In modern communications, wireless devices require separate filters for different frequencies, which occupy considerable space. With the advent of 6G entering commercial use, there will be a greater need for additional filters in communication devices, further squeezing the already limited space available.
To address this challenge, a research team at the University of Pennsylvania has designed an adjustable filter that can selectively filter different frequencies, eliminating the need for separate filters.
The key to making the filter adjustable lies in a unique material known as yttrium iron garnet (YIG), a mixture of rare-earth metal yttrium and iron oxide. YIG stands out for its ability to propagate magnon spin waves, a type of wave generated in magnetic materials when electrons rotate synchronously.
When exposed to a magnetic field, YIG produces magnon spin waves that change frequency. By adjusting the magnetic field, YIG filters can achieve continuous frequency tuning across an extremely wide band. Researchers indicate that this filter can tune frequencies anywhere between 3.4 GHz and 11.1 GHz, effectively covering most of the frequency spectrum allocated for civilian communication in the FR3 band (7.125-24.25 GHz).
In addition to frequency adjustability, this filter is remarkably compact, roughly the size of a 25-cent coin, which is ten times smaller than current commercial YIG filters. Moreover, due to a novel zero-static-power magnetic bias circuit designed by the researchers, the filter operates with minimal power consumption. This circuit generates a magnetic field without requiring any continuous power input; occasional pulses are sufficient to readjust the magnetic field, ensuring extremely low power consumption.
In fact, YIG was discovered as early as the 1950s, and YIG filters have existed for decades. However, what sets this research team apart is their innovation in not only utilizing YIG's properties to make the filter adjustable but also significantly reducing the filter's power consumption and size. As a result, this type of filter is poised to be widely applied in various communication devices such as smartphones in the future.
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