Nothing spoils the mood of a romantic dinner date like a jangling cellphone at the next table. But cellphone-proof restaurants could be on the way, courtesy of a team of engineers led by Hideo Oka of Japan’s Iwate University.
Oka is developing wall paneling that absorbs microwave signals, rendering cellphones useless. The paneling is made from two sheets of ordinary fiberboard that sandwich a third layer made of nickel-zinc ferrite powder and a binding compound. Electromagnetic waves transmitted by cellphones are absorbed by the ferrite particles and converted to small amounts of heat. The fact that they are absorbed rather than jammed is key, as the jamming of radio signals is illegal in many countries, including the United States.
Oka says the paneling halts about 97 percent of radio waves at a frequency range between 857MHz and 2.47GHz, encompassing most cellphone and wireless computer network broadcasts. Aesthetically, the paneling is still a work in progress: Oka chose fiberboard because natural wood has a tendency to warp. The next step is to test different fiberboards, in order to find the ones that are most economical. Oka’s group has presented its prototype to various building supply companies in the United States, Europe, and Asia, but the product will probably be in development for another two years before it hits the market.