CN106602231A - Quasi-surface plasmon ultra-wide band low-scattering slot antenna - Google Patents

Abstract

The invention discloses a quasi-surface plasmon ultra-broadband low-scattering slot antenna. The radiation aperture is a circular structure with the same area, and the radius of the circle is r ₁ =68mm; the thickness of the dielectric plate of the SSPP slot antenna is 1mm; the SSPP The 20mm×40mm feeding area on the back of the slot antenna is made of metal, the center of which is a 26mm×2mm slot, and the rest is not plated with metal. The dielectric constant of the dielectric plate is 2.65, and the loss tangent is less than 0.001. The invention realizes the ultra-wideband low-scattering slot antenna of the quasi-surface plasmon polaritons, the antenna has obvious RCS reduction effect in the azimuth of 1GHz-10GHz, the maximum reduction of MRCS is above 16.93dB, and the relative bandwidth of the SSPP slot antenna is 9.4 %, its frequency covers 5.25GHz to 5.77GHz, and the beam width of the SSPP antenna is at least 65° wider than that of the traditional antenna.

Description

A quasi-surface plasmon ultra-wideband low-scattering slot antenna

technical field

The invention belongs to the field of novel electromagnetic metamaterials and applications, in particular to an ultra-wideband low-scattering slot antenna of quasi-surface plasmons.

Background technique

Surface Plasmon Polaritons (SPP) is a surface electromagnetic wave mode, which usually exists on the surface of two materials with opposite dielectric constants. Because of its surface wave characteristics, electromagnetic waves (such as light waves) in certain frequency bands can be constrained to a subwavelength spatial extent. General surface plasmons mainly exist in nanostructures in the light wave band. The equivalent permittivity of an ideal conductor with a subwavelength small hole structure. When the electromagnetic wave is incident on the small hole, the attenuated waveguide mode of the small hole is excited. Only the fundamental mode that plays a leading role in supertransmission is considered. The calculation results show that: Ideal conductors for wavelength pinholes have similar equivalent dielectric constants to plasmonic materials. From this result, it can be known that when an electromagnetic wave is incident on an ideal conductor with a small subwavelength hole, surface waves similar to SPP will be excited, which are called quasi-surface plasmon polaritons (Spoof Surface Plasmon Polaritons, SSPP). SSPP research not only expands the research content of surface plasmons, but also expands its application fields. In order to excite quasi-surface plasmons in the microwave frequency range, scholars have proposed two methods: one is to excite SSPP by doping semiconductors, high-temperature superconducting materials, etc.; the other is to reduce the surface plasmon frequency of metals through the metal surface microstructure. . The former mainly uses methods such as photothermal excitation and ion implantation to control the carrier concentration to reduce the plasma frequency and realize SSPP in the low frequency range. The latter is due to the fact that the periodically structured metal surface can support the surface wave mode of SSPP. The rapid development of Metamaterial has injected new vitality into the SSPP research in the microwave band. The SSPP wave propagation characteristics of the three-dimensional periodic trough structure are analyzed, and the research results show that the designed trough structure can support 0.8THz SSPP wave propagation. Etch a "king"-shaped structure on the upper metal surface of the double-sided copper-clad laminate, and use this structure to excite SSPP. Combined with the gradual metasurface (Metasurface) structure, the SSPP in the microwave frequency band is coupled, and the propagation state of the SSPP surface wave on the structure is analyzed. The broadband SSPP characteristics of periodic structures are analyzed, and it is found that periodic CSRR rings can support the propagation of SSPP surface waves. The surface plasmon phenomenon of the circular quasi-metasurface is analyzed, and it is verified that the metasurface can excite SSPP under different polarizations. The research results show that the quasi-metasurface can effectively control the propagation direction of electromagnetic waves and improve the Scattering properties. These studies have promoted the development of SSPP, but because SSPP in the microwave band is very new, there are few reports on its application in antennas.

The existing quasi-surface plasmon structures in the microwave frequency band are very sensitive to the polarization of the incident wave due to the asymmetry of the designed structure itself; according to the magnetic resonance characteristics of the structure, most of them can only excite TM-polarized SSPP , and its application in antennas often brings about a substantial increase in cross-polarized components and enhanced co-polarized scattering, so it is difficult to take into account the radiation and scattering characteristics of the antenna.

