CN114498061B - Frequency selection surface unit, frequency selection surface and frequency selection method - Google Patents
Frequency selection surface unit, frequency selection surface and frequency selection method Download PDFInfo
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- H—ELECTRICITY
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- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
- H01Q15/0013—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
- H01Q15/002—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective said selective devices being reconfigurable or tunable, e.g. using switches or diodes
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
- H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
- H01Q15/0013—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
- H01Q15/0026—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective said selective devices having a stacked geometry or having multiple layers
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Abstract
The invention discloses a frequency selection surface unit, a frequency selection surface and a frequency selection method, wherein the frequency selection surface unit comprises: a first electromagnetic dipole antenna and a second electromagnetic dipole antenna; the first electromagnetic dipole antenna is arranged above the second electromagnetic dipole antenna and connected in a back-to-back mode to form a tightly coupled antenna with small space and dual polarization; the first electromagnetic dipole antenna includes: a first electric dipole antenna and a first metal pillar; the first electric dipole antenna is fixedly connected with the first metal column; the second electromagnetic dipole antenna includes: the second electric dipole antenna is fixedly connected with the second metal column; according to the invention, the broadband antenna with the electric dipole characteristic is arranged, and the electric dipole characteristic of the antenna is realized under the condition that the thickness of the antenna and an additional circuit structure are not increased, so that the frequency selection surface has the characteristics of low thickness, high selectivity and broadband.
Description
Technical Field
The present invention relates to the field of communications technologies, and in particular, to a frequency selective surface unit, a frequency selective surface, and a frequency selection method.
Background
For a mutually interfered system, the frequency selective surface can be used for shielding out-of-band signals, can be used for decoupling in an antenna system only through the frequency which needs to be passed by the system per se, and can be used as a covering layer to improve the performances of antenna gain, isolation, selectivity, beam regulation and the like. The frequency selective surface is a structure which utilizes the uniform distribution of periodic units, and is used as a spatial filter for carrying out frequency selection on the spatial electromagnetic waves, and the frequency selective surface with high selectivity is required in practical application.
Currently, the solutions for increasing the selectivity of the frequency selective surface are:
the first is to realize multi-order filtering through a multi-layer structure;
the second is by introducing a different coupling path;
the third is to adopt a 3D structure.
In the three solutions, the multilayer structure results in a large thickness of the design, whereas the 3D structure has a large thickness and requires a complicated assembly after processing.
Therefore, a frequency selective surface capable of realizing a low thickness, a high selectivity, and a high bandwidth is required to be adapted to various applications while improving the selective characteristics of the frequency selective surface.
Disclosure of Invention
The present invention provides a frequency selective surface unit, a frequency selective surface and a frequency selective method, aiming at the defects of the prior art, so as to solve the technical problems of high thickness, low selectivity and narrow bandwidth of the existing frequency selective surface.
The technical scheme adopted by the invention for solving the technical problem is as follows:
in a first aspect, the present invention provides a frequency selective surface unit comprising:
a first electromagnetic dipole antenna and a second electromagnetic dipole antenna; the first electromagnetic dipole antenna is arranged above the second electromagnetic dipole antenna and is connected in a back-to-back mode to form a tightly coupled antenna with small space and dual polarization;
the first electromagnetic dipole antenna comprises: a first electric dipole antenna and a first metal pillar; the first electric dipole antenna is fixedly connected with the first metal column;
the second electromagnetic dipole antenna comprises: the second electric dipole antenna is fixedly connected with the second metal column;
the first metal column fixedly connects the floor structure with the first electric dipole antenna, and the second metal column fixedly connects the floor structure with the second electric dipole antenna;
the second electric dipole antenna and the first electric dipole antenna are arranged back to back, and the second electric dipole antenna and the first electric dipole antenna form coupling connection through a coupling gap of the floor structure;
the first metal column and the second metal column are both magnetic dipoles; and receiving electromagnetic waves through the first electric dipole antenna, transmitting the electromagnetic waves to the second electric dipole antenna through the coupling gap of the floor structure, and transmitting the electromagnetic waves through the second electric dipole antenna to realize the frequency selection function of the frequency selection surface by using the filtering characteristics of the first electric dipole antenna and the second electric dipole antenna.
In one implementation, the first electric dipole antenna is a rectangular metal sheet;
the rectangular metal sheet is less than 0.1 wavelength away from the boundary of the frequency selective surface unit; the first electric dipole antenna is provided with a first area, a second area, a third area and a fourth area, and in the first area, the second area, the third area and the fourth area, hollowed linear gaps are formed between every two areas.
In one implementation manner, the first region, the second region, the third region, and the fourth region are mirror-symmetric structures; the first region, the second region, the third region and the fourth region are all C-shaped bent structures or arc-shaped structures.
