Mechanical tuning boosts performance of terahertz communication devices at high frequencies

Terahertz frequencies above 100 GHz offer extremely wide bandwidths suitable for next-generation wireless communications, and research toward their practical use is ongoing worldwide. In particular, the 150 GHz and 300 GHz bands are actively being studied in Japan due to their relatively low atmospheric attenuation, which enables stable signal propagation.

However, at such high frequencies, mechanical fabrication errors—typically around ±50 μm—can no longer be ignored. While this level of error is negligible for conventional sub-6 GHz modules, it becomes several percent of the wavelength at 300 GHz, where the wavelength is about 1 mm.

These errors can significantly impact the performance of devices, especially those connecting the chip to the antenna, and therefore require compensation mechanisms. Moreover, since 300 GHz exceeds the maximum operating frequency of standard CMOS transistors, it is difficult to implement active tuning circuits or electronic switches, highlighting the need for alternative approaches.

A joint research team from the Institute of Science Tokyo (Science Tokyo) and Hiroshima University has developed a mechanical tuning method using microactuators to improve the performance of terahertz communication devices. The work is published in the journal IEEE Access.

Inspired by optical cameras, which adjust focus by moving lenses to maximize the received light intensity from a specific distance, the researchers applied a similar concept to terahertz devices. As a demonstration, they introduced a mechanical tuning structure into a waveguide transition that connected an antenna to a chip.

A flexible, conductive membrane was used as a movable backshort (reflector) within the waveguide, and its position was precisely controlled using an impact-drive microactuator with sub-micron accuracy. The actuator drove a slider element that pushed the membrane, enabling high-precision adjustment of the reflector’s position.

As a result, the team successfully demonstrated impedance tuning of a 250 GHz waveguide transition, validating the effectiveness of mechanical tuning as a method of compensating for fabrication-induced performance variation.