Contents of the invention

The purpose of the present invention is to provide a quasi-surface plasmon ultra-wideband low-scattering slot antenna, which aims to solve the problem that the existing quasi-surface plasmon structure in the microwave frequency band is very sensitive to the polarization of the incident wave due to the structure itself , most of them can only excite TM-polarized SSPP, and its application in the antenna is difficult to take into account the radiation and scattering characteristics of the antenna.

The present invention is achieved in this way, a quasi-surface plasmon ultra-wideband low-scattering slot antenna, the radiation aperture of the quasi-surface plasmon ultra-wideband low-scattering slot antenna is a circular structure with the same area, and the circle The radius of the SSPP slot antenna is r ₁ =68mm; the thickness of the dielectric plate of the SSPP slot antenna is 1mm; the 20mm×40mm area of the back feed of the SSPP slot antenna is metal, and its center is a 26mm×2mm slot, and the rest of the position is not plated with metal, and the dielectric The dielectric constant of the plate is 2.65, and the loss tangent is less than 0.001.

Another object of the present invention is to provide a design method for the ultra-wideband low-scattering slot antenna of the quasi-surface plasmon. The sawtooth metal structure designs a circular quasi-metasurface that excites SSPP. The quasi-metasurface can excite SSPP on the metal structure parallel to the direction of the electric field in the low frequency band, forming a SSPP mode surface wave, and enhancing the energy propagation of the surface wave; the quasi-metasurface The thickness of the structure is 1.0mm, and the relevant dimensions of the metal bilateral sawtooth structure are: r ₁ =68mm, w ₁ =32mm, w ₂ =3.7mm, w ₃ =2mm, P=5mm, α=25deg, and the metal thickness is 0.036 mm; the dielectric constant of the dielectric board is 2.65, and there is no metal layer on the back of the dielectric board.

Further, the design method of the quasi-surface plasmon ultra-wideband low-scattering slot antenna uses a metal double-sided sawtooth structure to excite quasi-surface plasmons to realize the surface wave conversion from radiated electromagnetic waves to SSPP modes, and the electric field of incident electromagnetic waves E(x,y,z) is:

Among them, E ₀ is the magnitude of the field strength, Kz and Kx represent the components of the wave number in the z and x-axis directions, and the electric field direction is along the x-axis direction; the electric field component incident on the metal for:

The electric field component on the medium for:

k _z1 and ε ₁ represent the wave number and permittivity of the metal layer with bilateral sawtooth structure, k _z2 and ε ₂ represent the wave number and permittivity of the dielectric layer; when the electromagnetic wave passes between the metal layer and the dielectric layer, the attenuation of the electromagnetic wave The length is:

According to the continuity boundary condition, the following dispersion relation is further obtained:

Among them, k _x represents the electromagnetic wave propagation coefficient along the x-axis direction; for metal and dielectric structures, the refraction coefficient of SSPP (n _SSPP ) is:

Among them, ε1 and _ε2 are the dielectric constants _of different media, respectively. k _x further simplifies to:

Wherein, k ₀ =w/c=2πf/c is the wave number in free space, and c is the speed of light. written as:

The surface wave propagation coefficient k _x of the SSPP mode excited by the bilateral sawtooth metal structure is:

When 0<k ₀ d<π/2, k _x is a real number, and k _x >k ₀ .

The quasi-surface plasmon ultra-wideband low-scattering slot antenna provided by the present invention excites the SSPP in the microwave frequency band by designing an ultra-thin circular tapered bilateral sawtooth symmetric structure, and deeply analyzes the surface wave propagation and scattering under the SSPP mode condition characteristics, and then used it on the antenna radiation surface, designed a quasi-surface plasmon ultra-wideband low-scattering slot antenna, realized the regulation of the antenna scattering beam direction through SSPP, improved the antenna's scattering performance, and widened the antenna at the same time beam width.