In one implementation, in the first region, the second region, the third region, and the fourth region, each region is provided with a hollowed residual corner rectangle; the corner stub rectangles are arranged at the center of each area, and a branch is formed from the tail ends of the corner stub rectangles to one corner of the first electric dipole antenna.
In one implementation, the sum of the total length of the sides of the residual angle rectangle and the length of the branch is greater than 0.2 wavelength of the high-frequency zero point.
In one implementation, the structure of the second electric dipole antenna has the same structural characteristics as the first electric dipole antenna.
In one implementation, the floor structure is provided with a cross-shaped gap structure, the cross-shaped gap structure is a gap structure subjected to angle rounding, and the total side length of the cross-shaped gap structure is greater than or equal to 0.1 wavelength.
In one implementation, the cross-shaped gap structure is a larger-than-two-step structure formed along the orthogonal direction, or the cross-shaped gap structure is a linear and wavy structure formed along the orthogonal direction.
In one implementation, the intersection of the cross-shaped gap structure is a right-angle or arc-angle structure, and the end of the cross-shaped gap structure is any one of a right-angle structure, an obtuse-angle structure, an acute-angle structure, an angle-0-degree structure and an arc-shaped structure.
In a second aspect, the present invention provides a frequency selective surface comprising: a plurality of frequency selective surface units as described in the first aspect.
In a third aspect, the present invention provides a frequency selection method applied to the frequency selection surface according to the second aspect, the frequency selection method comprising:
generating a low-frequency transmission zero point through an electric dipole and a magnetic dipole of the electromagnetic dipole antenna;
generating a high-frequency transmission zero point through an open resonant ring formed by the first electric dipole antenna and the second electric dipole antenna;
and disconnecting and transmitting the corresponding frequency signal through the low-frequency transmission zero point and/or the high-frequency transmission zero point, or rejecting and receiving the corresponding frequency signal through the low-frequency transmission zero point and/or the high-frequency transmission zero point.
In one implementation, the generating a low-frequency transmission zero by an electric dipole and a magnetic dipole of an electromagnetic dipole antenna includes:
determining the input impedance of the electromagnetic dipole antenna according to the characteristic impedances of the electric dipole and the magnetic dipole;
adjusting an input impedance of the electromagnetic dipole antenna to 0 or infinity to create a low frequency transmission zero of the frequency selective surface.
In one implementation, the generating a high-frequency transmission zero through the split resonant loops of the first electric dipole antenna and the second electric dipole antenna includes:
determining the length of the split ring required for generating a first high-frequency according to the split ring of the first electric dipole antenna;
determining the length of the split ring resonator required for generating a second high-frequency according to the split ring resonator of the second electric dipole antenna;
adjusting the split resonant ring of the first electric dipole antenna to be in a resonant state according to a first current, and adjusting the split resonant ring of the second electric dipole antenna to be in an inoperative state according to a default current so as to generate a high-frequency transmission zero point based on the first electric dipole antenna;
adjusting the open resonant ring of the second electric dipole antenna to be in a resonant state according to a second current, and adjusting the open resonant ring of the first electric dipole antenna to be in an inoperative state according to a default current so as to generate a high-frequency transmission zero point based on the second electric dipole antenna;
and exchanging the zero position corresponding to the first high-frequency with the zero position corresponding to the second high-frequency, and generating two high-frequency transmission zeros again through the length difference of the split resonance ring of the first electric dipole antenna and the split resonance ring of the second electric dipole antenna so as to realize the out-of-band rejection characteristic.
The invention adopts the technical scheme and has the following effects:
the frequency selection surface is set to be a small antenna transceiving system based on the reciprocity theorem, electromagnetic waves are received through the first electric dipole antenna, transmitted to the second electric dipole antenna through the coupling gap of the floor structure and emitted by the second electric dipole antenna, and the frequency selection function of the frequency selection surface is realized through the filtering characteristics of the first electric dipole antenna and the second electric dipole antenna, so that the selectivity problem of the frequency selection surface is changed into the filtering characteristic problem of a designed antenna, and the filtering characteristic of the antenna is realized by using the radiation zero point of the antenna without increasing the thickness of the antenna and an additional circuit mechanism, so that the low thickness, high selectivity and broadband characteristics of the frequency selection surface are realized. The miniaturization of the cell structure is achieved by the tightly coupled design, so that a good angular stability of the frequency selective surface is achieved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
Fig. 1 is a schematic diagram of a frequency selective surface unit in one implementation of the invention.
Fig. 2 is a schematic structural diagram of a first electric dipole antenna in an implementation manner of the present invention.
Fig. 3 is a schematic structural view of a floor structure in one implementation of the invention.
Fig. 4 is a schematic diagram of a branch structure of each region in the first electric dipole antenna in another implementation manner of the present invention.
