A dual-mode dual-passband filter with bandwidth and frequency independent tunability and modulation method

Abstract

The disclosure provides a bandwidth and frequency independent adjustable dual-mode dual-passband filter and a modulation method, the filter comprising: a substrate, and a dual-mode resonator and a coupler arranged in the substrate, the dual-mode resonator comprising first and second dual-mode resonators of the same size arranged in parallel in the substrate in staggered layers, and each dual-mode resonator is loaded with a metal patch on one inner corner; the coupler comprises an odd-mode coupler and an even-mode coupler arranged between the first and second dual-mode resonators. The dual-mode resonator is an inner recess type square ring, a square patch is loaded on one corner of the inner recess type square ring to realize the separation of odd and even modes, and the inner recess area of the inner recess type square ring makes the odd and even modes respectively distributed on the main and vice diagonal protrusions of the inner recess type square ring which are perpendicular to each other. By changing the size of the metal patch and the length of the coupler, the independent adjustment of the dual-passband bandwidth and the working frequency is realized.

Description

Technical Field

[0001] This invention belongs to the field of microwave technology, and particularly relates to a dual-mode dual-passband filter with independently adjustable bandwidth and frequency and a modulation method thereon. Background Technology

[0002] Currently, the frequency bands used by various communication systems are concentrated in the low-frequency bands of radio frequency (RF) and microwave, making spectrum resources extremely congested. To achieve dual-band or multi-band communication, each band requires independent RF front-end components, resulting in a large system size, high power consumption, and high cost. Designing RF front-end components in a dual-band or multi-band configuration can significantly reduce system size, cost, and power consumption, enhance reliability, and promote the miniaturization and high integration of communication systems. Dual-mode dual-passband filters, containing two passbands, enable dual-frequency filtering. Simultaneously, dual-mode resonators reduce the number of resonators, making the filter structure more compact, and they are increasingly used in the design of high-performance filters for wireless communication systems.

[0003] Traditional dual-mode dual-passband microstrip filters are large in size due to limitations in substrate material, making them unsuitable for increasingly integrated wireless communication systems. LTCC (Low Temperature Co-fired Ceramic) technology, using a high-dielectric-constant ceramic dielectric, effectively reduces the physical structure of the resonator and enhances odd-even mode coupling strength. Therefore, LTCC dual-mode filters have become the best implementation method for miniaturized dual-mode filters. For example, patent application number 201710423794.6, entitled "An SHF Band LTCC Multimode Dual-Passband Filter," uses the LTCC process to fabricate resonator stubs within a ceramic substrate, forming two bandpass filter structures. This achieves the replacement of two single-passband filters with a dual-passband filter, resulting in a more compact and smaller filter structure.

[0004] However, the inventors discovered that the bandwidth and operating frequency of their dual-passband filter could not be independently adjusted. Adjusting the bandwidth of the high-frequency passband would affect the bandwidth of the low-frequency passband, and adjusting the operating frequency of the high-frequency passband would also change the operating frequency of the low-frequency passband. This made it impossible to achieve independent modulation of the bandwidth and operating frequency of the two passbands, thus limiting the performance of the filter. Summary of the Invention

[0005] To address the aforementioned problems, this disclosure proposes a dual-mode dual-passband filter and modulation method with independently adjustable bandwidth and frequency. By setting two concave square ring resonators of the same size and parallel to each other, and symmetrically loading metal patches onto a corner of the protrusion of the concave square ring resonators about their axes of symmetry, the odd-mode and even-mode resonant modes forming the two passbands are separated significantly. This decomposes the originally odd-mode coupled portion into odd-mode coupled and even-mode coupled portions, preventing them from interfering with each other. Therefore, the passband can be independently adjusted by independently controlling either the odd-mode or even-mode resonant frequency.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a dual-mode dual-passband filter with independently adjustable bandwidth and frequency, comprising: a substrate, and a dual-mode resonator and a coupler disposed within the substrate, characterized in that the dual-mode resonator comprises a first dual-mode resonator and a second dual-mode resonator of the same size disposed in parallel layers within the substrate; a first metal patch is loaded on one inner corner of the first dual-mode resonator, and a second metal patch is loaded on one inner corner of the second dual-mode resonator; the coupler comprises an odd-mode coupler and an even-mode coupler, disposed between the first dual-mode resonator and the second dual-mode resonator.

