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

Abstract

The application discloses a tunable one-way and two-way microwave wave trap filter and a design method, which has one-way and two-way filtering functions. The device structure mainly comprises an artificial surface plasmonic polariton planar waveguide and a yttrium iron garnet microwave resonator. Circular polarization spin polarized microwave fields with spin-momentum locking characteristics are generated at specific positions in the planar waveguide, and the magnon mode generated in the microwave resonator is spin-selectively coupled with the spin polarized microwave field. Under the critical coupling condition, the microwave input in one direction is completely filtered after the magnon, and the microwave input in the other direction is completely transmitted, so that the one-way filtering function of the microwave at a specific frequency is realized. Further loading of additional microwave resonators and through the extension of the experimental configuration, the two-way filtering function can also be realized. The application provides a more simple and flexible method to realize the multifunctional microwave wave trap filter without complex structure design and strict parameter control.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electromagnetic wave control, including microwave isolation technology, and in particular to a tunable one-way and two-way microwave notch filter and design method. BACKGROUND

[0002] The microwave notch filter is one of the key devices of modern wireless communication, radar and other systems, and it is the "interference killer" of the microwave system. In a communication system, the notch filter can be used to suppress adjacent channel interference; in a radar system, the transmitted signal leakage can be filtered out; in a measurement system, the interference frequency outside the measured signal can be isolated to improve measurement accuracy.

[0003] To meet the dynamic interference suppression needs of complex electromagnetic environments and promote the evolution of radio frequency systems to be adaptive and intelligent, tunable notch filters are always expected to be proposed and put into practical application. To break through the "frequency fixation" limitation of traditional notch filters, researchers have given some beneficial and optional technical solutions, including tuning by integrating varactor diodes and MEMS switches. However, these devices often face the challenges of poor stability and high power consumption, and the preparation cost is also relatively high.

[0004] In addition to the demand for dynamic regulation of the notch frequency, in a complex environment with multiple paths and multiple interference sources, a one-way or even direction-controllable notch filter is particularly important, as it can precisely suppress interference in the target direction while allowing normal transmission of signals in other directions, solving the limitations of traditional notch filters in "non-discriminatory suppression" or "fixed direction suppression".

[0005] Therefore, it is of great practical significance to design a tunable filter with both direction selection and frequency selection suppression capabilities based on new physical effects for signal processing in complex electromagnetic environments. SUMMARY

[0006] The present application proposes a tunable one-way and two-way microwave notch filter and design method, and the design principle is based on the spin-selective coupling effect and critical coupling effect of electromagnetic waves and magnons. The notch filter designed by this method has a simple structure, a theoretical filtering depth of up to 100%, and controllability of operating frequency and filtering direction. The realization of the tunable function of the device does not require additional integration of active electronic circuits or complex parameter conditions for control, and the processing difficulty and cost are relatively low.

[0007] To achieve the above purpose, the technical solutions of the present application are as follows:

[0008] A tunable one-way and two-way 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, are used to support spin-momentum locked microwave transmission, and a propagation direction-dependent circularly polarized magnetic field is generated at the inflection point of its cross structure.

[0010] At least one ferrite yttrium iron garnet microwave resonator, including but not limited to spherical and disc microwave resonators, is placed above the artificial surface plasmon polariton planar waveguide and excites a magneton mode under a bias magnetic field.

[0011] An electromagnet provides a bias magnetic field perpendicular to the artificial surface plasmon polariton planar waveguide to control the spin polarization direction of the magnet and adjust the resonant frequency of the magnet.

[0012] An electromagnetic coil is positioned below a ferrite yttrium iron garnet microwave resonator to precisely control the magneton resonant frequency;

[0013] The magneton mode achieves directional adjustable filtering through a microwave-magneton spin-selective coupling mechanism.

[0014] A design method for tunable unidirectional and bidirectional microwave notch filters, applied to the design of the aforementioned filters, the design method comprising:

[0015] A circularly polarized spin-polarized microwave field with spin-momentum locking characteristics is generated at a specific location in an artificial surface plasmon polariton planar waveguide. The magneton 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 magneton, while microwaves input in the other direction are completely transmitted, thus 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, a bidirectional filtering function is realized.

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

[0017] Furthermore, the magnetic mode is a quantized description of the spin wave mode. Under the combined action of an external bias magnetic field and a microwave magnetic field, the ferrite-yttrium-iron-garnet microwave resonator generates a spin wave mode with uniform precession, called a magnetic mode, whose resonant frequency ω... m The polarization direction of the magneton depends on the direction of the bias magnetic field, which can be flexibly adjusted by the bias magnetic field of the electromagnet.

