22 Mar 2004
Audio signals get their first airing at terahertz frequencies.
Researchers in Germany have transmitted audio signals via terahertz waves for the first time. This development could lead to a new type of high-speed short-range wireless communication network.
Terahertz (THz) radiation falls in the gap between infrared radiation and the high frequency radio waves currently used for mobile phones and other wireless communications systems. Apart from a few applications in biological imaging and spectroscopy, the technology has been relatively unexplored. However, as the demand for high data rate wireless communication continues to grow, researchers are turning to higher frequencies and starting to consider the THz region.
In the latest research, a team from the Technical University of Braunschweig built a new room-temperature semiconductor THz modulator. The researchers combined the modulator with a modified THz time-domain spectroscopy set-up to transmit audio signals at up to 25 kHz over a 75 MHz train of broadband THz pulses.
Music from a CD player was transmitted over the system. According to the researchers, the quality of the music that was played back via a loudspeaker was similar to that produced in a telephone.
As THz radiation is strongly absorbed by the atmosphere it suits short-range communication, such as picocells that cover single rooms. “THz communications will not replace cell phones,” said Martin Koch, who is one of the researchers. However, he does predict that wireless THz networks could one day replace wireless local area networks or Bluetooth, which is a short-range cable-replacement.
Siân Harris is features editor of Opto & Laser Europe magazine.