CN106033846A - A Polarization Conversion Surface Based on Subwavelength Resonant Structure - Google Patents

Abstract

The invention discloses a polarization conversion surface based on a sub-wavelength resonance structure. It is mainly obtained by the sub-wavelength resonant unit through horizontal and vertical periodic arrays. The sub-wavelength resonant unit has a square structure, including the top metal copper sheet, the upper dielectric board, the middle grounded metal copper sheet, the lower dielectric board and the bottom metal copper sheet, and the middle grounded metal The copper sheet is located between the upper dielectric plate and the lower dielectric plate; through-holes are provided on the five-layer material of the sub-wavelength resonant unit, and the top layer of metal copper sheet and the bottom layer of metal copper sheet are placed opposite to each other with polarization rotation to the opposite. The invention is low in cost, simple in structure, thin in thickness, light in weight, and good in conversion performance, and can flexibly control the polarization state of electromagnetic waves and selective transmission and reflection, and can be used in imaging, antennas, communication systems, electromagnetic countermeasures and governance, and military stealth There are many important applications in many fields.

Description

A Polarization Conversion Surface Based on Subwavelength Resonant Structure

technical field

The invention relates to the field of electromagnetic wave polarization conversion, in particular to a polarization conversion surface based on a sub-wavelength resonance structure for controlling the polarization state of electromagnetic waves in various wireless electromagnetic wave transmissions.

Background technique

Polarization is an important characteristic of electromagnetic waves, which can be described by the oscillation behavior of the electric field vector E during electromagnetic wave transmission. When the electromagnetic wave propagates forward along the direction of the wave vector k, as time changes, when the trajectory of the end of the electric field vector E is a straight line, a circle and an ellipse, the corresponding polarization states are linear polarization, Circular and elliptical polarization. In practical applications, the polarization characteristics of electromagnetic waves are often detected and their polarization states are changed.

In the fields of radar target recognition, communication, aerospace, electromagnetic countermeasures, etc., the propagation of electromagnetic waves and the receiving performance of signals are related to the polarization form of waves. As an important jamming and anti-jamming technology, polarization technology has also become a research hotspot in the field of military scientific research. Therefore, in order to adapt to the characteristics of modern information-intensive and changeable, antennas with only single-polarization characteristics can no longer meet the requirements, resulting in more and more research on fast polarization converters.

A polarizer or polarization converter is a device used to convert polarization forms such as linear polarization and circular polarization, vertical polarization and horizontal polarization. The polarization conversion mainly focuses on the following aspects: 1) High performance, that is, the converted polarized wave should have a high polarization isolation, close to the required polarization form; 2) Low loss, that is, the The energy loss is small; 3) Small size, that is, the space occupied by the entire converter is small.

Existing polarization converters are mainly divided into two types: one is to use traditional birefringent materials to use electromagnetic waves that have different refractive indices when propagating in different directions, and to achieve a specific phase difference at an appropriate thickness and frequency The other is based on the theory of electromagnetic metamaterial (metamaterial), the latest international research achievement in recent years, using the designability of the equivalent electromagnetic parameters of sub-wavelength structures to construct structures with different refractive indices, and then in smaller sizes A specific phase difference is achieved to complete the polarization conversion.

According to the principle of polarization decomposition, any polarized wave can be decomposed into two components according to any orthogonal polarization basis, usually using a linear polarization basis or a circular polarization basis. Any linearly polarized wave or elliptical polarized wave can be decomposed into two circularly polarized waves with opposite hand direction. Polarization converters can arbitrarily control the polarization state and selective transmission and reflection of electromagnetic waves, and have many important applications in the fields of imaging, antennas, communication systems, electromagnetic countermeasures and governance, and military stealth.

Contents of the invention

In order to solve the problems in the background technology, the purpose of the present invention is to provide a polarization conversion surface based on a sub-wavelength resonant structure.

