Niobium waveguide tech boosts B5G/6G signal transmission

Researchers from Nagoya University in Japan have created a waveguide made of niobium that speeds up the transition of Beyond 5G/6G (B5G/6G) signals. The frequency of data waves has continued to increase as B5G/6G technologies have been introduced. Although the currently used metal transmission lines can handle B5G/6G, researchers have focused on superconducting metals, such as niobium, that have lower transmission loss and can handle higher frequencies.

Taku Nakajima and Kazuji Suzuki from Nagoya University evaluated the use of niobium in a waveguide, a three-dimensional transmission line consisting of a metal tube that guides and confines waves along a specific path, reducing losses due to radiation and absorption. However, working with the metal was difficult as it was susceptible to deformation and damage during fabrication and handling.

Nakajima said fabricating a physical model of a waveguide was difficult, as it could not be processed with any precision. The result of the first cutting caused a milling burr, an unwanted projection of the metal. “We tried to search for the best cutting tool and cutting parameters and eventually found that diamond-like carbon-coated tools were the best,” Nakajima said.

Using this method, the researchers fabricated rectangular waveguides that can transmit radio waves in the 100 GHz band that are necessary for B5G/6G communications. The researchers compared the conductivity of their niobium waveguide with that of common non-superconducting waveguide materials: a gold-plated tellurium copper and aluminium alloy. Both materials were tested at room temperature and at low temperatures because the characteristics of superconducting metals change with cooling, entering the superconducting stage, which is characterised by low electrical resistance.

The researchers found that the conductivity improves as the temperature of the metal decreases, resulting in reduced losses in the circuit. The researchers used electromagnetic field simulations to calculate the conductivity and transmission loss of each metal. “The conductivity of niobium in the superconducting state was 1000 to 10,000 times higher than that of the aluminium alloy. Furthermore, the transmission loss of niobium in the superconducting state was calculated to be several 10ths that of other metals. These two factors contribute to the creation of a high-quality, high-precision communication environment,” Nakajima said.

The results of this study could help the researchers develop an ultra-sensitive receiving system in radio telescope receivers for astronomical observations, and in environmental measurement equipment for the Earth’s atmosphere. “This will open up new fields of scientific observation using high-frequency radio waves, such as the observation of very distant galaxies in the early universe, which emit only very weak radio waves, or the monitoring of changes in trace atmospheric constituents in the Earth’s upper atmosphere,” Nakajima said.

The research findings were published in the Journal of Physics.

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