Metasurface unit with adjustable broadband reflective phase-controlled spatiotemporal coding

Abstract

The disclosed embodiment of the present invention discloses a metasurface unit with adjustable broadband reflective phase-controlled space-time coding, wherein the metasurface unit with adjustable broadband reflective phase-controlled space-time coding includes: a top radiation metal layer, an intermediate dielectric plate layer, a bottom metal ground and two metallized vias arranged in sequence from top to bottom, wherein the first L-shaped metal strip includes two parts of L-shaped metal strips connected rotationally symmetrically about a radio frequency switch; the end of the second L-shaped metal strip is open-circuited, and the other end is connected to the end of the first L-shaped metal strip, and the second L-shaped metal strip includes two parts of L-shaped metal strips distributed rotationally symmetrically about the radio frequency switch; the two metallized vias electrically connect the first L-shaped metal strip with the bottom metal ground, the metallized vias are symmetrical about the center of the radio frequency switch, and the voltage controls the on and off of the radio frequency switch through the metallized vias; the bottom metal ground is in the center of the metasurface unit along the placement direction of the radio frequency switch.

Description

Technical Field

[0001] The present disclosure relates to the technical field of electromagnetic materials, and in particular to an adjustable broadband reflective phase-controlled spatiotemporal encoding metasurface unit. Background Art

[0002] New artificial electromagnetic materials, also known as electromagnetic metamaterials, have attracted widespread attention from all walks of life due to their ability to control the propagation of electromagnetic waves. As a two-dimensional form of electromagnetic metamaterials, artificial electromagnetic metasurfaces are usually composed of periodic subwavelength units. By designing the structural dimensions of artificial electromagnetic metasurface units, the metasurface units can accurately control the electromagnetic wave propagation characteristics such as phase, amplitude and polarization direction in a specific working frequency band.

[0003] Traditional phase control is often achieved by loading a phase shifter on the back stage of the RF terminal module. Artificial electromagnetic materials can use their dynamic electromagnetic response characteristics and time-division multiplexing technology to achieve more flexible electromagnetic wave control, which can better achieve the goal of system miniaturization and integration, so it has better application prospects in practical applications. As a time-varying material, the phase-controlled metasurface based on space-time coding can achieve flexible control of radar electromagnetic echo signals, and has great application value in synthetic aperture radar imaging detection, electronic countermeasures, etc.

[0004] At present, most artificial metasurfaces have the problems of difficult phase modulation and narrow working frequency band. After the design of many artificial metasurfaces is completed, the working frequency band is fixed, and there is no good adjustment method, which greatly limits the application of electromagnetic metasurfaces. Chinese patent CN110911845A discloses a broadband zero-cross polarization space-time coding digital metasurface unit, with an operating frequency band of 7.71-9.48GHz, a bandwidth of 1.77GHz, and a relative bandwidth of 20.5%. The bandwidth is relatively wide but does not cover the entire X-band, and the working frequency band is not adjustable; Chinese patent CN110896171A discloses an ultra-wideband polarization conversion metasurface structure, which can convert linear polarization waves into orthogonal polarization waves in an ultra-wideband range of 14.3GHz to 43.2GHz, but the structure is fixed and the phase cannot be dynamically adjusted. Summary of the invention

[0005] The embodiment of the present disclosure provides a metasurface unit with adjustable broadband reflective phase control and space-time coding. In view of the above-mentioned deficiencies in the prior art, the present disclosure proposes an adjustable broadband reflective phase control and space-time coding metasurface unit and a control method, which expands the working bandwidth and is flexible to adjust, facilitating the industrialization and integrated application of space-time coding metasurfaces.

[0006] In a first aspect, an embodiment of the present disclosure provides an adjustable broadband reflective phase-controlled spatiotemporal coding metasurface unit, comprising a top radiation metal layer (1), an intermediate dielectric plate layer (2), a bottom metal ground (3), and two metallized vias (4) and (5) arranged in sequence from top to bottom, wherein:

[0007] The top radiation metal layer (1) comprises a radio frequency switch (6), a first L-shaped metal strip (8), and a second L-shaped metal strip (9); the radio frequency switch (6) is located at the center of the metasurface unit; the first L-shaped metal strip (8) comprises two L-shaped metal strips that are rotationally symmetrically connected with respect to the radio frequency switch (6); the second L-shaped metal strip (9) has an open end and the other end connected to the end of the first L-shaped metal strip (8); the second L-shaped metal strip (9) comprises two L-shaped metal strips that are rotationally symmetrically distributed with respect to the radio frequency switch (6);