The technical solution adopted by the present invention to solve its technical problems is:

The polarization conversion surface is mainly obtained by the sub-wavelength resonant unit through horizontal and vertical periodic arrays to form a resonant surface. The sub-wavelength resonant unit has a square structure. The copper sheet and the underlying metal copper sheet as the bottom layer of the opposite circularly polarized patch.

Specifically, the sub-wavelength resonant unit includes five layers of materials, the first layer is a square plate-shaped top layer of metal copper with gaps, the second layer is an upper dielectric plate that plays a supporting role, the third layer is a middle ground metal copper sheet, and the second The fourth layer is the lower dielectric plate for support, the fifth layer is the bottom metal copper sheet with a square sheet with a gap, and the middle ground metal copper sheet is located between the upper dielectric plate and the lower dielectric plate; the five-layer material of the sub-wavelength resonant unit A through hole is provided on the top, and the top layer of metal copper sheet and the bottom layer of metal copper sheet are placed opposite to each other, and the rotation direction of the polarization is opposite to each other, and there is a difference of 90 degrees of rotation angle between them.

When the wireless microwave signal in the air is radiated to one side of the polarization conversion surface, each of the sub-wavelength resonant units on the polarization conversion surface will simultaneously undergo electrical resonance and magnetic resonance in the working frequency band, and the wireless The microwave signal is absorbed and fed to the surface on the other side through the through hole and radiated out to complete the polarization conversion.

The top metal copper sheet and the bottom metal copper sheet include a copper sheet and two groups of orthogonal slits arranged on the copper sheet, and each group of slits includes two symmetrical strip-shaped slits arranged radially on the edge of the copper sheet; The through hole is located on the diagonal of the top metal copper sheet or the bottom metal copper sheet, and the through holes of each layer run through the top metal copper sheet, the upper dielectric board, the middle ground metal copper sheet, the lower dielectric board and the bottom metal copper sheet coaxially .

The two groups of slits have different lengths, and the lengths of the two strip-shaped slits in each group of slits are the same. The two sets of slits on the top metal copper sheet and the two sets of slits on the bottom metal copper sheet are arranged oppositely, and the two sets of slits are adjusted by adjusting the positions of the two sets of slits. Left-handed circular polarization conversion and right-handed circular polarization conversion.

Under the incidence of arbitrary polarized waves on the surface of the invention, the reflected and transmitted waves are circularly polarized waves with the same hand direction, thereby realizing the conversion of polarization. The resonant surface composed of the sub-wavelength resonant unit can change the handedness of the reflected and transmitted waves by changing the orientation of the long slit and the short slit to obtain a left-handed circular polarization conversion surface or a right-handed circular polarization conversion surface.

The invention utilizes the characteristic that the sub-wavelength resonant structure will appear electromagnetic resonance in the working frequency band, and properly adjusts the shape and size of the sub-wavelength resonant structure to achieve perfect air matching. The polarization conversion surface is formed by periodic arrangement of many sub-wavelength resonant structural units. Since the structure size is in the sub-wavelength range, it can be equivalent to a homogeneous dielectric polarization conversion surface. The combination of the two parts of the circular polarization patch on the top layer of each unit and the opposite circular polarization patch on the bottom layer can realize the polarization control and conversion of any incident electromagnetic wave.

The beneficial effect that the present invention has compared with background technology is:

The invention has the advantages of simple design structure, light weight and thin thickness (3mm), which is only one seventeenth of the microwave wavelength at the corresponding working frequency.

The design of the invention has a small structure size, the unit size is lower than 1/4 of the working wavelength, and can be regarded as a homogeneous medium.

The performance of the present invention is excellent, verified by example simulation, on the working frequency, the incident left-handed circularly polarized component is totally reflected in the form of right-handed circularly polarized wave, and the loss is only about 0.2dB; The form of circularly polarized wave is fully transmitted, and the transmission loss is only about 0.3dB.

The structure of the present invention is changeable, and different shapes and sizes can be designed according to different frequency band requirements, and polarization conversion surfaces with different handedness can be realized by changing the direction of the slit according to the handedness of the polarization to be converted.

The invention can flexibly control the polarization state and selective transmission and reflection of electromagnetic waves, and has many important applications in the fields of imaging, antennas, communication systems, electromagnetic countermeasures and governance, and military stealth.

Description of drawings

Fig. 1 is a schematic diagram of the surface of the top layer, the middle layer and the bottom layer of the sub-wavelength resonance unit of the present invention.

Fig. 2 is a schematic diagram of the stacking of the top layer, the middle layer and the bottom layer of the sub-wavelength resonance unit of the present invention.

Fig. 3 is a surface schematic diagram of the top layer, middle layer and bottom layer of an example integral polarization switching surface after assembly.

Fig. 4 shows the reflection characteristics of the surface ports in the form of left-handed circularly polarized waves under the incident condition of left-handed circularly polarized waves according to the embodiment.

Fig. 5 shows the reflection characteristics of the surface ports in the form of right-handed circularly polarized waves when left-handed circularly polarized waves are incident on the embodiment.

Fig. 6 shows the transmission characteristics of the surface port in the form of left-handed circularly polarized waves under the incident condition of left-handed circularly polarized waves according to the embodiment.

Fig. 7 shows the transmission characteristics of the surface port in the form of right-handed circularly polarized waves under the incident condition of left-handed circularly polarized waves according to the embodiment.

Fig. 8 shows the reflection characteristics of the surface ports in the form of left-handed circularly polarized waves when right-handed circularly polarized waves are incident on the embodiment.

Fig. 9 shows the reflection characteristics of the surface ports in the form of right-handed circularly polarized waves when the right-handed circularly polarized waves are incident on the embodiment.

Fig. 10 shows the transmission characteristics of the surface port in the form of left-handed circularly polarized waves when right-handed circularly polarized waves are incident on the embodiment.

Fig. 11 shows the transmission characteristics of the surface port in the form of right-handed circularly polarized waves when the right-handed circularly polarized waves are incident on the embodiment.

In the figure: 1. Top metal copper sheet, 2. Upper dielectric board, 3. Middle grounded metal copper sheet, 4. Lower dielectric board, 5. Bottom metal copper sheet, 6. Through hole.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Embodiments of the present invention and its implementation work process are as follows:

As shown in Fig. 3, the implemented polarization conversion surface is mainly obtained by sub-wavelength resonant units passing through horizontal and vertical periodic arrays.

As shown in Figures 1 and 2, the sub-wavelength resonant unit has a square structure and includes five layers of materials. The first layer is a square sheet-shaped top layer of metal copper sheet 1 with gaps, and the second layer is an upper dielectric plate 2 that acts as a support. , the third layer is the middle ground metal copper sheet 3, the fourth layer is the lower dielectric board 4 for supporting, the fifth layer is the bottom layer metal copper sheet 5 in the shape of a square sheet with gaps, the middle ground metal copper sheet 3 is located on the upper dielectric Between the plate 2 and the lower dielectric plate 4; the five-layer material of the sub-wavelength resonant unit is provided with a through hole 6, and the top layer of metal copper sheet 1 and the bottom layer of metal copper sheet 5 are placed opposite to each other and the polarization is rotated between them. In the opposite direction, there is a difference of 90 degrees of rotation angle between them. The top metal copper sheet 1 matches the structure after the bottom metal copper sheet 5 rotates 90 degrees horizontally, or the bottom metal copper sheet 5 matches the structure after the top layer metal copper sheet 1 rotates 90 degrees horizontally, and the bottom metal copper sheet 5 can be formed by the top layer metal Copper sheet 1 is obtained by rotating and translating.

The top metal copper sheet 1 and the bottom metal copper sheet 5 include copper sheets and two groups of orthogonal slits arranged on the copper sheets, and each group of slits includes two symmetrical strip-shaped slits arranged radially on the edges of the copper sheets; The lengths of the groups of slits are different, and the lengths of the two bar-shaped slits of each group of slits are the same, and the two groups of slits of the top metal copper sheet 1 and the two groups of slits of the bottom metal copper sheet 5 are oppositely arranged.