Fig. 5 is a schematic diagram of a cross-shaped slit in another implementation of the present invention.
Fig. 6 is a schematic diagram of a filtered antenna in one implementation of the invention.
Fig. 7 is a schematic diagram of a specific structure of a frequency selective surface unit in an implementation of the present invention.
Fig. 8 is a diagram illustrating the frequency selection results of a frequency selective surface in one implementation of the invention.
Fig. 9 is an equivalent schematic of an electromagnetic dipole in one implementation of the invention.
Fig. 10 is a schematic diagram of the variation of the frequency selective surface with the height of the metal pillar in one implementation of the invention.
Fig. 11 is a schematic representation of the variation of the frequency selective surface with center-to-center spacing of metal posts in one implementation of the invention.
Fig. 12 is a schematic representation of the variation of the frequency selective surface with the diameter of the metal pillar in one implementation of the invention.
Fig. 13 is a schematic diagram of the variation of the high frequency transmission zero with the split resonant ring in one implementation of the invention.
Fig. 14 is a schematic diagram of the current distribution of the high frequency transmission zero in one implementation of the invention.
FIG. 15 is a schematic diagram of the current distribution of the transmission pole in one implementation of the invention.
Fig. 16 is a flow chart of a method of frequency selection in one implementation of the invention.
In the figure:
100. a first electric dipole antenna; 200. a floor structure; 300. a second electric dipole antenna; 410. a first metal pillar; 420. a second metal pillar; 1. a first region; 2. a second region; 3. a third region; 4. and a fourth region.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer and clearer, the present invention is further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Exemplary devices
As shown in fig. 1 to 8, the present embodiment provides a frequency selective surface, which includes a plurality of frequency selective surface units.
As shown in fig. 1, in one implementation of the present embodiment, the frequency selective surface unit includes:
a first electromagnetic dipole antenna and a second electromagnetic dipole antenna; the first electromagnetic dipole antenna is arranged above the second electromagnetic dipole antenna and is connected in a back-to-back mode to form a tightly coupled antenna with small space and dual polarization;
the first electromagnetic dipole antenna comprises: a first electric dipole antenna 100 and a first metal pillar 410; the first electric dipole antenna 100 is fixedly connected with the first metal column 410;
the second electromagnetic dipole antenna comprises: a second electric dipole antenna 300, a second metal column 420 and a floor structure 200, wherein the second electric dipole antenna 300 and the second metal column 420 are fixedly connected;
the first metal column 410 fixedly connects the floor structure 200 with the first electric dipole antenna 100, and the second metal column 420 fixedly connects the floor structure 200 with the second electric dipole antenna 300;
the second electric dipole antenna 300 and the first electric dipole antenna 100 are arranged back to back, and the second electric dipole antenna 300 and the first electric dipole antenna 100 form a coupling connection through a coupling gap of the floor structure 200; the first metal pillar 410 and the second metal pillar 420 are both magnetic dipoles; electromagnetic waves are received by the first electric dipole antenna 100, transmitted to the second electric dipole antenna 300 through the coupling gap of the floor structure 200, and emitted by the second electric dipole antenna 300, so that the frequency selection function of the frequency selection surface is realized by the filter characteristics of the first electric dipole antenna and the second electric dipole antenna.
The first metal pillar 410 and the second metal pillar 420 constitute a magnetic dipole.
The embodiment is based on the reciprocity theorem, the frequency selective surface is understood to be a small antenna transceiving system, so that the problem of selectivity of the frequency selective surface is changed into the problem of filtering characteristics of a designed antenna, the design of the frequency selective surface has good high selectivity and good angle stability by using the radiation zero point of the antenna, and the design of the broadband is realized, so that the difficulty of the selective design of the frequency selective surface is greatly reduced.
In this embodiment, the first electric dipole antenna 100 and the second electric dipole antenna 300 are connected back to form a small-sized "transceiving system", which receives electromagnetic waves, filters the electromagnetic waves, and transmits the electromagnetic waves, and the structural design principle of the system is shown in fig. 1.
According to the reciprocity theorem, the radiation null of the antenna can generate a transmission null corresponding to the frequency selective surface. Therefore, the selective transmission zero of the frequency selection surface is converted into the design of the radiation zero of the filter antenna, and the design of the radiation zero greatly reduces the design difficulty of the frequency selection surface. The design considerations for a filtering antenna are generally of two types: one is to realize the radiation zero point of the antenna through the filter circuit of the feed structure; another category is the realization of the radiating null by the structure of the antenna itself. According to the design idea of this embodiment, a broadband antenna with a filtering characteristic (i.e., an electromagnetic dipole antenna composed of the first electric dipole antenna 100 and the first metal column 410) is selected, and the filtering characteristic of the antenna is realized without increasing the thickness of the antenna and an additional circuit mechanism, so that the low thickness, high selectivity, broadband characteristic, and good angular stability of the frequency selective surface are realized.
