A multi-band polarization and propagation tunable electromagnetic metasurface

Abstract

This invention discloses an electromagnetic metasurface with tunable multi-band polarization and propagation characteristics, comprising a dielectric substrate and a periodic array fixed on the dielectric substrate. The periodic array includes multiple sets of two-dimensional array basic units with the same length and width. Each basic unit contains two metal rings with coincident centers and different radii. The larger metal ring has a first and a second notch, and the smaller metal ring has a third and a fourth notch. Each notch has the same width, the centerlines of the first and third notches coincide, the centerlines of the second and fourth notches coincide, and the angle between the line connecting the centerlines of the first and second notches and the center of the circle is 90°. This invention solves the problem that existing polarization conversion metasurfaces can only achieve polarization control of a single reflected or transmitted wave, and cannot achieve multi-band, multi-functional polarization control.

Description

Technical Field

[0001] This invention relates to the field of artificial electromagnetic materials technology, and in particular to an electromagnetic metasurface with tunable multi-band polarization and propagation characteristics. Background Technology

[0002] Electromagnetic wave polarization plays a crucial role in electromagnetic wave propagation, particularly in the visible spectrum and microwave frequency bands, where it has attracted increasing attention and interest. How to selectively adjust the polarization of electromagnetic waves during propagation is an important research topic. From the microwave band to the visible light range, polarization control devices show promising applications in multi-polarization communication, satellite communication, sensing, and spectral analysis. Compared to traditional polarization converters, polarization-converting metasurfaces offer advantages such as small size, ease of fabrication, easy integration, and low loss, making them an effective alternative to traditional polarization control devices.

[0003] With the deepening research into metasurfaces and metamaterials, numerous polarization-controlled metamaterials and metasurfaces have been designed. Based on the form of polarization conversion, they are categorized into linear-to-linear and linear-to-circular polarization wave conversions. Based on the direction of electromagnetic wave propagation, they are classified as reflective and transmissive polarization conversion metasurfaces. Currently, most polarization conversion metasurfaces can only achieve polarization control of a single reflected or transmitted wave, significantly limiting the degree of freedom in applications and preventing the realization of multi-band, multi-functional polarization control. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide an electromagnetic metasurface with tunable polarization characteristics across multiple frequency bands and functions.

[0005] Technical Solution: To achieve the above objectives, the present invention provides an electromagnetic metasurface with tunable multi-band polarization and propagation characteristics, comprising a dielectric substrate and a periodic array fixed on the dielectric substrate; the periodic array comprises multiple sets of two-dimensional arrays with the same length and width as basic units, each basic unit comprising two metal rings with coincident centers and different radii, the larger metal ring having a first cut and a second cut, and the smaller metal ring having a third cut and a fourth cut, each cut having the same width, the centerlines of the first cut and the third cut coinciding, the centerlines of the second cut and the fourth cut coinciding, and the angle between the line connecting the centerline of the first cut and the second cut and the center of the circle forming a 90° angle.

[0006] The thickness of the metal ring is 0.001-0.035 mm.

[0007] Specifically, the first and third notches are placed in the x-coordinate direction, and the second and fourth notches are placed in the y-coordinate direction. The incident wave is incident on the metasurface from the positive z-axis to the -z-axis direction, which can realize the function of different polarization characteristic control in three frequency bands. Four polarization control functions are realized in the first frequency band, two control functions are realized in the second frequency band, and four polarization control functions are realized in the third frequency band.

[0008] The first frequency band implements four polarization control functions:

[0009] After the polarization modulation effect of the metasurface, the reflected wave and the transmitted wave are right-hand circularly polarized waves of equal power.

[0010] A linearly polarized wave polarized in the y-direction is polarized by a metasurface, and the reflected and transmitted waves are left-handed circularly polarized waves of equal power.

[0011] Left-handed circular polarization, after being polarized by a metasurface, results in a reflected wave along the +z direction that is y-polarized, and a transmitted wave along the -z direction that is x-polarized.

[0012] After being polarized by a metasurface, the right-hand circularly polarized wave is reflected along the +z direction as an x-polarized wave and transmitted along the -z direction as a y-polarized linear wave.