The invention combines the gradual bilateral sawtooth structure and the circular symmetrical metasurface, and proposes an ultra-thin circular SSPP quasi-metasurface. The quasi-metasurface can excite the SSPP in the microwave frequency band, deeply analyze the surface wave propagation characteristics and scattering characteristics under the SSPP mode condition, and then apply it to the radiation surface of the antenna, realizing the ultra-wideband low-scattering gap of the quasi-surface plasmon Antenna, the scattering beam of the antenna is regulated due to the influence of SSPP. The antenna has obvious RCS reduction effect in the azimuth of 1GHz to 10GHz. The maximum reduction of MRCS is above 16.93dB. The relative bandwidth of the SSPP slot antenna is 9.4%. Covering 5.25GHz to 5.77GHz, the beam width of the SSPP antenna is at least 65° wider than that of the traditional antenna. Simulations and tests have verified that the SSPP slot antenna can control the scattered beam, improve the antenna's scattering performance, and realize the characteristics of ultra-wideband and low RCS. At the same time, SSPP can widen the antenna's beamwidth and optimize the antenna's radiation performance.

Description of drawings

Fig. 1 is a schematic diagram of a polarization-independent circular metasurface structure based on a gradient sawtooth structure provided by an embodiment of the present invention;

In the figure: (a) progressive bilateral sawtooth structure; (b) metasurface based on bilateral sawtooth structure.

Fig. 2 is a schematic diagram of a simulation model of a dispersion curve provided by an embodiment of the present invention.

FIG. 3 is a schematic diagram of a simulation result of a dispersion curve of a gradient sawtooth structure provided by an embodiment of the present invention.

Fig. 4 is a schematic diagram of the electric field distribution of the metasurface under the condition of different polarized incident waves at normal incidence provided by an embodiment of the present invention.

5 is a schematic diagram of a metasurface waveguide slot antenna with a bilateral sawtooth structure provided by an embodiment of the present invention;

In the figure: (a) waveguide slot antenna on conventional metal surface; (b) SSPP slot antenna.

Fig. 6 is a schematic diagram of S11 simulation results of different waveguide slot antennas provided by an embodiment of the present invention.

Fig. 7 is a schematic diagram of the simulation results of the two-dimensional pattern of the SSPP antenna provided by the embodiment of the present invention and the waveguide slot antenna on the traditional metal surface at 5.4GHz and 5.65GHz;

In the figure: (a) yoz plane of 5.4GHz radiation pattern; (b) xoz plane of 5.4GHz radiation pattern; (c) yoz plane of 5.65GHz radiation pattern; (d) xoz plane of 5.65GHz radiation pattern .

Fig. 8 is a schematic diagram of the three-dimensional pattern simulation results of the SSPP antenna provided by the embodiment of the present invention and the waveguide slot antenna on the traditional metal surface at 5.4GHz and 5.65GHz;

In the figure: (a) traditional waveguide slot antenna; (b) SSPP slot antenna; (c) traditional waveguide slot antenna; (d) SSPP slot antenna.

9 is a schematic diagram of the surface current distribution of the SSPP antenna provided by the embodiment of the present invention and the waveguide slot antenna on the traditional metal surface at 5.4 GHz;

In the figure: (a) conventional antenna; (b) metasurface antenna.

Fig. 10 is a schematic diagram of the comparison of the single-station RCS simulation results of the SSPP antenna under different polarization conditions compared with the traditional antenna provided by the embodiment of the present invention;

In the figure: (a) MRCS simulation comparison under TM polarization conditions; (b) MRCS simulation comparison under TE polarization conditions.

Fig. 11 is a schematic diagram of processed traditional waveguide slot antennas and SSPP slot antennas provided by an embodiment of the present invention.

Fig. 12 is a schematic diagram of S11 test results of different antennas provided by an embodiment of the present invention.

Fig. 13 is a schematic diagram of the pattern test results of the 5.4GHz and 5.65GHz traditional waveguide slot antennas and SSPP slot antennas provided by the embodiment of the present invention;

In the figure: (a) 5.4GHz pattern; (b) 5.65GHz pattern.

Fig. 14 is a schematic diagram of actual measurement results of antenna MRCS reduction under different polarization conditions provided by an embodiment of the present invention.

detailed description

In order to make the object, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the examples. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

In the present invention, by designing an ultra-thin circular gradual bilateral sawtooth symmetric structure, exciting the SSPP in the microwave frequency band, deeply analyzing the surface wave propagation and scattering characteristics under the SSPP mode condition, and then applying it to the antenna radiation surface, controlling the antenna scattering beam direction, broaden the beam width of the antenna, improve the scattering and radiation performance of the antenna, and realize the ultra-wideband low-scattering slot antenna of SSPP.

