While the roll-out of 5G networks is in full swing, scientists are already thinking about the next generation of mobile communications. This, the sixth generation, once again promises significantly higher data transmission rates, shorter delay times and a greater density of terminals. It will also integrate artificial intelligence, for example to coordinate devices in the Internet of Things or autonomous vehicles. “In order to serve as many users as possible at the same time and to transmit as much data as possible as fast as possible, the wireless networks of the future will have to consist of numerous small radio cells,” explains Professor Christian Koos, who is researching 6G technologies at KIT together with his colleague Professor Sebastian Randel. In these radio cells, the distances are short so that large data rates can be transmitted with minimum energy consumption and low electromagnetic immission. They require only small base stations that can be attached to streetlamps, for example.
To connect the individual cells, high-performance broadband radio links are needed, which in extreme cases must be able to transmit several hundred gigabits per second. Frequencies in the terahertz range are ideal for this purpose. However, the corresponding receivers are still comparatively complex and correspondingly expensive; in addition, they often represent the bottleneck for the attainable bandwidth. Researchers at the Karlsruhe Institute of Technology together with the diode manufacturer Virginia Diodes (VDI) in Charlottesville/USA, have now designed a simple and inexpensive receiver for terahertz signals that can be manufactured at low cost; their work has been presented in the journal Nature Photonics. The KIT team has achieved the highest data rate to date with wireless THz-transmission over more than 100 meters.
“A single diode is used as the receiver, with which the terahertz signal is rectified,” explains Dr. Tobias Harter, who built the receiver together with his colleague Christoph Füllner as part of his dissertation. This is a particularly fast Schottky diode. It acts as an envelope detector and recovers the amplitude of the terahertz signals. However, in order to decode the data signal, the time-varying phase of the terahertz wave is additionally required, which is usually lost during rectification. To solve this problem, the researchers use digital signal processing methods in combination with a special class of data signals in which the phase can be reconstructed from the amplitude using the so-called Kramers-Kronig relations. The Kramers-Kronig relation is a mathematical relationship between the real and imaginary parts of an analytical signal. With the new receiver, the scientists achieved a data transmission rate of 115 Gbit/s on a carrier frequency of 0.3 THz over a distance of 110 meters. “This is the highest data rate demonstrated to date with wireless terahertz transmission over more than 100 meters,” explains Füllner. The terahertz receiver developed at KIT is characterized by its simple design and is suitable for cost-effective production in large quantities.
Source: https://www.eenewseurope.com/news/simple-terahertz-receiver-makes-6g-mobile-networks-affordable/page/0/1 09 09 20
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