A broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling

Abstract

The present invention discloses an integrated substrate gap waveguide (ISGW) broadband bandpass filter with controllable electromagnetic coupling, comprising: a bottom dielectric plate, an intermediate dielectric plate and a top dielectric plate are sequentially arranged from bottom to top; a metal copper clad layer is printed on the lower surface of the bottom dielectric plate, a periodic metallized via is loaded internally, and a metal circular patch is printed on the upper surface. The transmission belt line of ISGW is printed on the upper surface of the intermediate dielectric plate, a circular patch is innovatively introduced on the transmission belt line of ISGW, and three pairs of radial grooves are cut on the circular patch. Changing the width of the groove can change the filter coupling coefficient to achieve electromagnetic coupling. By changing the logarithm of the etching groove, the number of transmission poles is controlled to achieve controllable electromagnetic coupling. A metal copper clad layer is printed on the upper surface of the upper dielectric plate, and an absolutely symmetrically loaded branch defect ground structure is innovatively introduced on the upper surface to achieve better filtering characteristics. The filter has good filtering effect and miniaturization characteristics, and can cover the N257 and N258 bands of 5G at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of filters, and in particular to a broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling. Background Art

[0002] With the development of communication technology, the amount of communication data has increased dramatically. In order to alleviate the requirements of large-scale data communication, the 5G communication frequency band has been increased to above 24.25GHz. The N257 and N258 frequency bands of 5G communication are 24.25-27.5GHz and 27.5-28.35GHz respectively. In the process of 5G application, the application frequency bands of different countries or telecom operators may be different. Therefore, the research on bandpass filters covering multiple 5G frequency bands is particularly important.

[0003] Integrated substrate gap waveguide is a new waveguide technology, which consists of three layers of dielectric substrates. The lower dielectric substrate is loaded with a periodic mushroom-shaped structure to achieve a bandgap effect on its band line. There is an integrated substrate gap waveguide transmission strip line between the middle dielectric substrate and the upper dielectric substrate, which has the advantages of low insertion loss, high power capacity and easy integration. Therefore, integrated substrate gap waveguide technology is widely used in the design of high-performance microwave / components. Summary of the invention

[0004] The main technical problem solved by the present invention is to provide a broadband integrated substrate gap waveguide filter that can cover the N257 and N258 frequency bands of 5G millimeter wave communications and achieve low in-band insertion loss, low latency and miniaturization performance.

[0005] In order to achieve the above object, the present invention provides the following scheme: a broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling, comprising: a top dielectric substrate, a middle dielectric substrate and a bottom dielectric substrate are arranged from top to bottom;

[0006] The bottom dielectric substrate is provided with periodic metal through holes, the lower surface of the bottom dielectric plate is printed with a first metal layer, and the upper surface of the bottom dielectric plate is provided with periodic metal patches at the center position of the periodic metal through holes.

[0007] The transmission strip line of the integrated substrate gap waveguide is printed on the upper surface of the intermediate layer dielectric substrate, and a circular metal patch is introduced on the transmission strip line of the integrated substrate gap waveguide;

[0008] Preferably, three pairs of radial grooves are etched on the circular metal patch, so that three pairs of completely symmetrical resonators are obtained from six fan-shaped areas to form a third-order planar bandpass filter stripline;

[0009] Preferably, a copper-clad metal layer is printed on the upper surface of the upper dielectric substrate, and a "king" - shaped absolutely symmetric loaded stub defect ground structure is etched on the upper surface copper-clad metal layer;

[0010] Preferably, the dielectric constant of the bottom dielectric substrate is less than that of the middle dielectric substrate, and both of the former are higher than the dielectric constant of the top interlayer dielectric board;

[0011] Preferably, the thickness of the bottom dielectric substrate is the same as that of the middle dielectric substrate and less than the thickness of the top interlayer dielectric board;

[0012] Preferably, the "king" - shaped absolutely symmetric loaded stub defect ground structure etched on the upper metal surface is completely aligned with the circular resonator patch part on the transmission line;

[0013] Preferably, the length and width of the metal groove etched on the circular metal patch are exactly the same;