[0013] The second frequency band implements two control functions:

[0014] When a linearly polarized wave polarized at -45° is incident on a metasurface, the electromagnetic wave is totally reflected, and the polarization characteristics remain unchanged.

[0015] When a linearly polarized wave polarized at +45° is incident on a metasurface, the electromagnetic wave is fully transmitted, and the polarization characteristics remain unchanged.

[0016] The third frequency band enables four polarization control functions:

[0017] After the polarization modulation effect of the metasurface, the reflected wave and the transmitted wave are left-hand circularly polarized waves of equal power.

[0018] The linear polarization in the y-direction is modulated by the metasurface, and the reflected and transmitted waves are right-hand circularly polarized waves of equal power.

[0019] Left-handed circular polarization, after being polarized by a metasurface, results in a reflected wave along the +z direction that is x-polarized, and a transmitted wave along the -z direction that is y-polarized.

[0020] After being polarized by a metasurface, the right-hand circularly polarized wave is reflected along the +z direction as a y-polarized wave and transmitted along the -z direction as a x-polarized linearly polarized wave.

[0021] Beneficial Effects: This invention has the following advantages: The multi-band polarization and propagation characteristic tunable electromagnetic metasurface proposed in this invention achieves four polarization characteristic transformation functions in the first frequency band, two propagation characteristic control functions in the second frequency band, and four polarization characteristic transformation functions in the third frequency band. The electromagnetic metasurface described in this invention provides diverse polarization and transmission characteristics, is simple to control, easy to manufacture, and greatly improves the degree of freedom in application, making it widely applicable in control devices or wireless communication systems. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the unit structure within the periodic structure of the electromagnetic metasurface in an embodiment of the present invention;

[0023] Figure 2 This is a schematic diagram of the periodic structure and function of the electromagnetic metasurface in an embodiment of the present invention;

[0024] Figure 3 These are the amplitude and phase curves of the reflection coefficient and transmission coefficient after a linearly polarized wave is incident on the metasurface in an embodiment of the present invention.

[0025] Figure 4 These are the axial ratio curves of reflected and transmitted circularly polarized waves in embodiments of the present invention;

[0026] Figure 5 This is the amplitude curve of the reflection coefficient and transmission coefficient after linearly polarized waves polarized in the -45° and +45° directions are incident on the metasurface in the embodiments of the present invention. Detailed Implementation

[0027] The technical solution of the present invention will be described in detail below with reference to the embodiments and accompanying drawings.

[0028] like Figure 1 The diagram shows a specific embodiment of a unit within the periodic structure of this invention. The electromagnetic metasurface comprises a supporting dielectric substrate 1, a first double-opening metal ring with an outer radius of R1, and a second double-opening metal ring with an outer radius of R2; the dielectric substrate 1 has a thickness of T, a length and width of P, and a relative permittivity ε. r The following options can be selected based on usage requirements: The first metal ring consists of a long circular arc segment 2 and a short circular arc segment 3, both with a width of W1. Between the two arc segments are a first cut 6 and a second cut 7, both with a width of S1. The second metal ring consists of a long circular arc segment 4 and a short circular arc segment 5, both with a width of W2. Between the two arc segments are a third cut 8 and a fourth cut 9, both with a width of S2. Place the first cut 6 and the third cut 8 in the x-coordinate direction, and place the second cut 7 and the fourth cut 9 in the y-coordinate direction.

[0029] By selecting structural parameters, the frequencies and operating bandwidths of the three frequency bands can be changed. The frequency bands are related to the structural parameters; changing the structural parameters will change the frequencies of the three bands, but the relative relationships between the bands and the functions they perform remain unchanged. This embodiment selects a set of parameters to obtain the three frequency bands. The parameters selected in this embodiment are: T = 1mm, ε... r =2.65, P=9mm, R1=4.4mm, R2=1.8mm, W1=0.3mm, W2=0.8mm, S1=0.75mm, S2=1mm, and the thickness of the metal ring is 0.001-0.035mm.

[0030] like Figure 2 The diagram shows the periodic structure and function of the electromagnetic metasurface of the present invention. The incident wave is incident on the metasurface from the positive z-axis to the -z-axis direction, and can achieve different polarization characteristics in three frequency bands. The first frequency band achieves four polarization control functions, the second frequency band achieves two control functions, and the third frequency band achieves four polarization control functions.

