CN113363718B - Enhanced electrically small antenna with stealth function - Google Patents

Enhanced electrically small antenna with stealth function Download PDF

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CN113363718B
CN113363718B CN202110625957.5A CN202110625957A CN113363718B CN 113363718 B CN113363718 B CN 113363718B CN 202110625957 A CN202110625957 A CN 202110625957A CN 113363718 B CN113363718 B CN 113363718B
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inner layer
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CN113363718A (en
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聂秋月
陈培奇
张仲麟
李维硕
艾昕
闫昌时
魏国强
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Harbin Institute of Technology
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/42—Housings not intimately mechanically associated with radiating elements, e.g. radome
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems

Abstract

The invention discloses an enhanced electric small antenna with a stealth function, relates to an antenna capable of enhancing a detection wave stealth signal and a communication signal of a self party, and aims to solve the problem that when two sets of plasma sources in the existing plasma stealth and enhancement device work simultaneously, the accurate regulation and control difficulty of plasma parameters is high due to the possibility of mutual interference, and the enhanced electric small antenna comprises the following steps: the outer plasma cover is a spherical shell-shaped plasma cover formed by outer plasma, and the density and collision frequency of the outer plasma in the outer plasma cover are uniformly distributed; the inner layer plasma cover is a spherical shell-shaped plasma cover formed by inner layer plasmas, and the density and collision frequency of the inner layer plasmas in the inner layer plasma cover are uniformly distributed; the inner plasma cover is arranged inside the outer plasma cover; the electric small dipole antenna is spherical, is concentrically arranged inside the inner layer plasma cover, and has no gap with the inner layer plasma cover.

Description

Enhanced electrically small antenna with stealth function
Technical Field
The invention relates to an antenna capable of realizing stealth of a detection wave and enhancement of own communication signals.
Background
The plasma stealth is a novel active stealth technology, and has the unique advantages of wide wave-absorbing frequency band, high absorptivity, no need of changing the structural design of a target appearance, dynamic continuous adjustability and the like. However, the plasma stealth technology at the present stage usually adopts a mode of rapidly starting the plasma when the communication system is not in operation to realize stealth, and the continuity and the stability are poor. One important reason is that the plasma, while stealth from the probe wave, also shields the own party's communication signal.
On the other hand, the rapid development of nano optics and plasmon enables people to regulate and control the behavior of electromagnetic waves more flexibly and effectively under the sub-wavelength scale. Although the proposed and experimental verification of these principles and methods mainly focuses on the optical band, when the normalized characteristic parameters (e.g., size, dielectric constant, magnetic permeability) of the system under study are consistent with those of the corresponding optical band, the related principles and methods can be generalized to the microwave band where the gas discharge plasma is located, and provide continuous power for the development of the plasma field.
For the plasma stealth technology, the principles and the methods are a new idea for improving the stealth performance of the plasma and solving the communication bottleneck problem of the plasma. For the former, the scattering offset method, the Kerker effect and the fanno resonance are powerful tools for modulating the scattering characteristics of the target. The basic principle of the scattering offset method is that the detection wave excites an electric polarization vector in the direction opposite to that of an inner layer target in an outer layer stealth medium, so that the scattering capacity of the target is reduced on the whole, and omnidirectional stealth is realized. Particularly, when the relative dielectric constant of the target is less than 0 or is a perfect electric conductor, the relative dielectric constant of the outer layer stealth medium should be 0-1. The basic principle of the Kerker effect is to suppress scattering in a particular direction by altering the electric or magnetic components of each order in the scattered field of the target. For example, electric dipole scattering and magnetic dipole scattering or electric quadrupole scattering constructive interference may achieve back stealth, and electric dipole scattering and magnetic dipole scattering destructive interference may achieve forward stealth. Fano resonance is a phenomenon in which continuous and discrete local states interfere to form asymmetric scattering. For a nanoshell structure, interference of dipole resonances at the inner and outer surfaces or interference of dipoles and quadrupole resonances at the outer surface results in a fanno minima, i.e., a minimum of scattering.