[0018] Furthermore, the microwave-magneton spin-selective coupling mechanism refers to the following: a magneton mode with a specific spin polarization is coupled only to a microwave field with the same spin polarization direction. The effect of this coupling is to filter microwave signals at a specific frequency. A magneton mode with a specific spin polarization does not couple to a microwave field with the opposite spin polarization direction, and microwave fields transmitted in that direction are not filtered by the magneton. Thus, the microwave-magneton spin-selective coupling mechanism ensures the realization of unidirectional filtering. In the case of perfect spin-selective coupling, the scattering parameters of the system are described by the following formula:

[0019]

[0020] Among them, S 11(22) =0, S 21 S represents the signal transmitted from port 2 to port 1. 12 S represents the signal transmitted from port 1 to port 2. 11 For the reflected signal of port 1, S 22 This represents the reflected signal from port 2; i represents the imaginary unit, ω represents the microwave frequency, and ω m Indicates the resonant frequency of the magneton mode; κ R κ represents the external dissipation rate of a ferrite-yttrium-iron-garnet microwave resonator for microwaves propagating to the right. L γ represents the external dissipation rate of the yttrium iron garnet microwave resonator for microwaves propagating to the left, while γ is the intrinsic loss rate of the yttrium iron garnet microwave resonator, which originates from impurities or defects in its preparation process.

[0021] If the magneton 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 magneto is only coupled 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 refers to: under the premise of achieving microwave-magneton spin-selective coupling, κ R ≠0,κ L =0, when the external dissipation rate κ R When the intrinsic dissipation γ is equal to twice the value of γ, the transmitted signal S in the corresponding transmission direction of the coupling... 21 The efficiency is further reduced to 0, at which point complete filtering of microwave unidirectional transmission is achieved, with a filtering efficiency of 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 additional yttrium iron garnet microwave resonator needs to be placed in a specific location where the magnetic field circular polarization direction is exactly opposite to the polarization direction of the initially loaded yttrium iron garnet microwave resonator. At the same time, the additional yttrium iron garnet microwave resonator needs to satisfy perfect spin-selective coupling and critical coupling conditions.

[0025] Furthermore, the two ferrite yttrium iron garnet microwave resonators and the 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 direction of the magnets in the two resonators is the same. At the same time, an electromagnetic coil needs to be embedded below each of the two resonators to independently control the resonant frequency of the two magnet modes.

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

[0027] The beneficial effects of this invention are as follows: It provides a microwave notch filter design scheme based on the physical mechanism of microwave and magnetic spin selective coupling, possessing high frequency tunability and directional controllability. This method can be applied to the fabrication of novel microwave filters and isolators. The SSPP planar waveguide used in this scheme has high compatibility with photonic integrated circuits and optical communication chips; therefore, this signal control scheme is expected to be applied in future integrated circuit designs. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the microwave notch filter structure provided in an embodiment of the present invention.

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

[0030] Figure 3 This 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, 1 is an artificial surface plasmon polariton planar waveguide; 2 is a first ferrite yttrium iron garnet spherical microwave resonator; 3 is a second ferrite yttrium iron garnet spherical microwave resonator; 4 is a first electromagnetic coil; 5 is a second electromagnetic coil; and 6 is an electromagnet. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0033] This 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, are used to support spin-momentum locked microwave transmission, and a propagation direction-dependent circularly polarized magnetic field is generated at the inflection point of its cross structure.

[0035] At least one ferrite yttrium iron garnet microwave resonator, including but not limited to spherical and disc-shaped microwave resonators, is placed above the artificial surface plasmon polariton planar waveguide and excited with a magneton mode under a bias magnetic field.

[0036] An electromagnet provides a bias magnetic field perpendicular to the artificial surface plasmon polariton planar waveguide to control the spin polarization direction of the magnet and the spin angular momentum direction, and to adjust the magnet resonance frequency over a wide range.

[0037] An electromagnetic coil is positioned below a ferrite yttrium iron garnet microwave resonator to precisely control the magneton resonant frequency;

[0038] The magneton mode achieves directional adjustable filtering through a microwave-magneton spin-selective coupling mechanism.

[0039] This invention provides a design method for the aforementioned tunable unidirectional and bidirectional microwave notch filters, comprising: generating a circularly polarized spin-polarized microwave field with spin-momentum locking characteristics at a specific location in an artificial surface plasmon polariton planar waveguide; the magneton mode generated in a 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 magneton, while microwaves input in the other direction are completely transmitted, thereby realizing the unidirectional filtering function of microwaves at a specific frequency; further, by loading additional ferrite-yttrium iron garnet microwave resonators and expanding the experimental configuration, the bidirectional filtering function is realized.