Specifically, as shown in fig. 2, in an implementation manner of the present embodiment, when the antenna transceiving system is disposed, the first electric dipole antenna 100 is a rectangular metal sheet; the first electric dipole antenna 100 is provided with four structures, namely a first region 1, a second region 2, a third region 3 and a fourth region 4, and in the first region 1, the second region 2, the third region 3 and the fourth region 4, a hollowed linear gap is formed between every two regions.
Furthermore, the first region 1, the second region 2, the third region 3 and the fourth region 4 are mirror-symmetrical structures with each other; the first region 1, the second region 2, the third region 3 and the fourth region 4 are all in a C-shaped bent structure or an arc-shaped structure. In the first region 1, the second region 2, the third region 3 and the fourth region 4, each region is provided with a hollowed residual corner rectangle; the corner residual rectangle is arranged at the center of each region, and a branch is formed from the end of the corner residual rectangle to one corner of the first electric dipole antenna 100. And the sum of the total length of the side lengths of the residual angle rectangles and the length of the branches is more than 0.2 wavelength of the high-frequency zero point.
It is worth mentioning that the structure of the second electric dipole antenna 300 is the same as the structure of the first electric dipole antenna 100.
In the actual setting process, the frequency selection surface is completely formed by the integrated process of a PCB (printed circuit board) without assembly, but is not limited to the PCB process, and the same performance can be realized by only realizing the same structural characteristics, such as a chip process, a CMOS (complementary metal oxide semiconductor) process and the like; as shown in fig. 2, the first electric dipole antenna 100 is a rectangle with a residual angle hollowed out in a rectangular metal sheet, wherein a branch is hollowed out along a line connected to one corner of the rectangular metal sheet along the center of the original rectangle and a length is generated at the end, and the sum of the total length of the sides of the residual angle rectangle and the length of the branch is greater than 0.2 wavelength of the high-frequency zero point. And a trapped wave structure is realized, and out-of-band transmission zero is realized. The first electric dipole antenna 100 is composed of four structures, i.e., a first region 1, a second region 2, a third region 3, and a fourth region 4.
As shown in fig. 2, in order to realize electromagnetic wave regulation in two polarization directions and operate in the same frequency range, in this embodiment, four structures, i.e., a first region 1, a second region 2, a third region 3, and a fourth region 4, are adopted to be mirror-symmetric.
In another implementation manner of this embodiment, if the operating frequency bands are not required to be consistent only for single-polarization operation or in different polarization directions, the four structures of the first region 1, the second region 2, the third region 3, and the fourth region 4 may not be consistent; the four structures of the first region 1, the second region 2, the third region 3 and the fourth region 4 may adopt a bending form similar to a C-shaped bending, which may be a multiple bending or an arc. The bent branch structure may be outward or inward, and some examples are shown in fig. 4. The distances of the four structures of the first region 1, the second region 2, the third region 3 and the fourth region 4 from the boundary (i.e., the boundary of the first electric dipole antenna 100) are very small (W7- (2 × L1+ W1) <0.1 wavelength), which results in the characteristic of a tightly coupled antenna, so that the bandwidth of the antenna is widened.
As shown in fig. 3, in one implementation manner of the present embodiment, the floor structure 200 is provided with a cross-shaped gap structure, the cross-shaped gap structure is a gap structure subjected to angle rounding, and the total side length of the cross-shaped gap structure is greater than or equal to the total side length of the floor structure. The cross-shaped gap structure is a stepped structure formed along the orthogonal direction and larger than two sections, or the cross-shaped gap structure is a linear and wavy structure formed along the orthogonal direction.
Furthermore, the intersection of the cross-shaped gap structure is a right-angle or arc-angle structure, and the end of the cross-shaped gap structure is any one of the right-angle structure, the obtuse-angle structure, the acute-angle structure, the 0-degree angle structure and the arc-shaped structure.
In the actual setup, the floor structure 200 is a Yellows cold cross-shaped gap, which serves to transmit two polarized electromagnetic waves between the different layers. The cross slit structure is a polygon with more than or equal to four sides and a change shape with smooth processing of the angle. Viewed from a plane structure, the electromagnetic wave transmission structure is in a step shape or a straight line shape along 2 sections in two orthogonal directions, and is in a wavy line shape, the total length of gaps in the two orthogonal directions is more than 0.1 wavelength, the width of the gaps is more than 0.001 wavelength, and the length and the width influence the transmission efficiency of electromagnetic waves of different layers. When the two polarized electromagnetic waves do not work in the same frequency band, the two orthogonal slots may be different. The slits 9 and 10 are divided into three parts and distributed with different slit widths, and can also be divided into a plurality of sections and have different slit widths. The angle 5 in the gap can be a right angle or a circular arc, the angles 6-9 can be right angles, obtuse angles, acute angles or 0 degree or arc, and an example of partial change is shown in fig. 5.