In the latter case, in recent years, researchers successfully popularize the local plasmon theory in the plasmon science to the field of gas discharge plasma, and the small electric dipole antenna is coated by the sub-wavelength plasma thin layer near field, so that the omnidirectional enhancement of the radiation capability of the small electric dipole antenna is realized in the MHz-GHz frequency band. The successful practice of the sub-wavelength plasma modulation enhanced microwave electromagnetic radiation technology provides a new research idea for solving the communication bottleneck problem in the plasma stealth technology.
Around this idea, "a device for enhancing electromagnetic radiation of a miniaturized omnidirectional antenna by using plasma modulation" disclosed in patent application No. CN201610356451.8 utilizes a single-layer plasma to coat the miniaturized omnidirectional antenna, so as to solve the problems that the conventional metal conductor antenna cannot achieve high gain and miniaturization at the same time, and the plasma antenna has low gain and high noise. In addition, the device can realize a stealth function due to the absorption and scattering effects of the plasma on the detection wave. However, the patent does not give specific conditions to be met by plasma size, density, and collision frequency when enhancement is achieved. In addition, for communication enhancement, a large number of experiments and numerical simulation studies show that the enhancement is achieved under the conditions that the plasma frequency is greater than the angular frequency of the communication wave and the absorption of electromagnetic waves by the plasma is weak. When the absorption of the plasma on the probe wave is strong, although the radar scattering cross section of the system can be reduced to realize stealth of the absorption type plasma, the enhancement effect is also deteriorated. For stealth, when the size of the system is far smaller than the wavelength of the detection wave, the condition for realizing stealth is that the angular frequency of the detection wave is larger than the frequency of plasma according to the theory related to the scattering offset method; when the size of the system is close to or larger than the wavelength of the detection wave, the scattering type stealth is realized on the premise that the frequency of the detection wave is far larger than that of the communication wave and the plasma has a certain density gradient. In general, the premise of this patent for achieving both stealth and communication enhancement is that the absorption of electromagnetic waves by the plasma is not strong and the frequency of the probe wave is greater than that of the communication wave.
The 'signal enhancement type plasma stealth antenna window' disclosed in the patent with the application number of CN201910678454.7 adopts a structure that double-layer plasma covers an electric small dipole antenna for the first time, and realizes the synergistic effect of stealth and communication enhancement, wherein the outer plasma cover with low density and low collision frequency is used for reducing the radar scattering cross section of the antenna window, and the inner plasma cover with high density and low collision frequency is used for enhancing communication signals. In 2020, Chen et al analyzed the physical mechanism of the synergistic effect of stealth and communication enhancement achieved by the double-layer plasma structure under the combination of 0.6GHz probe wave and 1GHz communication wave, and further extended the synergistic effect to other probe wave and communication wave combinations. However, in general, there are three problems with such a double layer plasma structure:
(1) existing bilayer plasma embodiments typically coat the high density inner plasma with a low density outer plasma. Essentially, the principle of stealth of the low-density outer layer plasma to the high-density inner layer plasma is a scattering offset method. The method is suitable for the synergistic effect of stealth and communication enhancement under the condition that the frequency of the detection wave is less than that of the communication wave. When the frequency of the detection wave is greater than or equal to the frequency of the communication wave, the density of the outer-layer plasma needs to be further improved, the reduction effect of the outer-layer plasma on the dominant enhancement effect of the inner-layer plasma is stronger, and the plasma hybridization theory shows that the optimal enhancement frequency point in the double-layer structure has larger deviation relative to the situation of only inner-layer effect, which is not beneficial to realizing better stealth and communication enhancement synergistic effect, especially the synergistic effect under the condition of given communication wave and detection wave frequency;
(2) the existing double-layer plasma structure adopts a simultaneous excitation mode, two sets of corresponding power supplies and matching equipment are generally needed, the system is complex and heavy, and the overall performance of the movable communication equipment can be seriously influenced;
(3) when two sets of plasma sources work simultaneously, the plasma parameters are difficult to accurately regulate due to possible interference between the two sets of plasma sources.
In summary, the current solutions for realizing the synergistic effect of stealth and communication enhancement based on plasma are limited to a certain combination of frequency of communication waves and detection waves, and a more general plasma structure and parameter design solution for realizing both stealth and communication enhancement is lacking.
Disclosure of Invention
The invention aims to solve the problems that when two sets of plasma sources in the existing plasma stealth and enhancement device work simultaneously, the plasma parameters are difficult to accurately regulate and control due to possible interference between the two sets of plasma sources, and provides an enhanced electrically small antenna with a stealth function.
The invention discloses an enhanced electric small antenna with a stealth function, which comprises an outer-layer plasma cover, an inner-layer plasma cover and an electric small dipole antenna;
the outer layer plasma cover is a spherical shell-shaped plasma cover formed by outer layer plasma, and the density and collision frequency of the outer layer plasma in the outer layer plasma cover are uniformly distributed;
the inner layer plasma cover is a spherical shell-shaped plasma cover formed by inner layer plasmas, and the density and collision frequency of the inner layer plasmas in the inner layer plasma cover are uniformly distributed;
the inner plasma cover is arranged inside the outer plasma cover;
the electric small dipole antenna is spherical, is concentrically arranged inside the inner layer plasma cover, and has no gap between the electric small dipole antenna and the inner layer plasma cover.
Further, a gap is formed between the inner plasma cover and the outer plasma cover.
Further, the outer plasma cover is eccentrically arranged with respect to the inner plasma cover.
Furthermore, the device also comprises a power supply, an outer layer plasma generating device and an inner layer plasma generating device;
the outer layer plasma generating device is used for generating an outer layer plasma cover;
inner plasma generating means for generating an inner plasma cover;
and the power supply is simultaneously connected with the outer layer plasma generating device and the inner layer plasma generating device and used for exciting the outer layer plasma generating device and the inner layer plasma generating device at different times, so that the inner layer plasma cover is closed when the outer layer plasma cover is opened, and the outer layer plasma cover is closed when the inner layer plasma cover is opened.
Further, the radius of the electrically small dipole antenna is r0And r is0Satisfy r0×2π/λ1<0.5；
Wherein λ is1Wavelength lambda of communication signal radiated by electrically small dipole antenna1＝2πc/ω1，ω1The angular frequency of the communication signal radiated by the electrically small dipole antenna, and c the propagation speed of light in vacuum.
Further, when the inner plasma cover is opened, the parameters of the inner plasma in the inner plasma cover should satisfy the following conditions:
Figure BDA0003101118280000031
wherein, ω isinIs the inner plasma frequency, dinIs the thickness of the inner plasma cover, vinIs the collision frequency, n, of the inner plasmainIs the density of the inner plasma, epsilon0Is a dielectric constant in vacuum, meFor electron mass, e represents the amount of elementary charge.
Further, when the outer plasma cover is opened, the parameters of the outer plasma in the outer plasma cover should satisfy the following conditions for realizing the omnidirectional enhancement of the communication signals:
Figure BDA0003101118280000041
wherein r isinAnd routRespectively the inner and outer diameters of the outer plasma body cover, voutIs the collision frequency, omega, of the sheath plasmaoutThe outer plasma frequency; omegaout1For the outer plasma frequency corresponding to the high-energy level first-order hybridization of the communication signal formed on the outer plasma cover, the expression is as follows:
Figure BDA0003101118280000042
further, when the outer plasma cover is opened, the parameters of the outer plasma in the outer plasma cover should satisfy the following conditions for realizing the omnidirectional enhancement of the communication signal:
Figure BDA0003101118280000043
wherein, ω isout2For the outer plasma frequency corresponding to the low-level first-order hybridization of the communication signal formed on the outer plasma cover, the expression is as follows:
Figure BDA0003101118280000044
further, the parameters of the outer plasma in the outer plasma cover should meet the following conditions for realizing omnidirectional stealth based on dipole-dipole Fano resonance; :
Figure BDA0003101118280000045
or
Figure BDA0003101118280000046
Wherein, ω is2For detecting the angular frequency of the wave, and omegain/ω2>1；k1And k2Is a constant with a value range of k being more than or equal to 0.051≤0.2，0.05≤k2≤0.5；noutIs the density of the sheath plasma; omegaout3The frequency of the outer plasma corresponding to the high-energy first-order hybridization formed on the outer plasma cover by the probe wave is represented by the following formula:
Figure BDA0003101118280000051
further, the parameters of the outer plasma in the outer plasma cover should satisfy the following conditions for realizing the backward stealth based on dipole-quadrupole fanno resonance:
Figure BDA0003101118280000052
or
Figure BDA0003101118280000053
Wherein k is3Is constant and has a value range of k being more than or equal to 1.72≤1.9。
The beneficial effects of the invention are:
(1) the frequency combination range of the detection wave and the communication wave, which can realize the synergistic effect of stealth and communication enhancement, is widened, namely the frequency of the detection wave can be smaller than the frequency of the communication wave and can be larger than or equal to the frequency of the communication wave;
(2) compared with the existing double-layer plasma structure, the inner-layer plasma and the outer-layer plasma adopt a staggered excitation mode, and can be realized only by one set of power supply and matching equipment, so that the overall structure and the weight of the system are effectively optimized, and the plasma parameters can be more favorably and accurately regulated and controlled.
Drawings
Fig. 1 is a schematic cross-sectional view of an enhanced electrically small antenna with a stealth function according to the present invention.
Detailed Description
The first specific embodiment aims to solve the communication bottleneck problem in the stealth technology of the plasma, and provides a more general design method of a plasma generation device capable of simultaneously realizing stealth and communication enhancement based on the franco resonance and plasma hybridization theory from the viewpoints of dynamic adjustability of the plasma and time sequence difference of detection/communication waves.
The enhanced electric small antenna with the stealth function can simultaneously realize stealth and communication enhancement and comprises a spherical shell type outer plasma cover, a spherical shell type inner plasma cover and a spherical electric small dipole antenna.
The inner layer plasma cover 2 is positioned in the outer layer plasma cover 1, and the center of the inner layer plasma cover 2 and the center of the outer layer plasma cover 1 can be superposed or in an eccentric state;
the spherical electric small dipole antenna 3 is coaxially nested with the inner plasma cover 2, and the spherical electric small dipole antenna 3 is not clearance with the inner plasma cover 2.
The plasma density and the collision frequency in the inner layer plasma cover and the outer layer plasma cover are uniformly distributed.
When the stealth is not needed, only the inner layer plasma is started, and the radiation signal of the small dipole antenna is enhanced through the inner layer plasma; when the stealth is needed, the inner layer plasma is closed, the outer layer plasma is opened, on one hand, the enhancement effect on the radiation signal of the electric small dipole antenna is kept, and on the other hand, compared with the situation that only the inner layer plasma is opened, the radar scattering cross section of the system under the detection wave is reduced.
And designing parameters of the inner and outer plasma covers according to the actual frequency of the communication wave and the detection wave. The specific method is that the angular frequency of the communication signal radiated by the electric small dipole antenna is set to be omega1Wavelength λ1＝2πc/ω1Angular frequency of probe wave is omega2Wavelength λ2＝2πc/ω2Where c is the propagation speed of light in vacuum. Let radius of spherical electric small dipole antenna be r0And r is0Satisfy r0×2π/λ1<0.5。
When only the inner layer plasma is started, in order to ensure that the enhancement effect of the inner layer plasma on the communication signals radiated by the electric small dipole antenna is more than 10dB, the parameters of the inner layer plasma satisfy the formula (1-1) -1-4
1<ωin/ω1≤2.5 (1-1)
0<din/λ1≤0.1 (1-2)
νin/ω1≤0.1 (1-3)
nin＝ωin 2ε0me/e2 (1-4)
Wherein, ω isinIs the inner plasma frequency, dinIs the thickness of the inner layer plasma,νinfor the inner plasma collision frequency, ninIs the inner plasma density epsilon0Denotes the dielectric constant in vacuum, meRepresents the electron mass and e represents the amount of elementary charge.
When only the outer layer plasma is started, on one hand, in order to enable the outer layer plasma to omnidirectionally increase communication signals radiated by the small dipole antenna, the plasma hybridization theory shows that the size, the collision frequency and the frequency of the outer layer plasma satisfy the formulas (1-6) - (1-8) - (1-9) or (1-10)
rin≥din+r0 (1-6)
(rout-rin)/λ1≤0.06 (1-7)
νout/ω1≤0.1 (1-8)
-0.1≤(ωout1-ωout)/ω1≤0.1 (1-9)
-0.2≤(ωout2-ωout)/ω1≤0.2 (1-10)
Wherein r isinAnd routRepresents the inner and outer diameters of the outer plasma spherical shell, voutRepresenting the collision frequency, ω, of the sheath plasmaoutIs the sheath plasma frequency, omegaout1And omegaout2Respectively represents the outer plasma frequency corresponding to the first-order hybridization of high and low energy levels formed by the communication wave on the outer plasma spherical shell, and the expressions of the two are respectively
Figure BDA0003101118280000071
Figure BDA0003101118280000072
On the other hand, in order to reduce the radar scattering cross section of the entire system, the probe wave angular frequency should satisfy the formula (1-13) as compared with the case where only the inner plasma is turned on
ωin/ω2>1 (1-13)
On this basis, two cases need to be discussed.
The first case is to realize omnidirectional stealth by means of dipole-dipole Fano resonance, and considering that the stealth is realized and the enhancement effect of outer plasma on an electric small dipole antenna needs to be ensured, the frequency of the outer plasma needs to satisfy the formulas (1-14) and (1-15)
-0.2≤(ωout3-ωout1)/ω1≤0.1 (1-14)
ωout＝ωout3+k1ω2 (1-15)
Or formulae (1-16) and (1-17)
-0.5≤(ωout3-ωout1)/ω1≤0.1 (1-16)
ωout＝ωout3+k2ω2 (1-17)
Wherein k is1And k2Is a constant with a value range of k being more than or equal to 0.051≤0.2，0.05≤k2≤0.5，ωout3The corresponding outer plasma frequency of the detection wave during high-energy level first-order hybridization formed on the outer plasma spherical shell is expressed by the formula
Figure BDA0003101118280000073
The above equations (1-14) and (1-15) or the equations (1-16) and (1-17) can be also independently implemented only for realizing the omnidirectional stealth by means of dipole-dipole fano resonance without having to be implemented simultaneously with the function of the outer plasma to omnidirectionally enhance the communication signal radiated from the electric small dipole antenna.
The second case is to realize the back stealth by means of dipole-quadrupole Fano resonance, and considering that the stealth is realized and the enhancement effect of the outer plasma on the electric small dipole antenna needs to be ensured, the size and the frequency of the outer plasma need to satisfy the formulas (1-9) or (1-10) and (1-19) and (1-20)
0.13≤rout/λ2R is less than or equal to 0.2 or less than or equal to 0.13in/λ2≤0.2 (1-19)
ωout＝k3ω2 (1-20)
Wherein k is3Is constant and has a value range of k being more than or equal to 1.72≤1.9。
The above equations (1-19) and (1-20) can be also separated, and are only used for realizing the omnidirectional stealth by means of dipole-dipole Fano resonance without simultaneously realizing the communication signal function capable of omnidirectionally increasing the radiation of the electric small dipole antenna by the outer plasma.
Knowing the sheath plasma frequency, the sheath plasma density n can be determined by the equation (1-21)out
nout＝ωout 2ε0me/e2 (1-21)
First preferred embodiment, this embodiment is further described as the first embodiment, and the enhanced electric small antenna with stealth function in this embodiment is a device capable of simultaneously realizing stealth and communication enhancement based on the carnot resonance and plasma hybrid effect, and includes an inner and an outer 2 spherical shell type plasma shells and a spherical electric small dipole antenna.
The outer layer plasma cover 1 and the inner layer plasma cover 2 are coaxially nested, and the inner layer plasma cover is tightly contacted with the spherical small electric dipole antenna 3 without a gap.
The frequency of the detection wave is 0.9GHz, the frequency of the communication wave is 1GHz, and the radius r of the spherical electric small dipole antenna00.6cm, inner layer plasma thickness din＝1cm，νin0.1GHz, inner and outer diameters r of outer layer plasmainAnd routRespectively 1.6cm and 2.1cm, vout＝0.1GHz。
When the stealth is not needed, only the inner layer plasma is started to make the density of the inner layer plasma nin＝3.66×1016m-3(ωin/ω11.72) at which the radiation gain of the electrically small dipole antenna is 28.815dB compared to the case without the plasma coating. In addition, when only the inner layer plasma is started, the back, the front and the space average radar scattering cross sections of the system are-31.995 dBsm, -31.968dBsm, -34.639dBsm respectively.
When needing to be hidden, the inner layer plasma is closed, the outer layer plasma is opened, the frequency of the detection wave, the frequency of the communication wave and the size of the outer layer plasma are known, and omega can be obtainedout1＝1.08×2πGHz，ωout2＝2.63×2πGHz，ωout30.97 × 2 π GHz. At this time due to (omega)out3-ωout1)/ω1When the formula (1-14) is satisfied, the system can realize omnidirectional stealth and omnidirectional enhancement. The actual outer layer plasma frequency and density are respectively taken as omega from the formulas (1-15) and (1-21)out＝1.13×2πGHz，nout＝1.58×1016m-3. At this time, compared with the case without plasma coating, the radiation gain of the electrically small dipole antenna is 14.84 dB; the back, forward and space average radar scattering cross sections of the system were-48.727 dBsm, -46.851dBsm, -50.202dBsm, respectively. Compared with the case of only inner layer plasma coating, the scattering cross sections of the back, front and space radar are respectively reduced by 16.732dBsm, 14.833dBsm and 15.563 dBsm.
A second preferred embodiment is a further description of the first embodiment, and the enhanced electric small antenna with stealth function in this embodiment is a device capable of simultaneously realizing stealth and communication enhancement based on the fano resonance and plasma hybridization effect, and includes an inner and an outer 2 dome-shaped plasma covers and a spherical electric small dipole antenna.
The outer plasma cover 1 and the inner plasma cover 2 are coaxially nested, and the inner plasma cover is tightly contacted with the spherical electric small dipole antenna 3 without gaps.
The frequency of the detection wave is 1GHz, the frequency of the communication wave is 1GHz, and the radius r of the spherical electric small dipole antenna00.6cm, inner layer plasma thickness din＝1cm，νin0.1GHz, inner and outer diameters r of outer layer plasmainAnd rout1.6cm and 2, respectively.1cm，νout＝0.1GHz。
When the stealth is not needed, only the inner plasma is started to ensure that the density of the inner plasma is nin＝3.66×1016m-3(ωin/ω11.72) at which the radiation gain of the electrically small dipole antenna is 28.815dB compared to the case without the plasma coating. In addition, when only the inner layer plasma is started, the back, the front and the space average radar scattering cross sections of the system are-19.845 dBsm, -19.816dBsm, -22.497dBsm respectively.
When needing to be hidden, the inner layer plasma is closed, the outer layer plasma is opened, the frequency of the detection wave, the frequency of the communication wave and the size of the outer layer plasma are known, and omega can be obtainedout1＝1.08×2πGHz，ωout2＝2.63×2πGHz，ωout31.08 × 2 pi GHz. At this time, the (omega) isout3-ωout1)/ω1If 0 satisfies equation (1-14), the system can achieve omnidirectional stealth and omnidirectional enhancement. The actual outer layer plasma frequency and density are respectively omega from the formulas (1-15) and (1-21)out＝1.13×2πGHz，nout＝1.58×1016m-3. At this time, compared with the case without plasma coating, the radiation gain of the electrically small dipole antenna is 14.84 dB; the back radar cross section, the front radar cross section and the space average radar cross section of the system are respectively-28.563 dBsm, -28.065dBsm, -30.983 dBsm. Compared with the case of only inner layer plasma coating, the scattering cross sections of the back, front and space radar are respectively reduced by 8.718dBsm, 8.249dBsm and 8.486 dBsm.
A third preferred embodiment is a further description of the first embodiment, and the enhanced electrically small antenna with a stealth function in this embodiment is a device capable of simultaneously realizing stealth and communication enhancement based on the franco resonance and plasma hybridization effects, and includes an inner and an outer 2 spherical plasma covers and a spherical electrically small dipole antenna.
The outer plasma cover 1 and the inner plasma cover 2 are coaxially nested, and the inner plasma cover is tightly contacted with the spherical electric small dipole antenna 3 without gaps.
