CN113506993A

CN113506993A - Medium type periodic structure with high frequency and low frequency

Info

Publication number: CN113506993A
Application number: CN202110675455.3A
Authority: CN
Inventors: 陆海鹏; 张珊; 朱亚光; 温开怀; 蔡长旭; 王蕾; 王帅; 陈海燕; 邓龙江
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2021-06-18
Filing date: 2021-06-18
Publication date: 2021-10-15
Anticipated expiration: 2041-06-18
Also published as: CN113506993B

Abstract

The invention belongs to the field of electromagnetic wave absorbing materials and the field of metamaterials, and particularly relates to a medium type periodic structure with high and low frequency. The invention realizes high and low frequency consideration only by using a magnetic material, realizes low frequency absorption by loading a top metal pattern layer and generating resonance with the magnetic material, and widens high frequency performance by digging a ring. The top metal pattern layer is adjustable and movable in position, can generate low-frequency resonance absorption in a P-S wave band through adjustment, can generate-12 dB absorption in 1.4GHz, and has the thickness less than 1/107 lambda of a low-frequency absorption frequency point; the high-frequency performance can be adjusted by adjusting the shape and the size of the ring, so that the high-frequency broadband absorption can be generated in the range of 3.6GHz-15 GHz. The invention has more flexible structure design, wider application range and relatively simple process.

Description

Medium type periodic structure with high frequency and low frequency

Technical Field

The invention belongs to the field of electromagnetic wave absorbing materials and the field of metamaterials, and particularly relates to a medium type periodic structure with high and low frequency.

Background

Stealth technology has been a research hotspot and difficulty in the military field, and particularly for an aircraft, stealth capability is a very important index. Early people reduce radar cross section through reasonable design appearance, and its stealthy ability is limited, and electromagnetic wave absorbing material provides an effectual stealthy way, and it can absorb the electromagnetic energy of enemy radar transmission to reduce the probability that is detected, realize stealthy effect. In the military field, with the high-speed development of microwave radar technology, the working frequency band of radar is continuously expanded, and as meter waves and decimeter waves in a low frequency band have the advantages of long detection distance, large scanning area, short defense and early warning time and the like, the radar has more and more important functions in radar detection. However, most of the wave-absorbing materials developed by people work in a higher frequency band, so in recent years, it is more urgent to reduce the detectivity of a long-wave radar to an aircraft, improve the stealth capability of the aircraft, improve the wave-absorbing performance of a microwave low frequency band, and design and realize a structure giving consideration to both the high frequency band and the low frequency band.

The metamaterial refers to artificial composite structures or composite materials with extraordinary physical properties which are not possessed by natural materials, and extraordinary functions which are not possessed by the existing ordinary materials in the nature can be obtained by orderly and reasonably designing the structural size. The wave-absorbing metamaterial can realize flexible regulation and control of equivalent electromagnetic parameters through the design of the geometric shape, the size, the arrangement and the like of the sub-wavelength units. The ultra-thin and perfect absorption band has the advantages of ultra-thin and perfect absorption, adjustable absorption band, strong designability and the like, thereby showing great application prospect in the stealth field. However, most of the currently developed wave-absorbing metamaterials are based on resonance absorption, so that the absorption frequency band is limited. The wave-absorbing metamaterial such as a multilayer composite structure and a non-planar structure, which is provided based on a novel absorption mechanism, can realize a certain absorption bandwidth, but is limited by the factors such as the number of stacked layers and the size of the non-planar structure, and the absorption bandwidth is difficult to further expand.

In the prior art, under the condition that the thickness of a magnetic material is small, high-frequency and low-frequency consideration is realized by compounding a dielectric material and the magnetic material, and the overall idea is to form a composite structure by digging holes in the magnetic material and filling the dielectric material loaded with metal patterns, so that high-frequency and low-frequency consideration is realized. It has many limitations: because the pattern is designed on the dielectric material to realize low-frequency absorption, the low-frequency realization range is very small; a dielectric material blanket is then hollowed out over the magnetic material and filled in at the hollowed-out location to widen the high frequency bandwidth, which makes the high frequency non-tunable. The performance of the whole material only depends on low-frequency design, the universality is poor due to the fact that high frequency cannot be adjusted, and the process is relatively complex.

Disclosure of Invention

Aiming at the problems or the defects, the invention provides a high-low frequency compatible medium type periodic structure to solve the problems of high frequency non-adjustability and relatively complex process of the existing high-low frequency compatible metamaterial wave absorber, and the invention is an ultrathin broadband composite metamaterial wave absorber.

