A broadband vertically coupled filter

Abstract

The application belongs to the field of microwave technology, and discloses a kind of wideband vertical coupling filter, including first metal ground plate and second metal ground plate, first metal ground plate and second metal ground plate between including first resonator layer, second resonator layer and third resonator layer in turn, there are several metal columns on second metal ground plate, the top of metal column is connected metal patch, all metal patch and metal column jointly enclose quasi-closed resonant cavity, first resonator layer includes first resonator, first resonator layer, second resonator layer and third resonator layer are located in quasi-closed resonant cavity, second resonator is connected to first resonator layer and third resonator layer respectively.This application can realize the low loss and miniaturization of wideband filter.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of microwave technology, and particularly relates to a wideband vertical coupling filter. BACKGROUND

[0002] In recent years, the research on AMC (Artificial Magnetic Conductor) in the millimeter wave band has attracted much attention. The core is composed of periodically arranged EBG (Electromagnetic Band Gap) structure units. When placed parallel to the ideal conductor, it can form a non-electric contact electromagnetic shielding structure. This structure stands out with the advantages of wide electromagnetic band gap, low loss and self-packaging. According to the structure, it can be divided into ridge gap waveguide, slot gap waveguide and suspended microstrip line gap waveguide. Among them, the printed ridge gap waveguide (Printed Ridge Gap Waveguide) has become a research hotspot due to its compact size, easy integration and air medium transmission characteristics.

[0003] In the field of filters, although the technology is constantly innovating and the design scheme is emerging in an endless stream, with the rapid growth of wireless communication demand, the iteration and upgrading of communication technology, and the widespread popularity of Internet of Things devices, improving the integration of microwave devices has become a key development direction, which makes the design of new filters have very high requirements for miniaturization. In the current research, the vertical coupling technology is often used to achieve the miniaturization goal of the filter, but this technology still has many shortcomings, such as insufficient out-of-band suppression depth, narrow stopband width, large loss, and the degree of miniaturization needs to be further improved. SUMMARY

[0004] In order to achieve the above purpose, the application provides a wideband vertical coupling filter, which introduces two weak coupling paths on the basis of traditional vertical coupling to construct a quasi-closed resonant cavity. The wideband vertical coupling filter of the application can realize low loss and miniaturization of the wideband filter.

[0005] In order to achieve the above purpose, the application is realized by the following technical scheme:

[0006] The application is a kind of broadband vertical coupling filter, including horizontally arranged first metal ground plate and second metal ground plate, first metal ground plate and second metal ground plate are sequentially arranged from top to bottom by first resonator layer, second resonator layer and third resonator layer, a plurality of EBG units are arranged between second metal ground plate and first resonator layer, electromagnetic shielding effect is formed by a plurality of periodically arranged EBG units between second metal ground plate and first resonator layer, which forms quasi-closed resonant cavity, confines energy in quasi-closed resonant cavity, improves unloaded quality factor, second resonator layer is connected with first resonator layer and third resonator layer respectively, first resonator layer, second resonator layer and third resonator layer are located in quasi-closed resonant cavity, and vertical coupling of electric and energy between first resonator layer, second resonator layer and third resonator layer is realized.

[0007] Further improvement of the application is that metal patches are periodically arranged vertically on the first resonator layer, and a plurality of metal columns corresponding to the metal patches are periodically arranged on the upper surface of the second metal ground plate, each corresponding metal column is connected with the metal patch to form an EGB unit.

[0008] Further improvement of the application is that a pair of symmetrically arranged first resonators are arranged in the first resonator layer, each first resonator is connected with a microstrip line, the quasi-closed resonant cavity has a first opening and a second opening, one of the microstrip lines extends from the first opening and serves as an input end Port1, and the other microstrip line extends from the second opening and serves as an output end Port2, thereby realizing electromagnetic signal feeding.

[0009] Further improvement of the application is that the microstrip line adopts a multi-section stepped impedance microstrip line, including a high impedance section arranged in a trapezoidal shape, a middle impedance section arranged in a rectangular shape, and a low impedance section arranged in a trapezoidal shape, a window is formed on the middle impedance section between the high impedance section and the middle impedance section arranged in a rectangular shape, and the middle impedance section and the low impedance section arranged in a trapezoidal shape are connected with each other, the microstrip line is connected with the first resonator through the low impedance section, and smooth transition of the microstrip line and the quasi-closed resonant cavity is realized.