[0008] The two metallized vias (4) and (5) pass through the intermediate dielectric layer (2) and are used to electrically connect the first L-shaped metal strip (8) to the bottom metal ground (3); the metallized vias (4) and (5) are symmetrical about the center of the radio frequency switch (6); and voltage controls the on and off of the radio frequency switch (6) through the metallized vias (4) and (5);

[0009] The bottom metal ground (3) is etched with three metal gaps (10), (11) and (12) at the center of the metasurface unit along the placement direction of the radio frequency switch (6), and the three metal gaps (10), (11) and (12) divide the bottom metal ground (3) into two parts;

[0010] The top radiation metal layer (1) is connected to the bottom metal ground (3) through the two metallized vias (4) and (5), and together achieves the effect of phase-controlled space-time coding under the control of the radio frequency switch (6).

[0011] Furthermore, the value range of the side length of the super surface unit is 0.221λ t ≤d≤0.256λ t ,λ t =c / f t , where f t is the center frequency of the operating frequency band, c is the speed of light in vacuum, λ t It is the wavelength corresponding to the center frequency of the working frequency band.

[0012] Furthermore, the width w3 of the L-shaped wider portion of the first L-shaped metal strip (8) is in the range of 0.0669λ t ≤w3≤0.0758λ t , the width w2 of the narrower part of the L-shaped part ranges from 0.0428λt ≤w2≤0.0485λ t , the range of the longitudinal length l2 is 0.134λ t ≤l2≤0.152λ t , where λ t is the wavelength corresponding to the center frequency of the working frequency band;

[0013] The value range of the L-shaped wider width w1 of the second L-shaped metal strip (9) is 0.0857λ t ≤w1≤0.0971λ t , the range of the longitudinal length l1 is 0.165λ t ≤l1≤0.187λ t , where λ t is the wavelength corresponding to the center frequency of the working frequency band;

[0014] The first L-shaped metal strip (8) and the second L-shaped metal strip (9) are connected to each other and together form a part of the radiator. The longitudinal gap distance d1 between the first L-shaped metal strip (8) and the second L-shaped metal strip (9) has a value range of 0.008λ. t ≤d1≤0.009λ t , the range of the lateral gap distance d2 is 0.008λ t ≤d1≤0.0238λ t , where λ t It is the wavelength corresponding to the center frequency of the working frequency band.

[0015] Furthermore, the radio frequency switch (6) is centrally symmetrically connected to the top radiation metal layer (1); and / or,

[0016] The top radiation metal layer (1), the middle dielectric plate layer (2), the bottom metal ground (3), the two metallized vias (4) (5) and the radio frequency switch (6) are respectively centrally symmetrical about the metasurface unit.

[0017] Furthermore, the inner side walls of the two metallized vias (4) and (5) are both covered with metal.

[0018] Furthermore, the intermediate dielectric plate layer (2) is made of dielectric material, the relative dielectric constant is 2 to 4.5, and the dielectric thickness h is in the range of 0.05λ t ≤h≤0.25λ t , where λ t It is the wavelength corresponding to the center frequency of the working frequency band.

[0019] Furthermore, the gap distances of the three metal gaps (10), (11) and (12) etched on the bottom metal ground (3) are in the relationship of d4=d5=d3 / 2, and the value range of the gap d3 is 0.005λ. t ≤d3≤0.006λ t , where λ t It is the wavelength corresponding to the center frequency of the working frequency band.

[0020] Furthermore, the bottom metal ground (3) is divided into two parts (13) and (14) by the metal gap (10). The bottom metal ground (3) serves as a metal bottom plate for blocking the transmission of electromagnetic waves. At the same time, the two parts (13) and (14) of the bottom metal ground (3) also serve as electrodes to be connected to the positive and negative electrodes of an external driving power source respectively.

[0021] In a second aspect, an embodiment of the present disclosure provides a phase control method of a metasurface unit as described in the first aspect, the control method comprising:

[0022] Utilizing a linearly polarized incident wave to illuminate the metasurface unit along a conducting direction of a radio frequency switch;

[0023] After the linearly polarized incident wave propagates to the bottom metal ground (3) of the metasurface unit, it is reflected back to the top radiation metal layer (1);

[0024] By applying voltage to the positive and negative electrodes of the power supply or disconnecting the voltage, the radio frequency switch is turned on or off to change the inductance value in the equivalent circuit, so as to adjust the phase of the metasurface unit.

[0025] Furthermore, the method further comprises:

[0026] An external driving power source is connected to the underlying metal ground, and the external driving power source is used to control the on and off of the radio frequency switch through a time-varying modulation method to regulate the dynamic electromagnetic response of the metasurface unit.

