"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.
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