Dual-band full-space amplitude and phase independent adjustable digital coding super surface
Technical Field
The invention discloses a dual-band full-space amplitude and phase independent adjustable digital coding super surface, belonging to the technical field of antennas and the field of novel artificial electromagnetic metamaterials.
Background
Metamaterials, sometimes also referred to as new artificial electromagnetic materials, new artificial electromagnetic media, Metamaterials, etc., have the meaning of "exceeding" expressed by the british name Metamaterials, latin language "meta-". The metamaterial is an artificial composite structure or an artificial composite material, wherein macroscopic basic units with specific geometric shapes are arranged periodically or aperiodically, so that the macroscopic basic units have extraordinary electromagnetic properties which are not possessed by natural materials. Because the electromagnetic metamaterial can realize flexible regulation and control of electromagnetic waves, the electromagnetic metamaterial has great application value in the aspect of electromagnetic stealth, and is widely concerned in the field of military at home and abroad. In recent years, a full-space electromagnetic metamaterial and a metamaterial surface are taken as one of important research branches of metamaterials, and have great application value in the aspect of realizing multifunctional application of electromagnetic waves.
A full-space electromagnetic meta-surface is a metamaterial in a two-dimensional form, typically consisting of a periodic or non-periodic two-dimensional array of sub-wavelength structuring elements. Compared with the common electromagnetic super surface, the full-space electromagnetic super surface can simultaneously regulate and control the amplitude and phase space distribution of reflection and transmission of the sub-wavelength structural unit on the super surface, thereby realizing the free regulation and control of the wave front, the polarization mode and the propagation direction of the transmission and reflection electromagnetic waves.
Disclosure of Invention
The technical problem is as follows: the invention aims to provide a double-frequency-band full-space amplitude and phase independent adjustable digital coding super surface, which can realize independent regulation and control of transmission and reflection electromagnetic waves of the super surface. In the transmission space, when the frequency of the incident electromagnetic wave is 7GHz, the basic unit can independently modulate the transmission amplitude and the phase of the incident electromagnetic wave; when the frequency of the incident electromagnetic wave is 17GHz, the basic unit can independently modulate the amplitude and the phase of the reflection of the incident electromagnetic wave. The phase and amplitude response distribution of the super surface is adjusted, so that the electromagnetic wave in the whole space is accurately regulated and controlled.
The technical scheme is as follows: the invention relates to a dual-band full-space amplitude phase independent adjustable digital coding super surface, which adopts the following technical scheme: the digital coding super surface is formed by periodically arranging 45 multiplied by 45 basic units, and each basic unit is formed by sequentially stacking a first metal layer, a first dielectric layer, a second metal layer, a second dielectric layer and a third metal layer; the first metal layer is a C-shaped metal ring, the second metal layer is a metal layer engraved with a C-shaped metal groove, and the third metal layer is a C-shaped metal ring; the sizes and the directions of the openings of the first metal layer C-shaped ring and the second metal layer C-shaped metal groove are always kept consistent, and the direction and the size of the opening of the C-shaped metal ring of the third metal layer can be independently designed and are not interfered by the first layer of metal ring; the opening angles of all the metal rings are-45 degrees and +45 degrees.
The structural period of the basic unit is 10 mm.
The thickness of the first dielectric layer is 3mm, the thickness of the second dielectric layer is 3mm, the dielectric constants of the two dielectric layers are 2.2 and 2.65, and the tangent loss angle is 0.001.
One side of the first metal layer C-shaped metal ring is provided with an opening which is symmetrical relative to a diagonal line; the second metal layer is a metal layer engraved with a C-shaped metal groove, and the geometric structure of the C-shaped metal groove is the same as that of the first metal layer.
The third metal layer is a C-shaped metal ring, one side of the metal ring is provided with an opening, and the opening is symmetrical relative to a diagonal line; the diameter of the third metal ring layer is smaller than the diameter of the first metal layer.
The opening directions and the opening sizes of the C-shaped metal rings of the first metal layer and the second metal layer are changed, the amplitude and the phase of the transmitted electromagnetic wave are effectively modulated, and the transmission phase and the amplitude are mapped with the opening sizes and the opening sizes of the C-shaped metal rings of the first metal layer and the third metal layer.
The design standard of the amplitude and the phase of the first metal layer is as follows:
in the formula: n is the number of basic units on the super surface, AnFor the nth fundamental unit amplitude and phase response on the super surface, Fn,dxn,dynThe focal length of the nth focal point on the focal plane and the position coordinate of the focal point on the focal plane are shown.
The amplitude and phase design standard of the first metal layer can be mapped to the opening direction and the opening size of the first metal layer C-shaped ring; and orderly arranging the C-shaped rings of the first metal layer and the third metal layer on the designed super surface containing the NxN units according to the obtained opening direction and opening size to realize a multi-focus focusing function in a near range, wherein the number and the intensity of focuses can be independently controlled.
The first metal layer C-shaped metal ring, the second metal layer C-shaped metal groove and the third metal layer C-shaped metal ring are formed by changing the opening directions alpha of the first metal layer C-shaped metal ring and the third metal layer C-shaped metal ring1,α2And the opening size beta of the C-shaped ring of the first metal layer and the third metal layer1And beta2The transmission coefficient and the reflection coefficient can be independently regulated and controlled by the value of (2).