[0027] The technical solution provided by the embodiments of the present disclosure may have the following beneficial effects:

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1) The present invention adopts a centrosymmetric space-time coding metasurface unit structure, and two centrosymmetric L-shaped metal strips are connected symmetrically about the center of the RF switch to extend the high-frequency current return path. The bottom metal ground is powered by an external circuit, and the RF switch is modulated by metallized vias to achieve broadband 180-degree time-varying phase control.

[0030] 2) The present invention can adjust the space-time coding metasurface unit structure and use the equivalent circuit theory to change the equivalent circuit inductance, thereby effectively guiding the regulation of the working frequency band of the metasurface unit.

[0031] The two examples given in the present disclosure respectively achieve a phase shift of 180°±30° in the 8.11GHz-13.58GHz operating frequency band (relative bandwidth 50.4%), and a phase shift of 180°±35° in the 7.79GHz-13.39GHz operating frequency band (relative bandwidth 52.8%). Simulation results show that the resonance points of the two embodiments have changed, that is, wide-band adjustable 1-bit phase encoding is achieved, and the simulation results are highly consistent with the theoretical analysis results.

[0032] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Other features, objectives and advantages of the present disclosure will become more apparent through the following detailed description of non-limiting embodiments in conjunction with the accompanying drawings. In the accompanying drawings:

[0034] Figure 1 A schematic diagram showing the overall structure of a metasurface unit according to an embodiment of the present disclosure is shown;

[0035] Figure 2 A schematic diagram of the top structure of a super surface unit according to an embodiment of the present disclosure is shown;

[0036] Figure 3 An equivalent schematic diagram showing a top radiation metal layer according to an embodiment of the present disclosure;

[0037] Figure 4 A schematic diagram of an equivalent circuit of a metasurface unit according to an embodiment of the present disclosure is shown;

[0038] FIG5( a ) and FIG5( b ) are schematic diagrams showing electric field distribution of a metasurface unit according to an embodiment of the present disclosure;

[0039] FIG6( a ) and FIG6( b ) are schematic diagrams showing reflection phase and return loss curves of a metasurface unit in Example 1 according to an embodiment of the present disclosure;

[0040] FIG. 7( a ) and FIG. 7( b ) show graphs of reflection phase and return loss of a metasurface unit according to Example 2 of an embodiment of the present disclosure;

[0041] Figure 8 A schematic diagram showing the change of the resonance point frequency in Example 1 and Example 2 according to an implementation of the present disclosure is shown. DETAILED DESCRIPTION

[0042] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement them. In addition, for the sake of clarity, parts not related to the description of the exemplary embodiments are omitted in the accompanying drawings.

[0043] In the present disclosure, it should be understood that terms such as "include" or "have" are intended to indicate the presence of features, numbers, steps, behaviors, components, parts, or a combination thereof disclosed in the specification, and do not exclude the possibility that one or more other features, numbers, steps, behaviors, components, parts, or a combination thereof exist or are added.

[0044] It should also be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present disclosure may be combined with each other. The present disclosure will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0045] The details of the embodiments of the present disclosure are described in detail below through specific examples.

[0046] Figure 1 A schematic diagram of the overall structure of a supersurface unit according to an embodiment of the present disclosure is shown. Figure 2 FIG. 2 shows a schematic diagram of the top structure of a super surface unit according to an embodiment of the present disclosure. Figure 1 and Figure 2 As shown, the metasurface unit includes: a top radiation metal layer 1, an intermediate dielectric layer 2, a bottom metal ground 3 and two metallized vias 4 and 5 arranged in sequence from top to bottom, wherein:

[0047] The top radiation metal layer 1 includes a radio frequency switch 6, a first L-shaped metal strip 8, and a second L-shaped metal strip 9. The radio frequency switch 6 is located at the center of the metasurface unit. The first L-shaped metal strip 8 includes two L-shaped metal strips that are rotationally symmetrically connected with respect to the radio frequency switch 6. The second L-shaped metal strip 9 has an open end and the other end connected to the end of the first L-shaped metal strip 8. The second L-shaped metal strip 9 includes two L-shaped metal strips that are rotationally symmetrically distributed with respect to the radio frequency switch 6.

[0048] Two metallized vias 4 and 5 pass through the intermediate dielectric layer 2, and are used to electrically connect the first L-shaped metal strip 8 to the bottom metal ground 3. The metallized vias 4 and 5 are symmetrical about the center of the RF switch 6, and the voltage controls the on and off of the RF switch 6 through the metallized vias 4 and 5;

[0049] The bottom metal ground 3 is etched with three metal gaps 10, 11 and 12 in the center of the metasurface unit along the placement direction of the RF switch 6. The three metal gaps 10, 11 and 12 divide the bottom metal ground 3 into two parts.