[0010] Further improvement of the application is that each first resonator is a quarter-wavelength asymmetric hairpin resonator, the first resonator includes a first short arm and a first long arm, thereby realizing differential coupling function, the first short arm and the first long arm of the same first resonator are parallel to each other and one end of the first short arm is connected with one end of the first long arm, the first long arms of the two symmetric first resonators are adjacent and spaced apart, and the first short arm of each first resonator is connected with a corresponding microstrip line.

[0011] The further improvement of the application is that a pair of symmetrically arranged second resonators is arranged in the second resonator layer, the second resonator is a quarter-wavelength asymmetrically folded resonator, the second resonator comprises a second short arm and a second long arm, the second short arm and the second long arm of the same second resonator are parallel to each other, and one end of the second short arm is connected to one end of the second long arm, the second short arms of the two second resonators are adjacent and arranged at a distance, and the second short arms of the two symmetrically arranged second resonators form a lateral coupling resonance, realizing multi-path transmission of signals.

[0012] The further improvement of the application is that a third resonator is arranged in the third resonator layer, the third resonator layer is a half-wavelength resonator with folded step impedance, the third resonator comprises two third short arms in the middle and two third long arms on both sides, one end of the two parallel third short arms is connected to the adjacent third long arm, and the two adjacent third short arms are connected, and the two third long arms and the two third short arms are arranged in parallel.

[0013] The further improvement of the application is that the end of each first short arm is adjacent to a first square patch resonator, the first square patch resonator is connected to the second long arm of the second resonator through a first metal connecting column, each third long arm of the third resonator is adjacent to a second square patch resonator, and the second square patch resonator is connected to the second long arm of the second resonator through a second metal connecting column, in the first resonator layer, the two symmetric first resonators are weakly coupled laterally, and the two symmetric first resonators and the first square patch resonator are laterally coupled, the first square patch resonator is vertically coupled to the second resonator through the first metal connecting column, electromagnetic energy in the first resonator layer is transmitted to the second resonator layer, in the second resonator layer, the two symmetrically arranged second resonators form a lateral coupling resonance, and the second resonator and the second square patch resonator are laterally coupled, and the second square patch resonator is vertically coupled to the third resonator through the second metal connecting column, electromagnetic energy in the second resonator layer is transmitted to the third resonator layer.

[0014] The beneficial effects of the application are:

[0015] The application introduces two weak coupling paths on the basis of traditional vertical coupling through the design of the first resonator layer, the second resonator layer and the third resonator layer.

[0016] The application can constrain energy in a quasi-closed electromagnetic cavity through the periodic distribution of the EBG unit structure, effectively reduces energy loss, and constructs a quasi-closed resonant cavity, which, in cooperation with the design of the multi-section stepped impedance microstrip line, can effectively reduce electromagnetic leakage and significantly improve the no-load quality factor Qe.

[0017] The application can effectively adjust the frequency position of the transmission zero point by precisely regulating the coupling strength of the weakly coupled resonance path, thereby significantly improving the out-of-band suppression performance and frequency selectivity of the filter. At the same time, by increasing the number of vertically coupled resonator layers, the distribution of the resonator in the vertical direction is further optimized, greatly reducing the size of the filter and the volume of the horizontal space, making the overall size small and convenient for processing and manufacturing. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a structural schematic diagram of a wideband vertical coupling filter of the application.

[0019] Figure 2 is a top perspective view of a wideband vertical coupling filter of the application.

[0020] Figure 3 is a schematic diagram of a single EGB unit structure of the application.

[0021] Figure 4 is a top view of a quasi-hermetic resonant cavity in a first resonator layer of the application.

[0022] Figure 5 is a schematic diagram of a microstrip line of the application.

[0023] Figure 6 is a top view of a structure in a first resonator layer of the application.

[0024] Figure 7 is a top view of a second resonator in a second resonator layer of the application.

[0025] Figure 8 is a top view of a third resonator and a second square patch resonator in a third resonator layer of the application.