Detection ofThe wave frequency is 1.5GHz, the communication wave frequency is 1GHz, and the radius r of the spherical electric small dipole antenna00.6cm, inner layer plasma thickness din＝1cm，νin0.1GHz, inner and outer diameters r of outer layer plasmainAnd routRespectively 1.6cm and 2.6cm, vout＝0.1GHz。
When the stealth is not needed, only the inner layer plasma is started to make the density of the inner layer plasma nin＝3.66×1016m-3(ωin/ω11.72) at which the radiation gain of the electrically small dipole antenna is 28.815dB compared to the case without the plasma coating. In addition, the back, forward and space averaged radar cross sections of the system were-40.253 dBsm, -39.462dBsm, -42.531dBsm, respectively, with the inner plasma.
When needing to be hidden, the inner layer plasma is closed, the outer layer plasma is opened, the frequency of the detection wave, the frequency of the communication wave and the size of the outer layer plasma are known, and omega can be obtainedout1＝1.13×2πGHz，ωout2＝2.14×2πGHz，ωout31.69 × 2 π GHz. At this time, the (omega) isout3-ωout2)/ω1When the formula (1-16) is satisfied, the system can realize omnidirectional stealth and omnidirectional enhancement. The actual outer layer plasma frequency and density are respectively omega from the formulas (1-17) and (1-21)out＝1.98×2πGHz，nout＝4.86×1016m-3. At this time, compared with the case without plasma coating, the radiation gain of the electrically small dipole antenna is 13.182 dB; the back, forward and space average radar scattering cross sections of the system were-50.004 dBsm, -43.518dBsm, -49.053dBsm, respectively. Compared with the case of only inner layer plasma cladding, the scattering cross sections of the back radar, the front radar and the space radar are respectively reduced by 9.751dBsm, 4.056dBsm and 6.522 dBsm.
A fourth preferred embodiment is a further description of the first embodiment, and the enhanced electrically small antenna with a stealth function in this embodiment is a device capable of simultaneously realizing stealth and communication enhancement based on the franco resonance and plasma hybridization effects, and includes an inner and an outer 2 spherical plasma covers and a spherical electrically small dipole antenna.
The outer layer plasma cover 1 and the inner layer plasma cover 2 are coaxially nested, and the inner layer plasma cover is tightly contacted with the spherical small electric dipole antenna 3 without a gap.
The frequency of the detection wave is 1.5GHz, the frequency of the communication wave is 1GHz, and the radius r of the spherical electric small dipole antenna00.6cm, inner layer plasma thickness din＝1cm，νin0.1GHz, inner and outer diameter r of outer plasmainAnd routRespectively 1.6cm and 2.6cm, vout＝0.1GHz。
When the stealth is not needed, only the inner layer plasma is started to make the density of the inner layer plasma nin＝3.66×1016m-3(ωin/ω11.72) at which the radiation gain of the electrically small dipole antenna is 28.815dB compared to the case without the plasma coating. In addition, the back, forward and space averaged radar cross sections of the system were-40.253 dBsm, -39.462dBsm, -42.531dBsm, respectively, with the inner plasma.
When the stealth is needed, the inner layer plasma is closed, and the outer layer plasma is opened, because of rout/λ2When 0.13 satisfies the formula (1-19), a back-to-back stealth can be achieved by the second stealth method. Get omegaout＝1.8ω2Then, the sheath plasma density n can be calculated from the equation (1-21)out＝9.04×1016m-3. Compared with the case without plasma coating, the radiation gain of the electric small dipole antenna is 12.56 dB; the back, front and space average radar cross sections of the system are-57.552 dBsm, -19.55dBsm, -27.914dBsm respectively. The backscatter radar cross section is reduced by 17.299dBsm compared to the inner plasma cladding alone.