Specifically, in one implementation manner of this embodiment, the magnetic dipole is a metal pillar antenna, the magnetic dipole is connected to the floor structure, and two ends of the magnetic dipole are respectively connected to the first electric dipole antenna 100 and the second electric dipole antenna 300.
In the actual setting process, the metal columns are used for forming magnetic dipoles, and the positions of the metal columns are located on the four structures, namely the first region 1, the second region 2, the third region 3 and the fourth region 4, and are respectively connected with the four structures.
In a specific design example, in order to realize broadband characteristics, an electromagnetic dipole antenna having broadband and dual-polarization characteristics is selected as shown in fig. 6. Two electromagnetic dipole antennas are placed back-to-back and connected through a coupling slot in the floor to implement a frequency selective surface, the structure of which is schematically shown in fig. 7. The dielectric plate material used was Rogers RO4350, the frequency selective surface had an overall thickness of 0.12 wavelength (center frequency), and the unit period was 0.19 wavelength.
The specific dimensions are (in mm): l1 = 2.1, L2 = 1.96, L3+ = 1.3, L3- = 1.0, L4 = 0.4, L5 = 0.6, L6 = 3.1, L7 = 0.65, W1 = 0.3, W2 = 0.35, W3 = 0.6, W4 = 0.4, W5 = 0.2, W6 = 0.2, W7 = 0.2, 2a = 0.4D = 1.5, H = 1.524.
Wherein, L1+ L2+ L3>0.4 wavelengths, H < =0.5 wavelengths, W1, W2, W3, W4, W5, W6, and W7 are all less than 0.5 wavelengths, D < W7, L6+2 x L4< = W7, L5< = W7, a >0.1mm, and W7- (2 x L1+ W1) <0.1 wavelength) the frequency response of the frequency selective surface realized in this embodiment is as shown in fig. 8, and the relative 3dB pass band bandwidth is 38.6%, the out-of-band rejection bandwidths of-20 dB are respectively 6.7% for the high band and 13.8% for the low band. The bandwidth is defined as follows:
because of the symmetry of the design, the frequency response of the frequency to the incident waves of the two polarization directions is consistent, and the dual-polarization characteristic is achieved.
The embodiment adopting the technical scheme has the following effects:
the embodiment is based on the reciprocity theorem, the frequency selective surface is set to be a small antenna transceiving system, electromagnetic waves are received through the first electric dipole antenna, and are transmitted to the second electric dipole antenna through the coupling gap of the floor structure, and are transmitted by using the second electric dipole antenna, so that the frequency selective function of the frequency selective surface is realized by using the filtering characteristics of the first electric dipole antenna and the second electric dipole antenna, the problem of selectivity of the frequency selective surface is changed into the problem of filtering characteristics of a designed antenna, the radiation zero point of the antenna is used, the filtering characteristics of the antenna are realized under the condition that the thickness of the antenna and an additional circuit mechanism are not increased, and the low thickness, high selectivity and broadband characteristics of the frequency selective surface are realized.
Exemplary method
As shown in fig. 9 to 16, based on the above embodiments, the present embodiment provides a frequency selection method applied to the frequency selection surface of the above embodiments.
As shown in fig. 16, in one implementation manner of this embodiment, the following steps are included:
step S100, generating a low-frequency transmission zero point through an electric dipole and a magnetic dipole of an electromagnetic dipole antenna;
step S200, generating a high-frequency transmission zero point through an open resonant ring formed by a first electric dipole antenna and a second electric dipole antenna;
and step S300, disconnecting and transmitting the corresponding frequency signal through the low-frequency transmission zero point and/or the high-frequency transmission zero point, or refusing to receive the corresponding frequency signal through the low-frequency transmission zero point and/or the high-frequency transmission zero point.
In one implementation, step S100 specifically includes:
step S101, determining the input impedance of the electromagnetic dipole antenna according to the characteristic impedance of the electric dipole and the magnetic dipole;
step S102, the input impedance of the electromagnetic dipole antenna is adjusted to 0 or infinity to generate a low-frequency transmission zero of the frequency selective surface.
In this embodiment, the implementation and control of each transmission zero on the frequency selective surface:
the implementation of the low-frequency transmission zero is as follows:
the electromagnetic dipole antenna may be equivalent to a circuit diagram as shown in fig. 9, and the electromagnetic dipole may be divided into two parts of an electric dipole and a magnetic dipole. The magnetic dipole may be equivalent to a transmission line having a characteristic impedance of
Electrical length of
Electric dipole equivalent to magnetic dipole load
Thus, an electromagnetic dipole can be equivalent to a transmission line model:
loaded electric dipole
：
Wherein,
characteristic impedance of electric dipole
，
And
is the length and equivalent width of the electric dipole,
and
loss constant and phase constant.