The application principle of the present invention will be described in detail below in conjunction with the accompanying drawings.

(1) SSPP quasi-metasurface

A circular quasi-metasurface that can excite SSPP is designed by using the gradient bilateral sawtooth metal structure, as shown in Figure 1. Figure 1(a) shows the metal structure of the gradient bilateral sawtooth, and Figure 1(b) shows that on the basis of the metal bilateral sawtooth structure, it is rotated around the center to form a circular quasi-metasurface. The designed quasi-metasurface can excite SSPP on the metal structure parallel to the direction of the electric field in the low frequency band, forming SSPP mode surface waves and enhancing the energy propagation of surface waves; the thickness of the quasi-metasurface structure is 1.0mm, and the correlation The dimensions are: r ₁ =68mm, w ₁ =32mm, w ₂ =3.7mm, w ₃ =2mm, P=5mm, α=25deg, and the metal thickness is 0.036mm. The dielectric constant of the dielectric board is 2.65, and there is no metal layer on the back of the dielectric board.

In the microwave frequency band, quasi-surface plasmons can be excited by using the metal double-sided sawtooth structure, and the surface wave conversion from radiated electromagnetic waves to SSPP modes can be realized. Since the circular structure has a strong central symmetry feature, the incident wave of TE and TM polarization can excite the SSPP and guide the propagation of the SSPP surface wave. For the quasi-metasurface structure in Figure 1, the electric field of the incident electromagnetic wave is:

Wherein, the electric field direction is along the x-axis direction. The electric field component incident on the metal is:

The electric field components on the medium are:

k _z1 and ε ₁ represent the wave number and permittivity of the bilateral sawtooth structure metal layer, k _z2 and ε ₂ represent the wave number and permittivity of the dielectric layer. According to formulas (2) and (3), it can be obtained that when the electromagnetic wave passes between the metal layer and the dielectric layer, the attenuation length of the electromagnetic wave is:

According to the continuity boundary condition, the following dispersion relation is further obtained:

Among them, k _x represents the electromagnetic wave propagation coefficient along the x-axis direction. For metal and dielectric structures, the index of refraction (n _SSPP ) of SSPP is:

Combining formulas (5) and (6), k _x can be further simplified as:

Wherein, k ₀ =w/c=2πf/c is the wave number in free space, and c is the speed of light. can be written as:

According to formula (9), we can see that Indicates the exponential decay relationship between the metal sawtooth structure and the medium. For the gradient bilateral sawtooth structure, considering the TM polarized incident wave, the reflection coefficient can be calculated according to the boundary conditions. The condition of surface wave from SSPP mode is k _x >k ₀ . If the conditions λ>>(Pw ₃ ) and λ>>P are satisfied, (λ is the operating wavelength), then the surface wave propagation coefficient k _x of the SSPP mode excited by the bilateral sawtooth metal structure is:

According to formula (10), when 0<k ₀ d<π/2, k _x is a real number, and k _x >k ₀ , so the propagation speed of the excited SSPP surface wave is lower than the speed of light. It can also be found from formula (10) that k _x will increase with the increase of P and d. At the same time, the surface wave cutoff frequency of the SSPP mode mainly depends on the sawtooth depth d, that is, the cutoff frequency of the designed quasi-metasurface can be improved by increasing the metal sawtooth depth. Therefore, the propagation speed of the surface wave in the SSPP mode is lower than the speed of light, and the surface wave can be trapped at the critical interface between the metal and the medium, and propagate forward along the sawtooth structure.

