Miniaturized low-profile frequency selective surface
Technical Field
The invention belongs to the technical field of spatial filtering devices, and particularly relates to a miniaturized low-profile frequency selective surface.
Background
The Frequency Selective Surface (FSS) is a two-dimensional infinite plane which is formed by periodically arranging metal patch units or gap units according to a certain rule, has the characteristics of band pass or band rejection, is a spatial filter, and is widely applied to military and civil fields such as satellite communication, reflector antennas, wave-absorbing materials and the like. However, in practical use, the frequency selective surface has a limited size in which an increase in the number of elements can improve the transmission characteristics of the frequency selective surface, and therefore miniaturization of the elements of the frequency selective surface is important.
At present, the miniaturization of a frequency selection surface unit has various realization modes and unit structures in China, for example, an authorization publication number CN 108963395A, a Chinese patent named as 'a miniaturized band elimination type frequency selection surface' discloses a miniaturized band elimination type frequency surface, which comprises a first dielectric plate, a third dielectric plate and a second dielectric plate which are stacked up and down, wherein an opening metal ring is arranged on the upper surface of the first dielectric plate and the lower surface of the second dielectric plate, four opening metal rings of a 'U' type structure are arranged on the upper surface and the lower surface of the third dielectric plate, and the opening metal rings of different layers are connected through metal through holes.
Disclosure of Invention
The invention provides a miniaturized low-section frequency selection surface aiming at the defects in the prior art, reduces the volume of the frequency selection surface and lowers the section of the frequency selection surface.
In order to achieve the purpose, the invention adopts the following technical scheme:
a miniaturized low-profile frequency selective surface includes M × N frequency selective surface units arranged periodically, wherein M and N are natural numbers greater than or equal to 5; the frequency selection surface unit comprises a middle medium plate, a first metal layer and a second metal layer are respectively printed on the upper surface and the lower surface of the middle medium plate, the first metal layer and the second metal layer are connected through a metal through hole formed in the middle medium plate, and the first metal layer and the second metal layer are square metal layers.
In order to optimize the technical scheme, the specific measures adopted further comprise:
further, the intermediate dielectric plate is a square plate with a relative dielectric constant of 4.4, the side length range of the intermediate dielectric plate is 9mm to 11mm, and the thickness range of the intermediate dielectric plate is 0.5mm to 2 mm.
Further, the first metal layer includes four first metal strip groups, and the four first metal strip groups are rotationally symmetric along a center normal of the first metal layer.
Further, the first metal strip group comprises two U-shaped metal strips and an L-shaped metal strip, and the opening directions of the two U-shaped metal strips are opposite.
Furthermore, the metal strips of the first metal strip group are uniform in width, long branches of the U-shaped metal strips are parallel to a group of opposite sides of the middle dielectric slab, and branches of the L-shaped metal strips are parallel to a group of adjacent sides of the middle dielectric slab respectively.
Further, the second metal layer includes four second metal strip groups, and the four second metal strip groups are rotationally symmetric along a center normal of the second metal layer.
Further, the second metal strip group comprises three L-shaped metal strips, the width of the metal strips of the second metal strip group is uniform, and long branches of the L-shaped metal strips are parallel to long branches of the U-shaped metal strips in the first metal strip group.
Furthermore, the U-shaped metal strips and the L-shaped metal strips in the first metal strip group are connected with the end points of the L-shaped metal strips in the second metal strip group through the metalized through holes.
The invention has the beneficial effects that:
the invention provides a miniaturized low-profile frequency selection surface, wherein metal layers are respectively arranged on the upper surface and the lower surface of a dielectric substrate, metal strips on the upper surface and the lower surface of the dielectric substrate are connected through metal through holes, equivalent inductance and capacitance values are increased, the unit size is further reduced, the miniaturization and low-profile effect of the frequency selection surface are effectively realized, the structure is simple, the processing is easy, and the frequency stability and the polarization stability of a wide angle can be realized.
Drawings
Fig. 1 is a schematic perspective view of a first metal layer according to the present invention.
Fig. 2 is a schematic perspective view of a second metal layer according to the present invention.
FIG. 3 is a schematic diagram of a first metal layer structure according to the present invention.
FIG. 4 is a schematic diagram of a second metal layer structure according to the present invention.
FIG. 5 is a graph of simulation results of the transmission coefficient of the miniaturized low-profile frequency selective surface of the present invention.
Detailed Description
The invention will now be described in further detail with reference to the accompanying figures 1-5.
