectively. 10 The near-end crosstalk and far-end crosstalk of the channel represent the isolation between channels.

[0086] In this embodiment, Figure 6 It can be seen that the substrate integrated waveguide filter of the dual-band filter has a 3dB insertion loss passband from 27 to 31.5GHz, and the return loss is less than -20dB. The coplanar waveguide filter has a passband from 5.5 to 6GHz and has a wide out-of-band suppression. In addition, it can be found that TEM and TE 10 The crosstalk between the two channels is less than -40dB, which indicates that TE 10 The mode and the TEM mode have a high degree of isolation and can be regarded as working independently without interfering with each other, which is conducive to the independent design and debugging of high and low frequency structures.

[0087] Figure 7 This is the dual-channel electric field distribution diagram of the dual-frequency filter when it works at low frequency. Figure 8 This is the dual-channel electric field distribution diagram when working at high frequency. The dark part in the figure represents the electric field strength in the signal transmission area, and its unit is kV / m. Figure 7 It can be seen that the TEM mode of the coplanar waveguide filter has good transmission in the low-frequency passband of the dual-band filter, while the substrate integrated waveguide filter has 10 The mode disappears during the transmission process. Figure 8 It can be seen that the TE of the substrate integrated waveguide filter in the high-frequency passband of the dual-band filter is 10 The mode transmission is good and the TEM mode of the coplanar waveguide filter disappears, achieving independent operation of high and low frequency filters.

[0088] In this embodiment, the dual-frequency filter of the MCRSICL structure designed by the present invention has the advantages of small size, high isolation, a large ratio between the frequencies of two different working frequency bands, and easy integration and design, and is suitable for miniaturized frequency selection filtering at the circuit board level / chip level.

[0089] In summary, the present invention uses the first conductor layer 11, the third conductor layer 15 and the plurality of through holes 2 of the substrate 1 as the outer conductors of the dual-frequency filter to set up an ultra-large-size substrate integrated waveguide cavity 4 to form a TE10 The MCRSICL dual-frequency filter of the present invention adopts dual-channel dual-mode transmission filtering, which shares the same cavity compared with the traditional multiple-cavity cascade type, greatly reducing the size; compared with the multi-mode resonator that uses the degenerate mode or other adjacent resonant modes as the working mode, the TEM and TE modes are used in the MCRSICL dual-frequency filter. 10 The transmission mode can achieve a larger center frequency ratio; compared with other mode composite filters, it is the first time that the ultra-large substrate integrated waveguide cavity 4 structure is combined with the coplanar waveguide bandpass filter. Although the two filters share the cavity, the filter structure does not overlap and can achieve separate adjustment and design of different mode filters, greatly reducing the design complexity and improving the design freedom. Thus, the small size, high isolation between the two bands, independent design, and large ratio of the center frequencies of the two working bands are achieved, making the dual-frequency filter more widely applicable, and the switching is simple and easy to integrate and design.