[0040] The tunability of this notch filter is reflected in the fact that the operating frequency can be flexibly and precisely adjusted by an external bias magnetic field, and the filtering direction can be flexibly switched by adjusting the direction of the magnetic field.

[0041] Tunable microwave notch filters such as Figure 1 As shown, it includes: a spoofsurface plasmon polariton (SSPP) planar waveguide 1 and a 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 substrate with a dielectric constant of 3.38 ± 0.05, and the dielectric layer thickness is t. s =0.813mm, double-sided copper cladding thickness 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, which converts the original microwave signal into the SSPP mode; Part II is a uniform metal groove structure region used to support the propagation of the SSPP mode. Figure 1 The upper left illustration shows a single unit structure in an SSPP planar waveguide with a groove period of p = 4.1 mm, a center width of SSPP transmission line w = 1.6 mm, h = 7.6 mm, a = 2.5 mm, and a gradient groove section where the length of adjacent grooves transitions to the same width as the center 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 10 GHz, and the insertion loss of the transmission signal is less than -3 dB below the cutoff frequency.

[0043] In this example, the microwaves in the SSPP planar waveguide exhibit a spin-momentum locking effect, such as Figure 1 As shown, when a signal is input to port 1, 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, pointing downwards (upwards). The propagation direction k, the interface normal n, and the spin angular momentum S of the circularly polarized magnetic field are also considered. T All three satisfy the right-hand rule (the right middle finger represents the k direction, the index finger represents n, and the thumb points to S). T ).like Figure 2 As shown, if a signal is input to port 2, the microwave transmitted to the left will excite a clockwise rotating circularly polarized magnetic field below the cross intersection. The direction of the spin angular momentum is perpendicular to the waveguide plane and downwards, which is exactly the opposite of 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-precessing mode under the combined excitation of an external bias magnetic field and a microwave magnetic field. This mode is quantized as a magneton. The resonant frequency ω of the magneton mode is... m and spin angular momentum S M The direction is flexibly controlled by the magnitude and direction of the applied bias magnetic field B. That is, the resonant frequency ω of the magneton mode. m The direction of the angular momentum of the magneton is determined by the direction of the bias magnetic field, which can be flexibly adjusted by the bias magnetic field of the electromagnet.

[0045] The microwave-magneton spin-selective coupling mechanism refers to the fact that a specific spin-polarized magneton mode is coupled only to a microwave field with the same spin angular momentum direction. The effect of this coupling is to filter microwave signals at a specific frequency. A specific spin-polarized magneton mode is not coupled to a microwave field with the opposite spin angular momentum direction, and the microwave field transmitted in that direction is not filtered by the magneton. Thus, the microwave-magneton spin-selective coupling mechanism ensures the realization of unidirectional filtering function.

[0046] In this example, the YIG ball is loaded. Figure 2 At the indicated location, an upward-vertically-oriented external magnetic field is applied, and the spin angular momentum S of the magneton mode in the YIG sphere... M The direction is upward, and it is only related to the same spin angular momentum S. T The microwave photonic mode is coupled in the direction of the signal, so only the signal propagating to the right is strongly dissipated by the magneton mode. Figure 2 Transmission spectrum S 21 (Solid line) shows a clear resonance valley; while the spin angular momentum S M A magneton oriented upwards, not with spin angular momentum S T Downward photonic mode coupling prevents the microwave signal propagating to the left from being dissipated by the magneton mode, S 12 (Dashed line) shows that the incident signal at port 2 is transmitted to port 1 almost without loss through the waveguide, at which point the system exhibits a unidirectional filtering result.

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

[0048]

[0049] Among them, S 11(22) =0, S 21(12) S represents the transmitted signal from port 2(1) to port 1(2) (i.e., the ratio of the amplitude of the signal emitted from port 2(1) to the amplitude of the signal received from port 1(2)). 11(22) The reflected signal of port 1(2); i represents the imaginary unit, ω represents the microwave frequency, ω m The resonant frequency of the magneton mode; k R(L) γ represents the external dissipation rate of the YIG sphere transmitting microwaves to the right (left), while γ is the intrinsic loss rate of the YIG sphere, which originates from impurities or defects in its fabrication process.

[0050] If the magneton 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 magneto is only coupled 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-magneton perfect spin-selective coupling. At this time, the reflection S of the system at port 1(2) is 0. 11(22) =0, transmission signal S 21 <1,S 12 =1, which implements the unidirectional filtering function.