[0031] The first frequency band achieves four polarization control functions: For example, linearly polarized waves polarized in the x-direction, after polarization control by a metasurface, produce right-hand circularly polarized waves of equal power in both reflected and transmitted waves; linearly polarized waves polarized in the y-direction, after polarization control by a metasurface, produce left-hand circularly polarized waves of equal power in both reflected and transmitted waves; left-hand circularly polarized waves, after polarization control by a metasurface, produce y-polarized waves reflected in the +z direction and x-polarized linearly polarized waves transmitted in the -z direction; and right-hand circularly polarized waves, after polarization control by a metasurface, produce x-polarized waves reflected in the +z direction and y-polarized linearly polarized waves transmitted in the -z direction.

[0032] The basic principles for implementing the four functions in the first frequency band are as follows:

[0033] (1) A linearly polarized wave propagating in the -z direction and polarized in the x direction is incident on a metasurface. After being modulated by the metasurface, the amplitudes of the x-polarized component and the y-polarized component in the reflected wave propagating in the +z direction are equal and the phase difference is +90°, forming a right-hand circularly polarized wave; the amplitudes of the x-polarized component and the y-polarized component in the transmitted wave propagating in the -z direction are equal and the phase difference is -90°, also forming a right-hand circularly polarized wave.

[0034] (2) A linearly polarized wave propagating in the -z direction and polarized in the y direction is incident on the metasurface. After being modulated by the metasurface, the amplitudes of the x-polarized component and the y-polarized component in the reflected wave propagating in the +z direction are equal and the phase difference is -90°, forming a left-hand circularly polarized wave; the amplitudes of the x-polarized component and the y-polarized component in the transmitted wave propagating in the -z direction are equal and the phase difference is +90°, also forming a left-hand circularly polarized wave.

[0035] (3) When a left-handed circularly polarized wave propagating along the -z direction is incident on the metasurface, after being modulated by the metasurface, the field components in the x direction propagating along the +z direction have equal amplitudes and opposite phases, thus canceling each other out, while the field components in the y direction have equal amplitudes and the same phase, thus superimposing each other out. Therefore, the reflected wave is only a linearly polarized wave polarized in the y direction. In the reflected wave propagating along the -z direction, the field components in the x direction have equal amplitudes and the same phase, thus superimposing each other out, while the field components in the y direction have equal amplitudes and opposite phases, thus canceling each other out. Therefore, the reflected wave is only a linearly polarized wave polarized in the x direction.

[0036] (4) When a right-hand circularly polarized wave propagating along the -z direction is incident on the metasurface, after being controlled by the metasurface, the field components in the x direction propagating along the +z direction have equal amplitudes and the same phase, and are superimposed on each other. The field components in the y direction have equal amplitudes and opposite phases, and are canceled on each other. Therefore, the reflected wave is only a linearly polarized wave polarized in the x direction. In the reflected wave propagating along the -z direction, the field components in the x direction have equal amplitudes and opposite phases, and are canceled on each other. The field components in the y direction have equal amplitudes and the same phase, and are superimposed on each other. Therefore, the reflected wave is only a linearly polarized wave polarized in the y direction.

[0037] The second frequency band enables two control functions: when a linearly polarized wave with a polarization of -45° is incident on the metasurface, the electromagnetic wave is totally reflected and the polarization characteristics remain unchanged; when a linearly polarized wave with a polarization of +45° is incident on the metasurface, the electromagnetic wave is completely transmitted and the polarization characteristics remain unchanged.

[0038] The basic principles for implementing the two functions in the second frequency band are as follows:

[0039] (1) When a linearly polarized wave polarized in the -45° direction is incident on a metasurface, the incident wave can be decomposed into a linearly polarized wave in the x-direction with an initial phase of 0° and a linearly polarized wave in the y-direction with an initial phase of -180°. After being controlled by the metasurface, the components of the x-polarized to x-polarized co-polarized reflection and the y-polarized to x-polarized cross-polarized reflection are superimposed with equal amplitude and phase, with a phase of -180°. The components of the x-polarized to y-polarized cross-polarized reflection and the y-polarized to y-polarized co-polarized reflection are also superimposed with equal amplitude and phase, with a phase of 0°. Therefore, the reflected wave is still a linearly polarized wave in the -45° direction. The components of the x-polarized to x-polarized co-polarized transmission and the y-polarized to x-polarized cross-polarized transmission are canceled out with equal amplitude and phase, and the components of the x-polarized to y-polarized cross-polarized transmission and the y-polarized to y-polarized co-polarized transmission are also canceled out with equal amplitude and phase. Therefore, there is no transmitted wave.

