Tunable one-way and two-way microwave notch filter and design method

Abstract

The invention discloses a tunable one-way and two-way microwave notch filter and a design method. The filter has one-way and two-way filtering functions. The structure of the device mainly comprises an artificial surface plasmon polariton planar waveguide and a ferrite yttrium iron garnet microwave resonator, a circular polarization spin polarization microwave field with a spin-momentum locking characteristic is generated at a specific position in the planar waveguide, a magneton mode generated in the microwave resonator and the spin polarization microwave field are subjected to spin selective coupling, and under the critical coupling condition, microwaves input in one direction are completely filtered after passing through magneton, and then are subjected to spin polarization. And the microwaves input in the other direction are completely transmitted, so that the unidirectional filtering function of the microwaves at a specific frequency is realized. And an additional microwave resonator is further loaded, and the bidirectional filtering function can be realized by expanding the experimental configuration. The invention does not need complex structural design and strict parameter regulation and control, and provides a simpler, more convenient and more flexible method to realize the multifunctional microwave notch filter.

Description

Technical Field

[0001] The present invention relates to the field of electromagnetic wave control, including microwave isolation technology, and in particular to a tunable unidirectional and bidirectional microwave notch filter and a design method thereof. Background Art

[0002] Microwave notch filters are key components in modern wireless communications, radar, and other systems. They are the "interference buster" of microwave systems. In communications systems, notch filters can suppress adjacent channel interference; in radar systems, they can filter out transmitted signal leakage; and in measurement systems, they can isolate interfering frequencies outside the measured signal, improving measurement accuracy.

[0003] To address the need for dynamic interference suppression in complex electromagnetic environments and drive the evolution of RF systems toward adaptive and intelligent capabilities, tunable notch filters are being proposed and put into practical use. To overcome the "fixed frequency" limitations of traditional notch filters, researchers have proposed several promising and viable technical solutions, including tuning through integrated varactor diodes and MEMS switches. However, these devices often face challenges with poor stability, high power consumption, and relatively high fabrication costs.

[0004] In addition to the need for dynamic control of notch frequencies, unidirectional or even direction-controllable notch filters are particularly important in complex environments with multiple paths and multiple interference sources. They can accurately suppress interference in the target direction while allowing signals in other directions to be transmitted normally, solving the limitations of traditional notch filters' "indiscriminate suppression" or "fixed-direction suppression."

[0005] Therefore, designing a tunable filter with both direction-selective and frequency-selective suppression capabilities based on new physical effects has important practical significance for signal processing in complex electromagnetic environments. Summary of the Invention

[0006] This invention proposes a tunable unidirectional and bidirectional microwave notch filter and design method. The design principle is based on the spin-selective coupling effect and critical coupling effect between electromagnetic waves and magnons. The notch filter designed using this method has a simple structure, a theoretical filtering depth of 100%, and controllable operating frequency and filtering direction. The device's tunability does not require the integration of additional active electronic circuits or the control of complex parameter conditions, making its manufacturing difficulty and cost relatively low.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] A tunable unidirectional and bidirectional microwave notch filter comprising:

[0009] Artificial surface plasmon polariton planar waveguides, including but not limited to those fabricated on microstrip lines, striplines, coplanar waveguides, and grounded coplanar waveguide structures, used to support spin-momentum locked microwave transmission, with propagation-direction-dependent circularly polarized magnetic fields generated at the inflection points of the cross structure;

[0010] At least one ferrite yttrium iron garnet microwave resonator, including but not limited to a spherical or disc-type microwave resonator, is placed above the artificial surface plasmon polariton planar waveguide to excite a magnon mode under a bias magnetic field;

[0011] an electromagnet providing a bias magnetic field perpendicular to the artificial surface plasmon polariton planar waveguide to control the magnon spin polarization direction and adjust the magnon resonance frequency;

[0012] an electromagnetic coil, placed beneath a ferrite yttrium iron garnet microwave resonator to precisely control the magnon resonance frequency;

[0013] The magnon mode realizes a directionally adjustable filtering function through a microwave-magnon spin selective coupling mechanism.

