JPH04506283A - shielded personal computer - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] Shielded Personal Computer The present invention provides a shielded personal computer. For computers, i.e. (high frequency) electromagnetic (radio) radiation, i.e. "eavesdropping", The data is therefore shielded against the possibility of reading it by unauthorized third parties. personal computers, which also maintain mobility, i.e., portability. related.

Such computers are used not only in military applications, but also often in industrial development departments. It is said to be extremely important for use in fields that require confidentiality, which also applies to The reason is that it can be done by an unqualified person (via electromagnetic fields induced from a computer). or at least make such activities significantly more difficult. This is because it can be done.

The easiest way to shield your computer from eavesdropping is to The computer would be built into a Faraday cage. This will cause the computer to The space for installing the computer can be properly shielded. But that's because the computer It can only be used within this room, which means it can no longer be moved. So above, operating in such necessarily small and windowless shielded rooms. The working conditions for the ing.

Therefore, personal combicoaters in ordinary work rooms can be designed to prevent eavesdropping. However, if the shield is built into the computer itself, There is a demand for this to be done in such a way, and this method is Since the computer is movable, operators can work in a familiar workspace. It has yet another advantage.

In commercially available shielded personal computers, attenuation is applied to the electrical module. It is done more electronically. Such shielded components, also called radiation-stopping equipment, Computers are classified into four classes, with class 1 having the lowest shielding and class 4 having the lowest shielding. The highest or shielded grade is the most reliable.

However, these commercially available persons shielded according to Technology Management Association regulations Similarly, information converted during work is transferred outside the workroom, sometimes hundreds of times. ~The extent that it can be read illegally even from several hundred meters away using a special eavesdropping device It emits radiation of magnitude . Movements that are completely unreadable outside the workroom The formula device is not yet known.

Therefore, it is an object of the present invention to prevent unauthorized reading or listening of unprotected data. is so strongly electromagnetically sealed that it is practically impossible to tested personal computers, especially those with requirements of at least grade 4 according to the current definition. It is a personal computer that satisfies the requirements.

This is because the outer computer housing is made of a ferromagnetic material with high magnetic permeability. , all of its parts are copper-plated and additionally tinned, and this outer composite that the computer housing includes a second inner Faraday cage; This is achieved in that all the lead-in lines are designed as damped HF conduits. Ko Specifications of individual electronic components of computer hardware and system configuration. Additional design measures enhance the shielding effectiveness.

Due to the design, unavoidable openings in the housing as well as signal lines to the outside (device Unwanted signal emissions from the computer cables are reduced.

The overlap of the two Faraday cages provides sufficient overall damping for proper specifications. can get.

The attached adsorbent converts the field energy into heat. outer faradeke The field consists of a ferromagnetic material with high magnetic permeability, especially for the attenuation of the magnetic field component. pa - The use of malloy or dynamo board■ is not necessarily possible due to manufacturing technology, Components made from deep-drawn tin plate must be heat treated if necessary. All materials are copper plated to increase surface conductivity. Electricity to the inserted contact strip The housing members are further tinted to increase electrical contact, but it Provides an additional adsorption effect due to magnetic permeability.

Copper plating and tin plating shall be applied to all connections not sealed by contact strips. is important for the shielding of

As mentioned above, burn out the entire outer housing as well as the printer housing. Manufactured from reconstituted deep-drawn tinplate. inner housing i.e. computer The actual housing surrounding the is preferably made of electrical steel with a thickness of 1 mm.

All external connection signal lines are double shielded, but the inner shield is the outer shield is connected to the computer's surrounding housing. .

As a result, components connected via cables (signal lines) are placed in the box and shielded. Although they can be included in septs, these cable connections are a weak point.

For this reason, additional measures must be taken, namely proper wiring termination, leakage resistance between individual shields. suitable cables to avoid sheath waves (i.e. standing waves) in the cable as well as in the cable. cable length is required.

