RU100338U1 - ELECTROMAGNETIC RADIATION PROTECTION DEVICE - Google Patents

Abstract

 A device for protection against electromagnetic radiation, which is a shielding structure, the cells of which are made in the form of transverse waveguides (ZPV), characterized in that it is supplemented by a multilayer carrier structure of the type "polymer-metal-polymer", inside which technological heterogeneities are made in the form of transverse rectangular waveguides forms combined into honeycomb lattices.

Description

The utility model relates to the field of protection against electromagnetic radiation (EMR) and can be used to protect electronic computers (EECS) both from external effects of electromagnetic radiation and in protection against spurious electromagnetic radiation and interference (PEMIN) EECS.

A utility model is known ("Multilayer electromagnetic screen", patent RU 85267 U1 Published: July 27, 2009), which is a multilayer electromagnetic screen containing two externally flat shielding layers, each of which is made of sheet soft magnetic isotropic steel, and placed between them, at least one volumetric shielding layer in the form of a rectangular steel grating made with the possibility of its cells functioning as transcendental waveguides with respect to the fundamental frequency harmonic raniruemogo field that allows for protection against low-frequency electromagnetic radiation.

The disadvantage of this utility model is the relatively low shielding coefficient of the electromagnetic screen and the functioning of this screen in the low-frequency region.

The closest in technical essence and the functions performed is the prototype device ("Device for electromagnetic shielding", patent RU 10973 U1 Published: 08.16.1999), which is a metal grid, the cells of which are made in the form of transcendental waveguides (CST) of a conical shape, which It allows protection against electromagnetic radiation in the frequency range from 10 MHz to 900 MHz, and can be used in various fields.

The disadvantage of this prototype device is the relatively low shielding coefficient of the electromagnetic screen and the operation of this screen in the frequency range from 10 MHz to 900 MHz.

The objective of the utility model is to increase the shielding coefficient and expand the frequency range due to the use of a multilayer screen structure, radio-absorbing polymer composite materials, technological inhomogeneities, made in the form of transcendent rectangular waveguides combined into cellular gratings.

This problem is solved in that the prototype device, which is a shielding structure, the cells of which are made in the form of transcendental waveguides (ZPV), according to the claimed utility model is supplemented by a multilayer carrier structure of the polymer-metal-polymer type, inside which technological heterogeneities are made in the form transcendental waveguides of a rectangular shape, combined in a cellular array.

The listed new set of essential features makes it possible to increase the shielding coefficient of the electromagnetic screen due to the use of a multilayer screen structure, radar absorbing polymer composite materials, and technological heterogeneities made in the form of transcendent rectangular waveguides combined into cellular gratings.

The analysis of the prior art made it possible to establish that analogues that are characterized by a set of features identical to all the features of the claimed technical solution are absent, which indicates the compliance of the claimed device with the patentability condition of "novelty". The "industrial applicability" of a utility model is due to the presence of an elemental base, on the basis of which devices that implement this utility model can be made.

The claimed utility model is illustrated by drawings, which show:

figure 1 - reflection and refraction of electromagnetic waves passing through the screen;

figure 2 is an embodiment of a device for protection against electromagnetic radiation;

The device operates as follows:

On the screen (Fig. 1) a plane electromagnetic wave is incident on one side. According to (Bogush V.F., Lynkov L.M., Electromagnetic radiation. Methods and means of protection. - Mn .: Bestprint, 2003. - p.119) shielding occurs due to the reflection of an electromagnetic wave from the surface of the screen and the attenuation of the refracted wave in the body of the screen . Let the vectors of the electric E ₁ and magnetic H ₁ fields of the incident plane wave P _{1 be} parallel to the plane of the screen. At point I ₁ , located at the interface between the air-polymer media, the wave P _{1 is} partially reflected (wave P _OT1 ) and partially refracted (wave P ₂ ). Propagating in the first layer of the screen, the refracted wave P ₂ decays exponentially and by the time the next interface between the polymer-metal media is reached, the intensities of both fields will be e ^{δecr / δ} times less than at a point on the screen surface (I _i , where δ _ecr is the wall thickness of the screen, and δ is the equivalent penetration depth. At the output of wave P ₂ from the first layer of the screen, point I ₂ , refraction (wave P ₃ ) and reflection (wave P _sp2 ) from the boundary of the polymer-metal media will again occur. The refracted wave P ₃ will enter the second layer of the screen, and the reflected P _sp2 will _attenuate, and at the point on the outer surface of this layer of the screen the field intensities will be e ^{δecr / δ} times less than at the entrance to the screen. The refracted wave P ₃ propagating in the second metallized layer of the screen also decays exponentially and by the time the next metal-polymer interface is reached, point I ₃ , the intensities of both fields will be e ^{δecr / δ} times less than at point I ₂ . At the output of wave P ₃ from the second layer of the screen, point I ₃ , refraction (wave P ₄ ) and reflection (wave P _sp3 ) from the metal-polymer media boundary occur again. The refracted wave P ₄ will enter the third layer of the screen, and the reflected P _sp3 will decay, and at the point on the outer surface of this metallized layer of the screen, the field strengths will be e ^{δecr / δ} times less than at the entrance to this layer of the screen. The refracted wave P ₄ also decays exponentially and by the time the next, last polymer – air interface is reached, point I ₄ , the intensities of both fields will be e ^{δecr / δ} times less than at point I ₃ . At the output of wave P ₄ from the third layer of the screen, point I ₄ , refraction (wave P ₅ ) and reflection (wave P _sp4 ) from the boundary of the polymer-air media will occur again. The reflected wave P _spr4 will _attenuate and at the point on the outer surface of this last layer of the screen, the field strengths will be e ^{δecr / δ} times less than at the entrance to this polymer layer. All this time, reflections of waves from the interfaces between the media to their complete attenuation in the body of the screen will occur on the screen. Refracted waves P ₅ will penetrate the screened space. Their total effect determines the field strengths E ₅ and H ₅ in this space. Moreover, all these processes are accompanied by loss of wave energy. The total screening coefficient is determined by the expression (Knyazev A.D., Design of electronic and electronic computing equipment taking into account electromagnetic compatibility. - M .: Radio and communications, 1989. - p. 45):

where η _neg - attenuation due to reflection;

η _swamp - attenuation due to absorption;

η _motr ^- attenuation due to multiple reflections;

To obtain the maximum shielding coefficient of a multilayer shielding structure, it is proposed to perform its technological inhomogeneities in the form of transverse rectangular waveguides (ZPV). This choice is justified by the fact that for certain ratios between the dimensions of the waveguide and the wavelength λ. electromagnetic field the possibility of its penetration into the screen is practically excluded. The transcendental waveguide with respect to the electromagnetic wave at the input behaves like a filter, which effectively attenuates oscillations at frequencies below a known limit, and to a much lesser extent attenuates oscillations at frequencies above this limit. A frequency below a known limit is called the critical frequency of the transcendental waveguide. and for a waveguide of a rectangular shape is determined by the following expression (Lebedev IV, Technique and devices microwave. - M .: Higher school, 1970. - p.31):

where m and n are indices indicating the number of half-waves along the x and y axis of the waveguide section;

λ _cr - critical wavelength;

µ ₀ is the magnetic constant;

ξ ₀ is the electric constant;

c is the speed of light;

The transcendental waveguide is directed to the inner, shielded region, so as not to create a local increase in the intensity of electromagnetic fields at its slice and thereby not to reduce its efficiency. To reduce the adverse effect of a large hole on the protective properties of the screens, it is replaced by a system of small holes, that is, essentially a honeycomb grill.

When modeling the structure that shields the effect of electromagnetic radiation, the restriction on the considered forms of technological heterogeneities was adopted above. Thus, the expression for determining the quality of shielding of such a design with technological heterogeneities in the form of rectangular waveguides combined in a honeycomb array is presented in the following form (Chernushenko, A.M., Designs of microwave devices and screens. - M .: Radio and communication, 1983 . - p. 145):

where A _M is an approximating factor determined on the basis of experimental data obtained during the tests, depending on the wavelength and characteristics of the EMP, is represented by the following expression (Chernushenko, A.M., Designs of microwave devices and screens. - M .: Radio and communication , 1983. - p. 156):

where γ is the normalizing factor, depending on the characteristics of the EMP, is determined using the following expression (Chernushenko, A. M., Designs of microwave devices and screens. - M .: Radio and communications, 1983. - p. 170):

where α is the EMR decay constant, and β is the current transfer coefficient. B _max [dB] - attenuation introduced by the waveguide, is represented by the following expression (Polonsky N. Design of electromagnetic screens for electronic equipment. - M .: Sov. Radio., 1979. - p.105);

where λ _min is the minimum wavelength in the spectrum of the acting EMR;

a is the cross-sectional area of the waveguide.

S is the attenuation introduced by the waveguide upon reflection, is determined using the following expression (Grigoriev, A.D., Yankevich V.B. Resonators and resonator slowdown microwave systems: numerical methods of calculation and design. - M .: Radio and communication, 1984. - p. 88):

where k is the radius of the near zone;

(Ohm) is the characteristic impedance of a waveguide for waves of type Hmn, is determined using the following expression (Baskakov S.I. Electrodynamics and propagation of radio waves.- M .: Higher School, 1992. - p. 172):

where z _c (Ohm) is the characteristic resistance of the medium, which is determined using the following expression (Baskakov S.I. Electrodynamics and propagation of radio waves.- M.: Higher School, 1992.