[0007] Preferably, the dual-mode resonator is in the shape of a square ring, with all four sides of the square ring recessed inward and the four corners of the square ring protruding to form four protrusions.

[0008] Preferably, the first metal patch and the second metal patch are loaded at the inner corner of a protrusion of the dual-mode resonator.

[0009] Preferably, the first metal patch and the second metal patch are symmetrically arranged about the axis of symmetry of the two dual-mode resonators.

[0010] Preferably, the odd-mode resonant mode and the even-mode resonant mode are distributed on the main and secondary diagonals of the dual-mode resonator.

[0011] Preferably, the odd-mode coupler is disposed between the odd-mode coupling paths of the two dual-mode resonators.

[0012] Preferably, the even-mode coupler is disposed between the even-mode coupling paths of the two dual-mode resonators.

[0013] Preferably, both the odd-mode coupler and the even-mode coupler are elongated metal strips.

[0014] Preferably, it further includes a shielding layer disposed within the substrate, and a signal input port, a signal output port, a first grounding port, and a second grounding port disposed on the outer surface of the substrate and sequentially distributed along the outer surface; the shielding layer includes a first shielding layer and a second shielding layer, which are arranged at intervals along the stacking direction inside the substrate.

[0015] Secondly, the present invention provides a modulation method for a dual-mode dual-passband filter with independently adjustable bandwidth and frequency, comprising: A first metal patch is loaded on a protrusion on the secondary diagonal of the first dual-mode resonator, and a second metal patch is loaded on a protrusion on the main diagonal of the second dual-mode resonator; the two metal patches are the same size and shape. The first dual-mode resonator and the second dual-mode resonator are placed parallel to each other in the substrate; wherein the first metal patch and the second metal patch are symmetrical about the axis of symmetry of the two dual-mode resonators and are far apart from each other; An odd-mode coupler is placed between the odd-mode coupling paths of the two two-mode resonators, and an even-mode coupler is placed between the even-mode coupling paths of the two two-mode resonators; the odd-mode coupler and the even-mode coupler are on a horizontal line and parallel to the two two-mode resonators. By adjusting the size of the metal patch and the length of the coupler, the odd-even mode coupling strength can be changed, thus achieving independent modulation of the high-frequency and low-frequency passband bandwidth and frequency.

[0016] Compared with the prior art, the beneficial effects of this disclosure are as follows: (1) In this invention, the presence of the metal patch is equivalent to electromagnetic perturbation of the concave square ring dual-mode resonator, thereby achieving decoupling of odd and even modes. The odd-mode coupler is located between the odd-mode coupling paths of the two dual-mode resonators, and the even-mode coupler is located between the even-mode coupling paths of the two dual-mode resonators. The odd-mode coupler can control the coupling strength between odd-mode resonant modes, and the even-mode coupler can control the coupling strength between even-mode resonant modes, so as to achieve independent control of the bandwidth and frequency of the dual passband.

[0017] (2) The metal patches loaded by the two concave square ring dual-mode resonators of the present invention present an axisymmetric loading form, which is beneficial to realize independent control of the resonant frequency and coupling strength of the two passbands.

[0018] (3) The present invention places two concave square ring dual-mode resonators in staggered layers inside the LTCC to achieve a wide range of free control over the coupling degree, so as to achieve independent adjustment of the two passband operating frequencies by loading the square patch without affecting the bandwidth.

[0019] (4) The filter of the present invention has an independently adjustable operating frequency and bandwidth, a simple structure, is easy to manufacture, has a wide range of applications, and strong scalability. It is characterized by small size, light weight, and low cost.

[0020] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] The accompanying drawings, which form part of this disclosure, are used to provide a further understanding of this disclosure. The illustrative embodiments of this disclosure and their descriptions are used to explain this disclosure and do not constitute a limitation thereof.

[0022] Figure 1 A perspective view of a dual-mode dual-passband filter with independently adjustable bandwidth and frequency provided in Embodiment 1 of this disclosure; Figure 2 for Figure 1 Frequency response curve of a dual-mode dual-passband filter; Figure 3 To reduce Figure 1 Perspective view of the filter obtained after determining the dimensions of the metal patch; Figure 4 for Figure 3 Frequency response curve of a dual-mode dual-passband filter; Figure 5 To increase Figure 1 A perspective view of the filter obtained after the length of the odd-mode coupler; Figure 6 for Figure 5 Frequency response curve of a dual-mode dual-passband filter; Figure 7 To reduce Figure 1 A perspective view of the filter obtained by increasing the size of the metal patch and the length of its even-mode coupler; Figure 8 for Figure 7 Frequency response curve of a dual-mode dual-passband filter; Figure 9 This invention provides a dual-mode dual-passband filter modulation method with independently adjustable bandwidth and frequency, as shown in Embodiment 2 of this disclosure.

[0023] Wherein, 1-substrate; 2-layer; 201-signal input port; 202-signal output port; 203-first grounding port; 204-second grounding port; 31-first shielding layer; 32-second shielding layer; 41-first dual-mode resonator; 42-second dual-mode resonator; 51-even-mode coupler; 52-odd-mode coupler; 61-input structure; 62-output structure; 71-first metal patch; 72-second metal patch. Detailed implementation methods; The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] Explanation of technical terms: (1) Filter: A passive device in the communication radio frequency channel, which is the radio frequency component connected to the antenna in the radio frequency remote unit. In the passband, the filter allows the required frequency to pass through with low loss; outside the passband, the filter can attenuate the unwanted frequency components to avoid interference to other parts of the system.

[0026] (2) Resonator: It is a basic component of the filter in the communication system. Among them, the dual-mode resonator refers to a resonator with two resonant modes, that is, the resonator can achieve resonance at two frequencies.

[0027] (3) Odd mode resonance mode and even mode resonance mode: Two resonance modes possessed by dual-mode resonators.

[0028] (4) Coupling: The mutual energy exchange between the two resonant modes of a dual-mode resonator can realize the expansion of the frequency resonant mode. That is, the stronger the coupling, the wider the bandwidth that can be achieved.

[0029] (5) Coupling path: Coupling path refers to the coupling caused by the distribution of electric and magnetic fields in the equivalent circuit, not the electrical connection in the three-dimensional structure. Such coupling will occur as long as two couplers are close to each other.

[0030] Example 1 like Figure 1 As shown, this embodiment discloses a dual-mode dual-passband filter with independently adjustable bandwidth and frequency, including: a substrate 1, a dual-mode resonator 41 (42) and a coupler 51 (52) disposed in the substrate 1.

[0031] The dual-mode resonator 41 (42) includes a first dual-mode resonator 41 and a second dual-mode resonator 42 of the same size, arranged in parallel layers within the substrate 1. A first metal patch 71 is loaded on one inner corner of the first dual-mode resonator 41, and a second metal patch 72 is loaded on one inner corner of the second dual-mode resonator 42. The distance between the two dual-mode resonators is related to the bandwidth and needs to be adjusted according to the bandwidth specifications.

[0032] The coupler includes an odd-mode coupler 52 and an even-mode coupler 51, which are disposed between two dual-mode resonators 41 (42).

[0033] Specifically, the dual-mode resonator 41 (42) is in the shape of a square ring. The four sides of the square ring are concave inward, and the four corners of the square ring protrude to form four protrusions, making the dual-mode resonator 41 (42) a concave square ring.

[0034] Due to the concave region of the concave square ring itself, the odd-mode resonance mode and the even-mode resonance mode are distributed on the main and secondary diagonals that are perpendicular to each other in the dual-mode resonator 41 (42), and the two diagonals are connected to the two protrusions respectively.

[0035] In this design, the odd-mode resonance of the first dual-mode resonator 41 is achieved through an electric field symmetrically distributed along the main diagonal of the square ring, while the even-mode resonance is achieved through an electric field symmetrically distributed along the secondary diagonal of the square ring. Similarly, the odd-mode resonance of the second dual-mode resonator 42 is achieved through an electric field symmetrically distributed along the secondary diagonal of the square ring, while the even-mode resonance is achieved through an electric field symmetrically distributed along the main diagonal of the square ring. The first and second dual-mode resonators 41 are located in different planes and are parallel to each other, with their main and secondary diagonals also parallel. Although the odd and even modes are distributed in different regions, they are not decoupled and cannot be modulated individually.