[0040] (2) When a linearly polarized wave polarized in the +45° direction is incident on the metasurface, the incident wave can be decomposed into linearly polarized waves in the x and y directions, both with an initial phase of 0°. After being controlled by the metasurface, the components of the x-polarized to x-polarized co-polarized reflection and the y-polarized to x-polarized cross-polarized reflection cancel each other out of phase. The components of the x-polarized to y-polarized cross-polarized reflection and the y-polarized to y-polarized co-polarized reflection also cancel each other out of phase, so there is no reflected wave. The components of the x-polarized to x-polarized co-polarized transmission and the y-polarized to x-polarized cross-polarized transmission are superimposed with equal amplitude and phase, and the phase is 0°. The components of the x-polarized to y-polarized cross-polarized transmission and the y-polarized to y-polarized co-polarized transmission are also superimposed with equal amplitude and phase, and the phase is 0°. Therefore, the polarization direction of the transmitted wave is still +45°.

[0041] The third frequency band enables four polarization control functions: For linearly polarized waves polarized in the x-direction, the reflected and transmitted waves are equal-power left-hand circularly polarized waves after polarization control via a metasurface; for linearly polarized waves polarized in the y-direction, the reflected and transmitted waves are equal-power right-hand circularly polarized waves after polarization control via a metasurface; for left-hand circularly polarized waves polarized in the +z direction, the reflected wave is x-polarized, and the transmitted wave is y-polarized; for right-hand circularly polarized waves polarized in the +z direction, the reflected wave is y-polarized, and the transmitted wave is x-polarized.

[0042] The basic principles for implementing the four functions in the third frequency band are as follows:

[0043] (1) A linearly polarized wave propagating in the -z direction and polarized in the x direction is incident on the metasurface. After being modulated by the metasurface, the amplitudes of the x-polarized component and the y-polarized component in the reflected wave propagating in the +z direction are equal and the phase difference is -90°, forming a left-hand circularly polarized wave; the amplitudes of the x-polarized component and the y-polarized component in the transmitted wave propagating in the -z direction are equal and the phase difference is +90°, also forming a left-hand circularly polarized wave.

[0044] (2) A linearly polarized wave propagating in the -z direction and polarized in the y direction is incident on the metasurface. After being modulated by the metasurface, the amplitudes of the x-polarized component and the y-polarized component in the reflected wave propagating in the +z direction are equal and the phase difference is +90°, forming a right-hand circularly polarized wave; the amplitudes of the x-polarized component and the y-polarized component in the transmitted wave propagating in the -z direction are equal and the phase difference is -90°, also forming a right-hand circularly polarized wave.

[0045] (3) When a left-handed circularly polarized wave propagating along the -z direction is incident on the metasurface, after being controlled by the metasurface, the field components in the x direction propagating along the +z direction have equal amplitudes and the same phase, and are superimposed on each other. The field components in the y direction have equal amplitudes and opposite phases, and are canceled on each other. Therefore, the reflected wave is only a linearly polarized wave polarized in the x direction. In the reflected wave propagating along the -z direction, the field components in the x direction have equal amplitudes and opposite phases, and are canceled on each other. The field components in the y direction have equal amplitudes and the same phase, and are superimposed on each other. Therefore, the reflected wave is only a linearly polarized wave polarized in the y direction.

[0046] (4) When a right-hand circularly polarized wave propagating along the -z direction is incident on the metasurface, after being controlled by the metasurface, the field components in the x direction propagating along the +z direction have equal amplitudes and opposite phases, thus canceling each other out, while the field components in the y direction have equal amplitudes and the same phase, thus superimposing each other out. Therefore, the reflected wave is only a linearly polarized wave polarized in the y direction. In the reflected wave propagating along the -z direction, the field components in the x direction have equal amplitudes and the same phase, thus superimposing each other out, while the field components in the y direction have equal amplitudes and opposite phases, thus canceling each other out. Therefore, the reflected wave is only a linearly polarized wave polarized in the x direction.

