Mechanical non-resonant one-bit phase electromagnetic reflection metasurface unit

Abstract

The invention discloses a mechanical non-resonant one-bit phase electromagnetic reflection metasurface unit, and belongs to the field of artificial electromagnetic materials. The unit comprises a non-resonant electromagnetic structure and a mechanical driving device. The non-resonant electromagnetic structure comprises a dielectric layer, an air layer and an adjustable metal backboard from top to bottom; the mechanical driving device adopts a bidirectional self-holding electromagnet, a screw rod of the bidirectional self-holding electromagnet is connected with the metal back plate, the back plate is driven to be switched between two preset positions through forward / reverse pulse current, the thickness of an air layer is accurately adjusted, and therefore one-bit dynamic switching of a reflection phase between 0 degree and 180 degrees is achieved through propagation phase accumulation. In the 5G millimeter wave frequency band of 20 GHz to 29.5 GHz, the reflection coefficients of the two states are both larger than 0.99, the phase difference is stabilized within 180 degrees + / -20 degrees, and good robustness is achieved for mechanical displacement deviation. The unit has the advantages of zero static energy consumption, low insertion loss, wide bandwidth, simple structure and simple control, and is suitable for a low-power-consumption intelligent reflecting surface and a dynamic beam forming system.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electromagnetic metasurface, in particular to a reconfigurable metasurface structure for dynamic electromagnetic beam control. More specifically, the present application relates to a mechanical non-resonant one-bit phase electromagnetic reflection metasurface unit for 5G millimeter wave communication frequency bands (N257, N258, N261). BACKGROUND

[0002] With the rapid development of the fifth generation mobile communication technology (5G), the millimeter wave frequency band has become a key frequency band for realizing high-speed wireless communication due to its advantages of large bandwidth and high speed. However, the millimeter wave signal is easily blocked by obstacles during transmission, and there is a serious non-line-of-sight transmission problem, which limits its application in actual scenarios. In order to enhance the coverage range and transmission reliability of the millimeter wave signal, beamforming technology and intelligent reflecting surface have become one of the research hotspots.

[0003] Traditional beam control technology mainly relies on phased array antenna systems to achieve beam scanning by adjusting the phase difference of each antenna unit. Although this method has significant effect, the system is usually complex and expensive, and each unit needs to be configured with an independent phase shifter and a complex feeding network, which makes it difficult to adapt to the needs of large-scale commercial deployment in terms of power consumption, volume and cost.

[0004] In recent years, metasurface, as a two-dimensional artificial electromagnetic material composed of subwavelength structure units, provides a new paradigm for electromagnetic wavefront control. At present, most reconfigurable metasurfaces are based on resonant control principle, that is, by designing specific metal patch resonant structures and using active devices (such as PIN diodes, varactor tubes, etc.) to change their resonant state, the discrete control of electromagnetic wave phase is realized. However, this kind of resonant scheme has obvious disadvantages: first, the resonant unit is sensitive to processing errors and has poor robustness; second, the integration of a large number of active devices will introduce high insertion loss, reducing system efficiency, and its supporting DC bias network also greatly increases the complexity and manufacturing cost of the system.

[0005] As an alternative, passive mechanical reconfigurable metasurfaces adjust their electromagnetic response by changing the physical structure of the unit, which fundamentally avoids the loss problem caused by active devices. However, existing mechanical control schemes (such as PB phase control based on unit rotation or foldable structure deformation, etc.) generally face problems such as slow system response, complex mechanical structure or difficulty in achieving precise control of large-scale independent units, which makes it difficult to meet the requirements of real-time communication for beam switching speed and high reliability of 5G.

[0006] In view of such a situation, the application provides a novel reconfigurable metasurface unit with the advantages of low insertion loss, wide bandwidth, low power consumption and simple control, and provides a feasible alternative path for the above problems. SUMMARY

[0007] The application aims to provide a mechanical non-resonant one-bit phase electromagnetic reflection metasurface unit for 5G millimeter wave N257, N258 and N261 frequency bands.

[0008] The mechanical non-resonant one-bit phase electromagnetic reflection metasurface unit comprises a non-resonant electromagnetic metasurface structure and a mechanical driving device.

[0009] The electromagnetic metasurface comprises a dielectric layer, an air layer and an adjustable metal back plate from top to bottom, and forms a pure dielectric non-resonant structure without metal patches.