The magnetic dipole consists of four short-circuited metal posts,
characteristic impedance equivalent to parallel double line
Half of the total.
Here, ,
the equivalent dielectric constant D is the center distance of the adjacent metal posts,
is the diameter of the metal post.
Thus, the equivalent input impedance of an electromagnetic dipole antenna is:
when in use
Or
The electromagnetic dipole is a transmission zero point, and can generate a transmission zero point of a corresponding frequency selection surface, specifically:
equations (6) and (7) represent two zeros at low frequencies, and H,
d may affect the frequency of both transmission zeros.
As shown in FIGS. 10-12, it can be seen that as H increases, there are two transmission zeros (H)
And
) Will increase because H does not affect
And
but will not affect
. When D and
when increased, two transmission zeros: (
And
) Will also increase. Therefore, two transmission zeros of low frequency can be independently controlled by the thickness of the dielectric plate and the short-circuited metal post.
In one implementation, step S200 specifically includes:
step S201, determining the length of a split ring resonator required for generating a first high-frequency according to the split ring resonator of the first electric dipole antenna;
step S202, determining the length of the split ring resonator required for generating the second high-frequency according to the split ring resonator of the second electric dipole antenna;
step S203, adjusting the open resonant ring of the first electric dipole antenna to be in a resonant state according to the first current, and adjusting the open resonant ring of the second electric dipole antenna to be in a non-working state according to a default current so as to generate a high-frequency transmission zero point based on the first electric dipole antenna;
step S204, adjusting the open resonant ring of the second electric dipole antenna to be in a resonant state according to the second current, and adjusting the open resonant ring of the first electric dipole antenna to be in a non-operating state according to the default current so as to generate a high-frequency transmission zero point based on the second electric dipole antenna;
step S205, the zero position corresponding to the first high frequency and the zero position corresponding to the second high frequency are exchanged, and two high frequency transmission zeros are generated again by the difference in length between the open loop resonator of the first electric dipole antenna and the open loop resonator of the second electric dipole antenna, so as to implement the out-of-band rejection characteristic.
The implementation of the high-frequency transmission zero point is as follows:
in order to realize the out-of-band rejection characteristic of the designed frequency selective surface, a high-frequency transmission zero point is introduced in a mode of an open resonant ring, and the resonant frequency of the open resonant ring is as follows:
in order to further improve the out-of-band rejection characteristics of the frequency selective surface of the design, an asymmetric design is adopted,
the two high-frequency transmission zero points are realized by different sizes of the split resonant rings, namely the length of the split resonant ring required for generating the first high-frequency is determined according to the split resonant ring of the first electric dipole antenna, and the length of the split resonant ring required for generating the second high-frequency is determined according to the split resonant ring of the second electric dipole antenna, wherein the lengths of the split resonant rings required for generating the first high-frequency and the second high-frequency are not equal. As shown in fig. 13, for comparison between the symmetric design and the asymmetric design, it can be found that the asymmetry can effectively improve the out-of-band rejection characteristic of high frequency, and the out-of-band-20 dB reaches the bandwidth of 1.2 GHz.
To further illustrate the effect of the split ring resonator, the frequency selective surface is designed to be at a high frequency null
, 
The current of (2) is shown in fig. 14.
From the current distribution, it can be found that when the frequency is
At the time, the open-ended resonant ring of the upper layer (i.e., the first electric dipole antenna) resonates, and the current used at this time is a first current (as shown in fig. 14, the first current is 500 to 600A/m); the open-loop resonant loop of the lower layer (i.e. the second electric dipole antenna) has a very weak current, and the current adopted at this time is a default current (as shown in fig. 14, the default current is 0 to 100A/m) and is in an inoperative state.
When the frequency is
Meanwhile, the open-loop resonant loop of the upper layer (i.e. the first electric dipole antenna) does not work when the current is weak, and the current adopted at this time is a default current (as shown in fig. 14, the default current is 0-100A/m); the open-loop resonant loop current of the lower layer (i.e. the second electric dipole antenna) is in a strong resonance state, and the current used at this time is the second current (as shown in fig. 14, the second current is 500-600A/m). It can be seen that the introduction of the split resonant ring, the strong resonance state of the split resonant ring, results in the current not being transmitted between the two electromagnetic dipoles, thereby forming a transmission zero point (as shown in fig. 15). When the frequency is in the band pass, the two electromagnetic dipoles work, and electromagnetic waves can be transmitted between the two layers of electromagnetic dipoles, so that the transmission characteristic is realized.