The through hole 6 is located at any place on the top layer of metal copper sheet 1 or the bottom layer of metal copper sheet 5 except for the line end point and intersection point, and the through hole 6 of each layer runs through the top layer of metal copper sheet 1 and the upper layer coaxially. A dielectric board 2 , a middle ground metal copper sheet 3 , a lower dielectric board 4 and a bottom metal copper sheet 5 .

As shown in Figure 1, if the top metal copper sheet 1 on the left side of the figure faces the electromagnetic wave reception, it is a right-handed circular polarization conversion surface, and if the bottom metal copper sheet 5 on the right side of the figure faces the electromagnetic wave reception, it is a left-handed circular polarization Convert surface.

An example of the basic dimensions of the sub-wavelength resonance unit provided by the present invention is shown in FIG. 1 . The length and width of each unit are a=12mm, and it is composed of five layers of materials: the thickness of the top metal copper sheet 1 and the bottom metal copper sheet 5 is tm=0.035mm, and the side length is patch=10.22mm; the upper dielectric board 2 Rogers 4350B plate with a dielectric constant of 3.5, its loss tangent is 0.0017, and its thickness is ts=1.5mm; the middle ground metal copper sheet 3 has a through hole 6 with a diameter of r_big=1mm; the lower dielectric plate layer 4, The material is the same as that of the upper dielectric plate 2.

The width of the gap between the top metal copper sheet 1 and the bottom metal copper sheet 5 is 0.3mm. The lengths of the two groups of slits are different, the long slit is ly=4.01mm, and the short slit is lx=2.41mm. Set a through hole with a diameter of r=0.6mm at the diagonal position of the top metal copper sheet 1 from the center where the horizontal and vertical components are both bias=1.8mm, and the through hole directly passes through the upper dielectric plate 2 and the middle ground metal The copper sheet 3 and the lower dielectric board 4 are connected to the sheet-shaped square metal copper sheet at the bottom.

The renderings of the top, middle and bottom layers of the polarization conversion surface in this example are shown in Figure 2, and the horizontal and vertical arrangement periods of each unit are a=12mm.

When the above-mentioned polarization conversion surface is working, the left-handed circularly polarized electromagnetic wave incident on the surface will generate electric resonance and magnetic resonance under the joint action of the top metal copper sheet 1 and the grounding metal copper sheet 3, forming the same as free space wave impedance. At this time, the perfectly matched left-hand circularly polarized electromagnetic wave will be absorbed by the full wave and enter the through hole 6 . It is equivalent to a coaxial input port. On the back side of the polarization conversion surface, due to the symmetry of the structure, the electromagnetic wave energy in the through hole 6 will perfectly match and transmit to the free space on the back side. Since the feed position of the bottom metal copper sheet 5 on the back is exactly symmetrical to the feed position of the top layer metal copper sheet 1, the polarization direction that comes out directly becomes a right-handed circularly polarized electromagnetic wave. That is to say, the whole unit realizes the perfect conversion of left-handed circularly polarized electromagnetic waves to right-handed circularly polarized electromagnetic waves under the condition of vertical incidence. Under the condition of oblique incidence, due to the mismatch of the interface, the incident left-handed circularly polarized electromagnetic wave will be partially reflected, and the reflected electromagnetic wave is right-handed circularly polarized electromagnetic wave. At the same time, the transmitted electromagnetic wave still satisfies that the emitted circularly polarized electromagnetic wave is right-handed. Therefore, no matter what angle the left-handed circularly polarized electromagnetic wave in free space is incident on the above-mentioned polarization conversion surface, a perfect polarization conversion effect can be achieved.

During the implementation of the embodiment, the electromagnetic simulation software CST is used for simulation, and the periodic boundary is used to obtain that the energy of the surface is reflected by right-handed circularly polarized waves when the incident electromagnetic wave is a left-handed circularly polarized wave, and when the incident electromagnetic wave is a right-handed circularly polarized wave When all the energy is transmitted as a right-handed circularly polarized wave. Regardless of whether it is a linearly polarized wave or an elliptical polarized wave, it can be decomposed into two circularly polarized waves with opposite hand directions. That is to say, in the case of an arbitrary wave incident, the reflection and transmission The waves are right-handed circularly polarized waves.