A typical personal computer consists of a computer unit (one housing). Chips on conductor sheet bars in microelectronics, mass storage devices and drives), keyboards, monitors (screens) and printers. Because the system is Bulls form critical radioactive cable connections that require special measures.

Information about the supply voltage lead-in lines (current cables) can be obtained by means of suitable filters. Separation from the transmitted signal can be achieved.

Openings for ventilation and cable entry as well as diskette and exchange plates. The openings for the signals are realized by waveguide-like cutouts, but they are physically Because of their size, they are used below the critical wavelength.

The shield is partially used for this special purpose of the shielded personal computer. Based on special application of known components for. Some are adapted for this special purpose. The target is newly designed parts, but the desired effect can be achieved by appropriate combination of these parts. Demonstrated.

Individual parts and measures are explained below for critical areas.

1. Radiation from the power supply line is sealed using a special line filter that is known per se. is coded.

2. Radiation from the printer, monitor, and keyboard lead wires should be removed from the housing. shielded by multi-screened data lines with special screw connections at It will be done.

3. Radiation from the ventilation holes is shielded by the use of honeycomb filters.

4. Radiation from openings for diskettes and exchange plates is New design seals the openings for diskettes and exchange plates as is coded.

5. Emissions through the main housing cover should be avoided using beryllium contact strips and screws. Shielded by a cover structure with less leakage.

6. The radiation of the system seat bar is preferably made of 1 mm thick electrolytic copper steel interior. Shielded by use of housing.

7. The radiation from the cathode ray tube of the monitor should be treated with a special plate with HF sealed gauze. more shielded.

8. Radiation from the printer's operation hole may cause the printer to stop when the cover is opened. more prevented.

Therefore, radiation suppression is first achieved by realizing a double Faraday cage . The outer cage provides protection for computers, printers, monitors and keyboards. Enclose all system components in the form of separate housings. At that time, The field lies in the common shield potential.

All electronic components are integrated into the outer housing in a potentially isolated and insulated manner. It is surrounded by a second Faraday cage. For that reason, the inside and outer shielding occur, but their shielding potentials are different from each other. ing.

The cable connections between the separate outer housings are double shielded circuits, but the inner The side cable shield is at the inner shielding potential and also the outer cable The shield is in the outer shield potential. Therefore, the double farade -cage not cleared by cable connection.

System overview Computer systems are usually coupled together by data cables (signal lines) It consists of four individual devices.

These four devices are ■, computer housing, and monitor housing. ■, Keyboard, ■, Printer housing.

Computers, monitors and printers must be equipped with appropriate HF filters. It has a power supply.

Power connections on computers, monitors and printers require HF signals from the power supply. With a normal room temperature equipment outlet equipped with an EMI filter to block out It will be done.

A special cover with HF conduit prevents the emission of radiation at the cable entry point. The zero ventilation hole is sealed with a honeycomb filter.

Radiation protection for individual components will be explained in detail below.

■、Computer The computer housing is fabricated from tempered deep drawn sheet steel. steel plate are copper plated and tinned for radiation reduction.

The housing has two large individuals, which are closed by a lid made of the same material. I'm being teased. These lids are screwed together multiple times during the folding process. Includes beryllium-copper contact strips to enhance contact. printer, model The connection cables to the monitor and keyboard are equipped with electrolytic copper HF conduit. It branches off from the housing via a fastening drawer section. The unused drawer section is It is sealed with an electrolytic copper plate approximately 1.5 mm thick. The cable drawer itself This is done by the well-known R+S HF plug-in connection. installed in all drawers that emit radiation. Calculations for HF conduit that can be There is.

Computer housing with line filter and cable exit ( The outer Faraday cage) contains the following slave housing:

a) Line filter housing (copper) b) CPU housing (copper) C) Mass storage housing with front plate (made of ordinary tin plate, but copper plated) and galvanized) d) Power supply housing (galvanized on both sides) Made of tin plate) e) Ventilation device f) Signal outlet (plug) for connecting data cables a) Line filter ·housing The line filter housing is made of a soldered copper plate (approximately 1 mm thick). , 'preferably electrical steel).

It is electrically conductive, HF-tight, and screws onto the computer's outer housing. It is. The line filter housing contains a special EMI filter. child EMI filters block HF signals that try to escape through the lines.

The principle of an EMI filter is known per se, but in this case, of course, a special Specifications are required. A conformally wound yoke provides common mode rejection. wife Therefore, the filter must be calculated for each size. important This is due to the location and physical out-of-spec of the parts. To avoid parasitic capacitance, The capacitor must be attached to the metal wall at certain points to ensure optimal attenuation. To obtain the capacitors for various types of line filter housings must be determined experimentally.

The back side of the line filter housing is equipped with a built-in fuse, which is known per se. A normal temperature outlet is installed.

b) CPU housing = Inner Faraday cage CPU housing is soldered It is made from a hardened copper plate (approximately 1 mm thick, preferably electrical steel). CPU The housing has a multi-screwed metal sealing lid that is serviceable. Can be removed for any purpose. Multiple screw fastenings are performed with calculated screw spacing. This is a connection method between the inner housing and the inner housing lid. In that case The same spacing is less than or equal to 172 critical wavelengths. CPU housing is CPU main seat It has a bar and an extension (insertion card) inserted into the bar. CPU housing The cable is insulated by six plastic spacers and attached to the computer's outer housing. is incorporated into the The signal line goes through the drawer on the housing wall to the CPU housing. These draw-outs are filled with HF-blocking foam. The tube protects against HF emissions. These lines are It leads to the connection plug (f) on the outer wall of the housing. HF conduit calculation As already mentioned, this will become clear from the examples given at the end of the description.

C) Mass storage housing with front plate Mass storage housing with front plate The housing is integrated into the computer housing from the front. mass storage device The housing includes a fixed plate, a diskette drive mechanism, and an exchange plate drive mechanism. It is included. The housing is made from copper-plated and tinned steel. The front plate is machined from a completely aluminum plate (preferably about 3 mm thick). It will be done.

The fixing plate is built into a module made of steel plate, and after the work is finished, the computer can be extracted from. The front plate of the module has a circumferential fold; It has a protrusion that attenuates radiation when pushed into the mass storage housing. It fits into the front plate of the engine.

The operating openings for the exchange plate and diskette drive mechanism are connected to the HF conduit. It is formed as follows. For calculations of HF conduit, as in the case below, please refer to this paper. We can use the example of the end of light.

The front panel has a key switch for the keyboard lock and power on switch, Built-in light emitting diode for running status and reset and load switch There is.

All entries and penetrations, e.g. light emitting diode holes, should be used as HF conduit. It is formed.

To improve contact, mass storage housings with front plates are attached to surrounding metal strips. more compressed. Due to the fixed screws or fastenings, this seal can be kept under high mechanical pressure. It is placed.

This metal strip is a commercial product consisting of conductive rubber and a copper-iron mixture. number k A pressure of g/- should be reached, for example with an M4 or M5 thread. Fixed is preferable.

d) Power supply housing The power supply housing is a sealed tin plate with galvanized on both sides. It is a keyboard housing. It consists of a switching power supply, a seat bar, and a heat exhaust ventilation system. including. The power supply housing is mounted on the CPU housing, i.e. it is inside is based on the shielding potential of Power supply housing and CPU housing The ohmic resistance at the point of contact between the It is also necessary to consider how to avoid such occurrences. By mounting directly on top of the It will be carried out where the water flows. Power supply housing to CPU housing By mounting directly on top, the circuit distance can also be minimized.

e) ventilation of the housing by means of ventilation devices; In order to ventilate the interior space, the outer housing of the computer has an opening.

These openings are protected against HF radiation by known honeycomb filters. It is.

Multiple built-in ventilation devices circulate internal air.

The heat of the CPU internal housing is exhausted to the outside by the exchanger principle.

f) Signal outlet (socket or plug) for connecting data cables Any conventional shielded socket or plug can be used here, but The filter between the socket and plug is the cable to the screen and printer. applied to.

■Monitor housing with line filter The monitor housing is commercially available. completely surrounds the monitor. fine mesh to observe the screen. A plastic plate with wire mesh inserted is used. This wire mesh is completely electrically conductive. and is combined with the monitor housing.

The wire mesh is made of an iron-steel alloy, and care must be taken to ensure good conductivity at the intersections of the individual wires. The mesh width must be determined from the critical wavelength, but is preferably 1 m. m or less.

The wire mesh should be tilted to the horizontal by 20° to 25°, especially 23°, so that color development is possible. Slanted. Such gauze netting made of nylon threads is known as contrast plate It is also used in X-ray technology. Until now such nets were white It was only available for black images. Only by tilting can a color-producing net be obtained. It will be done.

A line filter is used to filter the monitor's image information signal on the voltage supply line. used. One type of line filter is basically known. inner housing Because the monitor housing is not combined with the outer housing, two types of There is a quantity potential. The largest possible HF separation of the internal space is achieved. The line filter is mounted on the outside of the monitor housing, as shown in the figure. Individual Another housing part is made of a thin film which has been specially heat treated and is therefore magnetically significantly improved. Made of tin plate. For optimal attenuation of HF through the housing walls, tinplate The plates are copper plated and tinned. All housing parts are sealed They are screwed together using suzumetsuki. Housing member block The tin plate is improved by about 4 to 5 times over the ordinary tin plate by softening annealing.

But it is too soft transformer board or permalloy should not be too soft , by selecting a tin plate, the radioactive magnetic field or electric field due to the generation of a magnetic field is Further appearances can be prevented.

■, the printer housing with line filter is treated similarly and preferably The printer housing is made of copper-plated and tin-plated deep-drawn tin plate. , consisting of an upper plate and a lower plate. The top plate opens upward to operate the printer. be able to.

The EMI line filter is located on the rear wall of the printer housing in the inner housing. The flange-mounted individual housing members are preferably copper-plated or It is called and sparrowed. Shields also used in monitor housings The plastic plate here allows observation of the display elements of the printer.

As mentioned above, this plastic plate is also filled with fine wire mesh, but it is It is connected to the housing with a low ohm by a surrounding hold-down frame. Emissions from the housing To prevent radiation, a perimeter seal with beryllium-wire contact strips is provided. both The closing lever on the other hand ensures a high pressure against the sealing surface. mechanical and The contact strips making the electrical connection can be used, for example, in a mass storage housing with a front plate. It replaces the multiple screw fastenings used for joining.

The printer only works when the lid is closed. When the lid is opened, the printer Undesirable emissions may occur due to interruption of the mains voltage supply. I don't get it.

■、Keyboard The keyboard is built into an aluminum housing.

Keyboard keycaps are used for technical reasons, i.e. to prevent operator interaction. Further shielding is not possible due to necessity. Here, the HF shield is This is done through a special layout of keyboard logic. keyboard switch The operation of the plastic passes through a metal shield plate fitted through the seat bar. This is done by retraction. This shield plate is preferably made of aluminum with a thickness of 3 to 4 mm. It is said to be a mi board. Therefore, the drop-in wire itself forms an HF conduit.

■、Technical individual measures Signal line and data cable entry Every entry of the data line through the housing wall has several functions.

They connect the outer cable shield to the computer's outer shield potential. combine with the file. Additionally, they provide strain relief on the cable.

The entry tube is formed as an HF conduit, which further improves the HF sealing of the connection. be enhanced.

All parts of the wire entry section are made from high-grade electrical steel with sufficient hardness. outside c Contact to the housing is made by screws that also exert a high pressing force.

Housing ventilation For ventilation of the internal space, the outer housing of the computer has openings. child These openings are protected against the emission of HF radiation by honeycomb filters. There is. Such honeycomb filters are known in principle. In this example, silver A plated copper filter is used, which is inserted into a groove on the outer housing. entered. The size of the honeycomb filter is determined by the critical wavelength. This frame The thickness of the filter is approximately 2 an and the honeycomb is preferably e.g. 2.5 an. be fitted into the frame.

Because the outer surface of the housing is not homogeneous, damping in equipment is primarily due to the housing. depends on. That is, it can vary depending on the location of the housing. simple Testing can help determine what type of equipment is best suited.

For HF conduit calculations, the most unfavorable attenuation value is determined when considering the critical wavelength. Only the H1fl wave given is relevant (the H1o limit wavelength is affected by the width of the waveguide). ). For cable entry holes and ventilation grids, f > 2 GHz always holds true. Two.

Critical is the opening for the exchange plate and floppy disk. This is a consideration. For the exchange plate, the assumed waveguide is approximately 140/10 /Loomm (width/height/length).

abstract During use, unauthorized reading or capture of data outside the working area may actually occur. Shield your shielded portable personal computer to prevent damage. Ru. For this reason, the outer computer housing is made from a high permeability ferromagnetic material. The second inner Faraday cage was made by coating all the parts with copper and then coating with tin. This outer computer housing is inserted into a damped HF It is formed as a conduit.

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Claims (13)

[Claims] 1. Unauthorized reading or listening of data outside the normal working area is practically impossible. A shielded portable personal computer that is shielded so that it is impossible to Is the outer computer housing a ferromagnetic material with high magnetic permeability? all of its parts are copper plated and additionally plated with solute, and this outer the computer housing includes a second inner Faraday cage; , and a system characterized in that all the lead-in lines are formed as attenuated HF conduits. portable personal computer. 2. Claim 1, wherein the second inner Faraday cage is made of a copper plate. A shielded portable personal computer. 3. All outgoing and outgoing signal lines are double shielded and the inner shield is connected to the inner cage and the outer shield is connected to the computer's outer housing. and that all drop-in wires have screw connections at the housing. The cable is shielded by multi-shielded data lines. A shielded portable personal computer according to claim 1. 4. Ventilation cooling of the interior space is provided by at least one integrated ventilation device. The outer housing of the computer is protected by a honeycomb filter. Claim characterized in that the claim comprises a recess protected against the emission of HF radiation. The shielded portable personal computer according to item 1 or 2. 5. The front plate of the mass storage module has a circumferential fold, the fold being When inserted, the protrusion fits into the front plate of the mass storage device housing. mass storage housings with front plates are tightly packed with surrounding metal strips. sealed, and that the seal is placed under sufficiently high mechanical pressure by means of screw fixation. A shielded portable device according to any or several of the preceding claims, characterized in that: Personal computer. 6. The tube for the diskette and exchange plate must also be formed as an HF conduit. A shielded mobile according to any or several of the preceding claims, characterized in that: formula personal computer. 7. Radiation through the main housing lid is reduced by the use of beryllium contact strips and distortion. Any of the preceding claims characterized in that it is shielded by a lid structure without a or a shielded portable personal computer as described in some of the above. 8. The CPU housing has a multi-screwed metal sealing lid, and Any of the preceding claims, characterized in that the thread spacing is less than 1/2 of the critical wavelength. or a shielded portable personal computer as described in some. 9. Radiation of the device seat bar shall be shielded by sheathing in the inner housing. A shielded mobile according to any or several of the preceding claims, characterized in that: formula personal computer. 10. All electronic components are potential isolated and insulated within the external housing. and is surrounded by a second Faraday cage. A shielded portable device according to any or several of the preceding claims, characterized in that: Personal computer. 11. Radiation from the monitor's cathode ray tube is fully conductively coupled to the monitor housing By using a plastic plate with inserted fine mesh wire mesh according to any or several of the preceding claims, characterized in that it is shielded. Shielded portable personal computer. 12. The wire mesh is parallel with an angle of 20° to 25° to the horizontal and vertical. 11. The shielded shield according to claim 10, characterized in that the shield comprises a row of metal wires perpendicular to the portable personal computer. 13. The feature is that the printer stops when the printer lid is opened. A shielded portable personal computer according to any or several of the preceding claims, Naru Computer.