[0026] Figure 9 is a parameter simulation waveform diagram of the design of a wideband vertical coupling filter of the application.

[0027] wherein G1 is a first metal ground plate; G2 is a second metal ground plate; 10 is a first resonator layer; 11 is a second resonator layer; 12 is a third resonator layer; 1 is a metal column; 2 is a metal patch; 3 is a quasi-hermetic resonant cavity; 31 is a first opening; 32 is a second opening; 4 is a first resonator; 5 is a microstrip line; 51 is a high impedance section; 52 is an intermediate impedance section; 53 is a low impedance section; 521 is a window; 6 is a second resonator; 7 is a third resonator; RL1 is a first square patch resonator; RL3 is a second square patch resonator; 91 is a first metal connecting column; 92 is a second metal connecting column. DETAILED DESCRIPTION

[0028] In the following description of the present application, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, it will be recognized by one of ordinary skill in the art that the various implementations of the present application can be practiced without these specific details. In other instances, well-known structures and components are not described in detail in order to avoid obscuring aspects of the present application. Also, some of the features of the present application can be used to advantage without a complete understanding of the other features.

[0029] In the description of present application, it needs to be explained that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like is based on the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. In addition, the terms "first", "second", "third" are only for the purpose of description and cannot be understood as indicating or implying relative importance.

[0030] In the description of the present application, it needs to be explained that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connection" should be understood broadly, for example, it can be fixed connection, or detachable connection, or integrally connected; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through intermediate medium, or it can be the internal communication of two elements, it can be wireless connection, or wired connection. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0031] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as there is no conflict between them.

[0032] As shown in Figures 1-3 The present application discloses a kind of wideband vertical coupling filter, including horizontally arranged first metal ground plate G1 and second metal ground plate G2, first resonator layer 10, second resonator layer 11 And third resonator layer 12 are sequentially arranged from top to bottom between the first metal ground plate G1 and second metal ground plate G2, the second resonator layer 11 is connected first resonator layer 10 And third resonator layer 12 respectively, the first resonator layer 10, the second resonator layer 11 And third resonator layer 12 are located in the quasi-closed resonant cavity 3, realize the vertical coupling of electricity and energy between first resonator layer 10, second resonator layer 11 And third resonator layer 12, to generate more resonance point to realize wider band filter design, generate more transmission zero to expand the stopband range.

[0033] Metal patches 2 are periodically and vertically arranged on the first resonator layer 10, and a number of metal columns 1 corresponding to the metal patches 2 are periodically and vertically arranged on the upper surface of the second metal ground plate G2. Each corresponding metal column 1 is connected to the metal patch 2 to form a mushroom-shaped EGB unit structure.

[0034] like Figure 4 As shown, several EBG units are disposed between the second metal ground plane G2 and the first resonator layer 10. These periodically arranged EBG units together form a quasi-sealed resonant cavity 3, effectively suppressing the rapid attenuation of energy caused by outward electromagnetic field radiation. Furthermore, to achieve broadband filtering in the millimeter-wave band, the electromagnetic bandgap can be controlled by adjusting the lateral width W and longitudinal length L of the quasi-sealed resonant cavity 3. The electromagnetic shielding effect created by the two rows of mushroom-shaped EBG units surrounding the quasi-sealed resonant cavity 3 efficiently confines energy within the quasi-sealed resonant cavity 3, significantly improving the unloaded quality factor Qe.

[0035] like Figure 1 and Figure 4 As shown, a pair of symmetrically arranged first resonators 4 are provided in the first resonator layer 10, each of the first resonators 4 is connected to a microstrip line 5, and the quasi-closed resonant cavity 3 has a first opening 31 and a second opening 32, wherein one of the microstrip lines 5 extends from the first opening 31 and serves as an input end Port1, and the other microstrip line 5 extends from the second opening 32 and serves as an output end Port2, thereby realizing the feeding of electromagnetic signals through the microstrip-gap waveguide structure.