[0010] The mechanical driving device is a bidirectional self-holding electromagnet, and the screw rod is connected with the adjustable metal back plate.

[0011] The working frequency band of the metasurface unit is 20GHz to 29.5GHz, and the reflection coefficient is greater than 0.99 in the frequency band, and the reflection phase difference between the two states is 180°±20°.

[0012] Compared with the prior art, the application has the following beneficial effects:

[0013] 1) The working frequency band of the metasurface unit designed by the application completely covers the N257, N258 and N261 frequency bands, and the reflection phase difference is 180°±20° in the two working states, and the reflection coefficient is higher than 0.99, which is more suitable for indoor signal enhancement and other application scenarios.

[0014] 2) The metasurface unit designed by the application adopts a non-resonant pure dielectric structure, has high reflection efficiency, low insertion loss and wide frequency band characteristics, and is more suitable for the design and processing of millimeter wave frequency bands.

[0015] 3) The designed metasurface unit structure is based on a transmission line equivalent circuit model, the design method is clear and has good transferability; it is not sensitive to mechanical assembly errors, the phase and amplitude performance is stable, and the engineering practical value is high.

[0016] 4) The bidirectional self-holding electromagnet is used as the driving module, the structure is stable, only the energy is consumed in the state switching moment, the zero static power consumption is realized when maintaining the state; without complex DC bias network, the control system is greatly simplified.

[0017] 5) The designed metasurface unit is an ideal choice for constructing a low-power-consumption and high-performance intelligent reflecting surface, and has important application value in the fields of dynamic beamforming, enhanced millimeter wave signal coverage and other wireless communication fields. BRIEF DESCRIPTION OF DRAWINGS

[0018] Fig. 1 is a schematic diagram of the metasurface unit structure provided by the embodiment of the present application. Wherein (a) is an electromagnetic structure schematic diagram, (b) is a schematic diagram of two working states.

[0019] Figure 2 The transmission line equivalent circuit diagram of the metasurface unit provided by the embodiment of the present application.

[0020] Figure 3 The reflection amplitude simulation result of the metasurface unit provided by the embodiment of the present application.

[0021] Figure 4 The reflection phase simulation result of the metasurface unit provided by the embodiment of the present application.

[0022] Figure 5 The reflection amplitude simulation result when the metal back plate has displacement error.

[0023] Figure 6 The reflection phase simulation result when the metal back plate has displacement error. DETAILED DESCRIPTION

[0024] The present application will be further described below in conjunction with the drawings and specific embodiments. It should be understood that the present application can be implemented in various forms, and some exemplary and non-limiting embodiments shown in the following drawings and described below are not intended to limit the present application to the specific embodiments described.

[0025] Embodiment:

[0026] Figure 1 illustrates a mechanically non-resonant one-bit phase electromagnetic reflective metasurface unit structure operating in the 20GHz–29.5GHz frequency band, comprising a non-resonant electromagnetic structure and a mechanical drive component. Figure 1(a) shows a schematic diagram of the non-resonant electromagnetic structure of the metasurface unit. The dielectric layer is made of WL-CT300 substrate with a dielectric constant of 3.00, a loss tangent of 0.0036, and a preferred thickness h of 2mm. This material, due to the inclusion of ceramic powder, possesses excellent thinness and flatness. The adjustable metal backplate is made of copper.

[0027] The metasurface unit disclosed in this invention is a pure dielectric non-resonant structure without metal patches. Its electromagnetic response characteristics are based on the phase accumulation principle of non-resonant transmission lines and are mainly determined by the dielectric layer material and thickness, as well as the air layer thickness. Therefore, the design freedom of the unit period P is relatively high. When selecting a unit, the principle should be to avoid generating grating lobes and meet mechanical installation requirements. It is preferable to meet the subwavelength condition (i.e., P < λ, where λ is the operating wavelength) to ensure the array beam control performance.

[0028] Figure 1(b) illustrates the two operating states of the metasurface unit. Each unit is equipped with a bidirectional self-holding electromagnet (model SM0521 in this embodiment, operating voltage DC6V-12V, stroke 4mm). The electromagnet screw is connected to the center of an adjustable metal backplate. By applying positive / reverse current, the screw is driven to move forward / backward, thereby causing the metal backplate to switch between two fixed positions. The phase "0" and "1" states are encoded by changing the length of the electromagnetic wave propagation path.