[0014] A method for designing tunable unidirectional and bidirectional microwave notch filters is applied to the design of the above-mentioned filters, and the design method comprises:

[0015] A circularly polarized spin-polarized microwave field with spin-momentum locking characteristics is generated at a specific position in the artificial surface plasmon polariton planar waveguide. The magnon mode generated in the ferrite yttrium iron garnet microwave resonator undergoes spin-selective coupling with the spin-polarized microwave field. Under critical coupling conditions, microwaves input in one direction are completely filtered after passing through the magnons, while microwaves input in the other direction are completely transmitted, thereby realizing the unidirectional filtering function of microwaves at a specific frequency; by further loading additional ferrite yttrium iron garnet microwave resonators and expanding the experimental configuration, bidirectional filtering function is achieved.

[0016] Furthermore, a circularly polarized microwave field is generated at a specific position on the artificial surface plasmon polariton planar waveguide, and its polarization direction is locked with the microwave transmission direction, satisfying the right-hand rule, where the middle finger of the right hand points to the direction of the microwave wave vector k, the index finger points to the interface normal n, and the thumb points to the spin angular momentum S of the circularly polarized microwave magnetic field. T direction.

[0017] Furthermore, the magnon mode is a quantized description of the spin wave mode. Under the combined action of the external bias magnetic field and the microwave magnetic field, the ferrite yttrium iron garnet microwave resonator generates a spin wave mode with consistent spin precession, called a magnon, and its resonant frequency ω m It is flexibly adjusted by the electromagnet bias magnetic field, and the polarization direction of the magnon depends on the direction of the bias magnetic field.

[0018] Furthermore, the microwave-magnon spin-selective coupling mechanism means that the magnon mode of a specific spin polarization couples only with the microwave field with the same spin polarization direction as its own. The effect of the coupling is to filter the microwave signal at a specific frequency. The magnon mode of a specific spin polarization does not couple with the microwave field with the opposite spin polarization direction, and the microwave field transmitted in this direction is not filtered by the magnon. Therefore, the microwave-magnon spin-selective coupling mechanism ensures the realization of the unidirectional filtering function. In the case of perfect spin-selective coupling, the scattering parameter of the system is described by the following formula:

[0019]

[0020] Among them, S 11(22) =0, S 21 Indicates the transmission signal from port 2 to port 1, S 12 Indicates the transmission signal from port 1 to port 2, S 11 is the reflected signal of port 1, S 22 is the reflected signal of port 2; i represents the imaginary unit, ω represents the microwave frequency, ω m represents the resonant frequency of the magnon mode; κ R represents the external dissipation rate of the ferrite YIG microwave resonator for rightward transmission of microwaves, κ L represents the external dissipation rate of the ferrite yttrium iron garnet microwave resonator for leftward transmitted microwaves, γ is the intrinsic loss rate of the ferrite yttrium iron garnet microwave resonator, which comes from impurities or defects in its preparation process;

[0021] If the magnon is coupled only to the microwave input at port 1, then κ R ≠0,κ L =0, causing S 21 <1,S 12 = 1; if the magnon is coupled only to the microwave input at port 2, then κ R =0,κ L ≠0, causing S 21 =1,S 12 <1.

[0022] Furthermore, the critical coupling means that under the premise of achieving microwave-magnon spin selective coupling, κ R ≠0,κ L = 0, when the external dissipation rate κ R When the intrinsic dissipation γ is equal to 2 times, in the transmission direction corresponding to the coupling, the transmission signal S 21 It further drops to 0, at which point complete filtering of microwave unidirectional transmission is achieved, and the filtering efficiency reaches 100%.

[0023] Furthermore, the critical coupling effect is achieved by adjusting the height of the ferrite yttrium iron garnet microwave resonator relative to the waveguide plane.

[0024] Furthermore, the additionally loaded ferrite yttrium iron garnet microwave resonator needs to be placed at a specific position, where the circular polarization direction of the magnetic field should be exactly opposite to the polarization direction of the position where the initially loaded ferrite yttrium iron garnet microwave resonator is located. At the same time, the additionally loaded ferrite yttrium iron garnet microwave resonator needs to meet the perfect spin-selective coupling and critical coupling conditions.