[0036] like Figure 5 As shown, the microstrip line 5 adopts a multi-section stepped impedance microstrip line, including a high impedance section 51 arranged in a trapezoidal shape, an intermediate impedance section 52 arranged in a rectangular shape, and a low impedance section 53 arranged in a trapezoidal shape. The high impedance section 51 and the intermediate impedance section 52 arranged in a rectangular shape are connected to each other, and the intermediate impedance section 52 and the low impedance section 53 arranged in a trapezoidal shape are connected to each other. The microstrip line 5 is connected to the first resonator 4 through the low impedance section 53. This structure is based on microstrip-gap waveguide conversion to achieve a smooth transition between the microstrip line 5 and the quasi-sealed resonant cavity 3. A window 521 is provided on the intermediate impedance section 52 to further optimize the electromagnetic coupling characteristics.

[0037] like Figure 6As shown, each first resonator 4 is a quarter-wavelength asymmetric hairpin resonator, the wavelength refers to the working wavelength of the first resonator 4, the first resonator 4 includes a first short arm and a first long arm, and realizes a differentiated coupling function, the first short arm and the first long arm of the same first resonator 4 are parallel to each other and one end of the first short arm is connected to one end of the first long arm, the first long arms of two symmetrical first resonators 4 are adjacent and are arranged at a distance, and the first short arm of each first resonator 4 is connected to a corresponding microstrip line 5,

[0038] As shown in the figure, Figure 7 As shown, a pair of symmetrical second resonators 6 are arranged in the second resonator layer 11, the second resonator 6 is a quarter-wavelength asymmetric hairpin resonator, the second resonator 6 includes a second short arm and a second long arm, the second short arm and the second long arm of the same second resonator 6 are parallel to each other and one end of the second short arm is connected to one end of the second long arm, the second short arms of two second resonators 6 are adjacent and are arranged at a distance, and the second short arms of two symmetrical second resonators 6 form a lateral coupling resonance, realizing multi-path transmission of signals, and here the wavelength refers to the working wavelength of the second resonator 6.

[0039] As shown in the figure, Figure 8 As shown, the third resonator layer 12 is provided with a third resonator 7, the third resonator layer 12 is a half-wavelength resonator with folded step impedance, the third resonator 7 includes two third short arms in the middle and two third long arms on both sides, one end of the two parallel third short arms is connected to the adjacent third long arm, and the two adjacent third short arms are connected, and the two third long arms and the two third short arms are arranged in parallel, and here the wavelength refers to the working wavelength of the third resonator 7.

[0040] In order to realize the electrical connection and signal coupling between the first resonator layer 10, the second resonator layer 11 and the third resonator layer 12, as shown in the figure, Figure 1 and Figure 6 As shown in the figure, the end of each first short arm in the first resonator layer 10 is adjacent to a first square patch resonator RL1, the first square patch resonator RL1 is connected to the second long arm of the second resonator 6 through a first metal connecting column 91, and each third long arm of the third resonator 7 is adjacent to a second square patch resonator RL3, and the second square patch resonator RL3 is connected to the second long arm of the second resonator 6 through a second metal connecting column 92.

[0041] Through the above arrangement, in the first resonator layer 10, the two symmetrical first resonators 4 are laterally weakly coupled to resonate, and the two symmetrical first resonators 4 and the first square patch resonator RL1 are laterally coupled to resonate, the first square patch resonator RL1 is vertically coupled to the second resonator 6 through the first metal connecting column 91, the electromagnetic energy in the first resonator layer 10 is transmitted to the second resonator layer 11, in the second resonator layer 11, the two symmetrical second resonators 6 are laterally coupled to resonate, and the second resonator 6 and the second square patch resonator RL3 are laterally coupled to resonate, the second square patch resonator RL3 is vertically coupled to the third resonator 7 through the second metal connecting column 92, and the electromagnetic energy in the second resonator layer 11 is transmitted to the third resonator layer 12, the filter structure meets the high selectivity and miniaturization requirements of the millimeter wave filter through the three-dimensional space layout and multi-form coupling design.

[0042] As shown in Figure 6 , the short side length of the high impedance section in the microstrip line is , the width of the middle impedance section, i.e. the long side length of the high impedance section, is , the long side length of the low impedance section is , the first long arm length of the first resonator is , the width of the first resonator is , the first short arm length of the first resonator is , the gap width between the two first resonators is .

