Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX 78712.
Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, TX 78712.
Proc Natl Acad Sci U S A. 2021 Jul 27;118(30). doi: 10.1073/pnas.2024984118.
The quality factor of a passive, linear, small acoustic radiator is fundamentally limited by its volume normalized to the emitted wavelength, imposing severe constraints on the bandwidth and efficiency of compact acoustic sources and of metamaterials composed of arrangements of small acoustic resonators. We demonstrate that these bounds can be overcome by loading a piezoelectric transducer with a non-Foster active circuit, showing that its radiation bandwidth and efficiency can be largely extended beyond what is possible in passive radiators, fundamentally limited only by stability considerations. Based on these principles, we experimentally observe a threefold bandwidth enhancement compared to its passive counterpart, paving the way toward non-Foster acoustic radiation and more broadly active metamaterials that overcome the bandwidth constraints hindering passive systems.
无源线性小声学辐射器的品质因数从根本上受到其体积与发射波长之比的限制，这对紧凑声学源和由小声学谐振器排列组成的超材料的带宽和效率都施加了严格的限制。我们证明，通过用非福斯特有源电路加载压电换能器，可以克服这些限制，表明其辐射带宽和效率可以大大扩展到无源辐射器所允许的范围之外，其仅受稳定性考虑的限制。基于这些原理，我们实验观察到与无源对应物相比，带宽提高了三倍，为非福斯特声学辐射以及更广泛的克服阻碍无源系统的带宽限制的有源超材料铺平了道路。