[0052] Upon reaching Figure 2 Following unidirectional filtering induced by perfect spin-selective coupling, further tuning the longitudinal distance Z from the YIG sphere to the SSPP planar waveguide can alter the external dissipation rate κ. R The size of S, thereby further reducing the S 21 Up to 0. For example... Figure 2 As shown, when Z is adjusted to make the system reach the critical coupling condition κ R =2γ, at the magneton resonance frequency ω = ω m At this location, the transmitted signal S 21 The experiment demonstrates an extremely deep resonance valley in dB coordinates, achieving an exceptionally high microwave filtering depth of approximately -60 dB. Based on this microwave-magneton perfect spin-selective coupling and critical coupling effect, the unidirectional microwave notch filter theoretically has an upper limit of 100% unidirectional filtering capability, i.e., S... 21 =0,S 12 =1, microwaves in a specific direction are completely blocked.

[0053] In the above unidirectional filtering case, if the direction of the north and south magnetic poles of the external magnetic field is reversed, κ can be made R =0,κ L ≠0, the filtering direction changes, meaning the microwave incident at port 2 is completely blocked, S 12 Microwaves incident at ports 0 and 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 adjusted by the magnitude of the applied bias magnetic field.

[0055] Furthermore, this unidirectional notch filtering case can be extended 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 yttrium iron garnet spherical microwave resonator 2 required to achieve unidirectional filtering, another second yttrium iron garnet spherical microwave resonator 3 needs to be additionally installed on the planar waveguide. The sample is placed between the magnetic poles of the electromagnet 6, with the direction of the magnetic field B perpendicular to the sample plane and upward. Electromagnetic coils 4 and 5 are embedded below the first yttrium iron garnet spherical microwave resonator 2 and the second yttrium iron garnet spherical microwave resonator 3 to independently control the magnetic resonant frequencies in the two YIG spheres. The local magnetic field strength generated by electromagnetic coil 4 is δB1, and the local magnetic field strength generated by electromagnetic coil 5 is δB2. The magnetic resonant frequencies generated by the first yttrium iron garnet spherical microwave resonator 2 and the second yttrium iron garnet spherical microwave resonator 3 are denoted as ω1 and ω2, respectively. 1(2) ∝B+δB 1(2) .

[0057] The additional second gyrometric ferrite garnet spherical microwave resonator 3 is positioned above the cross intersection, and the direction of its local magnetic field's circularly polarized spin angular momentum is opposite to the direction of the spin angular momentum at the first gyrometric ferrite garnet spherical microwave resonator 2.

[0058] The coupling between the first yttrium iron garnet spherical microwave resonator 2 and the second yttrium iron garnet spherical microwave resonator 3 and the artificial surface plasmon polariton planar waveguide 1 is as follows: the first yttrium iron garnet spherical microwave resonator 2 is coupled only to the microwave input at port 1 and decoupled from the microwave input at port 2. Conversely, the second yttrium iron garnet spherical microwave resonator 3 is decoupled from the microwave input at port 1 and coupled only to the microwave input at port 2.

[0059] Furthermore, when the coupling between the magnetic mode and the microwave in the YIG sphere simultaneously satisfies both perfect spin-selective coupling and critical coupling conditions, the two YIG spheres filter the microwave at their respective resonant frequencies, with the directions of their filtered microwaves being exactly opposite. For example... 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 embodiments, adjusting the local magnetic field B+δB2 of the second ferrite yttrium iron garnet spherical microwave resonator 3 can 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 achieves bidirectional notch filtering function.

[0061] The above embodiments are only used to illustrate the design concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications made based on the principles and design ideas disclosed in the present invention are within the protection scope 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 those fabricated on microstrip lines, striplines, or coplanar waveguide structures, are used to support spin-momentum locked microwave transmission, and a propagation direction-dependent circularly polarized magnetic field is generated at the inflection point of the cross structure. At least one ferrite yttrium iron garnet microwave resonator, including a spherical or disc-shaped microwave resonator, is placed above the artificial surface plasmon polariton planar waveguide and excites a magneton mode under a bias magnetic field. An electromagnet provides a bias magnetic field perpendicular to the artificial surface plasmon polariton planar waveguide to control the spin polarization direction of the magnet and adjust the resonant frequency of the magnet. An electromagnetic coil is positioned below a ferrite yttrium iron garnet microwave resonator to precisely control the magneton resonant frequency; The magneton mode achieves directional adjustable filtering through a microwave-magneton spin-selective coupling mechanism.

