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Mit dem lästigen Handyklingeln in Theatern oder Kinos könnte bald Schluss sein: Japanische Wissenschaftler haben eine neuartige Wandvertäfelung entwickelt. 

Dem lästigen Handyklingeln in Restaurants, Theatern oder Kinos haben japanische Wissenschaftler jetzt den Kampf angesagt. Sie entwickelten eine Wandvertäfelung, die elektromagnetische Wellen absorbiert und so den Kontakt zwischen Handy und Sendestation unterbindet.

Alternative zu Störsendern

Die von Hideo Oka und seinen Kollegen von der japanische Iwate University konstruierte Täfelung besteht aus zwei Schichten Holz, in die eine dritte Schicht aus magnetischem Nickel-Zink-Ferrit eingebettet ist. Treffen elektromagnetische Wellen auf die Metallschicht, werden sie zu 97 Prozent absorbiert.

Die Wandverkleidung ist nur vier Millimeter dick und kann deshalb in praktisch jedem beliebigen Raum verbaut werden. Die Funkblockade biete eine gute Alternative zu Störsendern, die in vielen Ländern verboten seien, so die Entwickler gegenüber dem Magazin «New Scientist».  

Netze entwirren 

Die Vertäfelung könnte nicht nur Besucher in Restaurants und Kinos vor der Belästigung schützen, sondern ließe sich auch in normale Wohnungen integrieren. Die Japaner denken dabei an jene Landsleute, die ihre Hightech-Haushalte bereits mit internen Funknetzwerken ausgerüstet haben. 

Theoretisch kann so der Computer schnurlos Daten an den Drucker senden oder Videorecorder und Waschmaschine steuern. In der Praxis kommen sich aber häufig heimische Funknetze mit der Technik des Nachbarn oder mit Mobilfunknetzen ins Gehege. Die richtige Wandverkleidung werde das Durcheinander der Netze entwirren, versprechen die Ingenieure.

 Quelle: www.netzeitung.de vom 28. Juni 2002

Hier ist der ganze Original-Artikel, auf den sich die Meldung bezieht:

Magnetic wood blocks mobile phone signals

27 June 02  

Exclusive from New Scientist Print Edition  

Magnetic wood could be a major plank in the battle against noisy cellphone users. The high-tech material absorbs microwave radio signals, making it impossible to use a mobile phone in any room lined with it. Or a radio for that matter. So theatres and restaurants, for example, can stop people using cellphones on their premises without resorting to signal jammers.

The anti-cellphone sandwich  

These are illegal in some countries, including the US, Britain and Australia. Jammers also cause wider problems because their signals can spill out of the building they are covering, interfering with other people's calls.  

The magnetic wood - so called because it is packed with minute magnetic particles - is the brainchild of Hideo Oka and a team of electronics engineers at Iwate University in Morioka, northern Japan. They chose wood as their preferred blocking material because it offers more natural, aesthetic options for interior design. Oka hopes that it will soon be possible to buy the novel wood panelling by the metre at your local hardware store.

While normal wood is transparent to radio waves, Oka's blocks them because it contains fine particles of a magnetic material called nickel-zinc ferrite. When an electromagnetic wave hits the ferrite particles, the magnetic part of the wave is absorbed.

Bluetooth frequencies  

The team looked at four different ways of making wood absorb radio waves before hitting on the best one. The first was simply wood coated with a ferrite powder. The others were made by mixing ferrite powder with cider wood powder and pressing it into boards, or impregnating the wood with particles, or sandwiching wood pulp containing ferrite powder between two thin wooden panels.

Oka tested each wood in turn by putting collars of each material over a short antenna that broadcasts radio waves at the typical GSM mobile phone frequencies of 900 megahertz and 1.8 gigahertz.

The antenna can also broadcast at frequencies up to 2.5 gigahertz, which covers the range commonly used for wireless networks like Bluetooth and the emerging IEEE 802.11 standard, better known as Wi-Fi. A receiver measured the strength of the radio waves transmitted through the material.    

Ferrite sandwich  

In the end, Oka found that ferrite sandwiched between thin sheets of wood performed best. Further tests showed that a 4-millimetre-thick sandwich absorbed the most microwave radiation, cutting the wave's power by 97 per cent. Increasing the thickness of the outer wooden sheets of the sandwich increased the frequency of radio waves that the shield would absorb.  

The wood-based shields could be used to make doors and walls for rooms or even entire buildings where mobile phones simply won't work. While the prospect of being forcefully cut off might horrify some cellphone addicts, Oka says theatre-goers and restaurant customers might appreciate the silence.  

Panels that absorb radio waves could also help with a problem emerging in Japanese cities, where many homes are being fitted with wireless computing networks. If several networks are set up close together, they can interfere with each other. The new panels could divide up the house into different areas, allowing several networks can operate close by.  

Oka believes he can make the wood cheap enough for it to be viable. And he now hopes to cut the cost still further by making the panels from recycled magnetic materials and waste wood.  

Quelle:

http://www.newscientist.com/news/news.jsp?id=ns99992461

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