[0014] Preferably, the metal groove etched on the circular metal patch is completely symmetric about the X - axis;

[0015] Preferably, the metal groove etched on the circular metal patch is completely symmetric about the Y - axis;

[0016] Preferably, the length and width of the bottom dielectric substrate, the middle dielectric substrate and the top dielectric substrate are the same;

[0017] The bottom dielectric substrate of the broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling provided by the present invention is provided with 12×12 periodically arranged metal through - holes of exactly the same size. A metal layer is printed on the lower surface, and metal patches are printed at positions corresponding to the metal through - holes on the upper surface. On the upper surface of the middle dielectric substrate, a transmission line of an integrated substrate gap waveguide is printed. A circular metal patch is introduced on the transmission line of the integrated substrate gap waveguide, and three pairs of radiating slots that are completely symmetric about the Y - axis are etched on the circular metal patch, obtaining three pairs of completely symmetric resonators from six fan - shaped regions. A metal layer is printed on the upper layer of the upper dielectric substrate, and a "king" - shaped absolutely symmetric loaded stub defect ground structure is etched on the upper - layer metal surface. The transmission line of the integrated substrate gap waveguide is composed of three pairs of completely symmetric resonators obtained from six fan - shaped regions, forming a third - order planar band - pass filter transmission line, thereby obtaining a broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling. The present invention solves the problem of high in - band loss of traditional filters, solves the problems of the need to couple multiple resonators and difficulty in integration of traditional broadband filters, and at the same time has the advantages of high out - of - band suppression, good frequency selectivity, easy processing, and stable structure.

[0018] The present invention provides a broadband integrated substrate gap waveguide filter with electromagnetic coupling controllability. By etching a pair of metal slots perpendicular to the Y direction on a circular metal patch, a pair of identical resonators can be obtained, and a first-order filter with a controllable center frequency can be formed.

[0019] By etching a pair of metal slots in the ±a° directions perpendicular to the Y direction of the circular metal patch, two pairs of identical resonators can be obtained, and two transmission poles can be obtained. By adjusting the angle of the obliquely etched slots, a second-order filter with a controllable center frequency can be formed.

[0020] According to this design, the number of transmission poles can be controlled by controlling the number of slots on the circular metal patch of the filter, and the position of the transmission poles of the filter can be controlled by controlling the angle of the obliquely etched slots, realizing controllability of the bandwidth and transmission poles.

[0021] The proposed filter structure resonates at three frequencies: high, medium, and low. At the low resonance frequency, the main resonators are the radiation slots perpendicular to the strip line in the middle; at the high resonance frequency, the main resonators are the corresponding obliquely cut radiation slots; at the medium resonance frequency, strong resonances occur, and both the vertical radiation slots and the obliquely cut radiation slots produce strong resonances.

[0022] The design process of the broadband integrated substrate gap waveguide filter provided by the present invention can control the bandwidth of the filter by adjusting the angle and number of slots on the circular metal patch, and finally achieve a fractional bandwidth of the filter greater than 20%, realizing the design of a broadband filter.

[0023] The broadband integrated substrate gap waveguide filter structure provided by the present invention can be widely used in low-frequency, high-frequency millimeter-wave, and terahertz frequency bands on the basis of only scaling its size. The design process of the present invention is applied to the millimeter-wave frequency band, but its application scope is not limited to the millimeter-wave frequency band.

[0024] On the upper layer of the broadband integrated substrate gap waveguide filter with electromagnetic coupling controllability provided by the present invention, a "king" - shaped absolutely symmetric loaded stub defected ground structure is etched on the metal layer surface. This absolutely symmetric loaded stub defected ground (SLB - DGS) structure enables the resonators on both sides of the circular metal patch to only have electrical coupling at the middle connection position, avoiding magnetic coupling. Its specific corresponding positions are as Figure 2 shown. The SLB - DGS is decomposed into multiple U - shaped complementary split - ring resonators (CSRRs), as Figure 7 , when there is a CSRR on an infinite conductor, in the case of ignoring conductor losses, the CSRR can be equivalent to a resonant circuit of a capacitor C C and an inductor L C . The resonant frequency of this resonant circuit is:

[0025] f n =(L C C C ) -1 / 2 / 2π BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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 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 these drawings without paying creative labor.

