Non-reciprocal acoustoelectric amplifiers for very high frequency sound waves

https://techxplore.com/news/2023-02-non-reciprocal-acoustoelectric-amplifiers-high-frequency.html

"three-layer heterostructure comprised of a semiconducting film, a piezoelectric film and a silicon substrate... run continuously with high gain (i.e., ratio of output to input power) adding very little noise to an original signal and without consuming too much power... boost signal these GHz 1,000X only degrading signal to noise background by factor of 2... transmit signals going in wrong direction through amplifier 300,000X less than signals going through right way... dissipating heat generated"

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