[0025] Furthermore, two ferrite yttrium iron garnet microwave resonators and artificial surface plasmon polariton planar waveguides need to be placed together in the same electromagnet, with the bias magnetic field perpendicular to the waveguide plane to ensure that the spin polarization directions of the magnons in the two resonators are the same. At the same time, an electromagnetic coil needs to be embedded under each of the two resonators to independently control the resonant frequencies of the two magnon modes.

[0026] Furthermore, two magnon modes with the same spin polarization block microwaves in different directions. When the resonant frequencies of the two magnon modes are adjusted to be consistent, bidirectional filtering is achieved at a specific frequency.

[0027] The present invention provides a microwave notch filter design scheme based on the physical mechanism of selective coupling between microwaves and magnon spins, with high frequency tunability and directional controllability. This method can be applied to the fabrication of novel microwave filters and isolators. The SSPP planar waveguide employed in this scheme is highly compatible with photonic integrated circuits and optical communication chips, making this signal control scheme promising for future integrated circuit design. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic structural diagram of a microwave notch filter provided by an embodiment of the present invention.

[0029] Figure 2 It is a schematic diagram of the microwave-magnon spin selective coupling mechanism and a schematic diagram of the one-way notch filter transmission spectrum test results in an embodiment of the present invention.

[0030] Figure 3 1 is a schematic diagram of the system structure of the bidirectional notch filter and its transmission spectrum test results in an embodiment of the present invention.

[0031] In the figure, there is an artificial surface plasmon polariton planar waveguide 1; a first ferrite yttrium iron garnet spherical microwave resonator 2; a second ferrite yttrium iron garnet spherical microwave resonator 3; a first electromagnetic coil 4; a second electromagnetic coil 5; and an electromagnet 6. DETAILED DESCRIPTION

[0032] In order to make the objectives, technical solutions and advantages of the present invention more clear and explicit, the present invention is further described in detail below with reference to specific examples and the accompanying drawings.

[0033] The present invention provides a tunable unidirectional and bidirectional microwave notch filter, comprising:

[0034] Artificial surface plasmon polariton planar waveguides, including but not limited to those fabricated on microstrip lines, striplines, coplanar waveguides, and grounded coplanar waveguide structures, used to support spin-momentum locked microwave transmission, with propagation-direction-dependent circularly polarized magnetic fields generated at the inflection points of the cross structure;

[0035] At least one ferrite yttrium iron garnet microwave resonator, including but not limited to a spherical or disc-type microwave resonator, is placed above the artificial surface plasmon polariton planar waveguide to excite a magnon mode under a bias magnetic field;

[0036] an electromagnet providing a bias magnetic field perpendicular to the artificial surface plasmon polariton planar waveguide to control the magnon spin polarization direction (i.e., the direction of the spin angular momentum) and to adjust the magnon resonance frequency over a wide range;

[0037] an electromagnetic coil, placed beneath a ferrite yttrium iron garnet microwave resonator to precisely control the magnon resonance frequency;

[0038] The magnon mode realizes a directionally adjustable filtering function through a microwave-magnon spin selective coupling mechanism.

[0039] The present invention provides the above-mentioned tunable unidirectional and bidirectional microwave notch filter design method, comprising: generating a circularly polarized spin-polarized microwave field with spin-momentum locking characteristics at a specific position in an artificial surface plasmon polariton planar waveguide, and the magnon mode generated in a ferrite yttrium iron garnet microwave resonator undergoing spin-selective coupling with the spin-polarized microwave field. Under critical coupling conditions, microwaves input in one direction are completely filtered after passing through the magnon, while microwaves input in the other direction are completely transmitted, thereby realizing a unidirectional filtering function of microwaves at a specific frequency; further loading additional ferrite yttrium iron garnet microwave resonators and expanding the experimental configuration to realize a bidirectional filtering function.

[0040] The tunability of the notch filter is reflected in the following aspects: the operating frequency can be flexibly and accurately adjusted by an external bias magnetic field, and the filtering direction can be flexibly switched by regulating the direction of the magnetic field.