Has the advantages that: the invention provides a dual-band full-space amplitude and phase independent adjustable digital coding super surface, and a basic unit forming the super surface has the capability of simultaneously and independently adjusting amplitude and phase. When the incident electromagnetic wave is 7GHz, the amplitude and phase response of the transmitted electromagnetic wave can be controlled through the openings and the orientations of the first metal layer and the second metal layer; when the incident electromagnetic wave is 17GHz, the amplitude and phase response of the reflected electromagnetic wave can be adjusted through the opening and the orientation of the third metal layer, and the transmission response and the reflection response in two frequencies are independent of each other, so that the frequency separation is good. Compared with the existing full-space electromagnetic metamaterial, the dual-band full-space amplitude phase independent adjustable digital coding metamaterial provided by the invention can control amplitude and phase response at the same time, provides a larger degree of freedom for regulation and control of electromagnetic waves, and promotes development of the full-space electromagnetic super surface.
Drawings
Figure 1 is a perspective view of a base unit,
fig. 2 shows the structural dimensions of the basic cell. By varying alpha1,α2,β1And beta2The transmission coefficient and the reflection coefficient can be independently regulated and controlled by the value of (2).
FIG. 3a shows the magnitude of cell transmission as a function of α1Simulation results of the variation, FIG. 3b shows the cell transmission phase as a function of β1Varying simulation results.
FIG. 4a shows unit reflection amplitude as a function of α1Simulation results of the variation, FIG. 4b shows the unit reflection phase as a function of β1Varying simulation results.
FIG. 5 is a simulation plot of the electric field intensity of the super-surface in the XOY plane, with an incident frequency of 7 GHz.
FIG. 6 is a simulation plot of the electric field intensity of the super-surface in the YOZ and XOY planes, with an incident frequency of 7 GHz.
FIG. 7 is a simulated far-field pattern of the super-surface, with an incident frequency of 17 GHz.
Fig. 8 shows the far-field pattern of the super-surface test, with an incident frequency of 17GHz, phi being 0 degrees and 90 degrees.
FIG. 9 shows the super-surface test near-field electric field intensity, the incident frequency is 7GHz, and the focal plane distance is 80 mm.
Detailed Description
The dual-band full-space amplitude phase independent adjustable digital coding super surface is formed by periodically arranging 45 multiplied by 45 basic units, wherein each basic unit is formed by sequentially stacking a first metal layer 1, a first dielectric layer 2, a second metal layer 3, a second dielectric layer 4 and a third metal layer 5; the first metal layer 1 is a C-shaped metal ring, the second metal layer 3 is a metal layer engraved with a C-shaped metal groove, and the third metal layer 5 is a C-shaped metal ring; the sizes and the directions of the openings of the C-shaped metal grooves of the first metal layer 1 and the second metal layer 3 are always consistent, and the directions and the sizes of the openings of the C-shaped metal rings of the third metal layer 5 can be independently designed and are not interfered by the first metal ring layer; the opening angles of all the metal rings are-45 degrees and +45 degrees.
4 focal points with different intensities are formed in the transmission space, and 4 beams are formed in the reflection space.
The structural period of the basic unit is 10 mm.
The thickness of the first dielectric layer 2 is 3mm, the thickness of the second dielectric layer 4 is 3mm, the dielectric constants of the two dielectric layers are 2.2 and 2.65, and the tangent loss angle is 0.001.
One side of the first metal layer 1C-shaped metal ring is provided with an opening which is symmetrical about a diagonal line; the second metal layer 3 is a metal layer engraved with a C-shaped metal groove, and the geometric structure of the C-shaped metal groove is the same as that of the first metal layer 1.
The third metal layer 5 is a C-shaped metal ring, one side of the metal ring is provided with an opening, and the opening is symmetrical about a diagonal line; the diameter of the third metal ring layer 5 is smaller than the diameter of the first metal layer 1.
The opening directions and the opening sizes of the C-shaped metal rings of the first metal layer 1 and the second metal layer 3 are changed, the amplitude and the phase of the transmitted electromagnetic wave are effectively modulated, and the transmission phase and the amplitude are mapped with the opening sizes and the openings of the C-shaped metal rings of the first metal layer 1 and the third metal layer 3.
The following describes in detail a dual-band full-space amplitude and phase independent adjustable digital coding metamaterial provided by the present invention with reference to the accompanying drawings: firstly, a unit with independent and adjustable full-space amplitude and phase is designed. Simulating the unit by CST MWS electromagnetic simulation software, and respectively simulating to obtain transmission and reflection coefficient phase amplitude and variable alpha at two working frequencies of 7GHz and 17GHz1,α2,β1And beta2The variation relationship of (a).
Secondly, according to the formula:
the phase and amplitude of incident wave reaching each unit are calculated at the frequency of 7GHz, the phase and amplitude obtained according to the formula can form a plurality of focuses on focal planes with different focal lengths, the intensity of the focuses and the number of the focuses can be independently controlled, in the invention, at the position where F is 80mm, 4 focuses with different intensities are formed and are symmetrically dispersed on an X axis and a Y axis respectively, wherein the intensity of the focus on the Y axis is 3dB greater than that of the focus on the X axis. As can be clearly observed in fig. 4 and 5, the simulation results agree well with the design.
In the far field, a 2bit phase response can be used to form a plurality of beams in arbitrary directions. In the present invention, 4 beams symmetrical about the X axis and the Y axis are formed in the far field by corresponding reflection phase responses using a unit cell consisting of 45 × 45 basic cells. As shown in fig. 6, when the reflection amplitudes of the elements are all set to 0.8, the intensity of each beam at this time is 7dB greater than when the reflection amplitude is set to 0.3.
As shown in fig. 7, the test electric field strength results of the super-surface sample composed of 45 × 45 basic units at the focal plane of 80mm are shown, and the test results are in good agreement with the simulation results.
As shown in fig. 8, two-dimensional test results of patterns of a super-surface sample composed of 45 × 45 basic units in far fields at Φ equal to 0 degree and 90 degrees are given, and the test results are in good agreement with simulation results.