[0047] like Figure 3 The figure shows the amplitude and phase curves of the reflection coefficient and transmission coefficient after a linearly polarized wave polarized in the x (or y) direction is incident perpendicularly on the metasurface in an embodiment of the present invention. Figure 3 In the middle, R xx (or R) yy R represents the reflection coefficient of a linearly polarized wave in the x (or y) direction after reflection, indicating that the wave remains linearly polarized in the x (or y) direction. xx (or R) yy ) represents the reflection coefficient of the same polarization, and or

[0048] R yx (or R) xy R represents the reflection coefficient of a linearly polarized wave in the x (or y) direction, which is converted into a linearly polarized wave in the y (or x) direction after reflection. yx (or R) yx ) represents the reflection coefficient of cross-polarization, and or

[0049]

[0050] T xx (or T) yy T represents the transmission coefficient of a linearly polarized wave in the x (or y) direction transmitted through a metasurface; it remains a linearly polarized wave in the x (or y) direction. xx (or T) yy ) represents the transmission coefficient of the same polarization, and or

[0051]

[0052] T yx (or T) xy T represents the transmission coefficient that converts a linearly polarized wave in the x (or y) direction into a linearly polarized wave in the y (or x) direction after it is transmitted through the metasurface. yx (or T) xy ) represents the transmission coefficient of cross-polarization, and or from Figure 3 As can be seen from subgraphs (a) and (b), the amplitudes of the above-mentioned reflection coefficients or transmission coefficients are nearly equal in a wide frequency band of 5-16 GHz, and close to 0.5, thus achieving the condition that the amplitudes of each component are equal in the technical solution.

[0053] from Figure 3 From (c) and (d), it can be seen that the phase of the co-polarized reflection coefficients in the three frequency bands satisfies: The phase of the same polarization transmission coefficient satisfies: The phase of the cross-polarized reflection and transmission coefficients is around 6.5-8 GHz in the first frequency band: (or -270°), in the second frequency band around 9.5-11GHz. And in the third frequency band around 13.5-15GHz

[0054] This embodiment combines Figure 3 The technical solution further details the working principles of each frequency band.

[0055] The operating principles of the four functions within the first frequency band (6.5-8GHz) are as follows:

[0056] (1) Linearly polarized wave propagating along the -z direction and in the x direction When incident on a metasurface, reflection and transmission occur; in the reflected wave propagating along the +z direction, the electric field in the x-direction is of the same polarization. amplitude phase Cross-polarized y-direction electric field amplitude phase Since the amplitudes of the electric fields in the two directions are equal in the reflected wave: Phase difference: Therefore, the reflected wave propagating along the +z direction is a right-hand circularly polarized wave.

[0057] In a transmitted wave propagating along the -z direction, the electric field in the x-direction with the same polarization amplitude phase Cross-polarized y-direction electric field amplitude phase Because the electric field amplitudes in the two directions of the transmitted wave are equal. Phase difference Therefore, the transmitted wave propagating along the -z direction is also a right-hand circularly polarized wave.

[0058] (2) Linearly polarized wave propagating along the -z direction and polarized in the y direction When incident on a metasurface, reflection and transmission occur; in the reflected wave propagating along the +z direction, the electric field in the x-direction is cross-polarized. amplitude phase Electric field in the same polarization y direction amplitude Phase is Since the amplitudes of the electric fields in the two directions are equal in the reflected wave: Phase difference Therefore, the reflected wave propagating along the +z direction is a left-handed circularly polarized wave.

[0059] In a transmitted wave propagating along the -z direction, the electric field in the cross-polarized x direction amplitude phase Electric field in the same polarization y direction amplitude Phase is Because the electric field amplitudes in the two directions of the transmitted wave are equal. phase Therefore, the transmitted wave propagating along the -z direction is a left-handed circularly polarized wave.

[0060] Since the amplitudes of the reflection and transmission coefficients of the same polarization and the cross-polarization are both 0.5, the amplitudes of the field quantities will be equal in the subsequent discussion of the working principle unless otherwise specified.