Using the eigenmode of CST, the dispersion curve of the gradient sawtooth structure is simulated, the simulation model is shown in Figure 2, and the dispersion curve obtained by simulation is shown in Figure 3. It can be seen from the figure that different sawtooth depths d correspond to different cutoff frequencies. When the sawtooth depth d=4.47mm, 8.62mm and 12.61mm, the corresponding cutoff frequencies are 8.07GHz, 4.74GHz and 2.83GHz respectively; it can be seen that: with As the sawtooth depth d increases, the cutoff frequency shifts toward lower frequencies. When the sawtooth depth d=4.47mm, the cutoff frequencies of the fundamental mode, the first-order mode and the second-order mode are 2.83GHz, 3.05GHz and 3.50GHz respectively; when the sawtooth depth d=8.62mm, the cutoff frequencies of the first three modes are respectively are 4.74GHz, 5.49GHz and 6.31GHz; when the sawtooth depth d=12.61mm, the cutoff frequencies of the first three modes are 8.07GHz, 9.45GHz and 10.86GHz respectively. It can be seen that under the same sawtooth depth condition, the cutoff frequency increases with the increase of the mode; with the increase of the mode, the cutoff frequency is closer to the propagation effect of the speed of light. According to the design requirements, the metal sawtooth structure with d=12.61mm was finally selected.

In order to verify the surface wave characteristics of the microwave SSPP mode, the electric field distribution on the xoy surface of the metasurface at 1 GHz and 2 GHz was analyzed, as shown in Figure 4. From the simulation results of the electric field distribution in the figure, it can be seen that for the incident electromagnetic wave of TM polarization, the surface wave of the SSPP mode is formed at the position parallel to the y-axis direction, but the surface wave in the x-axis direction is not obvious, and other positions are due to The coupling effect between sawtooth also has obvious surface wave propagation effect. For the TE polarized incident electromagnetic wave, a very obvious SSPP mode surface wave is formed at the position parallel to the x-axis direction, while the surface wave in the y-axis direction is not obvious, and the gradual sawtooth structure at the rest of the position is also due to the gap between the sawtooth The coupling effect forms the apparent surface wave propagation. The surface wave of the SSPP mode shows that the designed metal graded sawtooth structure can excite quasi-surface plasmons in the microwave frequency band, and the designed metasurface has polarization-independent characteristics; the simulation results also show that the polarization-independent structure based on the graded sawtooth structure The circular metasurface can convert the electromagnetic wave of normal incidence into the surface wave of SSPP mode.

(2) Ultra-wideband low-scattering slot antenna for quasi-surface plasmons

The designed SSPP slot antenna structure is shown in Figure 5. The radiation aperture of the antenna is a circular structure with the same area, and the radius of the circle is r ₁ =68mm; the thickness of the dielectric plate of the SSPP slot antenna is 1mm, and the thickness of the aperture metal plate of the traditional waveguide slot antenna is 1mm. The 20mm×40mm area of the back feed of the SSPP slot antenna is metal, and its center is a 26mm×2mm slot, and the rest of the position is not plated with metal. The dielectric constant of the dielectric plate is 2.65, and the loss tangent is less than 0.001. The red arrow marks the feeding excitation of the slot antenna. The simulation analysis of antenna radiation and scattering performance is carried out by using HFSS.

The antenna S parameter simulation results are shown in Figure 6. The bandwidth of the traditional antenna satisfying S ₁₁ <-10dB is 5.34-5.86GHz, and the bandwidth of the SSPP slot antenna satisfying S ₁₁ <-10dB is 5.28-5.72GHz. The working bandwidth of the antenna is shifted to low frequency . Figures 7 and 8 show the two-dimensional and three-dimensional pattern of the metal antenna at 5.4GHz and 5.65GHz. From the 5.4GHz and 5.65GHz two-dimensional pattern curves in Figure 7, it can be seen that the cross-polarization components of the SSPP slot antenna at 5.4GHz and 5.65GHz are slightly larger than those of the traditional waveguide slot antenna, and the backward radiation is enhanced , the front-to-back ratio of the antenna decreases. The beamwidths of the traditional antenna and the SSPP slot antenna are 146° and 200° in the xoz plane at 5.4GHz, 70° and 72° in the yoz plane, and 151° and 172° in the xoz plane at 5.65GHz , the yoz surface beamwidths are 58° and 105°. It can be seen from the antenna three-dimensional pattern 8 that the beam of the SSPP antenna is significantly wider than that of the waveguide slot antenna on the metal surface. Figure 9 shows the surface current distribution of the SSPP antenna and the waveguide slot antenna on the traditional metal surface. From the current distribution density, it can be found that compared with the current density of the metal aperture, the current density along the horizontal direction is significantly enhanced, that is, through the sawtooth structure The intensity of the surface wave is improved, and the broadening of the beam width is realized.