[0043] As shown in Figure 7 , the key dimensions involved in the second resonator are , , , , , , and the gap width between the two second resonators is .

[0044] As shown in Figure 8 , the key dimensions involved in the third resonator are , , , , , , and the gap width between the two third short arms of the third resonator is .

[0045] For each of the above dimensions, the numerical value can be as shown in Table 1:

[0046] Table 1

[0047] The simulation results of the wideband vertically coupled filter designed with the above dimensions are shown in the following table. Figure 9 As can be seen from the simulation results, the passband range covers 31.95GHz-39.1GHz, the center frequency is 35.53GHz, the -3dB bandwidth is 7.15GHz, the corresponding fractional bandwidth is 20.1%, and the wideband signal transmission capability is achieved. At the same time, the filter has very low insertion loss, the minimum passband insertion loss is only 0.15dB, and the maximum insertion loss is controlled within 0.18dB in the frequency band of 32.78GHz to 38.28GHz, effectively guaranteeing the high efficiency and low loss characteristics of signal transmission in the passband.

[0048] The filter exhibits excellent selectivity on both sides of the frequency band, Figure 9 The S21 parameter drop rate on the left side of the intermediate frequency band is 27.6dB / GHz, and on the right side is 26.3dB / GHz. This result reflects that the filter can quickly suppress out-of-band signals at the passband boundary, forming a steep transition band characteristic.

[0049] In terms of stopband performance, the filter exhibits excellent wide stopband suppression capability. At a frequency of 31GHz, a stopband suppression of up to 38.76dB is achieved; in the wide frequency range of 5-25.2GHz and 45.4-70GHz, the stopband suppression is all more than 25dB. The above performance indicators show that the wideband vertically coupled filter has reached a high level in terms of passband transmission efficiency and stopband suppression capability.

[0050] The wideband vertically coupled filter provided by the embodiment of the present application is designed by the first resonator layer, the second resonator layer and the third resonator layer, two weak coupling paths are innovatively introduced on the basis of the traditional vertical coupling, a multi-dimensional coupling network is constructed, the volume of the horizontal space is reduced, the overall size is small and compact, and the processing and manufacturing are facilitated. At the same time, the wideband vertically coupled filter has high compatibility and can easily realize system integration with other microwave and millimeter wave circuits. In addition, by means of the periodic distribution of the EBG unit structure, a quasi-closed resonant cavity is constructed, and the design of the multi-section stepped impedance microstrip line can effectively reduce electromagnetic leakage and significantly improve the unloaded quality factor Qe, and the resonant point can be determined by the length and width of the quasi-closed resonant cavity, the design of each size on each resonator, and the size parameters of the multi-section stepped impedance microstrip line.

[0051] The above only describes the embodiments of the present application and is not intended to limit the present application. The present application can have various changes and modifications for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the scope of the claims of the present application.

Claims

1. A broadband vertically coupled filter comprising a first metal ground plate (G1) and a second metal ground plate (G2) arranged horizontally, characterized in that: A first resonator layer (10), a second resonator layer (11) and a third resonator layer (12) are sequentially arranged from top to bottom between the first metal ground plate (G1) and the second metal ground plate (G2); a plurality of EBG units are arranged between the second metal ground plate (G2) and the first resonator layer (10); a quasi-sealed resonant cavity (3) is formed between the second metal ground plate (G2) and the first resonator layer (10) by the plurality of periodically arranged EBG units, thereby forming an electromagnetic shielding effect, confining energy within the quasi-sealed resonant cavity (3), and improving the no-load quality factor; the second resonator layer (11) is respectively connected to the first resonator layer (11) and the second resonator layer (12); The invention relates to a quasi-sealed resonator layer (10) and a third resonator layer (12), wherein the first resonator layer (10), the second resonator layer (11) and the third resonator layer (12) are located in the quasi-sealed resonator cavity (3), realizing vertical electrical and energy coupling between the first resonator layer (10), the second resonator layer (11) and the third resonator layer (12), and periodically setting a metal patch (2) on the first resonator layer (10), and periodically setting a plurality of metal columns (1) corresponding to the metal patch (2) on the upper surface of the second metal ground plate (G2), and each corresponding metal column (1) is connected to the metal patch (2) to form an EGB unit.