[0050] The top radiation metal layer 1 is connected to the bottom metal ground 3 through two metallized vias 4 and 5, and under the control of the radio frequency switch 6, they jointly achieve the effect of phase regulation space-time coding.

[0051] In some embodiments, the metasurface unit is an adjustable broadband reflective phase-controlled spatiotemporal coding metasurface unit.

[0052] In some embodiments, the value range of the side length of the super surface unit is 0.221λ t ≤d≤0.256λ t ,λ t =c / f t , where f t is the center frequency of the operating frequency band, c is the speed of light in vacuum, λ t It is the wavelength corresponding to the center frequency of the working frequency band.

[0053] In some embodiments, the width w3 of the L-shaped wider portion of the first L-shaped metal strip 8 is in the range of 0.0669λ t ≤w3≤0.0758λ t , the value range of the narrower width w2 is 0.0428λ t ≤w2≤0.0485λ t , the range of the longitudinal length l2 is 0.134λ t ≤l2≤0.152λ t , where λ t is the wavelength corresponding to the center frequency of the working frequency band;

[0054] The value range of the L-shaped wider width w1 of the second L-shaped metal strip 9 is 0.0857λ t ≤w1≤0.0971λ t , the range of the longitudinal length l1 is 0.165λ t ≤l1≤0.187λ t , where λ t is the wavelength corresponding to the center frequency of the working frequency band;

[0055] The first L-shaped metal strip 8 is connected to the second L-shaped metal strip 9, and together they form a part of the radiator. The longitudinal gap distance d1 between the first L-shaped metal strip 8 and the second L-shaped metal strip 9 has a value range of 0.008λ. t ≤d1≤0.009λ t , the range of the lateral gap distance d2 is 0.008λ t ≤d1≤0.0238λ t , where λ t It is the wavelength corresponding to the center frequency of the working frequency band.

[0056] In some embodiments, the capacitance value in the equivalent circuit of the metasurface unit can be adjusted by adjusting the distance between the first L-shaped metal strip 8 and the second L-shaped metal strip 9, thereby adjusting the working frequency band of the metasurface unit.

[0057] In some embodiments, the RF switch 6 is centrally symmetrically connected to the top radiative metal layer 1 .

[0058] In some embodiments, the RF switch may use a PIN diode.

[0059] In some embodiments, inner sidewalls of the two metallized vias 4 and 5 are both covered with metal.

[0060] In some embodiments, the intermediate dielectric layer 2 is made of dielectric material, the relative dielectric constant is 2 to 4.5, and the dielectric thickness h is in the range of 0.05λ t ≤h≤0.25λ t , where λ t It is the wavelength corresponding to the center frequency of the working frequency band.

[0061] In some embodiments, the gap distances of the three metal gaps 10, 11 and 12 etched on the bottom metal ground 3 are in the relationship of d4=d5=d3 / 2, and the value range of the gap d3 is 0.005λ t ≤d3≤0.006λ t , where λ t It is the wavelength corresponding to the center frequency of the working frequency band.

[0062] In some embodiments, the bottom metal ground 3 is separated by a metal gap 10, and the bottom metal ground 3 serves as a metal bottom plate to block the transmission of electromagnetic waves. At the same time, the two parts 13 and 14 of the bottom metal ground 3 also serve as electrodes to connect the positive and negative electrodes of the external driving power supply respectively.

[0063] In some embodiments, the present disclosure provides a phase control method of the above-mentioned metasurface unit, including:

[0064] Using a linearly polarized incident wave to illuminate the metasurface unit along the conduction direction of the radio frequency switch;

[0065] After the linearly polarized incident wave propagates to the bottom metal ground 3 of the metasurface unit, it is reflected back to the top radiation metal layer 1;

[0066] By applying voltage to the positive and negative poles of the power supply or disconnecting the voltage, the RF switch is turned on or off to change the inductance value in the equivalent circuit to adjust the phase of the metasurface unit. ;

[0067] Figure 3 FIG. 2 shows an equivalent schematic diagram of a top radiation metal layer according to an embodiment of the present disclosure. Figure 3As shown, metallized vias 4 and 5 are always grounded, and the top radiation metal layer is equivalent to an ideal electric field wall. The equivalent circuit of the metasurface unit is as follows: Figure 4 shown.