The specific technical scheme is as follows:

a dielectric type periodic structure with both high frequency and low frequency is provided, the unit structure is arranged in a matrix mode.

The unit structure sequentially comprises a top metal pattern layer, a middle dielectric layer and a metal bottom plate from top to bottom.

The top metal pattern layer is a square metal ring, and each side of the square is continuously bent by 90 degrees in the same mode into a snake-like pattern formed by alternately connecting vertical strips and transverse strips; the two ends of the square edge are not bent, the length of the two ends which are not bent is equal to the length of the transverse bar, and the vertical bars are sequentially reduced towards the two ends by the length of the two vertical bars at the centers of the vertical bars and are connected by the transverse bar; wherein the width of horizontal bar equals, and unilateral horizontal bar quantity is the odd number.

The middle medium layer is made of a flexible magnetic wave-absorbing material, is arranged on the metal bottom plate in a size-adaptive manner, and is formed by digging out an annular through hole from a complete square middle medium layer, and the top metal pattern layer is arranged on the middle medium layer but is not overlapped with the annular through hole.

Further, the annular through hole is a circular ring or a regular polygonal ring; the square ring (square) is optimized, and compared with other shapes, the square ring can adjust the input impedance in a wider frequency band so as to widen the wave-absorbing bandwidth.

The invention realizes high and low frequency consideration only by using a magnetic material, realizes low frequency absorption by loading a top metal pattern layer and generating resonance with the magnetic material, and widens high frequency performance by digging a ring. The top metal pattern layer is adjustable and can move in position (can be arranged on the outer side of the ring and can also be arranged on the inner side of the ring), the top metal pattern layer can generate low-frequency resonance absorption in a P-S wave band through adjustment, can generate-12 dB absorption in 1.4GHz, and the thickness of the top metal pattern layer is less than 1/107 lambda of a low-frequency absorption frequency point; the high-frequency performance can be adjusted by adjusting the shape and the size of the ring, so that the high-frequency broadband absorption can be generated in the range of 3.6GHz-15 GHz. The structure design is more flexible, the application range is wider, and the process is relatively simple.

Drawings

FIG. 1 is a perspective view of a unit structure according to an embodiment;

FIG. 2 is a top view of a cell structure according to an embodiment;

FIG. 3 shows the results of simulation of the absorption performance of the unit structure according to the embodiment;

FIG. 4 shows the results of the simulation of the absorption performance of the unit structures of different sizes in the examples;

FIG. 5 shows the simulation results of the absorption performance of the TE wave and the TM wave in the embodiment;

FIG. 6 shows simulation results of absorption performance at different incident angles according to the embodiment;

FIG. 7 is a perspective view of an embodiment of a complete magnetic material;

FIG. 8 shows the simulation result of the absorption performance of the complete magnetic material according to the embodiment;

FIG. 9 is a schematic perspective view of an embodiment of a media construction of an excavating ring only;

FIG. 10 shows the result of an absorption performance simulation of an embodiment of an excavating ring-only medium structure;

fig. 11 is a schematic perspective view of a patterned wave-absorbing structure only according to an embodiment;

FIG. 12 shows the simulation result of the fitting absorption performance of the patterned wave-absorbing structure according to the embodiment.

Detailed Description

The invention is further described below with reference to the figures and examples.

Example 1

The structure of this embodiment is shown in fig. 1, and fig. 2 is a top view of the structure shown in fig. 1. The unit structure is composed of a top metal pattern layer, a middle dielectric layer and a bottom metal bottom plate.

The middle medium layer is formed by hollowing out a square ring part from the center of the complete magnetic substrate. In this example, the specific preferred dimensions of the basic cell structure are: the unit side length p is 10mm, the side length a of the outer ring of the hollowed square ring (square) structure is 4.5mm, and the side length b of the inner ring is 3.3 mm.

The length of a vertical bar at the center of the top metal pattern layer is 1.34mm, the r is sequentially reduced to 0.17mm at equal intervals, the length of a transverse bar is 0.51mm, the edge width of a square metal ring is 0.1mm, and the thickness of the square metal ring is 0.017 mm; the thickness of the intermediate medium layer is 2 mm.

