We report on a piezoelectric micromachined ultrasonic transducer (PMUT) driven in a nonlinear regime, generating chaotic amplitude modulated ultrasonic waves. At large enough drives, the PMUT enters in the Duffing regime which opens a hysteresis with two available states. By modulating the frequency of the driving signal, the system may switch between both states, and selecting the appropriate modulation frequency enables to enter in the chaotic regime. The chaos is then imprinted as a modulation of the PMUT’s amplitude. We characterize this regime in the three accessible domains: electrical, mechanical and acoustic, and demonstrate they are fully correlated. We then focus on the generated acoustic signals and demonstrate that the chaotic modulation propagates according to the PMUT’s linear regime. Remarkably, the detected acoustic waves are strongly correlated to the on-chip piezoelectric measurements, regardless of the acoustic beam profile. The frequency spectrum of the chaotic modulation spreads around the ultrasonic carrier, mimicking a noise modulated carrier signal. We exploit this property for jamming applications where the chaotic PMUT is used to mask surrounding acoustic waves. Unlike most jamming applications, our approach does not require driving signals with a broad frequency spectrum, the noisy pattern arising directly from the structure’s dynamics. Using two PMUTs, one in the linear and the other in the nonlinear regime, we realize a proof-of-concept where the ultrasound generated by the first PMUT is drowned out by the chaotic PMUT signal. We demonstrate that the carrier frequency of the jamming PMUT does not need to match perfectly the one of the linear PMUT. This chaos generation is generic and could be adapted to any PMUT, and thanks to the rich frequency spectrum of the chaotic modulation, the frequency of the signal to jam does not need to be precisely known.

我们报告了在非线性机制中驱动的压电微机械超声换能器 (PMUT)，产生混沌调幅超声波。在足够大的驱动器下，PMUT 进入 Duffing 状态，这会打开具有两个可用状态的滞后。通过调制驱动信号的频率，系统可以在两种状态之间切换，选择合适的调制频率可以进入混沌状态。然后将混沌印记为 PMUT 幅度的调制。我们在三个可访问的域中描述了这种机制：电气、机械和声学，并证明它们是完全相关的。然后，我们将重点放在生成的声学信号上，并证明混沌调制根据 PMUT 的线性机制传播。值得注意的是，无论声束轮廓如何，检测到的声波都与片上压电测量密切相关。混沌调制的频谱在超声载波周围扩展，模拟噪声调制载波信号。我们将这一特性用于干扰应用，其中混沌 PMUT 用于屏蔽周围的声波。与大多数干扰应用不同，我们的方法不需要具有宽频谱的驱动信号，噪声模式直接来自结构的动力学。使用两个 PMUT，一个处于线性状态，另一个处于非线性状态，我们实现了概念验证，其中第一个 PMUT 生成的超声波被混沌 PMUT 信号淹没。我们证明了干扰 PMUT 的载波频率不需要与线性 PMUT 的载波频率完全匹配。这种混沌生成是通用的，可以适用于任何 PMUT，并且由于混沌调制的丰富频谱，不需要精确知道干扰信号的频率。