Claims (6)

1. An enhanced electric small antenna with a stealth function is characterized by comprising an outer-layer plasma cover (1), an inner-layer plasma cover (2) and an electric small dipole antenna (3);
the outer layer plasma cover (1) is a spherical shell-shaped plasma cover formed by outer layer plasma, and the density and collision frequency of the outer layer plasma in the outer layer plasma cover (1) are uniformly distributed;
the inner layer plasma cover (2) is a spherical shell-shaped plasma cover formed by inner layer plasmas, and the density and collision frequency of the inner layer plasmas in the inner layer plasma cover (2) are uniformly distributed;
the inner layer plasma cover (2) is arranged inside the outer layer plasma cover (1);
the electric small dipole antenna (3) is spherical, the electric small dipole antenna (3) is concentrically arranged in the inner layer plasma cover (2), and no gap exists between the electric small dipole antenna (3) and the inner layer plasma cover (2);
when the outer layer plasma cover (1) is opened, the inner layer plasma cover (2) is closed, and when the inner layer plasma cover (2) is opened, the outer layer plasma cover (1) is closed;
when the outer plasma cover (1) is opened, the parameters of the outer plasma in the outer plasma cover (1) meet the following conditions for realizing the omnidirectional enhancement of communication signals:
Figure FDA0003605645430000011
wherein r isinAnd routRespectively the inner diameter and the outer diameter of the outer plasma cover (1), voutIs the collision frequency, omega, of the sheath plasmaoutThe outer plasma frequency; d is a radical ofinThe radius of the electrically small dipole antenna (3) is r which is the thickness of the inner plasma cover (2)0，λ1Wavelength lambda of a communication signal radiated by an electrically small dipole antenna (3)1＝2πc/ω1，ω1The angular frequency of the communication signal radiated by the electrically small dipole antenna (3), c the propagation speed of light in vacuum, omegaout1The frequency of the outer plasma corresponding to the high-energy-level first-order hybrid formed on the outer plasma cover (1) by communication signals is expressed as follows:
Figure FDA0003605645430000012
when the outer plasma cover (1) is opened, the parameters of the outer plasma in the outer plasma cover (1) meet the following conditions for realizing the omnidirectional enhancement of communication signals:
Figure FDA0003605645430000013
wherein, ω isout2For the outer plasma frequency corresponding to the low-level first-order hybridization of communication signals formed on the outer plasma cover (1), the expression is as follows:
Figure FDA0003605645430000021
the parameters of the outer plasma in the outer plasma cover (1) meet the following conditions for realizing omnidirectional stealth based on dipole-dipole Fano resonance:
Figure FDA0003605645430000022
or
Figure FDA0003605645430000023
Wherein, ω is2For detecting the angular frequency of the wave, and omegain/ω2>1；ωinIs the inner layer plasma frequency, epsilon0Is dielectric constant in vacuum, k1And k2Is a constant with a value range of k being more than or equal to 0.051≤0.2，0.05≤k2≤0.5；noutIs the density of the outer plasma; m is a unit ofeE represents the amount of elementary charge, being the electron mass; omegaout3Represents the outer layer plasma corresponding to the high-energy level first-order hybridization formed by the detection wave on the outer layer plasma cover (1)The body frequency, expressed as:
Figure FDA0003605645430000024
parameters of the outer plasma in the outer plasma cover (1) meet the following conditions for realizing the backward stealth based on dipole-quadrupole Fano resonance:
Figure FDA0003605645430000025
or
Figure FDA0003605645430000026
Wherein the wavelength λ of the probe wave2＝2πc/ω2，k3Is a constant with a value range of k being more than or equal to 1.73≤1.9。
2. An enhanced electrically small antenna with stealth functionality according to claim 1, characterised by a gap between the inner plasma-cover (2) and the outer plasma-cover (1).
3. An enhanced electrically small antenna with stealth functionality according to claim 2, characterised in that the outer plasma-cover (1) is placed off-centre from the inner plasma-cover (2).
4. An enhanced electrically small antenna with stealth function according to claim 1, 2 or 3, further comprising a power supply, an outer layer plasma generating device and an inner layer plasma generating device;
the outer layer plasma generating device is used for generating an outer layer plasma cover (1);
the inner layer plasma generating device is used for generating an inner layer plasma cover (2);
and the power supply is simultaneously connected with the outer layer plasma generating device and the inner layer plasma generating device and is used for exciting the outer layer plasma generating device and the inner layer plasma generating device in time staggered mode.
5. An enhanced stealth antenna as in claim 4, wherein r is0Satisfy r0×2π/λ1<0.5。
6. An enhanced electrically small antenna with stealth function according to claim 5, characterized in that when the inner plasma cover (2) is opened, the parameters of the inner plasma in the inner plasma cover (2) should satisfy the following conditions:
Figure FDA0003605645430000031
wherein, vinIs the collision frequency, n, of the inner plasmainIs the density of the inner plasma.
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