[0068] When no voltage is applied to the positive and negative poles of the power supply, the RF switch is not turned on, which is equivalent to an open circuit. As shown in Figure 5(a), the electric field is mainly concentrated around the lateral gap d1 between the two L-shaped metal strips. The lateral gap d1 mainly affects the C2 value in the equivalent circuit diagram, and then affects the resonance characteristics. At this time, the phase response of the reflected wave is defined as the off state of the metasurface, which is the "0" state.

[0069] When voltage is applied to the positive and negative poles of the power supply, the RF switch is turned on, which is equivalent to a path. As shown in Figure 5(b), the electric field is mainly concentrated around the tops of the two L-shaped metal strips. At this time, the longitudinal gap d1 remains unchanged. The resonance characteristics of the equivalent circuit are mainly affected by the longitudinal lengths l1 and l2 and d2 of the two L-shaped metal strips. The longitudinal length mainly affects the values ​​of the inductances L1 and L2 in the equivalent circuit diagram, and then affects the resonance characteristics. At this time, the phase response of the reflected wave is defined as the conduction state of the metasurface, which is the "1" state.

[0070] The on and off of the RF switch mainly affects the high-frequency electromagnetic wave induced current path, thereby changing the size of the inductance value in the equivalent circuit. Comparing the two states of the metasurface, the main difference in the electric field characteristics lies in the electric field distribution outside the L-shaped metal strip. Due to the bending characteristics of the L-shaped metal strip, the high-frequency current path is longer and the equivalent electrical size of the unit is increased, which can ensure stable 1-bit 180-degree phase response control between the on state and the off state in a wider frequency band;

[0071] In the case that the longitudinal gap d1 of the top radiation metal layer 1 remains unchanged, by extending the size w5 of the metal arm 7, adjusting the size of the lateral gap d2 and the length of the metal arm l1, the capacitance value of C2 in the equivalent circuit can be basically unchanged, and the values ​​of the inductances L1 and L2 in the equivalent circuit diagram can be changed. According to the resonant frequency formula Under the condition that the capacitance of the equivalent circuit remains basically unchanged, changing the equivalent inductance value can effectively adjust the working frequency band of the coded metasurface unit;

[0072] After adjusting the lateral gap, the electric field distributions of the turn-off mode and the turn-on mode remain basically consistent within the operating frequency band, thereby obtaining a stable phase difference between the two modes.

[0073] In some embodiments, the external driving power supply is connected to the underlying metal ground 13 and 14 after being radio frequency isolated. The external driving power supply controls the on and off of the radio frequency switch through time-varying modulation to regulate the dynamic electromagnetic response of the time-varying coded metasurface.

[0074] In some embodiments, the top radiative metal layer 1, the middle dielectric layer 2, the bottom metal ground 3, the two metallized vias 45 and the RF switch 6 are all centrally symmetric about the metasurface unit, which can achieve lower cross polarization and ensure the consistency of the reflected wave amplitude and phase.

[0075] The specific details of the present disclosure are described below through detailed examples.

[0076] Example 1

[0077] Reference Figure 1 As shown, this embodiment comprises, from top to bottom: a top radiating metal layer 1, an intermediate dielectric board layer 2 and a bottom metal ground 3, the upper surface of the intermediate dielectric board layer 2 is connected to the top radiating metal layer 1, the lower surface of the intermediate dielectric board layer 2 is connected to the bottom metal ground 3, two metallized vias 4 and 5 pass through the dielectric board layer from the top metal layer and are electrically connected to the metal ground 3, the inner side walls of the metallized vias are all covered with metal, the RF switch 6 is located at the center of the top radiating metal layer to connect the two L-shaped metal strips 8 and 9, the metal wall 7 connects the two metal strips, and the bottom metal ground 3 is divided into parts 13 and 14 by metal gaps 10, 11 and 12.