[0027] Figure 1 This is a structural diagram of a broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling according to an embodiment of the present invention;

[0028] Figure 2 A top view of a broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling according to an embodiment of the present invention;

[0029] Figure 3 This is a bottom surface diagram of a top dielectric plate of a broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling according to an embodiment of the present invention;

[0030] Figure 4 This is a top surface diagram of a top dielectric plate of a broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling according to an embodiment of the present invention;

[0031] Figure 5 A coupling topology diagram of a broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling according to an embodiment of the present invention;

[0032] Figure 6 A simplified coupling topology diagram of a broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling according to an embodiment of the present invention;

[0033] Figure 7 The decomposition analysis and equivalent circuit of the upper metal surface defect structure of the broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling according to the embodiment of the present invention;

[0034] Figure 8 The electric field mode distribution diagrams of three resonant frequencies are analyzed for the eigenmode of the broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling according to the embodiment of the present invention;

[0035] Fig. 9 This is a graph showing the S parameter results of a broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling according to an embodiment of the present invention;

[0036] Fig.10This is a time delay result diagram of a broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling according to an embodiment of the present invention;

[0037] Fig.11 This is a comparison diagram of S11 parameters of two pairs of radial slots and three pairs of radial slots in the broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling according to an embodiment of the present invention;

[0038] Fig.12 This is a comparison diagram of the effect of the angle of the radial slot on FTP1 of the broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling according to an embodiment of the present invention;

[0039] Fig.13 A graph showing the relationship between the width of the radial slots opened in the broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling and the coupling coefficient between the filter resonators according to an embodiment of the present invention; DETAILED DESCRIPTION

[0040] 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.

[0041] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] like Figure 1-4 As shown, the present invention provides an electromagnetically coupled controllable broadband integrated substrate gap waveguide filter, comprising: a bottom dielectric substrate (4), a middle dielectric substrate (5) and a top dielectric substrate (9) arranged in sequence from bottom to top. The three dielectric plates have the same length and width and are fixed together by bonding or plastic screws. The dielectric constant of the middle dielectric plate (5) is the largest, the dielectric constant of the bottom dielectric plate (4) is the second largest, and the dielectric constant of the top dielectric plate (9) is the smallest. The loss tangent of the top dielectric plate (9) is required to be relatively high, and a dielectric plate with a small loss tangent and a small dielectric constant should be selected as much as possible to reduce the loss. The thickness of the bottom dielectric plate (4) is greater than the thickness of the middle dielectric plate (5) and the thickness of the top dielectric plate (9).

[0043] A 12×12 periodic metal through hole (2) is punched inside the bottom dielectric substrate (4), a metal grounding layer (1) is printed on the lower surface, and a circular metal patch (3) is printed on the upper surface at the center position corresponding to the periodic metal through hole (2).

[0044] On the upper surface of the middle-layer dielectric substrate (5), an integrated substrate gap waveguide transmission line (6) is printed. A circular metal patch (13) is printed and loaded at the middle position of the integrated substrate gap waveguide conduction band (6) to form a resonator. A pair of slots (7) are etched along the diameter in the X direction of the circular metal patch (13). A pair of slots (8) and (12) are respectively opened at the 42.5° and -42.5° directions in the X direction of the circular metal patch (13), and finally three pairs of completely symmetric resonators are formed. Thus, a broadband integrated substrate gap waveguide filter is obtained. It should be noted that the angles of the obliquely etched metal slots (8) and (12) are not limited to ±42.5°.

[0045] On both sides of the circular metal patch resonator 8 on the upper surface of the middle-layer dielectric substrate (5), a 50-ohm microstrip line feeder (6) is printed respectively. It is encapsulated between the middle-layer dielectric substrate (5) and the top-layer dielectric substrate (9), so that the characteristic impedance of the broadband integrated substrate gap waveguide filter remains stable when the frequency changes, which is convenient for integration and testing.