- the characteristic impedance of the waveguide for waves of type E _mn is determined using the following expression (Baskakov S.I. Electrodynamics and propagation of radio waves.- M.: Higher School, 1992. - p. 172):

G is the correction coefficient of reflection of the waveguide, depending on the change in the characteristic resistance of the medium filling the waveguide Z _c , and the characteristic resistance of the waveguide for waves of various types , and is determined using the following expression

(Fradin, A. 3. Antennas for microwave frequencies. - M.: Soviet Radio, 1957. - p. 480):

There is a mutual influence between the waveguides in the honeycomb structure. The interconnection between the waveguides leads to an increase in the total resistance of the entire screen, which entails an increase in the screening coefficient of the entire structure as a whole. The mutual influence of the waveguides on each other is taken into account using a correction coefficient determined using the following expression (Shabunin, S.N., Solovyanova I.P. Waveguides and volume resonators. - Yekaterinburg: Ural State Technical University, 1998. - p. 220):

Next, we calculate the number of technological heterogeneities in the form of transcendental waveguides of a rectangular shape based on the criterion screening coefficient (for example, we want to achieve a screening coefficient of at least 80 dB). The limit (criterion) value of the screening coefficient of a continuous multilayer screen is determined on the basis of the expression (Shapiro, D.N. Fundamentals of the theory of electromagnetic screening. - L.: Publishing House "Energy", 1975. - p. 68):

where V _Σeq - the equivalent amount of shielding, depending on the number and geometric dimensions of the layers that make up the screen;

v _eq is the equivalent volume of one waveguide of the honeycomb lattice;

N _B - the required number of transcendental waveguides in the honeycomb lattice of the shielding structure.

From the last expression, we obtain the correction factor for the number of waveguides in the honeycomb array to provide the required shielding quality, which is represented by the following expression:

Thus, the correction factor for the number of waveguides makes it possible to take into account the multilayer shielding structure by the presence in the denominator of the limiting value of the shielding coefficient η _{E (H) lim} [dB] of the continuous multilayer shielding structure, as well as by the equivalent volume, which depends on the geometric dimensions of the shielding structure and the thickness of its constituent layers.

The correction factor for the number of waveguides N _B determines the required number of transcendental waveguides in the honeycomb lattice of the shielding structure, depending on the limit (criteria) requirements for shielding quality, geometric dimensions and electrophysical properties used for shielding materials.

Having taken into account all the components for calculating the screening coefficient of a multilayer structure with technological heterogeneities in the form of transcendental waveguides, we obtain the following expression:

Using this expression in Mathcad, the following results were obtained:

Table 1 f [GHz] one 2 3 four 5 6 7 8 9 10 92 91.2 91 90.5 90 89.5 89 88 87 85

From table 1 it can be seen that the range of operation of the electromagnetic screen reaches 10 GHz and the screening coefficient of this screen is not lower than 85 dB.

The efficiency of the proposed utility model in comparison with the prototype device can be characterized by the ratio of the screening coefficient of the prototype device and the proposed model. We denote this relation by the letter _η . The prototype device ("Device for electromagnetic shielding", patent RU 10973 U1 Published: 08.16.1999) provides a shielding coefficient of up to 70 dB. Denote it by the η _prototype. The screening coefficient of the claimed utility model, calculated using expression 15 in the Mathcad environment with the following initial data:

- wavelength where f = 10 GHz;

- EMR decay constant α = 3.83 · 10 ⁸ , and current transfer coefficient β = 2.33 · 10 ⁹ , which implies that the approximating factor A _M = 1.707;

- the minimum wavelength λ _min = 3 m;

- screen dimensions: length A = 0.2 m, width B = 0.4 m, height H = 0.4 m;

- the cross-sectional area of the waveguide a = 0.006 m, and the length of the waveguide is equal to the length of the screen h = H = 0.2 m;

- magnetic permeability μ ₀ = 4π · 10 ^-7 GN / m, and the electric constant ξ ₀ = 8, 85418782 · 10 ^-12 F / m;

is 85 dB. Denote it by η of the _{utility model.} From here we get:

Claims (1)

A device for protection against electromagnetic radiation, which is a shielding structure, the cells of which are made in the form of transverse waveguides (ZPV), characterized in that it is supplemented by a multilayer carrier structure of the type "polymer-metal-polymer", inside which technological heterogeneities are made in the form of transverse rectangular waveguides forms combined into honeycomb lattices.