In a specific implementation, the frequency selective surface element is provided with a size of 0.19 wavelength and a thickness of 0.12 wavelength, and consists of 45 × 45 elements, and the overall size is 8.56 wavelength × 0.12 wavelength. Tests show that the designed frequency selection surface still keeps good selection characteristics and out-of-band rejection characteristics under 40-degree incident waves, and has the characteristics of wide band, low thickness, high selectivity and good angle stability; in addition, by exchanging the zero position corresponding to the first high-frequency with the zero position corresponding to the second high-frequency, and by the difference in length between the open resonant loop of the first electric dipole antenna and the open resonant loop of the second electric dipole antenna, two high-frequency transmission zeros can be generated again, so as to realize the out-of-band rejection characteristic.
The embodiment adopting the technical scheme has the following effects:
the embodiment is based on the reciprocity theorem, the frequency selective surface is set to be a small antenna transceiving system, electromagnetic waves are received through the first electric dipole antenna, and are transmitted to the second electric dipole antenna through the coupling gap of the floor structure, and are transmitted out by using the second electric dipole antenna, so that the frequency selective function of the frequency selective surface is realized by using the filtering characteristics of the first electric dipole antenna and the second electric dipole antenna, the problem of selectivity of the frequency selective surface is changed into the problem of filtering characteristics of a designed antenna, the filtering characteristics of the antenna are realized by using the radiation zero point of the antenna without increasing the thickness of the antenna and an additional circuit mechanism, and the low thickness, high selectivity, broadband characteristics and good angle stability of the frequency selective surface are realized.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above may be implemented by instructing relevant hardware by a computer program, and the computer program may be stored in a non-volatile storage medium, and when executed, may include the processes of the embodiments of the methods described above. Any reference to memory, storage, databases, or other media used in embodiments provided herein may include non-volatile and/or volatile memory.
In summary, the present invention provides a frequency selective surface unit, a frequency selective surface and a frequency selection method, including: a first electromagnetic dipole antenna and a second electromagnetic dipole antenna; the first electromagnetic dipole antenna is arranged above the second electromagnetic dipole antenna and connected in a back-to-back mode to form a tightly coupled antenna with small space and dual polarization; the first electromagnetic dipole antenna includes: a first electric dipole antenna and a first metal pillar; the first electric dipole antenna is fixedly connected with the first metal column; the second electromagnetic dipole antenna includes: the second electric dipole antenna is fixedly connected with the second metal column; according to the invention, the first electromagnetic dipole antenna and the second electromagnetic dipole antenna are set as the broadband antennas with filtering characteristics, and the filtering characteristics of the antennas are realized under the condition of not increasing the thickness of the antennas and an additional circuit structure, so that the frequency selection surface has the characteristics of low thickness, high selectivity and broadband.
It will be understood that the invention is not limited to the examples described above, but that modifications and variations will occur to those skilled in the art in light of the above teachings, and that all such modifications and variations are considered to be within the scope of the invention as defined by the appended claims.
Claims (10)
1. A frequency selective surface element, said frequency selective surface element comprising:
a first electromagnetic dipole antenna and a second electromagnetic dipole antenna; the first electromagnetic dipole antenna is arranged above the second electromagnetic dipole antenna and is connected in a back-to-back mode to form a tightly coupled antenna with small space and dual polarization;
the first electromagnetic dipole antenna comprises: a first electric dipole antenna and a first metal pillar; the first electric dipole antenna is fixedly connected with the first metal column;
the second electromagnetic dipole antenna comprises: the second electric dipole antenna is fixedly connected with the second metal column;
the first metal column fixedly connects the floor structure with the first electric dipole antenna, and the second metal column fixedly connects the floor structure with the second electric dipole antenna;
the second electric dipole antenna and the first electric dipole antenna are arranged back to back, and the second electric dipole antenna and the first electric dipole antenna form coupling connection through a coupling gap of the floor structure;
the first metal column and the second metal column are both magnetic dipoles; receiving electromagnetic waves through the first electromagnetic dipole antenna, transmitting the electromagnetic waves to the second electromagnetic dipole antenna through a coupling gap of the floor structure, and transmitting the electromagnetic waves by using the second electromagnetic dipole antenna;
adjusting input impedances of the first electromagnetic dipole antenna and the second electromagnetic dipole antenna to be 0 or infinity, respectively, to generate a low-frequency transmission zero point, and generating a high-frequency transmission zero point through an open resonance loop formed by the first electric dipole antenna and an open resonance loop formed by the second electric dipole antenna, respectively, to realize a frequency selection function of the frequency selection surface by filter characteristics of the first electromagnetic dipole antenna and the second electromagnetic dipole antenna;
the first electric dipole antenna is a rectangular metal sheet;
the rectangular metal sheet is less than 0.1 wavelength away from the boundary of the frequency selective surface unit;
the first electric dipole antenna is provided with a first area, a second area, a third area and a fourth area, and hollowed linear gaps are formed between every two areas in the first area, the second area, the third area and the fourth area; the first region, the second region, the third region and the fourth region are all C-shaped bent structures or arc-shaped structures;
the structure of the second electric dipole antenna has the same structural characteristics as the first electric dipole antenna.