[0041] Tunable microwave notch filters such as Figure 1 As shown, it includes: an artificial surface plasmon polariton (SSPP) planar waveguide 1 and a ferrite yttrium iron garnet (YIG) spherical microwave resonator 2.

[0042] In this example, the artificial surface plasmon polariton planar waveguide 1 is fabricated on a RO4003C dielectric plate with a dielectric constant of 3.38±0.05, and the dielectric layer thickness is t s =0.813mm, the thickness of double-sided copper is t c =0.035mm. The SSPP planar waveguide consists of two parts: Part I is a gradient metal groove structure used for momentum matching conversion, converting the original microwave signal into the SSPP mode; Part II is a uniform metal groove structure area to support SSPP mode propagation. Figure 1 The upper left inset shows a unit structure in an SSPP planar waveguide with a groove period of p = 4.1 mm, a central width of the SSPP transmission line of w = 1.6 mm, h = 7.6 mm, and a = 2.5 mm. In the gradient groove section, the length of adjacent grooves transitions to the same width as the central transmission line with a gradient of Δh = 0.5 mm. Figure 1 The transmission signal test results of the SSPP planar waveguide show that its cutoff frequency is 10GHz. Below the cutoff frequency, the transmission signal insertion loss is less than -3dB.

[0043] In this example, microwaves in the SSPP planar waveguide have a spin-momentum locking effect, such as Figure 1 As shown, a signal is input to port 1, and the microwave propagating to the right excites a circularly polarized microwave magnetic field rotating clockwise (counterclockwise) above (below) the intersection of the cross structure. The microwave photon spin angular momentum S T The direction is perpendicular to the waveguide plane and points downward (upward). The propagation direction k, the interface normal n and the spin angular momentum S of the circularly polarized magnetic field T The three satisfy the right-hand rule (the middle finger of the right hand represents the k direction, the index finger represents the n direction, and the thumb points to the S direction). T ).like Figure 2 As shown in the figure, if a signal is input to port 2, the microwave transmitted to the left will excite a clockwise circularly polarized magnetic field below the cross point, and the direction of the spin angular momentum is perpendicular to the waveguide plane and downward, which is exactly opposite to the direction of the circularly polarized spin angular momentum generated when the signal is input to port 1.

[0044] In this example, the first ferrite yttrium iron garnet spherical microwave resonator 2 generates a spin wave mode with consistent spin precession under the joint excitation of the external bias magnetic field and the microwave magnetic field, and its quantization is described as magnon. The resonant frequency ω of the magnon mode is m and spin angular momentum S M The direction is flexibly controlled by the magnitude and magnetic pole direction of the external bias magnetic field B. That is, the resonant frequency ω of the magnon mode m It is flexibly adjusted by the electromagnet bias magnetic field, and the direction of the magnon angular momentum depends on the direction of the bias magnetic field.

[0045] The microwave-magnon spin-selective coupling mechanism means that the magnon mode of a specific spin polarization only couples with the microwave field with the same spin angular momentum direction as its own. The effect of the coupling is to filter the microwave signal at a specific frequency. The magnon mode of a specific spin polarization does not couple with the microwave field with the opposite spin angular momentum direction, and the microwave field transmitted in this direction is not filtered by the magnon. Therefore, the microwave-magnon spin-selective coupling mechanism ensures the realization of the unidirectional filtering function.

[0046] In this example, the YIG ball is loaded Figure 2 At the position shown, a vertical upward external magnetic field is applied, and the spin angular momentum S of the magnon mode in the YIG sphere M The direction is upward, which is only with the same spin angular momentum S T direction of the microwave photon mode, so only the signal transmitted to the right is strongly dissipated by the magnetic submode. Figure 2 Medium transmission spectrum S 21 (solid line) shows a clear resonance valley; and the spin angular momentum S M The upward-oriented magneton has no direct contact with the spin angular momentum S T The downward photon mode is coupled, so the microwave signal transmitted to the left is not dissipated by the magnetic submode, S 12 The (dashed line) shows that the incident signal at port 2 is transmitted to port 1 almost losslessly through the waveguide. At this time, the system exhibits a unidirectional filtering result.

[0047] The directional coupling between the spin-momentum locked microwave field and the magnon in the SSPP planar waveguide is called spin-selective coupling. The scattering parameter of the system can be expressed as:

[0048]

[0049] Among them, S 11(22) =0, S 21(12) represents the transmission signal from port 2(1) to port 1(2) (i.e., the ratio of the amplitude of the output signal of port 2(1) to the amplitude of the incident signal of port 1(2), S 11(22) is the reflected signal of port 1(2); i represents the imaginary unit, ω represents the microwave frequency, ω m represents the resonant frequency of the magnon mode; k R(L) represents the external dissipation rate of the YIG sphere for microwaves transmitted to the right (left), and γ is the intrinsic loss rate of the YIG sphere, which comes from impurities or defects in its preparation process.

[0050] If the magnon is coupled only to the microwave input at port 1, then κ R ≠0,κ L =0, causing S 21 <1,S 12 = 1; if the magnon is coupled only to the microwave input at port 2, then κ R =0,κL ≠0, causing S 21 =1,S 12 <1.

[0051] Figure 2 The configuration shown guarantees k R ≠0,k L = 0, which is called microwave-magnon perfect spin selective coupling. At this time, the reflection S 11(22) =0, transmission signal S 21 <1,S 12 =1, realizing the one-way filtering function.

[0052] In reaching Figure 2 After the perfect spin-selective coupling-induced unidirectional filtering, further tuning the longitudinal distance Z from the YIG sphere to the SSPP planar waveguide can change the external dissipation rate κ. R size, thereby further reducing S 21 To 0. Figure 2 As shown, when Z is regulated to make the system reach the critical coupling condition κ R =2γ, at the magnon resonance frequency ω=ω m At, the transmission signal S 21 The dB coordinate shows a very deep resonance valley, and the experiment achieves an extremely high microwave filtering depth of about -60dB. Based on the perfect spin-selective coupling and critical coupling effect of microwave-magnon, the unidirectional microwave notch filter can theoretically reach 100%, that is, S 21 =0,S 12 =1, microwaves in a specific direction are completely blocked.

[0053] In the above one-way filtering case, if the direction of the north and south magnetic poles of the external magnetic field is reversed, κ R =0,κ L ≠0, the filtering direction changes, that is, the incident microwave at port 2 is completely blocked, S 12 = 0, the microwave incident on port 1 can be completely transmitted, S 21 =1.

[0054] In this implementation case, below the cutoff frequency of the SSPP planar waveguide and within the operating frequency range of the YIG spherical microwave resonator, the device filtering frequency can be flexibly controlled by the magnitude of the external bias magnetic field.

[0055] Furthermore, this unidirectional notch filtering case can be expanded to bidirectional notch filtering.

[0056] The device diagram and design principle of the bidirectional notch filter are as follows: Figure 3As shown, in addition to the artificial surface plasmon polariton planar waveguide 1 and the first ferrite yttrium iron garnet spherical microwave resonator 2 required to realize the unidirectional filtering function, another second ferrite yttrium iron garnet spherical microwave resonator 3 needs to be additionally loaded into the planar waveguide. The sample is placed between the magnetic poles of the electromagnet 6. The direction of the magnetic field B is perpendicular to the sample plane and upward. Electromagnetic coils 4 and 5 are embedded below the first ferrite yttrium iron garnet spherical microwave resonator 2 and the second ferrite yttrium iron garnet spherical microwave resonator 3 to independently control the magnon resonance frequency in the two YIG spheres. The local magnetic field intensity generated by the electromagnetic coil 4 is δB1, and the local magnetic field intensity generated by the electromagnetic coil 5 is δB2. The magnon resonance frequencies generated in the first ferrite yttrium iron garnet spherical microwave resonator 2 and the second ferrite yttrium iron garnet spherical microwave resonator 3 are respectively recorded as ω1 and ω2, ω 1(2) ∝B+δB 1(2) .

[0057] The additionally loaded second ferrite yttrium iron garnet spherical microwave resonator 3 is placed above the cross point, and the direction of the circularly polarized spin angular momentum of its local magnetic field is opposite to the direction of the spin angular momentum at the first ferrite yttrium iron garnet spherical microwave resonator 2 .

[0058] The coupling conditions of the first ferrite yttrium iron garnet spherical microwave resonator 2 and the second ferrite yttrium iron garnet spherical microwave resonator 3 with the artificial surface plasmon polariton planar waveguide 1 are as follows: the first ferrite yttrium iron garnet spherical microwave resonator 2 is only coupled with the microwave input from port 1 and decoupled from the microwave input from port 2; on the contrary, the second ferrite yttrium iron garnet spherical microwave resonator 3 is decoupled from the microwave input from port 1 and only coupled with the microwave input from port 2.

[0059] Furthermore, when the coupling between the magnon mode in the YIG sphere and the microwave satisfies both the perfect spin selective coupling and critical coupling conditions, the two YIG spheres filter the microwaves at their respective resonant frequencies, and the directions of their respective microwave filtering are exactly opposite. Figure 3 The test results on the right show that at ω=ω1, S 21 =-55dB, at ω=ω2, S 12 =-55dB.

[0060] In the above embodiment, the local magnetic field B+δB2 of the second ferrite yttrium iron garnet spherical microwave resonator 3 can be adjusted to continuously change its filtering frequency ω2, indicating that the filtering function has polychromaticity. When the magnetic field is adjusted so that ω2 = ω1, the system realizes a bidirectional notch filtering function.

[0061] The above embodiments are intended only to illustrate the design concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. The scope of protection of the present invention is not limited to the above embodiments. Therefore, any equivalent changes or modifications made based on the principles and design concepts disclosed in the present invention are within the scope of protection of the present invention.

Claims

1. A tunable unidirectional and bidirectional microwave notch filter, characterized in that: include: Artificial surface plasmon polariton planar waveguides, including but not limited to those fabricated on microstrip lines, striplines, coplanar waveguides, and grounded coplanar waveguide structures, used to support spin-momentum locked microwave transmission, with propagation-direction-dependent circularly polarized magnetic fields generated at the inflection points of the cross structure; At least one ferrite yttrium iron garnet microwave resonator, including but not limited to a spherical or disc-type microwave resonator, is placed above the artificial surface plasmon polariton planar waveguide to excite a magnon mode under a bias magnetic field; an electromagnet providing a bias magnetic field perpendicular to the artificial surface plasmon polariton planar waveguide to control the magnon spin polarization direction and adjust the magnon resonance frequency; an electromagnetic coil, placed beneath a ferrite yttrium iron garnet microwave resonator to precisely control the magnon resonance frequency; The magnon mode realizes a directionally adjustable filtering function through a microwave-magnon spin selective coupling mechanism.

2. A method for designing tunable unidirectional and bidirectional microwave notch filters, applied to the design of the filter according to claim 1, characterized in that: The design method includes: A circularly polarized spin-polarized microwave field with spin-momentum locking characteristics is generated at a specific position in the artificial surface plasmon polariton planar waveguide. The magnon mode generated in the ferrite yttrium iron garnet microwave resonator undergoes spin-selective coupling with the spin-polarized microwave field. Under critical coupling conditions, microwaves input in one direction are completely filtered after passing through the magnons, while microwaves input in the other direction are completely transmitted, thereby realizing the unidirectional filtering function of microwaves at a specific frequency; by further loading additional ferrite yttrium iron garnet microwave resonators and expanding the experimental configuration, bidirectional filtering function is achieved.

3. The method for designing a tunable unidirectional and bidirectional microwave notch filter according to claim 2, wherein: A circularly polarized microwave field is generated at a specific position on the artificial surface plasmon polariton planar waveguide, and its polarization direction is locked with the microwave transmission direction, satisfying the right-hand rule: the middle finger of the right hand points to the direction of the microwave wave vector k, the index finger points to the interface normal n, and the thumb points to the spin angular momentum S of the circularly polarized microwave magnetic field. T direction.