[0090] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A dual-frequency filter, characterized in that: A substrate is provided with a plurality of through holes, wherein the substrate comprises a first conductor layer, a first dielectric layer, a second conductor layer, a second dielectric layer, and a third conductor layer which are stacked in sequence; The plurality of through holes enclose a plurality of substrate integrated waveguide cavities located between the first conductor layer and the third conductor layer on the substrate, and the plurality of substrate integrated waveguide cavities are arranged side by side along the first direction of the substrate to form a substrate integrated waveguide filter; A plurality of planar bandgap units are etched on the second conductor layer, and the plurality of planar bandgap units are arranged side by side along the first direction of the substrate to form a coplanar waveguide filter, and the coplanar waveguide filter is located in the substrate integrated waveguide cavity; The plurality of through holes are all circular through holes, and the plurality of through holes include: A first through hole array, the first through hole array comprising two rows of transverse through hole grids arranged side by side along a second direction of the substrate, the second direction being orthogonal to the first direction; a second through hole array, the second through hole array comprising a plurality of columns of longitudinal through hole grids arranged side by side along a first direction of the substrate, the plurality of columns of longitudinal through hole grids being spaced apart in the first direction to enclose a plurality of the substrate integrated waveguide cavities with the two columns of transverse through hole grids; The second through hole array includes a first longitudinal through hole grid, a second longitudinal through hole grid, a third longitudinal through hole grid, a fourth longitudinal through hole grid and a fifth longitudinal through hole grid, and the five columns of the longitudinal through hole grids and the two columns of the transverse through hole grids enclose four substrate integrated waveguide cavities; The coplanar waveguide filter comprises two planar bandgap units, the four substrate integrated waveguide cavities are respectively a first substrate integrated waveguide cavity, a second substrate integrated waveguide cavity, a third substrate integrated waveguide cavity, and a fourth substrate integrated waveguide cavity along the first direction, one of the two planar bandgap units is distributed in the first substrate integrated waveguide cavity and the second substrate integrated waveguide cavity, and the other is distributed in the third substrate integrated waveguide cavity and the fourth substrate integrated waveguide cavity; The four substrate integrated waveguide cavities are divided into two groups along the central cross section passing through the center of the through hole in the third longitudinal through hole grid, and the two groups of substrate integrated waveguide cavities are symmetrically arranged about the central cross section passing through the center of the through hole in the third longitudinal through hole grid; The two planar bandgap units are symmetrically arranged about a central cross section passing through the center of a through hole in the third longitudinal through hole grid; Each of the planar bandgap units includes a pair of planar electromagnetic bandgaps, a pair of long branches and a pair of short branches, the planar electromagnetic bandgap is arranged between the long branches and the short branches, the pair of long branches of one of the two planar bandgap units is arranged in the first substrate integrated waveguide cavity, the pair of planar electromagnetic bandgaps is arranged in the second substrate integrated waveguide cavity, and the pair of short branches is arranged in the center of the second conductor layer, the pair of long branches of the other planar bandgap unit is arranged in the fourth substrate integrated waveguide cavity, the pair of planar electromagnetic bandgaps is arranged in the third substrate integrated waveguide cavity, and the pair of short branches is arranged in the center of the second conductor layer, and the long branches and short branches are used to enhance the electromagnetic coupling of the planar electromagnetic bandgap.

2. The dual-frequency filter according to claim 1, characterized in that: The length of the first substrate integrated waveguide cavity and the fourth substrate integrated waveguide cavity along the first direction is a first cavity length, and the length of the second substrate integrated waveguide cavity and the third substrate integrated waveguide cavity along the first direction is a second cavity length.

3. The dual-frequency filter according to claim 1, characterized in that: The length of the planar electromagnetic bandgap along the first direction is the first bandgap length, the length of the planar electromagnetic bandgap along the second direction is the first bandgap width, the gap width of the planar electromagnetic bandgap is the third slot width, and the line distance between the planar electromagnetic bandgap and the inner conductor is the first line distance.

4. The dual-frequency filter according to claim 1, characterized in that: The length of the long branch node along the second direction of the substrate is the first branch node length, the groove width of the long branch node is the first groove width, the line width between the two grooves of the long branch node is the first line width, the width of the short branch node along the second direction is the second branch node length, the groove width of the short branch node is the second groove width, the line width between the two grooves of the short branch node is the first line width, the line length between the long branch node and the short branch node is the first line length, and the line width between the long branch node and the short branch node is the second line width.

5. The dual-frequency filter according to claim 1, characterized in that: The materials of the first conductor layer, the second conductor layer and the third conductor layer are metallic silver materials; the materials of the first dielectric layer and the second dielectric layer are FerroA6M materials.

6. The dual-frequency filter according to claim 1, characterized in that: The thicknesses of the first conductor layer, the second conductor layer and the third conductor layer are all the first thickness, the thicknesses of the first dielectric layer and the second dielectric layer are all the second thickness, and the lengths from the first conductor layer to the third conductor layer are all the first length.

7. The dual-frequency filter according to any one of claims 1 to 6, characterized in that: The plurality of planar bandgap units and the plurality of through holes are arranged independently of each other.

8. The dual-frequency filter according to claim 7, characterized in that: The dual-frequency filter comprises a first port, a second port, a third port and a fourth port, wherein the first port is connected to the second port through the coplanar waveguide filter so as to adopt the TEM mode for transmission and frequency selection filtering and work at the low frequency in the dual-frequency filter; the third port is connected to the fourth port through the substrate integrated waveguide filter so as to adopt the TE10 mode for transmission and frequency selection filtering and work at the high frequency in the dual-frequency filter.

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