2. A broadband vertically coupled filter according to claim 1, characterized in that: A pair of symmetrically arranged first resonators (4) are provided in the first resonator layer (10), each of the first resonators (4) is connected to a microstrip line (5), and the quasi-sealed resonant cavity (3) has a first opening (31) and a second opening (32), wherein one of the microstrip lines (5) extends from the first opening (31) and serves as an input end Port1, and the other microstrip line (5) extends from the second opening (32) and serves as an output end Port2, thereby realizing the feeding of electromagnetic signals.

3. The broadband vertically coupled filter according to claim 2, wherein: The microstrip line (5) adopts a multi-section stepped impedance microstrip line, including a high impedance section (51) arranged in a trapezoidal shape, an intermediate impedance section (52) arranged in a rectangular shape, and a low impedance section (53) arranged in a trapezoidal shape. A window (521) is provided on the intermediate impedance section (52) between the high impedance section (51) and the intermediate impedance section (52) arranged in a rectangular shape. The intermediate impedance section (52) and the low impedance section (53) arranged in a trapezoidal shape are connected to each other. The microstrip line (5) is connected to the first resonator (4) through the low impedance section (53), thereby achieving a smooth transition between the microstrip line (5) and the quasi-sealed resonant cavity (3).

4. The broadband vertically coupled filter according to claim 3, wherein: Each first resonator (4) is a quarter-wavelength asymmetric hairpin resonator. The first resonator (4) includes a first short arm and a first long arm to realize a differentiated coupling function. The first short arm and the first long arm of the same first resonator (4) are parallel to each other and one end of the first short arm is connected to one end of the first long arm. The first long arms of two symmetrical first resonators (4) are adjacent and spaced apart. The first short arm of each first resonator (4) is respectively connected to a corresponding microstrip line (5).

5. The broadband vertically coupled filter according to claim 4, wherein: A pair of symmetrically arranged second resonators (6) are provided in the second resonator layer (11). The second resonator (6) is a quarter-wavelength asymmetric hairpin resonator. The second resonator (6) includes a second short arm and a second long arm. The second short arm and the second long arm of the same second resonator (6) are parallel to each other, and one end of the second short arm is connected to one end of the second long arm. The second short arms of the two second resonators (6) are adjacent and spaced apart. A lateral coupling resonance is formed between the second short arms of the two symmetrically arranged second resonators (6), thereby realizing multi-path transmission of signals.

6. The broadband vertically coupled filter according to claim 5, characterized in that: A third resonator (7) is arranged in the third resonator layer (12), and the third resonator layer (12) is a half-wavelength resonator with folded step impedance. The third resonator (7) includes two third short arms located in the middle and two third long arms located on both sides, one end of the two parallel third short arms is respectively connected to the adjacent third long arms and the adjacent two third short arms are connected, and the two third long arms and the two third short arms are arranged in parallel.

7. The broadband vertically coupled filter according to claim 6, wherein: A first square patch resonator (RL1) is adjacently arranged at the end of each first short arm, and the first square patch resonator (RL1) is connected to the second long arm of the second resonator (6) through a first metal connecting column (91). A second square patch resonator (RL3) is adjacently arranged at each third long arm of the third resonator (7), and the second square patch resonator (RL3) is connected to the second long arm of the second resonator (6) through a second metal connecting column (92). In the first resonator layer (10), two symmetrical first resonators (4) are laterally weakly coupled and resonate with each other, and at the same time, the two symmetrical first resonators (4) and the first square patch resonator (R The first square patch resonator (RL1) is vertically coupled with the second resonator (6) through the first metal connecting column (91), and the electromagnetic energy in the first resonator layer (10) is transferred to the second resonator layer (11). In the second resonator layer (11), a lateral coupling resonance is formed between the two symmetrically arranged second resonators (6). At the same time, a lateral coupling resonance is formed between the second resonator (6) and the second square patch resonator (RL3). The second square patch resonator (RL3) is vertically coupled with the third resonator (7) through the second metal connecting column (92), and the electromagnetic energy in the second resonator layer (11) is transferred to the third resonator layer (12).

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