[0036] In one specific embodiment, a first metal patch 71 is applied to the inner corner of a protrusion of the first dual-mode resonator 41, and a second metal patch 72 is applied to the inner corner of a protrusion of the second dual-mode resonator 42. The metal patches are equivalent to applying electromagnetic perturbations to the concave square ring resonator to achieve the separation of odd and even modes.

[0037] Specifically, the first metal patch 71 and the second metal patch 72 are symmetrically arranged about the axis of symmetry of the first dual-mode resonator 41 and the second dual-mode resonator 42. By loading the metal patches at symmetrical positions, the odd-mode electric field distribution can be distinguished from the even-mode electric field distribution, thus achieving odd-even mode decomposition.

[0038] The metal patch can be square, triangular, or other shapes. By adjusting the shape of the metal patch, its size can be changed, thereby adjusting the decoupling strength. In this specific embodiment, the metal patch is preferably square and completely fills the protrusion.

[0039] In one specific embodiment, odd-mode coupler 52 and even-mode coupler 51 are on a horizontal line and parallel to the two dual-mode resonators. Odd-mode coupler 52 is positioned between the odd-mode coupling paths of the two dual-mode resonators to control the coupling strength between the odd-mode resonant modes; even-mode coupler 51 is positioned between the even-mode coupling paths of the two dual-mode resonators to control the coupling strength between the even-mode resonant modes. Through odd-mode and even-mode decoupling, independent coupling of the odd-mode and even-mode resonant modes is achieved, thereby enabling independent modulation of the bandwidth and operating frequency of both the high-frequency and low-frequency passbands.

[0040] Figure 2 for Figure 1 The frequency response curve of the dual-mode dual-passband filter shows that the high-frequency passband and low-frequency passband of the dual-mode dual-passband filter have the same bandwidth.

[0041] In one specific embodiment, both the odd-mode coupler 52 and the even-mode coupler 51 are elongated metal strips, the length of which is related to the coupling strength.

[0042] In one specific embodiment, the input structure 61 and the output structure 62 realize signal input and output through electrical coupling, and the input structure 61 and the output structure 62 are respectively connected to the signal input port 201 and the signal output port 202.

[0043] In one specific embodiment, the dual-mode dual-passband filter further includes a shielding layer 31 (32) disposed in the substrate 1, and a signal input port 201, a signal output port 202, a first grounding port 203 and a second grounding port 204 disposed on the outer surface of the substrate 1 and sequentially distributed along the outer surface; the shielding layer 31 (32) includes a first shielding layer 31 and a second shielding layer 32, which are arranged sequentially at intervals along the stacking direction inside the substrate 1.

[0044] In one specific embodiment, the substrate 1 is a ceramic substrate with a dielectric constant of 6~10 and a dielectric loss factor tanα≤0.005.

[0045] Specifically, the first shielding layer 31 and the second shielding layer 32 are located at both ends of the laminate 2. Both ends of the first shielding layer 31 and the second shielding layer 32 extend to the edge of the substrate 1 to be electrically connected to the first grounding port 203 and the second grounding port 204.

[0046] This specific embodiment proposes an LTCC dual-mode dual-passband filter with independently adjustable bandwidth and operating frequency. The dual-mode resonator is a concave square ring. A square patch is loaded at one corner of the concave square ring to separate odd and even modes. The concave region of the concave square ring itself ensures that the odd and even modes are distributed on the mutually perpendicular main and secondary diagonal protrusions of the concave square ring, respectively. By setting two parallel dual-mode resonators, the odd and even modes are independently coupled based on their close proximity, providing a foundation for achieving independently adjustable dual-passband bandwidth. Furthermore, by changing the size of the metal patch and the length of the coupler, the dual-passband bandwidth and operating frequency can be independently adjusted. The dual-mode dual-passband filter provided by this disclosure can achieve independently adjustable dual-passband bandwidth and operating frequency, and has the characteristics of small size, light weight, and low cost, making it suitable for use in modern communication systems.

[0047] The following section verifies that the dual-mode dual-passband filter has independently adjustable dual-passband bandwidth and operating frequency.