The MRCS results of the conventional waveguide slot antenna and the SSPP quasi-metasurface slot antenna are shown in Fig. 10. Through the comparison of MRCS simulation results, it can be seen that compared with the traditional waveguide slot antenna, the SSPP slot antenna can obtain obvious RCS reduction in the range of 1GHz to 10GHz, and the maximum RCS reduction exceeds 15dB.

(3) Experimental test and analysis of SSPP slot antenna

The processed traditional waveguide slot antenna and SSPP slot antenna are shown in Figure 11, and these two antennas were placed in a microwave anechoic chamber for testing. The vector network analyzer used is AgilentN5230C, and the tested horn antenna can work in the frequency range of 1GHz to 18GHz. Figure 12 shows the S ₁₁ test results of the antenna, and Figure 13 shows the test results of the antenna's pattern at 5.4GHz and 5.65GHz. According to the test results of S ₁₁ , the traditional waveguide slot antenna can obtain 9.1% relative bandwidth of 5.32GHz-5.83GHz; the SSPP slot antenna achieves 9.4% relative bandwidth, and its frequency covers 5.25GHz-5.77GHz.

Figure 13 shows the pattern test results of the two antennas at 5.4GHz and 5.65GHz. The 3dB beamwidths of the E plane and H plane of the 5.4GHz traditional waveguide slot antenna pattern are 132° and 66° respectively, and the beamwidths of the 5.65GHz antenna pattern are 143° and 56°; the measured SSPP slot antenna is at 5.4GHz The beamwidths of SSPP and 5.65GHz are 185°, 70° and 167°, 102°, respectively. Compared with traditional antennas, the beamwidth of SSPP antennas is at least 65° wider. It can be seen that the beam broadening of the SSPP slot antenna is obvious, and the comparison between the simulation and the measured results shows a good agreement.

The MRCS test results of the two antennas are shown in Figure 14. It can be seen from the figure that the SSPP antenna has a more obvious MRCS reduction effect than the traditional waveguide slot antenna in the range of 1GHz to 10GHz, but the reduction effect at 2.8GHz to 4GHz is slightly worse. The maximum MRCS reduction of the x-polarized antenna at 2.04GHz is 16.93dB, and the maximum MRCS reduction of the y-polarized antenna at 1.78GHz is 23.83dB. The RCS reduction at 2 GHz is mainly due to the metasurface based on quasi-surface plasmons in the microwave band changing the direction of the scattered beam of electromagnetic waves. The reasons why the MRCS reduction effects under different polarizations are not completely consistent include two aspects. One is that the antenna slot structure is a long and narrow slot, and the other is that the antenna itself has polarization characteristics. Comparing Figure 10 and Figure 14, it can be seen that the consistency between the actual measurement and the simulation is good.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention should be included in the protection of the present invention. within range.

Claims (3)

1. The ultra-wideband low-scattering slot antenna of the quasi-surface plasmon is characterized in that the radiation caliber of the ultra-wideband low-scattering slot antenna of the quasi-surface plasmon is a circular structure with the same area, and the radius of a circle is r₁The dielectric plate of the SSPP slot antenna is 68mm, the thickness of the dielectric plate of the SSPP slot antenna is 1mm, the area of the power feeding position of the back surface of the SSPP slot antenna, which is 20mm × 40mm, is metal, the center position of the slot is 26mm × 2mm, the rest positions are not plated with metal, the dielectric constant of the dielectric plate is 2.65, and the loss tangent is less than 0.001.

2. The design method of the quasi-surface plasmon ultra-wideband low-scattering slot antenna as claimed in claim 1, wherein the design method of the quasi-surface plasmon ultra-wideband low-scattering slot antenna utilizes a graded double-edge sawtooth metal structure to design a circular quasi-super surface for exciting SSPP, and the quasi-super surface can excite SSPP on the metal structure with a low frequency band parallel to the electric field direction to form an SSPP mode surface wave and enhance energy propagation of the surface wave; the thickness of the quasi-super-surface structure is 1.0mm, and the relevant sizes of the metal bilateral sawtooth structure are respectively as follows: r is₁＝68mm,w₁＝32mm,w₂＝3.7mm,w₃2mm, 5mm, 25deg, 0.036mm metal thickness, 2.65 dielectric constant and no metal layer on the back of the dielectric plate.