It should be noted that the terms "upper", "lower", "left", "right", "front", "back", etc. used in the present invention are for clarity of description only, and are not intended to limit the scope of the present invention, and the relative relationship between the terms and the terms is not limited by the technical contents of the essential changes.
1-2, in one embodiment of the present invention, a miniaturized, low-profile frequency selective surface comprises M × N periodically arranged frequency selective surface elements, wherein M and N are natural numbers greater than or equal to 5; the frequency selection surface unit comprises a middle medium plate, a first metal layer and a second metal layer are respectively printed on the upper surface and the lower surface of the middle medium plate, the first metal layer and the second metal layer are connected through a metal through hole formed in the middle medium plate, and the first metal layer and the second metal layer are square metal layers.
In this embodiment, set up the metal level respectively on the upper and lower surface of one deck dielectric substrate, through the metal strap of metal through-hole connection dielectric substrate upper and lower surface, increase equivalent inductance and capacitance value, further reduce the unit size, effectively realize frequency selective surface's miniaturization and low section effect, simple structure, easily processing can realize wide angle's frequency stability and polarization stability.
In one embodiment of the present invention, as shown in fig. 3-4, the first metal layer includes four first metal strip groups that are rotationally symmetric along a normal of a center of the first metal layer. The first metal strip group comprises two U-shaped metal strips and an L-shaped metal strip, the line width of each metal strip is uniform, the line width is W, and each metal strip end point is connected with a bonding pad. The opening directions of the two U-shaped metal strips in the first metal strip group are opposite, the length of a long branch of each U-shaped metal strip is L1, the length of a short branch of each U-shaped metal strip is L2, the lengths of branches of the L-shaped metal strips are L1 and L3 respectively, and the distance between the two U-shaped metal strips and the distance between the U-shaped metal strips and the L-shaped metal strips are W1.
The second metal layer comprises four second metal strip groups which are rotationally symmetrical along the central normal of the first metal layer. The second metal strip group comprises three L-shaped metal strips, the line width of each metal strip is uniform and is W, and the end point of each metal strip is connected with a bonding pad. The length of the long branch of the L-shaped metal strip is L4, the length of the short branch of the L5, and the intervals of the three L-shaped metal strips are W2.
In the embodiment, 24 pads in the first metal layer are connected with 24 metal through holes in the dielectric substrate, the diameter of a cross-sectional circle of each metal through hole is d1, and the diameter of each pad is d 2; and 24 bonding pads in the second metal layer are connected with 24 metal through holes in the dielectric substrate, the diameter of the cross section circle of each metal through hole is d1, and the diameter of each bonding pad is d 2.
In one embodiment of the present invention, the dielectric substrate is a square plate with a relative dielectric constant of 4.4, and has a length p of 10mm and a thickness h of 1 mm. The first metal layer is a square with the side length L being 9.6mm, and the distance between the edge of the first metal layer and the same edge of the upper surface of the dielectric substrate is g; the second metal layer is a square with the side length L of 9.6mm, and the distance between the edge of the second metal layer and the same edge of the lower surface of the dielectric substrate is g.
The dimensions of the various parts of the invention are shown in table 1 below:
TABLE 1
As shown in fig. 5, in one embodiment of the present invention, the transmission coefficient of the above embodiment is simulated by using commercial simulation software HFSS _13.0.2, and fig. 5(a) and (b) are transmission coefficient curves from incident angles of 0 ° to 80 ° for TE waves and TM waves, respectively, and it can be seen that a stop band is generated at a frequency of 1.42GHz, corresponding to a free space wavelength of 211.3mm, and the frequency selective surface proposed by the present invention in this embodiment is a cell size of 0.047 resonance wavelengths, where the resonance wavelengths are wavelengths at which electromagnetic waves propagate in free space. The simulation results show that the frequency selection surface provided by the invention achieves the aims of miniaturization and low section of the frequency selection surface unit structure.
In summary, the frequency selective surface provided by the invention can be manufactured on a layer of dielectric substrate, and the unit structure is simple and the cost is low. The frequency selection surface unit can have larger equivalent inductance and capacitance by utilizing a plurality of U-shaped and L-shaped metal strips, the equivalent inductance and capacitance can be increased by utilizing the metal strips which are connected with the upper surface and the lower surface of the dielectric substrate by utilizing the metal through holes, the size of the unit is further reduced, and the metal strip groups are rotationally and symmetrically distributed in the center of the unit, so that the frequency selection surface with the small size and the low section has low sensitivity to the polarization and the incident angle of electromagnetic waves.
The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention.