Integrated protection of special shielded rooms.

Vyacheslav Sergeevich Barsukov, Candidate of Technical Sciences

Source: «Special Equipment» magazine

The basis of the modern approach to information protection is ensuring physical protection, which is implemented, first of all, by means of restricting access and blocking physical leakage channels.

Moreover, the modern systemic approach to ensuring information protection predetermines the need to ensure environmental protection of service personnel and users.

Taking this into account, the article examines modern possibilities for creating integrated protection for special shielded rooms that simultaneously provide electromagnetic, acoustic and environmental safety.

As is known, scientific and technological progress develops in a spiral.

A person periodically turns to the same urgent unsolved problem, trying to solve it each time at a new, higher technological level.

A similar situation has arisen at present with the problem of passive protection of information, the solution of which is associated with the creation of effective electromagnetic screens based on new modern technologies and materials.

Recently, a new, dualistic approach has emerged in solving this problem, aimed at creating not only effective screens, but also environmentally friendly protected premises.

Constant improvement of special equipment stimulates the search for new, increasingly effective electromagnetic screens, including for protection against information leakage via technical channels from special protected rooms, in particular, rooms for processing encrypted information, rooms for conducting confidential negotiations, chambers for setting up and testing special equipment, etc.

Until now, the main requirement for all types of electromagnetic screens was to obtain the maximum possible attenuation coefficient of the electromagnetic wave at the exit from the screen material.

The passage of an electromagnetic wave through a shield in a protected shielded room is shown schematically in Fig. 1.

In general, assessing the effectiveness of shielding, taking into account real conditions, is a fairly complex task. However, in many cases, approximate expressions can be used for a preliminary assessment (see, for example, “Confident”, No. 6 — 99).

In this case, the effectiveness of shielding can be represented by the sum of the corresponding components:

E shield = E absorb + E reb + E int. reb,

where E absorb is the shielding efficiency due to energy absorption by the screen;

E refl is the shielding efficiency due to wave reflection by the screen;

E int. refl is the shielding efficiency due to multiple internal re-reflection of the wave from the screen surfaces.

However, for protected premises, taking into account modern requirements for environmental safety, the requirements for maximum possible shielding are clearly insufficient and it is necessary to present a second, no less important, requirement to ensure standardized attenuation of the reflected signal that is dangerous to personnel.

And under conditions of volume resonance of a shielded room, even small emissions at individual frequencies of the technical equipment used there can be amplified a thousand times and exceed the established standards that are safe for humans.

For example, for the microwave range, the level of radiation exposure above 10 μW/cm2 is dangerous for humans. It became possible to meet modern requirements for protected premises only after the appearance of new protective materials on the Russian market, a brief analysis of which is provided in the next section.

Overview of the Russian market

The research and production company FERRAT offers ferrite radio-absorbing coatings (RAC) of the Ferrylen and Ferrylar families.

The specified RPPs have high wave absorption characteristics in a wide range and are intended, first of all, for lining the inner surface of anechoic chambers (AEC) required for testing electrical and radio devices for electromagnetic compatibility.

However, the specified RPPs can also be used to create environmentally friendly protected premises.

When using RPPs “Ferrylen-1” and “Ferrylen-2”metal sheets with ferrite tiles glued to them (with dimensions of 60x60x6.5 mm and a weight of 33 kg/m2) are attached to the walls and ceiling of the BEC. The floor for measuring the electromagnetic waves emitted by the device being tested is made of metal, and when determining noise immunity, it is covered with RPP.

For a significant expansion of the frequency range, the RPP “Ferrilar-5” can be used, which is distinguished by the fact that several layers of radio-absorbing mats made of basalt fibers with a certain number of semiconducting threads are glued to the outer surface of the ferrite coating.

A thin white dielectric film is glued to the outer surface of the mats, which ensures comfort in the BEC and protects the dielectric coating from dust and possible damage. In this case, the thickness of the RPP increases to 170 mm, and the weight — to 38 kg/m2 (excluding the metal sheet).

Frequency dependence of the reflection coefficient of the RPP «Ferrylen-2″ and «Ferrylar-5″at normal incidence of a plane wave in the range from 30 to 1000 MHz is shown in Fig. 2, and for comparison in the same figure is shown the characteristics of a similar material from TDK (Japan).

A whole bunch of modern radio-absorbing coatings is offered on the Russian market by the company “Forpost-7”.

First of all, this is an ultra-wideband Ferrite-dielectric absorber of electromagnetic waves (FDEW), designed for cladding ceilings, walls, floors of universal anechoic chambers and shielded rooms that provide conditions for high-precision measurements of electronic equipment and antenna technology.

FDPEV meets the requirements of international standards IEC 801.3 and ANSI 63.4 for testing technical equipment for electromagnetic compatibility and is a three-layer product consisting of a metal substrate, ferrite and dielectric materials, connected into a prefabricated panel using glue.

The dielectric material is made of foam glass in the form of wedge-shaped matching elements. Structurally, FDPEVis a panel with mechanical fastening units to the ceiling and walls of the chamber, so if necessary, it can be dismantled without destroying the absorber.

FDPEV is an environmentally friendly absorber, does not emit harmful substances during operation, is stable in its radiotechnical characteristics (in the range from 0.03 to 40 GHz (!) the reflection coefficient changes from -12 to -40 dB), is resistant to high temperatures and open fire.

A distinctive feature of this radio-absorbing coating is the achievement of an optimal ratio of thickness and electrophysical properties of ferrite and dielectric materials.

A magnetic screen made of amorphous metal alloy (AMA) tapes is designed to shield constant and variable magnetic fields of electronic equipment, to manufacture protective clothing, curtains, protective curtains in office premises with increased electromagnetic field intensity, to create multilayer structures and volumes that shield the Earth's magnetic field.

It is a flexible sheet material of the “rogozhka” type with a plain weave, made of KNSR tapes, 850-1750 mm wide and 0.02-0.04 mm thick.

The length of the supplied material is not limited. The peculiarity of this material is that it provides a shielding efficiency 10 times greater than a permalloy screen of the same mass.

Shielding fabric with microwire is designed to reduce the level of electromagnetic radiation in domestic conditions by at least three times (from 10 dB). The fabric is made of cotton threads of plain weave.

As an active component, it contains a combined thread obtained by duplicating an amorphous ferromagnetic microwire in glass insulation with a cotton base thread. The fabric is used to make special curtains, drapes, and for sewing work clothes.

Heat, sound and radio insulation boards based on cellular concrete with carbon filler are intended for interior decoration of industrial and residential premises in order to reduce the harmful effects of thermal, sound and electromagnetic radiation on humans (see Table 1).

Table 1. Main characteristics of cellular concrete with carbon filler

Heat-sound-radio insulation boards based on foam glass with carbon filling are highly effective heat-sound insulation structural materials.

They do not burn, do not emit toxic substances during operation, are resistant to water and most chemical reagents, resistant to rot, microorganisms and rodents.

They are mainly used as sound- and radio-absorbing coatings for various types of objects and as thermal insulation.

In terms of the range of physical, technical and operational characteristics, they are not inferior to similar samples from foreign manufacturers.

Woven radio-absorbing material (WRM) is designed to absorb electromagnetic radiation energy. The material is used primarily to protect against microwave radiation, especially to combat reflections.

When used in a confined space, the material prevents standing waves. WRM is a flexible woven covering that can be attached either directly to the protected surface or in the form of curtains.

The covering material is non-flammable, stops burning when the open flame is removed, is resistant to moisture, fuels and lubricants and detergents, and does not emit harmful substances. The color and size of the material can be any (see Table 2).

Table 2. Main characteristics of TRM

The special radioprotective fabric “Vostok” is of particular interest., designed for shielding special rooms (negotiation rooms, rooms for preparing and processing confidential information, etc.) to protect against unauthorized information retrieval (radio bugs, PEMIN) in the frequency range from 1 to 2000 MHz.

The results of the study of the shielding efficiency of the protective fabric “Vostok” are presented in Table. 3.

Table 3. Frequency dependence of the attenuation of the Vostok radioprotective fabric.

The suppliers of the radioprotective fabric “Vostok” are the company “Progresstech” and the association “EVRAAS”.

Specialists from the Russian company “Tiko” have developed the protective paint “Tikolac”, coatings from which are capable of reliably protecting against the adverse effects of electromagnetic radiation in a wide frequency range from several hertz to tens of gigahertz.

If radiation at low frequencies is mainly reflected, then at high and microwave frequencies — most of it is absorbed, turning into heat due to the occurrence of eddy currents.

By changing the composition of the filler (it is a subject of know-how), it is possible to control the “reflection — absorption” ratio. One layer of “Tikolac” with a thickness of only 70 microns reduces the intensity of EMI by 3 — 3.5 times.

It is enough to apply the paint «Tikolac» to the internal or external surface of a building or structure — and you will receive a protective coating that reduces the penetrating power of electromagnetic radiation coming from external sources many times over, and absorbs electromagnetic waves from various devices located inside the premises.

In addition, this protective coating can reduce the impact of geomagnetic storms.

The paint retains its qualities at temperatures from -60 to +150 ° C, is moisture-resistant, and is not affected by sunlight.

The protective coating «Tikolac» can be applied to any finishing material: wallpaper, paint, lining, ceramic tiles, etc. The protective coating is applied to gypsum boards for internal partitions, chipboard panels, plywood, fiberboard, PVC wall panels, various insulation materials, etc. «Tikolac» is non-toxic, which is confirmed by the hygienic certificate of the Ministry of Health of the Russian Federation.

The scope of application of the new paint is very wide:

— creation of screens for protection against electromagnetic radiation;
— protection of residential and office buildings from the neighborhood power lines, radar installations, television, radio broadcasting and radiotelephone stations;
— protection against electrostatic charges in rooms and on the surface of equipment;
— interior treatment of cars;
— protection of structures from the effects of stray currents;
— creation of highly efficient low-voltage heating elements;
— anti-corrosion coating and sealing.

Paint consumption, depending on the purpose of use, is 200-400 g per square meter of surface. The protective paint «Tikolac» costs 50 US dollars per 1 kg (20 times less than foreign analogues). Since 1999, serial production of «Tikolac» paint has been established at one of the enterprises in Moscow.

The results of the comparative analysis of some of the radioprotective materials considered above are presented in Table 4.

Table 4. Comparative characteristics of modern protective materials

Special protected rooms

In order to effectively counteract unauthorized information retrieval using radio equipment from premises, technical communication lines and computer equipment, the company “Fortuna-Invest” has developed and offers a standard design for equipment for a special shielded room, which can be used as a room for confidential negotiations, an encryption booth, a communications hub and other special applications.

As is known, when using various embedded radio transmitting devices, as well as external radio-electronic devices for reading PC data or receiving reflected radio signals modulated by acoustic vibrations, an information leakage channel is formed.

Currently, the most reliable protection against leakage is provided by electromagnetic and acoustic screens.

An electromagnetic shield is usually made in the form of an electrically sealed steel metal case equipped with special filters for inputting electrical communications and providing shielding of electromagnetic waves up to 100 dB in the frequency range from 0.15 to 1500 MHz.

However, in ordinary shielded rooms of small volumes, due to re-reflections during operation of even weakly radiating equipment, for example, a personal computer at various frequencies, resonances arise that increase the intensity of the electromagnetic field emitted by the equipment up to 1000 times. P

in this case, the maximum permissible levels of exposure to electromagnetic radiation on people, especially microwave radiation, can be exceeded many times, amounting to 10 μW/cm2. In order to suppress the resulting resonances of the electromagnetic field, panels with a special radio-absorbing coating are installed in the room.

Depending on the operating frequency range of the equipment used, single-layer or multi-layer radio-absorbing coatings are used.

To ensure the required sound insulation, an acoustic screen is usually used, made of special vibration-absorbing and sound-insulating panels suitable for finishing the interior surfaces of office walls and other work spaces.

The main technical characteristics of such panels are given in Table 5.

Table 5. Main characteristics of acoustic panels

The analysis of the declared characteristics shows that the problem of creating environmentally safe protected premises is most effectively solved by using the above-mentioned “Ferrylar-5” radio-absorbing panels. In this case, the problems of electromagnetic and acoustic protection, as well as environmental safety of personnel, are solved simultaneously.

All materials used to construct the protected room are environmentally friendly and meet fire safety requirements. The structure (composition and sequence of layers) of the integrated protective panel is shown in Fig. 3

Fig. 3. Structure of the integrated panel for the protected room.

Of course, the potential technical characteristics of the protected room are determined mainly by the characteristics of the integrated panel.

However, the actual characteristics depend significantly on the quality of the work performed, among which the following can be noted:

— preparation of the interior surface of the room (walls, floor, ceiling) for the installation of an electromagnetic screen (ES);
— design and manufacture of ES;
— installation of fastening fittings for attachments;
— installation ES;
— manufacture and installation of the protective surface of the screen;
— output of electrical communications through electrostatic precipitators;
— preparation of the surface of shielded walls, floors and ceilings for finishing;
— installation of a ventilation system with a waveguide filter;
— installation of a shielded door.

It should be noted that full compliance with the requirements for environmental protection of personnel in a shielded room is quite an expensive undertaking. Therefore, in practice, cheaper intermediate options using, for example, protective paint, film, curtains, draperies, etc. are of some interest.

The choice of a specific option depends, to a certain extent, on the task at hand. For example, when using radiating devices in a protected room, environmental protection using the protective paint “Tikolac” discussed above is very effective.

We cannot fail to mention alternative options. An unusual solution to the problem of environmental protection of a person was found by a group of Moscow scientists.

They developed a device for protecting a person from energy anomalies “Gamma-7.N”, which is a broadband autoconverter of ultra-weak electromagnetic fields, operating from the energy of an environmental anomaly without using an additional power source.

In the absence of energy anomalies, the neutralizer is in a weakly active state from the natural fields of the Earth and surrounding objects.

When placed in the zone of an energy anomaly created by a technical device, the neutralizer automatically switches to a working state, generating a stable high-frequency field that counteracts the energy anomaly of the technical device.

The interaction of the radiation of the neutralizer and the anomalous radiation of the technical device leads to a weakening of the bio-effect of the latter by 30 — 100 times, thus reducing the impact of radiation from technical devices on the body.

This is how external radiation is neutralized.

Structurally, the neutralizer is made in the form of a multi-stage spiral made of a special alloy, laid out according to a certain ratio of axes.

The All-Russian Center for Disaster Medicine «Protection», based on the positive results of studies of the effect of the neutralizer «Gamma-7.N» on the state of the human body when exposed to electromagnetic radiation, recommended the neutralizer «Gamma-7» (modifications «Gamma-7.N», «Gamma-7.N-RT» and «Gamma-7.N-IZ») as a means of protecting humans from the negative effects of electromagnetic radiation.

The effectiveness of the neutralizer has been confirmed by the Research Institute of Occupational Medicine. The State Standard of Russia has approved its implementation.

Thus, at present, new materials have appeared on the Russian market for the creation of environmentally friendly stationary premises with a high level of protection. These materials are special broadband absorbers made in the form of ceramic plates and foam glass that prevent the penetration of electromagnetic field resonances in the frequency range from 30 to 40,000 (!) MHz.

Working in a room with such an absorber, even for a long time, is safe and comfortable for the user.

For simpler situations, you can use cheaper materials in the form of protective paint, film, tapes, fabric, etc.

The problem of creating environmentally safe protected premises is most effectively solved using integrated protective panels that provide electromagnetic, acoustic and environmental protection at the same time.