The scattering parameters of the polarization conversion surface obtained by using the CST frequency domain simulation in the embodiment are shown in Fig. 4-11. It can be seen from Figures 4 to 7 that the incident left-handed circularly polarized waves are all reflected in the form of right-handed circularly polarized waves, and it can be seen from Figure 5 that the loss during reflection at the frequency of 5.8GHz is only 0.2dB. It can be seen from Figures 8 to 11 that the incident right-handed circularly polarized waves are all transmitted in the form of right-handed circularly polarized waves, and it can be seen from Figure 11 that the transmission loss is about 0.3dB at a frequency of 5.8GHz.

The working frequency of the structure introduced in this example is 5.8GHz, and its function is incident electromagnetic wave with arbitrary polarization, and its reflected wave and transmitted wave are only right-handed circularly polarized waves.

If it is to work at other frequencies, the size of the sub-wavelength resonant structural unit needs to be adjusted according to the working wavelength ratio. At the same time, the handedness of the circular polarization can be changed by adjusting the slot lengths of the top layer and the bottom layer.

The above is only a preferred example of the specific frequency of 5.8GHz in the present invention, and does not limit the present invention in any form. Any skilled person who is familiar with this field may use the technical content disclosed above to change or modify the equivalent The equivalent examples of changes, but any simple modification, equivalent change and modification made to the above examples according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still belong to the scope of the technical solution of the present invention.

Claims (4)

1. a polarization conversion surface based on secondary wavelength resonance structure, it is characterised in that: described polarization conversion Surface is mainly obtained through horizontal and vertical periodic array by secondary wavelength resonant element, secondary wavelength resonant element in Square structure, including five layer materials, ground floor is the top-level metallic copper sheet (1) of square lamellar gap with seam, The second layer is passive upper dielectric-slab (2), and third layer is middle ground metal copper sheet (3), the Four layers is passive lower dielectric-slab (4), and layer 5 is the underlying metal copper sheet of square lamellar gap with seam (5), middle ground metal copper sheet (3) is positioned between dielectric-slab (2) and lower dielectric-slab (4)；Secondary Five layer materials of wave resonance unit are provided with the through hole (6) run through, top-level metallic copper sheet (1) and bottom Metal copper sheet (5) faces to be put and polarizes oppositely oriented each other.

A kind of polarization conversion surface based on secondary wavelength resonance structure the most according to claim 1, it is special Levy and be: when on the side surface that the Wireless microwave signal amplitude in air is mapped to described polarization conversion surface, Each described the wavelength resonant element on polarization conversion surface can occur electric resonance and magnetic in working band simultaneously Resonance, feeds opposite side surface radiateing by Wireless microwave signal absorption and by through hole (6), and then Complete the conversion of polarization.

A kind of polarization conversion surface based on secondary wavelength resonance structure the most according to claim 1, it is special Levy and be: described top-level metallic copper sheet (1) and underlying metal copper sheet (5) include copper sheet and be located at copper sheet On mutually orthogonal two group gap, often group gap include two symmetrical bars being disposed radially within copper sheet edge Shape gap；Through hole (6) is positioned in top-level metallic copper sheet (1) or underlying metal copper sheet (5) diagonal positions, Through hole (6) is coaxial through top-level metallic copper sheet (1), upper dielectric-slab (2), middle ground metal copper sheet (3), lower dielectric-slab (4) and underlying metal copper sheet (5).

A kind of polarization conversion surface based on secondary wavelength resonance structure the most according to claim 3, it is special Levy and be: the length in two groups of described gaps is different, and two the bar shaped gap lengths often organizing gap are identical, top Two groups of gaps of layer metal copper sheet (1) and two groups of gaps of underlying metal copper sheet (5) are arranged contrary, pass through The position adjusting two groups of gaps realizes left-hand circular polarization conversion and right-handed circular polarization conversion.