Terahertz transmitter exceeds 100 Gbps

Terahertz wireless could make spaceborne satellite communications as fast as fibre-optic links.

Researchers at Hiroshima University, Japan’s National Institute of Information and Communications Technology and Panasonic has announced the development of a terahertz (THz) transmitter capable of transmitting digital data at a rate exceeding 100 gigabits per second over a single channel in the 300 GHz band.

This technology enables data rates 10 or more times faster than those that will offered by 5G networks; the latter is expected to appear around 2020.

Details of the technology were presented at the International Solid-State Circuits Conference (ISSCC) 2017, held in San Francisco in February.

The THz band is a new and vast-frequency resource expected to be used for future ultrahigh-speed wireless communications.

The research group has developed a transmitter that achieves a communication speed of 105 Gbps using the frequency range from 290 GHz to 315 GHz.

This range of frequencies is currently unallocated but falls within the frequency range from 275 GHz to 450 GHz, the usage of which is to be discussed at the World Radiocommunication Conference (WRC) 2019 under the International Telecommunication Union Radiocommunication Section (ITU-R).

Last year, the researchers demonstrated that the speed of a wireless link in the 300 GHz band could be greatly enhanced by using quadrature amplitude modulation (QAM).

This year, they showed data rates six times higher per channel, exceeding 100 Gbps for the first time with an integrated circuit-based transmitter.

At this data rate, the whole content of a DVD could be transferred in a fraction of a second.

“This year, we developed a transmitter with 10 times higher transmission power than the previous version’s. This made the per-channel data rate above 100 Gbps at 300 GHz possible,” said Professor Minoru Fujishima, Graduate School of Advanced Sciences of Matter, Hiroshima University.

“We usually talk about wireless data rates in megabits per second or gigabits per second,” said Professor Fujishima. “But we are now approaching terabits per second using a plain, simple, single communication channel.”

Although fibre-optic technology has already achieved ultrahigh-speed wired links, wireless links have been left far behind.

Terahertz could offer ultrahigh-speed links to satellites as well, which could in turn significantly boost inflight network connection speeds, for example.

Other possible applications include fast download from content servers to mobile devices and ultrafast wireless links between base stations.

“Another completely new possibility offered by terahertz wireless is high-data-rate, minimum-latency communications,” said Professor Fujishima.

Optical fibres are made of glass, which slows down the speed of light. This makes fibre optics inadequate for applications requiring real-time responses.

“Today, you must make a choice between ‘high data rate’ (fibre optics) and ‘minimum latency’ (microwave links). You can’t have both,” said Professor Fujishima.

“But with terahertz wireless, we could have light-speed, minimum-latency links supporting fibre-optic data rates.”

The research group plans to further develop 300 GHz ultrahigh-speed wireless circuits.

Image courtesy Fujishima et al (Hiroshima University)

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