2. The frequency selective surface unit of claim 1, wherein the first region, the second region, the third region, and the fourth region are mirror images of each other.
3. The frequency selective surface unit of claim 2, wherein in the first region, the second region, the third region, and the fourth region, each region is provided with a hollowed-out stub rectangle; the residual angle rectangle is arranged at the center of each area, and a branch is formed from the tail end of the residual angle rectangle to one corner of the first electric dipole antenna.
4. The frequency selective surface unit according to claim 1, wherein the floor structure is provided with a cross-shaped gap structure, the cross-shaped gap structure being angle-rounded, and the cross-shaped gap structure having a total side length greater than or equal to 0.1 wavelength.
5. The frequency selective surface unit of claim 4, wherein the cross-shaped slot structure is a more than two-step structure formed along orthogonal directions, or the cross-shaped slot structure is a linear, wavy structure formed along orthogonal directions.
6. The frequency selective surface unit according to claim 4, wherein the cross-shaped slot structure has a right-angle or arc-angle-shaped cross-section, and the end of the cross-shaped slot structure is any one of a right-angle structure, an obtuse-angle structure, an acute-angle structure, a 0-degree-angle structure and an arc-shaped structure.
7. A frequency selective surface, comprising: a plurality of frequency selective surface units as claimed in any one of claims 1 to 6.
8. A frequency selection method applied to the frequency selection surface of claim 7, the frequency selection method comprising:
generating a low-frequency transmission zero point through an electric dipole and a magnetic dipole of the first electromagnetic dipole antenna, and generating a low-frequency transmission zero point through an electric dipole and a magnetic dipole of the second electromagnetic dipole antenna;
generating high-frequency transmission zero points through an open resonant ring formed by the first electric dipole antenna and an open resonant ring formed by the second electric dipole antenna;
and disconnecting and transmitting the corresponding frequency signal through the low-frequency transmission zero point and/or the high-frequency transmission zero point, or rejecting and receiving the corresponding frequency signal through the low-frequency transmission zero point and/or the high-frequency transmission zero point.
9. The frequency selection method of claim 8, wherein generating the low frequency transmission zero by the electric dipole and the magnetic dipole of the first electromagnetic dipole antenna comprises:
determining the input impedance of the first electromagnetic dipole antenna according to the characteristic impedance of the electric dipole and the magnetic dipole of the first electromagnetic dipole antenna;
adjusting an input impedance of the first electromagnetic dipole antenna to 0 or infinity to generate a low frequency transmission zero of the first electromagnetic dipole antenna.
10. The frequency selection method according to claim 8, wherein the generating of the high-frequency transmission zero by the split resonance loop formed by the first electric dipole antenna and the split resonance loop formed by the second electric dipole antenna, respectively, comprises:
determining the length of the split ring required for generating a first high-frequency according to the split ring of the first electric dipole antenna;
determining the length of the split ring resonator required for generating a second high-frequency according to the split ring resonator of the second electric dipole antenna;
adjusting the split resonant ring of the first electric dipole antenna to be in a resonant state according to a first current, and adjusting the split resonant ring of the second electric dipole antenna to be in an inoperative state according to a default current so as to generate a high-frequency transmission zero point based on the first electric dipole antenna;
adjusting the open resonant ring of the second electric dipole antenna to be in a resonant state according to a second current, and adjusting the open resonant ring of the first electric dipole antenna to be in an inoperative state according to a default current so as to generate a high-frequency transmission zero point based on the second electric dipole antenna;
and exchanging the zero position corresponding to the first high-frequency with the zero position corresponding to the second high-frequency, and generating two high-frequency transmission zeros again through the length difference of the split resonance ring of the first electric dipole antenna and the split resonance ring of the second electric dipole antenna so as to realize the out-of-band rejection characteristic.
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| CN108717992A (en) * | 2018-04-09 | 2018-10-30 | 杭州电子科技大学 | The Dual-polarized electricity magnetic-dipole antenna of millimeter wave differential feed |
| CN110011048A (en) * | 2019-04-26 | 2019-07-12 | 华南理工大学 | A kind of wideband dual polarized filtering dipole antenna of no additional circuit |
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| CN110011048A (en) * | 2019-04-26 | 2019-07-12 | 华南理工大学 | A kind of wideband dual polarized filtering dipole antenna of no additional circuit |
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