[0029] Figure 2 This is the equivalent circuit diagram of the transmission line of the metasurface unit disclosed in the embodiments of the present invention. This circuit model clearly explains its non-resonant operating mechanism. The dielectric layer and air layer can be regarded as a transmission line with characteristic impedance, and the adjustable metal backplate can be regarded as a short-circuit load after neglecting its minor losses. The input impedance from port a to the adjustable metal backplate is... Where Z0 = 377Ω is the free-space characteristic impedance, ε r1 β1 is the relative permittivity of the air layer (theoretical value is 1). β1 is the propagation constant of the incident electromagnetic wave, and d1 is the thickness of the air layer.

[0030] Furthermore, the input impedance when looking from the input port towards port a Where ε r2 β2 is the dielectric constant of the dielectric layer, β2 is the propagation constant of the incident electromagnetic wave, and d2 is the thickness of the dielectric layer.

[0031] Furthermore, the reflection coefficient of this link can be derived. Reflection phase angle In this embodiment of the invention, the air layer thicknesses for the two reflection states are d and d, respectively.11 =0mm,d 12 =4mm, the corresponding reflection phase difference is close to 180°. This phase difference is caused by the accumulation of phase shift caused by the propagation of electromagnetic waves in two transmission lines of different lengths, which meets the one-bit phase modulation requirement.

[0032] The amplitude response of the reflection coefficient of the metasurface unit is as follows: Figure 3 As shown, under both of the above conditions, the reflection coefficients in the 20GHz to 29.5GHz frequency band are both higher than 0.99.

[0033] The phase response of the reflection coefficient of the metasurface unit is as follows: Figure 4 As shown, under the above two states, the reflection phase difference between the two states in the 20GHz to 29.5GHz frequency band satisfies 180°±20°.

[0034] Figure 5 and Figure 6 The impact of metal backplate displacement error on performance was further analyzed. When the air layer thickness in working state "0" is 0.0mm to 0.1mm and the air layer thickness in working state "1" is 3.8mm to 4.1mm, the reflection coefficient is still higher than 0.99 and the phase difference is within 180°±30°. This indicates that the non-resonant phase modulation mechanism has a certain robustness to assembly errors.

[0035] The above-described embodiments are merely one implementation of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this invention should be determined by the appended claims.

Claims

1. A mechanical non-resonant one-bit phase electromagnetic reflecting metasurface unit, characterized in that, The application relates to a super surface unit, which comprises a non-resonant electromagnetic structure and a mechanical driving device; the non-resonant electromagnetic structure comprises, from top to bottom, a dielectric layer, an air layer and an adjustable metal back plate; the mechanical driving device is a bidirectional self-holding electromagnet, the output screw rod of which is mechanically connected with the adjustable metal back plate; the bidirectional self-holding electromagnet is configured to drive the screw rod and the adjustable metal back plate to move to a first position to make the air layer have a first thickness when a positive electric pulse is received, and to drive the screw rod and the adjustable metal back plate to retreat to a second position to make the air layer have a second thickness when a reverse electric pulse is received; the phase accumulation effect of electromagnetic wave propagation is utilized to realize the switching of the reflection phase of the super surface unit between two states through the change of the thickness of the air layer, the reflection phase difference between the two states is about 180 DEG, and one-bit phase dynamic regulation is completed.

2. A mechanical non-resonant one-bit phase electromagnetic reflecting metasurface unit according to claim 1, characterized in that, The adjustable metal back plate is made of a high-conductivity metal material and is driven by the bidirectional self-holding electromagnet to dynamically switch the thickness of the air layer between the first thickness and the second thickness.

3. A mechanical non-resonant one-bit phase electromagnetic reflecting metasurface unit according to claim 1, wherein, The size of the adjustable metal back plate is equal to or slightly smaller than the size of the unit.

4. A mechanical non-resonant one-bit phase electromagnetic reflecting metasurface unit according to claim 1, characterized in that, The working voltage of the bidirectional self-holding electromagnet is DC 6V-12V, and the stroke is 4mm.

5. A mechanical non-resonant one-bit phase electromagnetic reflecting metasurface unit according to claim 1, wherein, The working frequency band of the super surface unit is 20GHz to 29.5GHz; in the frequency band, the reflection coefficient amplitudes in the two working states are greater than 0.99, and the reflection phase difference between the two states is in the range of 180 DEG+ / -20 DEG.

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