[0078] Reference Figure 2 The side length a of the adjustable broadband reflective phase-controlled space-time coding metasurface unit ranges from 0.221λ t ≤d≤0.256λ t , the value range of the top width w3 of the first L-shaped metal strip 8 is 0.0669λ t ≤w3≤0.0758λ t , the value range of width w2 is 0.0428λ t ≤w2≤0.0485λ t , the range of the longitudinal length l2 is 0.134λ t ≤l2≤0.152λ t , the value range of the top width w1 of the second L-shaped metal strip 9 is 0.0857λ t ≤w1≤0.0971λ t , the range of the longitudinal length l1 is 0.165λ t ≤l1≤0.187λ t The first L-shaped metal strip 8 and the second L-shaped metal strip 9 are connected to form a part of the radiator, and the longitudinal gap d1 between the two metal strips is 0.008λ. t ≤d1≤0.009λ t , lateral gap d2 distance 0.008λ t ≤d1≤0.0238λ tThe intermediate dielectric layer 2 is made of dielectric material with a relative dielectric constant of 2 to 4.5 and a dielectric thickness h in the range of 0.05λ. t ≤h≤0.25λ t , the bottom metal ground 3 is etched with metal gaps 10, 11 and 12, the metal gap value relationship is d4 = d5 = d3 / 2, and the value range of the spacing d3 is 0.005λ t ≤d3≤0.006λ t ,λ t =c / f t , where f t is the center frequency of the operating frequency band, c is the speed of light in vacuum, λ t It is the wavelength corresponding to the center frequency of the working frequency band, and the incident direction of the electromagnetic wave is along the on-off direction of the RF switch. The bottom metal ground 3 serves as a metal bottom plate to block the transmission of electromagnetic waves, and 13 and 14 also serve as electrodes to connect the positive and negative electrodes of the external driving power supply respectively. The top radiation metal layer 1, the intermediate dielectric plate layer 2, the bottom metal ground 3, the two metallized vias 4, 5 and the RF switch 7 are all centrally symmetrical about the unit. The external driving power supply is connected to the bottom metal ground 13 and 14 after RF isolation. The external driving power supply controls the on-off of the RF switch through time-varying modulation to regulate the dynamic electromagnetic response of the time-varying coded metasurface.

[0079] In Example 1, the specific values ​​of various parameters are as follows, but not limited to these values: the center frequency band of the working frequency band of the space-time coding phase control metasurface unit is 8GHz-13.58GHz, the center frequency is 10.79GHz, the working frequency band is in the X band and Ku band of electromagnetic waves, the adjustable broadband reflection-type phase control space-time coding metasurface unit has a side length a=7.04mm, the top width w3=2.11mm of the first L-shaped metal strip 8, the width w2=1.32mm, the longitudinal length l2=4.23mm, the top width w1=3.11mm of the second L-shaped metal strip 9, the longitudinal length l2=4.23mm, the top width w2=3.11mm of the second L-shaped metal strip 9, the longitudinal length l3=4.23mm, the top width w2=3.11mm of the second L-shaped metal strip 9, the longitudinal length l4=4.23mm, the top width w3=3.11mm of the second L-shaped metal strip 9, the longitudinal length l5=4.23mm, the top width w4=3.11mm of the second L-shaped metal strip 9, the longitudinal length l6=4.23mm, the top width w5=3.11mm of the second L-shaped metal strip 9, the longitudinal length l7=4.23mm, the top width w6=3.11mm of the second L-shaped metal strip 9, the longitudinal length l8=4.23mm, the top width w7=3.11mm of the second L-shaped metal strip 9, the longitudinal length l9=4.23mm, the top width w8=3.11mm of the second L-shaped metal strip 9, the longitudinal length l2=4.23mm, the top width w9=3.11mm of the second L-shaped metal strip 9, the longitudinal length l1=4.23mm, the top width w9=3.11mm of the second L The longitudinal length l1=5.15mm, the first L-shaped metal strip 8 and the second L-shaped metal strip 9 are connected to form a part of the radiator together, the longitudinal gap d1=0.26mm, the transverse gap d2=0.26mm between the two metal strips, and the metal arm length w5=2.05mm at this time. The middle dielectric layer 2 adopts dielectric material with a relative dielectric constant of 2.65 and a dielectric thickness h=2.64mm. The bottom metal ground 3 etches metal gaps 10, 11 and 12, and the metal gap value relationship is d4=d5=d3 / 2=0.088mm. The diameter of the metalized via is 0.25mm.

[0080] In this embodiment, the RF switch uses a diode SMP1340-079. The working bandwidth of SMP1340-079 can theoretically cover the entire C band / X band, and part of the Ku band. When it is turned on, it is equivalent to a lumped inductor Ls =0.7nH, the lumped resistance R=1.7Ω is connected in series, which can be equivalent to an open circuit when it is cut off.

[0081] The following simulation experiment verifies the reflection phase and return loss of the working frequency band of the embodiment 1 of the present disclosure. In this embodiment, it is assumed that the number of time-varying metasurface units is infinitely uniformly distributed in the horizontal plane, and the embodiment of the present disclosure is simulated using electromagnetic simulation software.

[0082] Simulation content and results: Under vertical incidence, a linearly polarized electromagnetic wave is incident along the direction of the RF switch, and the Floquet port is used to perform electromagnetic simulation on the metasurface unit to obtain the reflection phase and return loss curves, as shown in Figure 6(a) and Figure 6(b). From the return loss curve shown in Figure 6(a) and the reflection phase phase difference shown in Figure 6(b), it can be seen that before and after the RF switch is turned on, the adjustable broadband reflection-type phase-controlled space-time coding metasurface unit achieves a stable phase difference of 180°±30° in the 8.11GHz-13.58GHz frequency band (relative bandwidth 50.4%), the center frequency of the working frequency band is 10.81GHz, and the return loss S 11 is 0.82dB, the transmission coefficient S 12 Below -60dB, at the same time Figure 8 The solid line curve shows the frequency of the resonance point of Example 1. The simulation results show that the metasurface unit has good performance.

[0083] Example 2

[0084] In Example 2, the overall composition and specific structure of the adjustable broadband reflective phase-controlled space-time coding metasurface unit are the same as those in Example 1, see Figure 1 and Figure 2 In Example 2, the specific values ​​of various parameters are as follows, but not limited to these values: the working frequency band of the space-time coded phase-controlled metasurface unit is 7.79GHz-13.31GHz, the center frequency is 10.55GHz, and the working frequency band is in the C band and the X band. Since the capacitance value C2 in the equivalent circuit is most affected by the gap d1 and is less affected by other gaps, while ensuring that other structural parameters are the same as in Example 1, the lateral gap d2=0.66mm between the two metal strips is widened, and the length of the metal arm l1=5.1mm is extended, so that the capacitance value C2 in the equivalent circuit remains unchanged while changing the inductance value. According to the resonant frequency formula:

[0085]

[0086] It can be seen that when the equivalent capacitance value C2 remains unchanged, changing the equivalent inductance value can effectively change the resonant frequency, thereby changing the working frequency band of the embodiment. Therefore, after changing the length of the metal strip, the working frequency band in embodiment 1 is successfully adjusted to the working frequency band of embodiment 2.

[0087] The following simulation experiment verifies the reflection phase and return loss of the working frequency band of the embodiment 2 of the present disclosure. In this embodiment, it is assumed that the number of time-varying metasurface units is infinitely uniformly distributed in the horizontal plane, and the embodiment of the present disclosure is simulated using electromagnetic simulation software.

[0088] Simulation content and results: Under vertical incidence, a linearly polarized electromagnetic wave is incident along the direction of the RF switch, and the Floquet port is used to perform electromagnetic simulation on the metasurface unit to obtain the reflection phase and return loss curves, as shown in Figure 7(a) and Figure 7(b). From the return loss curve shown in Figure 7(a) and the reflection phase difference in Figure 7(b), it can be seen that before and after the RF switch is turned on, the adjustable broadband reflection-type phase-controlled space-time coding metasurface unit achieves a stable phase difference of 180°±35° in the 7.79GHz-13.39GHz frequency band (relative bandwidth 52.8%), the center frequency of the working frequency band is 10.59GHz, and the return loss S 11 is 0.86dB, the transmission coefficient S 12 The value is lower than -60dB. The simulation results show that the metasurface unit still has good performance after shifting the working frequency band. Figure 8 The middle dashed curve shows the frequency of the resonance point of Example 2. Compared with Example 1, the resonance point of Example 2 is shifted at the same time, which effectively changes the working frequency band of the example.

[0089] The above electromagnetic simulation results show that the metasurface unit of this example realizes wide-band (relative bandwidth greater than 45%) reflective 1-bit space-time coding phase control, and combined with equivalent circuit theory, it realizes flexible adjustment of the working frequency band. The frequency band is adjustable and the working performance is stable.

[0090] The above description is only a preferred embodiment of the present disclosure and an explanation of the technical principles used. Those skilled in the art should understand that the scope of the invention involved in the present disclosure is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with the technical features with similar functions disclosed in the present disclosure (but not limited to) by each other.