[0061] (3) Left-hand circularly polarized wave propagating along the -z direction Its x-component The initial phase is y component initial phase When incident on a metasurface, reflection and transmission occur. In the reflected wave, along the x-direction... Components of the same polarization reflection field phase Cross-polarized reflection field of components phase The two waves are of equal amplitude and opposite phase, thus canceling each other out; the reflected wave has no x-component. In the y-direction, Cross-polarized reflection field of components phase Component-polarized reflection field phase The two waves, being of equal amplitude and in phase, superimpose to form the y-component of the reflected wave; therefore, the reflected wave is a linearly polarized wave with y-polarization.

[0062] In the transmitted wave, in the x-direction, Components of the same polarization transmission field phase Cross-polarization transmission of components phase The two components, being of equal amplitude and in phase, are superimposed to obtain the x-component of the transmitted wave; in the y-direction, Cross-polarization transmission of components phase Components of the same polarization transmission field phase The two waves are of equal amplitude and opposite phase, thus canceling each other out. The transmitted wave has no y-component; therefore, the transmitted wave is an x-polarized linearly polarized wave.

[0063] (4) Right-hand circularly polarized wave propagating along the -z direction Its x-component The initial phase is y component initial phase When incident on a metasurface, reflection and transmission occur. In the reflected wave, along the x-direction... Components of the same polarization reflection field phase Cross-polarized reflection field of components phase The two waves are of equal amplitude and in phase, and are superimposed to obtain the x-component of the reflected wave; in the y-direction, Cross-polarized reflection field of components phase Component-polarized reflection field phase The two waves are of equal amplitude and opposite phase, thus canceling each other out. The reflected wave has no y-component; therefore, the reflected wave is an x-polarized linearly polarized wave.

[0064] In the transmitted wave, in the x-direction, Components of the same polarization transmission field phase Cross-polarization transmission of components phase The two waves are of equal amplitude and opposite phase, canceling each other out; the transmitted wave has no x-component; in the y-direction, Cross-polarization transmission of components phase Components of the same polarization transmission field phase The two waves, being of equal amplitude and in phase, superimpose to form a transmitted wave with components; therefore, the transmitted wave is a linearly polarized wave with y-polarization.

[0065] The working principles of the two functions in the second frequency band (9.5-11GHz) are as follows:

[0066] (1) A linearly polarized wave polarized in the -45° direction can be decomposed into x-components. and y component amplitude initial phase initial phase Electromagnetic waves incident on a metasurface undergo reflection and transmission; in the x-direction, Homopolarized reflection field phase Cross-polarized reflection field phase The two components, being of equal amplitude and in phase, are superimposed to obtain the x-component of the reflected field. In the y-direction, Cross-polarized reflection field phase Homopolarized reflection field phase The two components, being of equal amplitude and in phase, are superimposed to obtain the y-component of the reflected field. and With equal amplitude and a 180-degree phase difference, the reflected wave is a linearly polarized wave polarized at -45°. In the x-direction of the transmitted wave... Homopolarized transmission field phase Cross-polarized transmission field phase The two waves are of equal amplitude and opposite phase, canceling each other out, resulting in no x-component in the transmitted wave; in the y-direction, Cross-polarized transmission field phase Homopolarized transmission field phase The two are of equal amplitude and opposite phase, and cancel each other out. The transmitted wave has no y component, so there is no transmitted wave, which means that the polarization-invariant total internal reflection characteristic is obtained.

[0067] (2) A linearly polarized wave polarized in the +45° direction can be decomposed into x-components. and y component The two amplitudes are equal. Initial phase is the same Electromagnetic waves incident on a metasurface undergo reflection and transmission; in the x-direction, Homopolarized reflection field phase Cross-polarized reflection field phase The two waves are of equal amplitude but opposite phase and cancel each other out, so the reflected wave has no x-component. In the y-direction, Cross-polarized reflection field phase Homopolarized reflection field phase The two waves are of equal amplitude but opposite phase and cancel each other out, so the reflected wave has no y-component. Therefore, there is no reflected wave. In the x-direction of the transmitted wave, Homopolarized transmission field phase Cross-polarized transmission field phase The two components, with equal amplitude and phase, are superimposed to obtain the x-component of the transmitted wave. In the y-direction, Cross-polarized transmission field phase Homopolarized transmission field phase The two components, with equal amplitude and phase, are superimposed to obtain the y-component of the transmitted wave. and Since the amplitudes are equal and the phases are both 0°, the transmitted waves are linearly polarized waves polarized in the 45° direction.