3. The method for designing the quasi-surface plasmon ultra-wideband low-scattering slot antenna as claimed in claim 2, wherein the quasi-surface plasmon ultra-wideband low-scattering slot antenna is designed by using a metal double-sided sawtooth structure to excite quasi-surface plasmons, so as to realize surface wave conversion from radiated electromagnetic waves to SSPP modes, and the electric field of the incident electromagnetic waves is:

$E(x,y,z)=E_0{e}^{i(k_{x}x-k_z|z|-\mathrm{\&omega;}t)};$

wherein the direction of the electric field is along the direction of the x axis; the components of the electric field incident on the metal are:

$E_{(x,y,z)}^{metallic}=\left[\begin{array}{c}{E}_x^m\\ E_y^m\\ E_z^m\end{array}\right]=\left[\begin{array}{c}{E}_0{e}^{i(k_{x}x-k_{z1}|z|-\mathrm{\&omega;}t)}\\ 0\\ E_0(-k_x/k_{z1})e^{i(k_{x}x-k_{z1}|z|-\mathrm{\&omega;}t)}\end{array}\right];$

the electric field components on the medium are:

$E_{(x,y,z)}^{dielectric}=\left[\begin{array}{c}{E}_x^d\\ E_y^d\\ E_z^d\end{array}\right]=\left[\begin{array}{c}{E}_0{e}^{i(k_{x}x-k_{z2}|z|-\mathrm{\&omega;}t)}\\ 0\\ E_0(-{\mathrm{\&epsiv;}}_1{k}_x/{\mathrm{\&epsiv;}}_2{k}_{z1})e^{i(k_{x}x-k_{z2}|z|-\mathrm{\&omega;}t)}\end{array}\right];$

k_z1and₁representing wave number and dielectric constant, k, of the double-sided sawtooth structure metal layer_z2And₂represents the wave number and dielectric constant of the dielectric layer; when the electromagnetic wave is transmitted between the metal layer and the dielectric layer, the attenuation length of the electromagnetic wave is as follows:

$\hat{z}=\frac{1}{\left|k_z\right|};$

according to the continuity boundary condition, the following dispersion relation is further obtained:

$k_x=\frac{\mathrm{\&omega;}}{c}{n}_{SSPP};$

$k_{z1,2}^2={\mathrm{\&epsiv;}}_{1,2}{(\mathrm{\&omega;}/c)}^2-k_x^2;$

wherein k is_xRepresents an electromagnetic wave propagation coefficient along the x-axis direction; refractive index n of SSPP for metal and dielectric structures_SSPPComprises the following steps:

$n_{sspp}=\sqrt{{\mathrm{\&epsiv;}}_1{\mathrm{\&epsiv;}}_2/({\mathrm{\&epsiv;}}_1+{\mathrm{\&epsiv;}}_2)};$

k_xfurther simplifying as follows:

$k_x=\frac{\mathrm{\&omega;}}{c}\sqrt{{\mathrm{\&epsiv;}}_1{\mathrm{\&epsiv;}}_2/({\mathrm{\&epsiv;}}_1+{\mathrm{\&epsiv;}}_2)}=k_0\sqrt{{\mathrm{\&epsiv;}}_1{\mathrm{\&epsiv;}}_2/({\mathrm{\&epsiv;}}_1+{\mathrm{\&epsiv;}}_2)};$

wherein k is₀W/c 2 pi f/c is the wave number in free space, c is the speed of light,write as:

$k_{z1,2}^2={\mathrm{\&epsiv;}}_{1,2}{k}_0^2\&lsqb;1-{\left(\frac{{\mathrm{\&epsiv;}}_1{\mathrm{\&epsiv;}}_2}{{\mathrm{\&epsiv;}}_1+{\mathrm{\&epsiv;}}_2}\right)}^2\&rsqb;;$

surface wave propagation coefficient k of SSPP mode excited by bilateral sawtooth metal structure_xComprises the following steps:

$k_x=k_0\sqrt{1+\frac{{(P-w_3)}^2}{P^2}{\tan }^2\left(k_{0}d\right)};$

when 0 is present<k₀d<At pi/2, k_xIs a real number, and k_x>k₀。