“At its core, the terahertz receiver consists a single diode, which rectifies the terahertz signal,” says Dr. Tobias Harter, who carried out the demonstration together with his colleague Christoph Füllner in the framework of his doctoral thesis.
The diode is a so-called Schottky barrier diode, that offers large bandwidth and that is used as an envelope detector to recover the amplitude of the terahertz signal. Correct decoding of the data, however, additionally requires the time-dependent phase of the terahertz wave that is usually lost during rectification. To overcome this problem, researchers use digital signal processing techniques in combination with a special class of data signals, for which the phase can be reconstructed from the amplitude via the so-called Kramers-Kronig relations. The Kramers-Kronig relation describe a mathematical relationship between the real part and the imaginary part of an analytic signal. Using their receiver concept, the scientists achieved a transmission rate of 115 Gbit/s at a carrier frequency of 0.3 THz over a distance of 110 m.
“This is the highest data rate so far demonstrated for wireless terahertz transmission over more than 100 m,” Füllner says.
The terahertz receiver developed by KIT stands out due to its technical simplicity and lends itself to cost-efficient mass production.
T. Harter, C. Füllner, J. N. Kemal, S. Ummethala, J. L. Steinmann, M. Brosi, J. L. Hesler, E. Bründermann, A.-S. Müller, W. Freude, S. Randel, C. Koos: Generalized Kramers-Kronig Receiver for Coherent THz Communications. Nature Photonics, 2020. DOI: 10.1038/s41566-020-0675-0.