[0068] The working principles of the four functions in the third frequency band (13.5-15GHz) are as follows:

[0069] (1) Linearly polarized wave propagating along the -z direction and in the x direction When incident on a metasurface, reflection and transmission occur; in the reflected wave propagating along the +z direction, the electric field in the x-direction is of the same polarization. phase Cross-polarized y-direction electric field phase The two have equal amplitudes and phase differences. Therefore, the reflected wave propagating along the +z direction is a left-handed circularly polarized wave. In a transmitted wave propagating along the -z direction, the electric field in the x-direction with the same polarization phase Cross-polarized y-direction electric field phase The two have equal amplitudes and phase differences. Therefore, the transmitted wave propagating along the -z direction is also a left-handed circularly polarized wave.

[0070] (2) Linearly polarized wave propagating along the -z direction and polarized in the y direction When incident on a metasurface, reflection and transmission occur; in the reflected wave propagating along the +z direction, the electric field in the x-direction is cross-polarized. phase Electric field in the same polarization y direction The phase is The two have equal amplitudes and phase differences. Therefore, the reflected wave propagating along the +z direction is a right-hand circularly polarized wave. In a transmitted wave propagating along the -z direction, the electric field in the cross-polarized x direction phase Electric field in the same polarization y direction The phase is Both have equal amplitude and phase. Therefore, the transmitted wave propagating along the -z direction is a right-hand circularly polarized wave.

[0071] (3) Left-hand circularly polarized wave propagating along the -z direction Its x-component The initial phase is y component initial phase Electromagnetic waves incident on a metasurface undergo reflection and transmission. In the reflected wave, along the x-direction... Components of the same polarization reflection field phase Cross-polarized reflection field of components phase The two components, being of equal amplitude and in phase, are superimposed to obtain the x-polarization component of the reflected wave; in the y-direction, Cross-polarized reflection field of components phase Component-polarized reflection field phase The two waves are of equal amplitude and opposite phase, thus canceling each other out; therefore, the reflected wave has no y-polarization component, meaning the reflected wave is an x-polarized linearly polarized wave.

[0072] In the transmitted wave, in the x-direction, Components of the same polarization transmission field phase Cross-polarized transmission field of components phase The two waves are of equal amplitude and opposite phase, canceling each other out; the transmitted wave has no x-component; in the y-direction, Cross-polarized transmission field of components phase Components of the same polarization transmission field phase The y-component of the transmitted wave according to the theory of equal amplitude, in-phase, and superposition. Therefore, the transmitted wave is a linearly polarized wave with y-polarization.

[0073] (4) Right-hand circularly polarized wave propagating along the -z direction Its x-component The initial phase is y component initial phase When electromagnetic radiation is incident on a metasurface, it produces reflection and transmission. In the reflected wave, in the x-direction... Components of the same polarization reflection field phase Cross-polarized reflection field of components phase The two waves are of equal amplitude and opposite phase, canceling each other out; the reflected wave has no x-component; in the y-direction, Cross-polarized reflection field of components phase Component-polarized reflection field phase The two waves, being of equal amplitude and in phase, superimpose to form the y-component of the reflected wave; therefore, the reflected wave is a linearly polarized wave with y-polarization.

[0074] In the transmitted wave, in the x-direction, Components of the same polarization transmission field phase Cross-polarization transmission of components phase The two components, being of equal amplitude and in phase, are superimposed to obtain the x-component of the transmitted wave; in the y-direction, Cross-polarization transmission of components phase Components of the same polarization transmission field phase The two waves are of equal amplitude and opposite phase, thus canceling each other out. The transmitted wave has no y-component; therefore, the transmitted wave is an x-polarized linearly polarized wave.

[0075] like Figure 4 The figure shows the axial ratio curves of reflected and transmitted circularly polarized waves in an embodiment of the present invention. It illustrates the characteristics of reflected and transmitted circularly polarized waves in the first and third frequency bands. As can be seen from the figure, in the first frequency band (6.8 GHz to 7.9 GHz) and the third frequency band (13.3 GHz to 14.6 GHz), the axial ratio of reflected and transmitted waves is less than 3 dB, meeting the requirements for circular polarization.