The absorption properties obtained by fitting with CST software are shown in fig. 3. The absorption rate is more than 90% at the low frequency of about 1.4GHz, the absorption rate is more than 90% at the high frequency of 4.8GHz-9.5GHz, the absorption rate is more than 80% at the high frequency of 4.1GHz-15GHz, and the relative bandwidth reaches 112%. When the side length p of the basic unit of the structure is changed, the size of the metal pattern on the top layer is changed in the same proportion, and the simulation is carried out on the side length p, and the result figure 4 shows that the low-frequency absorption peak moves from 0.5GHz to 2GHz along with the periodic change, and the initial frequency of the high-frequency broadband absorption moves to the low frequency along with the periodic increase.

When TE waves and TM waves are vertically incident, CST simulation is carried out by utilizing the medium type periodic structure, the result is shown in figure 5, the results of two polarization modes are consistent, and the structure is proved to be insensitive to polarization. Simulation results when the incident angles of the TE and TM polarizations were varied, fig. 6 shows that the absorption performance remained relatively stable at an incident angle of 30 deg..

Comparative example 2

The absorption properties of the completed magnetic medium (schematic shown in fig. 7) are shown in fig. 8. A square ring part is hollowed from the center of the complete magnetic substrate to obtain a ring-only dielectric structure, which does not include a top metal pattern layer, and FIG. 9 is a schematic perspective view of the structure. The absorption performance obtained by fitting with CST software is shown in FIG. 10, and compared with the complete magnetic medium layer, the high-frequency performance of the medium structure with holes only in the range of 4.7GHz-15GHz is improved. The absorptivity is above 90% in the high frequency range of 3.5GHz-8.4 GHz.

Comparative example 3

The patterned metamaterial wave-absorbing structure is that the square ring part indicated by 4 in fig. 1 is not hollowed, and the magnetic medium layer is kept intact, so that the three-dimensional schematic diagram of the patterned periodic structure unit shown in fig. 11 is obtained. The absorption performance obtained by fitting with CST software is shown in fig. 12, and the absorption rate is above 90% at a low frequency of about 1.35 GHz.

According to the embodiment and the comparative example, the design is carried out by only using the magnetic material, the high-frequency and low-frequency consideration is realized, the low-frequency absorption is realized by the resonance generated by the top metal pattern layer and the magnetic material, and the high-frequency performance is widened by digging the ring. The top metal pattern layer is adjustable and can move in position (can be arranged on the outer side of the ring and can also be arranged on the inner side of the ring), and the top metal pattern layer can generate low-frequency resonance absorption in a P-S wave band through adjustment; the high-frequency performance can realize high-frequency broadband absorption in a frequency band of 3.6GHz-15GHz by the shape and the size of the adjusting ring.

The adjustability of the high frequency can be understood, for example, in the case that the low frequency and high frequency performance to be achieved is determined, the ideal low frequency absorption is realized through design, the size and the position of the pattern are determined, and the high frequency can achieve the required performance by adjusting the size or the shape of the hole on the premise of ensuring the low frequency performance. The invention has more flexible structure design, wider application range and relatively simple process.

Claims

1. A dielectric type periodic structure with high and low frequency compatibility is characterized in that: arranging the square unit structures in a matrix mode;

the unit structure comprises a top metal pattern layer, a middle dielectric layer and a metal bottom plate from top to bottom in sequence;

the top metal pattern layer is a square metal ring, and each side of the square is continuously bent by 90 degrees in the same mode into a snake-like pattern formed by alternately connecting vertical strips and transverse strips; the two ends of the square edge are not bent, the length of the two ends which are not bent is equal to the length of the transverse bar, and the vertical bars are sequentially reduced towards the two ends by the length of the two vertical bars at the centers of the vertical bars and are connected by the transverse bar; wherein the widths of the transverse strips are equal, and the number of the transverse strips on one side is odd;

2. The dielectric periodic structure for both high and low frequencies as set forth in claim 1, wherein: the annular through hole is a circular ring or a regular polygonal ring.

3. The dielectric periodic structure for both high and low frequencies as set forth in claim 1, wherein: the length of a vertical bar at the center of the top metal pattern layer is 1.34mm, the vertical bar is sequentially reduced by 0.17mm at equal intervals, the length of a transverse bar is 0.51mm, the edge width of a square metal ring is 0.1mm, and the thickness of the square metal ring is 0.017 mm; the hollowed ring is a square ring, the side length a of the outer ring is 4.5mm, and the side length b of the inner ring is 3.3 mm; the thickness of the intermediate medium layer is 2mm, and p is 10 mm.