[0048] (1) Change the size of the metal patch like Figure 3 As shown, the dimensions of the square metal patches loaded on the first dual-mode resonator 41 and the second dual-mode resonator 42 are adjusted to reduce the area of ​​the square metal patches. The area of ​​the metal patch is related to the coupling strength, so reducing the area of ​​the metal patch also reduces the separation degree of the odd and even modes.

[0049] Specifically, firstly, by Figure 2 It can be seen that the filter's reflection coefficient dB(S11) has a bandwidth in both the low and high frequency bands, and both bands exhibit two distinct downward peaks. For example, there are two downward peaks at 4.4 GHz and 4.6 GHz, which correspond to two resonant frequencies in the high-frequency range: one even-mode resonant frequency and one odd-mode resonant frequency. By changing the size of the metal patch, the separation between the even and odd modes is reduced, making these two frequencies equal, thus forming... Figure 4 In the middle, the dashed line of the high-frequency passband on the right has only one downward tip, which means that the coupling strength of odd-mode and even-mode resonances is increasing; while the low-frequency passband on the left still has two obvious downward tips.

[0050] from Figure 4 As can be seen, the high-frequency passband and low-frequency passband bandwidths of the dual-mode dual-passband filter are the same, which is consistent with... Figure 2 In comparison, the operating frequency of its high-frequency passband changes significantly, while the operating frequency of its low-frequency passband does not change significantly, indicating that only the independent control of the operating frequency of the high-frequency passband in the dual passband is achieved.

[0051] As can be seen, based on the dual-mode dual-passband filter with independently adjustable bandwidth and frequency provided in this disclosure, by reducing the area of ​​the square metal patch, independent modulation of the high-frequency passband operating frequency can be achieved without affecting the low-frequency passband.

[0052] (2) Change the length of the coupler like Figure 5 As shown, the odd-mode coupler 52 of the first dual-mode resonator 41 was adjusted by increasing its length. Since the coupler length is related to the coupling strength, increasing the coupler length also increases the separation between odd and even modes.

[0053] based on Figure 1 The frequency response curve after increasing the length of the odd-mode coupler 52 is shown in the figure below. Figure 6 As shown, the high-frequency passband and low-frequency passband bandwidths of a dual-mode dual-passband filter are different, and... Figure 2 In comparison, the bandwidth of its low-frequency passband remains largely unchanged, while the bandwidth of its high-frequency passband shows a significant change.

[0054] As can be seen, based on the dual-mode dual-passband filter with independently adjustable bandwidth and frequency provided in this disclosure, by increasing the length of the odd-mode coupler, independent modulation of the high-frequency passband bandwidth can be achieved without affecting the low-frequency passband.

[0055] (3) Change the size of the metal patch and change the length of the coupler. like Figure 7As shown, the size of the square patch loaded on the first dual-mode resonator 41 and the second dual-mode resonator 42 was reduced, and the even-mode coupler 51 in the second dual-mode resonator 42 was increased, which reduced the separation between odd and even modes and increased the even-mode coupling strength between the two dual-mode resonators. Based on Figure 1 After adjustment, the corresponding frequency response curve is as follows: Figure 8 As shown, the high-frequency passband and low-frequency passband bandwidths of the dual-mode dual-passband filter are different, and... Figure 2 In comparison, the bandwidth and operating frequency of its high-frequency passband and low-frequency passband have changed significantly, indicating that independent control of the dual-passband bandwidth and operating frequency has been achieved.

[0056] Example 2 like Figure 9 As shown in the illustration, this specific embodiment provides a modulation method for a dual-mode dual-passband filter with independently adjustable bandwidth and frequency, comprising: A first metal patch is loaded on a protrusion on the secondary diagonal of the first dual-mode resonator, and a second metal patch is loaded on a protrusion on the main diagonal of the second dual-mode resonator; the two metal patches are the same size and shape. The first dual-mode resonator and the second dual-mode resonator are placed parallel to each other in the substrate; wherein the first metal patch and the second metal patch are symmetrical about the axis of symmetry of the two dual-mode resonators and are far apart from each other; An odd-mode coupler is placed between the odd-mode coupling paths of the two two-mode resonators, and an even-mode coupler is placed between the even-mode coupling paths of the two two-mode resonators; the odd-mode coupler and the even-mode coupler are on a horizontal line and parallel to the two two-mode resonators. By adjusting the size of the metal patch and the length of the coupler, the odd-even mode coupling strength can be changed, thus achieving independent modulation of the high-frequency and low-frequency passband bandwidth and frequency.