[0076] like Figure 5 The figure shows the amplitude curves of the reflection coefficient and transmission coefficient after linearly polarized waves polarized in the -45° and +45° directions are incident on the metasurface in an embodiment of the present invention. From Figure 5 (a) shows the results of polarization at -45 degrees. It can be seen that in the second frequency band, the reflection coefficient is close to 0 dB, while the transmission coefficient is relatively small, meaning that electromagnetic waves are mainly subjected to total internal reflection. Figure 5 (b) shows the results of polarization at +45 degrees. It can be seen that in the second frequency band, the transmission coefficient is close to 0dB, while the reflection coefficient is small, meaning that electromagnetic waves are mainly fully transmitted.

[0077] In summary, the multi-band polarization and propagation characteristic tunable electromagnetic metasurface proposed in this invention achieves four polarization characteristic transformation functions in the first frequency band, two propagation characteristic control functions in the second frequency band, and four polarization characteristic transformation functions in the third frequency band. The electromagnetic metasurface described in this invention provides diverse polarization and propagation characteristics, is simple to control, easy to fabricate, and greatly improves the degree of freedom in application, making it widely applicable in control devices or wireless communication systems.

Claims

1. An electromagnetic metasurface with tunable multi-band polarization and propagation characteristics, characterized in that: The magnetic supersurface comprises a dielectric substrate and a periodic array fixed on the dielectric substrate. The periodic array includes multiple sets of two-dimensional array basic units with the same length and width. Each basic unit contains two metal rings with coincident centers and different radii. The larger metal ring has a first and a second notch, and the smaller metal ring has a third and a fourth notch. Each notch has the same width, and the centerlines of the first and third notches coincide, as do the centerlines of the second and fourth notches. The first and third notches are placed in the x-coordinate direction, and the second and fourth notches are placed in the y-coordinate direction. An incident wave is incident on the supersurface from the positive z-axis to the -z-axis direction, enabling different polarization characteristic modulation functions in three frequency bands. Four polarization modulation functions are achieved in the first frequency band, two modulation functions in the second frequency band, and four polarization modulation functions in the third frequency band.

2. The electromagnetic metasurface with tunable multi-band polarization and propagation characteristics according to claim 1, characterized in that: The first frequency band implements four polarization control functions, namely: x After the polarization modulation effect of the metasurface, the linearly polarized wave with directional polarization is reflected and transmitted as right-hand circularly polarized waves of equal power. A linearly polarized wave polarized in the y-direction is polarized by a metasurface, and the reflected and transmitted waves are left-handed circularly polarized waves of equal power. Left-handed circular polarization, after being polarized by a metasurface, results in a reflected wave along the +z direction that is y-polarized, and a transmitted wave along the -z direction that is x-polarized. After being polarized by a metasurface, the right-hand circularly polarized wave is reflected along the +z direction as an x-polarized wave and transmitted along the -z direction as a y-polarized linear wave.

3. The electromagnetic metasurface with tunable multi-band polarization and propagation characteristics according to claim 1, characterized in that: The second frequency band enables two control functions: When a linearly polarized wave polarized in the -45º direction is incident on a metasurface, the electromagnetic wave is totally reflected, and the polarization characteristics remain unchanged. When a linearly polarized wave polarized in the +45º direction is incident on a metasurface, the electromagnetic wave is fully transmitted, and the polarization characteristics remain unchanged.

4. The electromagnetic metasurface with tunable multi-band polarization and propagation characteristics according to claim 1, characterized in that: The third frequency band enables four polarization control functions: x After the polarization modulation effect of the metasurface, the linearly polarized wave with directional polarization is reflected and transmitted as left-hand circularly polarized waves of equal power. The linear polarization in the y-direction is modulated by the metasurface, and the reflected and transmitted waves are right-hand circularly polarized waves of equal power. Left-handed circular polarization, after being polarized by a metasurface, results in a reflected wave along the +z direction that is x-polarized, and a transmitted wave along the -z direction that is y-polarized. After being polarized by a metasurface, the right-hand circularly polarized wave is reflected along the +z direction as a y-polarized wave and transmitted along the -z direction as a x-polarized linearly polarized wave.

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