6G: All-silicon polarization multiplexer; non-volatile hBN switch; tunable YIG filter.
Researchers from the University of Adelaide and Osaka University propose an ultra-wideband integrated terahertz polarization (de)multiplexer implemented on a substrateless silicon base, which they tested in the sub-terahertz J-band (220-330 GHz) for 6G communications.
“Our proposed polarization multiplexer will allow multiple data streams to be transmitted simultaneously over the same frequency band, effectively doubling the data capacity,” said Withawat Withayachumnankul, a professor in the School of Electrical and Mechanical Engineering at the University of Adelaide, in a release. “This large relative bandwidth is a record for any integrated multiplexers found in any frequency range. If it were to be scaled to the center frequency of the optical communications bands, such a bandwidth could cover all the optical communications bands.”
The multiplexer can be integrated on the same platform with a beamforming device previously developed by the team. They anticipate commercial prototypes and early-stage projects using the technology within three to five years. [1]
Researchers from the Universitat Autonoma de Barcelona, King Abdullah University of Science and Technology, University of Texas at Austin, Tyndall National Institute, and University College Cork developed a switch using hexagonal boron nitride (hBN) that is suitable for 6G networks. The switch is capable of performing at twice the operating frequency of current silicon-based devices, with a frequency range of up to 120 GHz.
Additionally, the non-volatile hBN switch allows its ON or OFF state to be activated by applying an electrical voltage pulse instead of a constant signal, reducing energy requirements.
The memristive device uses two-dimensional networks of hBN arranged in a superposition of layers (between 12 and 18 layers in total) that can operate at 260 GHz and with a sufficiently high stability to be implemented in electronic devices. [2]
Researchers from the University of Pennsylvania built an adjustable yttrium iron garnet (YIG) filter that can successfully prevent interference in the FCC’s Frequency Range 3 (FR3) band, which includes frequencies from about 7 GHz to 24 GHz.
“The FR3 band is most likely to roll out for 6G or Next G, and right now the performance of small-filter and low-loss switch technologies in those bands is highly limited. Having a filter that could be tunable across those bands means not having to put in another 100+ filters in your phone with many different switches. A filter like the one we created is the most viable path to using the FR3 band,” said Troy Olsson, associate professor in electrical and systems engineering at Penn Engineering, in a release. Olsson noted that many of those higher-frequency bands are already used for military and commercial satellite internet communications. “Being tunable is going to be really important, because at these higher frequencies you may not always have a dedicated block of spectrum just for commercial use.”
YIG propagates a magnetic spin wave, and when exposed to a magnetic field, the magnetic spin wave generated changes frequency. By adjusting the magnetic field, the new filter can be tuned to any frequency between 3.4 GHz and 11.1 GHz, which covers a significant portion of the FR3 band. “We hope to demonstrate that a single adaptable filter is sufficient for all the frequency bands,” said Xingyu Du, a doctoral student at Penn Engineering, in a release.
The filter requires very little power thanks to the use of a zero-static-power, magnetic-bias circuit and is about the size of a quarter, much smaller than current commercial YIG filters. [3]
[1] W. Gao, M. Fujita, S. Murakami, T. Nagatsuma, C. Fumeaux, W. Withayachumnankul, Ultra-Wideband Terahertz Integrated Polarization Multiplexer. Laser Photonics Rev 2024, 2400270. https://doi.org/10.1002/lpor.202400270
[2] Pazos, S., Shen, Y., Zhang, H. et al. Memristive circuits based on multilayer hexagonal boron nitride for millimetre-wave radiofrequency applications. Nat Electron 7, 557–566 (2024). https://doi.org/10.1038/s41928-024-01192-2
[3] Du, X., Idjadi, M.H., Ding, Y. et al. Frequency tunable magnetostatic wave filters with zero static power magnetic biasing circuitry. Nat Commun 15, 3582 (2024). https://doi.org/10.1038/s41467-024-47822-3
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