2. A design method for tunable unidirectional and bidirectional microwave notch filters, applied to the design of the filter as described in claim 1, characterized in that, The design method includes: A circularly polarized spin-polarized microwave field with spin-momentum locking characteristics is generated at the inflection point of the cross structure in an artificial surface plasmon polariton planar waveguide. The magneton 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 from one direction are completely filtered after passing through the magneton, while microwaves input from the other direction are completely transmitted, thus 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 realized.

3. The design method for tunable unidirectional and bidirectional microwave notch filters according to claim 2, characterized in that, At the inflection point of the cross structure on the artificial surface plasmon polariton planar waveguide, a circularly polarized microwave field is generated. Its polarization direction is locked to the microwave propagation direction, satisfying the right-hand rule, with the right-hand center pointing towards the microwave wave vector. Direction, index finger pointing towards the interface normal. The thumb points to the spin angular momentum of the circularly polarized microwave magnetic field. direction.

4. The design method for tunable unidirectional and bidirectional microwave notch filters according to claim 2, characterized in that, The magnetic mode is a quantized description of a spin wave mode. Under the combined action of an external bias magnetic field and a microwave magnetic field, a ferrite-yttrium-iron garnet microwave resonator generates a spin wave mode with uniform precession, called a magnetic mode, whose resonant frequency... The polarization direction of the magneton depends on the direction of the bias magnetic field, which can be flexibly adjusted by the bias magnetic field of the electromagnet.

5. The design method for tunable unidirectional and bidirectional microwave notch filters according to claim 2, characterized in that, The microwave-magneton spin-selective coupling mechanism refers to the following: a magneton mode with a specific spin polarization couples only with microwave fields whose spin polarization direction is the same. The effect of this coupling is to filter microwave signals at a specific frequency. A magneton mode with a specific spin polarization does not couple with microwave fields with opposite spin polarization directions, and microwave fields propagating in the opposite spin polarization direction are not filtered by the magneton. Therefore, the microwave-magneton spin-selective coupling mechanism ensures the realization of unidirectional filtering. In the case of perfect spin-selective coupling, the system's scattering parameters are described by the following formula: ； in, , This indicates the transmission signal from port 2 to port 1. This indicates the transmission signal from port 1 to port 2. The reflected signal is from port 1. This is the reflected signal from port 2; Represents the imaginary unit. Indicates microwave frequency. Represents the resonant frequency of the magneton mode; This indicates the external dissipation rate of the ferrite-yttrium-iron-garnet microwave resonator for microwaves propagating to the right. This indicates the external dissipation rate of the ferrite-yttrium-iron-garnet microwave resonator for microwaves propagating to the left. The intrinsic loss rate of the ferrite yttrium iron garnet microwave resonator originates from impurities or defects in its manufacturing process; If the magneton is only coupled to the microwave input at port 1, then , causing If the magneton is only coupled to the microwave input at port 2, then , causing .

6. The design method for tunable unidirectional and bidirectional microwave notch filters according to claim 5, characterized in that, The critical coupling refers to the situation where, under the premise of achieving microwave-magneton spin-selective coupling, the critical coupling is achieved. When the external dissipation rate Equal to twice the intrinsic dissipation At that time, the transmitted signal is in the transmission direction corresponding to the coupling. The efficiency is further reduced to 0, at which point complete filtering of microwave unidirectional transmission is achieved, with a filtering efficiency of 100%.

7. The design method for tunable unidirectional and bidirectional microwave notch filters according to claim 6, characterized in that, 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 design method for tunable unidirectional and bidirectional microwave notch filters according to claim 2, characterized in that, The additional yttrium iron garnet microwave resonator must be placed at the inflection point of the cross structure. The circular polarization direction of the magnetic field at the inflection point of the cross structure should be exactly opposite to the polarization direction of the initially loaded yttrium iron garnet microwave resonator. At the same time, the additional yttrium iron garnet microwave resonator must satisfy the conditions of perfect spin selective coupling and critical coupling.

9. The design method for tunable unidirectional and bidirectional microwave notch filters according to claim 8, characterized in that, 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 direction of the magnets in the two resonators is the same. At the same time, an electromagnetic coil needs to be embedded below each of the two resonators to independently control the resonant frequency of the two magnet modes.

10. The design method for tunable unidirectional and bidirectional microwave notch filters according to claim 9, characterized in that, Two magnetic submodes with the same spin polarization block microwaves in different directions. When the resonant frequencies of the two magnetic submodes are tuned to be the same, bidirectional filtering is achieved at a specific frequency.

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