[0057] This specific embodiment proposes a modulation method for a dual-mode dual-passband filter with independently adjustable bandwidth and frequency. By loading a square patch at one corner of a concave square ring dual-mode resonator, odd and even modes are separated. The concave region of the concave square ring itself ensures that the odd and even modes are distributed on the mutually perpendicular main and secondary diagonal protrusions of the ring. By setting two parallel dual-mode resonators, independent coupling of the odd and even modes is achieved based on their close proximity to each other, providing a foundation for independently adjustable dual-passband bandwidth. Furthermore, by changing the size of the metal patch and the length of the coupler, the independent adjustment of the dual-passband bandwidth and operating frequency is achieved.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A dual-mode dual-passband filter with independently adjustable bandwidth and frequency, comprising: A substrate, and a dual-mode resonator and coupler disposed within the substrate, characterized in that the dual-mode resonator is in the shape of a square ring, with all four sides of the square ring recessed inward and the four corners of the square ring protruding to form four protrusions; the dual-mode resonator includes a first dual-mode resonator and a second dual-mode resonator of the same size disposed in parallel and staggered layers within the substrate. A first metal patch is loaded at one interior corner of a first dual-mode resonator, and a second metal patch is loaded at one interior corner of a second dual-mode resonator; the first metal patch and the second metal patch are symmetrically arranged about the axis of symmetry of the two dual-mode resonators and are far apart from each other. The coupler includes an odd-mode coupler and an even-mode coupler, and is disposed between the first two-mode resonator and the second two-mode resonator; the odd-mode coupler is disposed between the odd-mode coupling paths of the two two-mode resonators; the even-mode coupler is disposed between the even-mode coupling paths of the two two-mode resonators.

2. The dual-mode dual-passband filter with independently adjustable bandwidth and frequency as described in claim 1, characterized in that, The first and second metal patches are loaded at the inner corner of a protrusion of the dual-mode resonator.

3. The dual-mode dual-passband filter with independently adjustable bandwidth and frequency as described in claim 1, characterized in that, Odd-mode and even-mode resonant modes are distributed on the main and secondary diagonals of the dual-mode resonator.

4. The dual-mode dual-passband filter with independently adjustable bandwidth and frequency as described in claim 1, characterized in that, Both the odd-mode coupler and the even-mode coupler are elongated metal strips.

5. The dual-mode dual-passband filter with independently adjustable bandwidth and frequency as described in claim 1, characterized in that, It also includes a shielding layer disposed within the substrate, and a signal input port, a signal output port, a first grounding port, and a second grounding port disposed on the outer surface of the substrate and sequentially distributed along the outer surface; the shielding layer includes a first shielding layer and a second shielding layer, which are arranged sequentially at intervals along the stacking direction inside the substrate.

6. A modulation method for a dual-mode dual-passband filter with independently adjustable bandwidth and frequency, characterized in that, include: A first metal patch is loaded onto a protrusion on the sub-diagonal of the first dual-mode resonator, and a second metal patch is loaded onto a protrusion on the main diagonal of the second dual-mode resonator. The two metal patches are the same size and shape; the first dual-mode resonator and the second dual-mode resonator are both square rings, with the four sides of the square rings concave inwards and the four corners of the square rings protruding to form four protrusions. The first dual-mode resonator and the second dual-mode resonator are placed in parallel layers in the substrate in a staggered manner; wherein the first metal patch and the second metal patch are symmetrical about the axis of symmetry of the two dual-mode resonators and are far apart from each other. An odd-mode coupler is placed between the odd-mode coupling paths of the two two-mode resonators, and an even-mode coupler is placed between the even-mode coupling paths of the two two-mode resonators; the odd-mode coupler and the even-mode coupler are on a horizontal line and parallel to the two two-mode resonators. By adjusting the size of the metal patch and the length of the coupler, the odd-even mode coupling strength can be changed, thus achieving independent modulation of the high-frequency and low-frequency passband bandwidth and frequency.

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