4. The method for designing a tunable unidirectional and bidirectional microwave notch filter according to claim 2, wherein: The magnon mode is a quantized description of the spin wave mode. Under the combined action of the external bias magnetic field and the microwave magnetic field, the ferrite yttrium iron garnet microwave resonator generates a spin wave mode with consistent spin precession, called a magnon, and its resonant frequency ω m It is flexibly adjusted by the electromagnet bias magnetic field, and the polarization direction of the magnon depends on the direction of the bias magnetic field.

5. The method for designing a tunable unidirectional and bidirectional microwave notch filter according to claim 2, wherein: The microwave-magnon spin-selective coupling mechanism means that the magnon mode of a specific spin polarization only couples with the microwave field with the same spin polarization direction. The coupling effect is to filter the microwave signal at a specific frequency. The magnon mode of a specific spin polarization does not couple with the microwave field with the opposite spin polarization direction. The microwave field transmitted in this direction is not filtered by the magnon. Therefore, the microwave-magnon spin-selective coupling mechanism ensures the realization of the unidirectional filtering function. In the case of perfect spin-selective coupling, the scattering parameter of the system is described as follows: Among them, S 11(22) =0, S 21 Indicates the transmission signal from port 2 to port 1, S 12 Indicates the transmission signal from port 1 to port 2, S 11 is the reflected signal of port 1, S 22 is the reflected signal of port 2; i represents the imaginary unit, ω represents the microwave frequency, ω m represents the resonant frequency of the magnon mode; κ R represents the external dissipation rate of the ferrite YIG microwave resonator for rightward transmission of microwaves, κ L represents the external dissipation rate of the ferrite yttrium iron garnet microwave resonator for leftward transmitted microwaves, γ is the intrinsic loss rate of the ferrite yttrium iron garnet microwave resonator, which comes from impurities or defects in its preparation process; If the magnon is coupled only to the microwave input at port 1, then κ R ≠0,κ L =0, causing S 21 <1,S 12 = 1; if the magnon is coupled only to the microwave input at port 2, then κ R =0,κ L ≠0, causing S 21 =1,S 12 <1.

6. The method for designing a tunable unidirectional and bidirectional microwave notch filter according to claim 5, wherein: The critical coupling means that under the premise of achieving microwave-magnon spin selective coupling, κ R ≠0,κ L = 0, when the external dissipation rate κ R When the intrinsic dissipation γ is equal to 2 times, in the transmission direction corresponding to the coupling, the transmission signal S 21 It further drops to 0, at which point complete filtering of microwave unidirectional transmission is achieved, and the filtering efficiency reaches 100%.

7. The method for designing a tunable unidirectional and bidirectional microwave notch filter according to claim 6, wherein: The critical coupling effect is achieved by adjusting the height of the ferrite yttrium iron garnet microwave resonator relative to the waveguide plane.

8. The method for designing a tunable unidirectional and bidirectional microwave notch filter according to claim 2, wherein: The additionally loaded ferrite yttrium iron garnet microwave resonator needs to be placed at a specific position, where the circular polarization direction of the magnetic field should be exactly opposite to the polarization direction of the position where the initially loaded ferrite yttrium iron garnet microwave resonator is located. At the same time, the additionally loaded ferrite yttrium iron garnet microwave resonator needs to meet the perfect spin selective coupling and critical coupling conditions.

9. The method for designing a tunable unidirectional and bidirectional microwave notch filter according to claim 8, wherein: Two ferrite yttrium iron garnet microwave resonators and an artificial surface plasmon polariton planar waveguide need to be placed together in the same electromagnet, with the bias magnetic field perpendicular to the waveguide plane to ensure that the spin polarization directions of the magnons in the two resonators are the same. At the same time, an electromagnetic coil needs to be embedded under each of the two resonators to independently control the resonant frequencies of the two magnon modes.

10. The method for designing a tunable unidirectional and bidirectional microwave notch filter according to claim 9, wherein: Two magnon modes with the same spin polarization block microwaves in different directions. When the resonant frequencies of the two magnon modes are adjusted to be consistent, bidirectional filtering is achieved at a specific frequency.

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