[0046] On the upper surface of the top-layer dielectric substrate (9), a metal ground (11) is printed. At the position corresponding to the circular metal patch (13) in the metal ground (11), a "king" - shaped absolutely symmetric loaded stub defected ground structure (111) is etched. This absolutely symmetric loaded stub defected ground structure enables the resonators on both sides of the circular metal patch to only generate electrical coupling at the middle connection position, avoiding magnetic coupling. Its specific corresponding position is as Figure 2 shown, improving the performance of the third-order filter. It should be noted that the structure of the absolutely symmetric loaded stub defected ground is not limited to the "king" - shaped.

[0047] By adjusting the angles of the obliquely etched metal slots (8) and (12) and the metal slot (7) perpendicular to the Y direction, the coupling between the resonators is adjusted, so as to adjust the position of each transmission pole and then adjust the position of the frequency band.

[0048] The coupling topology of the broadband integrated substrate gap waveguide filter with controllable electromagnetic coupling provided by the present invention is as Figure 5 shown. This coupling topology characterizes the coupling mechanism of this third-order filter, which is respectively divided into two main coupling links with exactly the same coupling. Link 1: resonator 1 - resonator 2 - resonator 3, Link 2: resonator 1' - resonator 2' - resonator 3', realizing the basic performance of the third-order filter. In addition, there are also multiple electrical coupling branches. Link 3: resonator 1 - resonator 4 - resonator 3, Link 4: resonator 1' - resonator 4' - resonator 3', optimizing the performance of the filter; its coupling coefficients are mainly divided into electrical coupling and magnetic coupling. Magnetic coupling: M 12 、M 23 、M 1’2’ 、M 2’3’ ,Electrical coupling: M 14 、M 24、M 34 、M 1’4’ 、M 2’4’ 、M 3’4’ ; Because the filter is absolutely symmetrical about the Y axis, the coupling conditions of the two coupling branches are exactly the same. By etching three pairs of metal grooves in the fan-shaped metal area on each side, three magnetically coupled resonators are realized. We can further Figure 8 The initial filter coupling topology diagram is simplified to Fig. 9 The filter coupling topology is shown.

[0049] The electromagnetically coupled controllable broadband integrated substrate gap waveguide filter provided by the present invention is a third-order filter through design analysis and simulation results, and the passband range is 22.99-28.67GHz. When a transmission zero is generated at 20.06Hz, 20.62GHz and 29.27, a good suppression effect is achieved outside the band of the filter, and good filtering characteristics are obtained. The generalized coupling matrix of the filter can be obtained as follows:

[0050] S 1 2 3 L S 0.0 0.9396446 0.0 0.0 0.0 1 0.9396446 -0.0487641 0.5554452 0.5161902 -0.3492159 2 0.0 0.5554452 -0.6002261 0.8212632 0.0 3 0.0 0.5161902 0.8212632 0.3653428 0.8721010 L 0.0 -0.3492159 0.0 0.8721010 0.0

[0051] like Fig.10 As shown in Figure 2, the number of passband transmission poles can be controlled by adjusting the number of metal slots. Fig.11 As shown in the figure, the position of the transmission pole in the passband can be controlled by adjusting the angle of each metal slot. A specific analysis shows that as the angle of the oblique metal slot increases, the low-frequency transmission pole moves toward the low frequency, and the high-frequency transmission pole moves toward the high frequency, so that the transmission pole position of the filter can be controlled, and the filter bandwidth can be controlled. Fig.13 As shown, the eigenmode resonant frequency can be adjusted by adjusting the width of the radial slot, thereby changing the coupling coefficient of the filter. Specific analysis shows that the high and low resonant frequencies increase with the increase of the width of the radial slot, and the coupling coefficient decreases with the increase of the width of the radial slot. Specific embodiment:

[0053] In a specific embodiment, the top dielectric substrate (10) is made of Rogers RT 5880 dielectric material with a dielectric constant of 2.2, a loss tangent of 0.0009, and a thickness of 0.508 mm; the middle dielectric substrate (5) is made of Rogers 4350 dielectric material with a dielectric constant of 3.66, a loss tangent of 0.004, and a thickness of 0.508 mm; the bottom dielectric substrate (4) is made of Rogers 4003C dielectric material with a dielectric constant of 3.55, a loss tangent of 0.0027, and a thickness of 0.813 mm; the overall size of the filter is 26.4 mm*26.4 mm*1.829 mm. Figure 6The impedance bandwidth of S11<-10dB in the passband is 22.99-28.67GHz, and the relative bandwidth of the passband is 20.56%. The out-of-band suppression of the filter is good. The stop-band suppression is S21 generally lower than -20dB in the frequency band below 21.7GHz, and the stop-band suppression is S21 generally lower than -15dB in the frequency band above 29GHz. Two transmission zeros are introduced on both sides of the passband to achieve better out-of-band suppression. The overall group delay in the passband is less than 0.5ns, achieving a lower group delay.

[0054] Compared with the prior art, the present invention has the following advantages:

[0055] It has a wider passband within the passband range;

[0056] During the design process, the order of the filter can be controlled by the logarithm of the etched grooves on the circular metal patch, thereby achieving control of the filter bandwidth.

[0057] During the design process, the center frequency of the transmission pole of the filter can be controlled by the angle of the etched groove on the circular metal patch, thereby controlling the frequency band of the filter.

[0058] Solve the problem that traditional broadband filters need to couple multiple independent resonators and are difficult to integrate;

[0059] It solves the problem that traditional 5G millimeter wave single-frequency filters can only cover a single 5G millimeter wave frequency band;

[0060] Achieved lower group delay performance;

[0061] It has the advantages of high out-of-band suppression, good frequency selectivity, easy processing and stable structure.

[0062] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0063] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An electromagnetically coupled controllable integrated substrate gap waveguide planar broadband bandpass filter, characterized in that: Including: A bottom dielectric substrate (4), an intermediate dielectric substrate (5), and a top dielectric substrate (9) sequentially arranged from bottom to top; The bottom dielectric substrate (4) is printed with a metal copper-clad layer (1) on the lower surface, internally loaded with periodic metallized vias (2), and printed with metallized circular patches (3) on the upper surface; The upper surface of the intermediate dielectric substrate (5) is printed with a transmission line (6) of an integrated substrate gap waveguide. A circular metal patch (13) is introduced on the transmission line of the integrated substrate gap waveguide. Three pairs of radiating slots are cut on the circular metal patch (13) to obtain six fan-shaped regions. A pair of fan-shaped regions that are symmetric up and down form a pair of identical resonators. Based on this, three pairs of completely symmetric resonators are obtained to form a third-order planar bandpass filter; The upper surface of the top dielectric substrate (9) is printed with a metal copper-clad layer (10), and a "king" - shaped absolutely symmetric loaded stub defected ground structure (11) is etched on the upper surface metal copper-clad layer; The radiating slots opened on the circular metal patch (13): The first pair of radiating slots (7) are completely perpendicular to the direction of the transmission line (6), and the second pair of radiating slots (8) and the third pair of radiating slots (12) respectively have the same included angle with respect to the first pair of slots (7); After the radiating slots are opened on the circular metal patch (13), there is a part of the metal patch connected in the middle.

2. The electromagnetically coupled controllable integrated substrate gap waveguide planar broadband bandpass filter according to claim 1, characterized in that: The "king" - shaped absolutely symmetric loaded stub defected ground structure etched on the metal copper-clad layer (10) is completely aligned with the part of the circular metal patch (13) on the transmission line (6).

3. The electromagnetically coupled controllable integrated substrate gap waveguide planar broadband bandpass filter according to claim 1, characterized in that: Changing the angle of the radiating metal slots can control the position of the transmission poles of the filter.

4. The electromagnetically coupled controllable integrated substrate gap waveguide planar broadband bandpass filter according to claim 1, characterized in that: Changing the number of radiating metal slots can control the order of the filter, and thus control the bandwidth of the filter.

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