Claims

1. An adjustable broadband reflective phase-controlled spatiotemporal encoding metasurface unit, characterized by: It comprises a top radiation metal layer (1), an intermediate dielectric layer (2), a bottom metal ground (3) and two metallized vias (4) and (5) which are arranged in sequence from top to bottom, wherein: The top radiation metal layer (1) comprises a radio frequency switch (6), a first L-shaped metal strip (8), and a second L-shaped metal strip (9); the radio frequency switch (6) is located at the center of the metasurface unit; the first L-shaped metal strip (8) comprises two L-shaped metal strips that are rotationally symmetrically connected with respect to the radio frequency switch (6); the second L-shaped metal strip (9) has an open end and the other end connected to the end of the first L-shaped metal strip (8); the second L-shaped metal strip (9) comprises two L-shaped metal strips that are rotationally symmetrically distributed with respect to the radio frequency switch (6); The two metallized vias (4) and (5) pass through the intermediate dielectric plate layer (2) and are used to electrically connect the first L-shaped metal strip (8) to the bottom metal ground (3); the metallized vias (4) and (5) are symmetrical about the center of the radio frequency switch (6); and the voltage controls the on and off of the radio frequency switch (6) through the metallized vias (4) and (5); The bottom metal ground (3) is etched with three metal gaps (10), (11) and (12) at the center of the metasurface unit along the placement direction of the radio frequency switch (6), and the three metal gaps (10), (11) and (12) divide the bottom metal ground (3) into two parts; The top radiation metal layer (1) is connected to the bottom metal ground (3) through the two metallized vias (4) and (5), and together achieves the effect of phase-controlled spatiotemporal coding under the control of the radio frequency switch (6); The width w3 of the L-shaped wider part of the first L-shaped metal strip (8) ranges from 0.0669λ t ≤w3≤0.0758λ t , the width w2 of the narrower part of the L-shaped part ranges from 0.0428λ t ≤w2≤0.0485λ t , the range of the longitudinal length l2 is 0.134λ t ≤l2≤0.152λ t , where λ t is the wavelength corresponding to the center frequency of the working frequency band; The value range of the L-shaped wider width w1 of the second L-shaped metal strip (9) is 0.0857λ t ≤w1≤0.0971λ t , the range of the longitudinal length l1 is 0.165λ t ≤l1≤0.187λ t , where λ t is the wavelength corresponding to the center frequency of the working frequency band; The first L-shaped metal strip (8) is connected to the second L-shaped metal strip (9), and together they form a part of the radiator. The longitudinal gap distance d1 between the first L-shaped metal strip (8) and the second L-shaped metal strip (9) has a value range of 0.008λ. t ≤d1≤0.009λ t , the range of the lateral gap distance d2 is 0.008λ t ≤d1≤0.0238λ t , where λ t is the wavelength corresponding to the center frequency of the working frequency band; The gap distances of the three metal gaps (10), (11) and (12) etched on the bottom metal ground (3) are in the relationship of d4=d5=d3 / 2, and the value range of the gap d3 is 0.005λ. t ≤d3≤0.006λ t , where λ t It is the wavelength corresponding to the center frequency of the working frequency band.

2. The metasurface unit according to claim 1, characterized in that: The value range of the side length of the super surface unit is 0.221λ t ≤d≤0.256λ t ,λ t =c / f t , where f t is the center frequency of the operating frequency band, c is the speed of light in vacuum, λ t It is the wavelength corresponding to the center frequency of the working frequency band.

3. The metasurface unit according to claim 1, characterized in that: The radio frequency switch (6) is centrally symmetrically connected to the top radiation metal layer (1); and / or, The top radiation metal layer (1), the middle dielectric plate layer (2), the bottom metal ground (3), the two metallized vias (4) (5) and the radio frequency switch (6) are respectively centrally symmetrical about the metasurface unit.

4. The metasurface unit according to claim 1, characterized in that: The inner side walls of the two metallized vias (4) and (5) are both covered with metal.

5. The metasurface unit according to claim 1, characterized in that: The intermediate dielectric plate layer (2) is made of dielectric material, the relative dielectric constant is 2 to 4.5, and the dielectric thickness h is in the range of 0.05λ t ≤h≤0.25λ t , where λ t It is the wavelength corresponding to the center frequency of the working frequency band.

6. The metasurface unit according to claim 1, characterized in that: The bottom metal ground (3) is divided into two parts (13) and (14) by the metal gap (10). The bottom metal ground (3) serves as a metal bottom plate for blocking the transmission of electromagnetic waves. At the same time, the two parts (13) and (14) of the bottom metal ground (3) also serve as electrodes and are respectively connected to the positive and negative electrodes of an external driving power source.

7. A phase control method for a metasurface unit according to any one of claims 1 to 6, characterized in that: The control method comprises: Utilizing a linearly polarized incident wave to illuminate the metasurface unit along a conducting direction of a radio frequency switch; After the linearly polarized incident wave propagates to the bottom metal ground (3) of the metasurface unit, it is reflected back to the top radiation metal layer (1); By applying voltage to the positive and negative electrodes of the power supply or disconnecting the voltage, the radio frequency switch is turned on or off to change the inductance value in the equivalent circuit, so as to adjust the phase of the metasurface unit.

8. The method according to claim 7, characterized in that The method further comprises: An external driving power source is connected to the underlying metal ground, and the external driving power source is used to control the on and off of the radio frequency switch through a time-varying modulation method to regulate the dynamic electromagnetic response of the metasurface unit.

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