In recent years, there has been an increased interest in continuous monitoring of patients and their Implanted Medical Devices (IMDs) with different wireless technologies such as ultrasounds. This paper demonstrates a high data-rate intrabody communication link based on Lithium Niobate (LN) Piezoelectric Micromachined Ultrasonic Transducers (pMUTs). The properties of the LN allow to activate multiple flexural mode of vibration with only top electrodes. When operating in materials like the human tissue, these modes are merging and forming a large communication bandwidth. Such large bandwidth, up to 400 kHz, allows for a high-data rate communication link for IMDs. Here we demonstrate a full communication link in a tissue phantom with a fabricated LN pMUT array of 225 elements with an area of just 3 by 3 mm square, showing data-rates up to 800 kbits/s, starting from 3.5 cm and going up to 13.5 cm, which covers the vast majority of IMDs.

In this paper we present laterally vibrating resonators (LVRs) based on X-cut lithium niobate (LN) exhibiting a maximum quality factor (Q) around 1200 and an electromechanical coupling (k _t ² ) of 30%. This paper shows how the highest k _t ² ever attained in X-cut LN resonators can be combined with very high Q to achieve a resonator figure of merit (FoM = k _t ² · Q) of 360. In this paper, we validate the theoretical prediction of k _t ² versus the resonator orientation in the YZ plane and investigate what geometrical parameters mostly impact the Q of these devices.

The present work reports on the novel implementation of a miniaturized receiver for underwater networking merging a Piezoelectric Micromachined Ultrasonic Transducer (PMUT) array and signal conditioning circuitry in a single, packaged device. Tests in both a large water tank and a pool demonstrated that the system can attain large enough Signal-to-Noise Ratio (SNR) for communication at distances beyond two meters. An actual communication test, implementing an Orthogonal Frequency Division Multiplexing (OFDM) scheme, was used to characterize the performance of the link in terms of Bit Error Rate (BER) vs SNR. In comparison to previous work demonstrating high-data rate communication for intra-body links and acoustic duplexing, this implementation allows for significantly larger distances of transmission, while addressing the signal conditioning and submersible packaging needs for underwater conditions, thus enabling PMUT arrays for operating as complete underwater communication receivers. [2020-0185]

Wirelessly networked systems of underwater devices are becoming the basis of many commercial, scientific, and military applications. In spite of increased attention in the last few years, underwater wireless networking technology still suffers from major limitations, including severe hardware dependence. In this paper, we introduce the SEANet Project, an NSF-funded effort that aims at developing a new generation of programmable platforms and a networking testbed to enable the vision of a programmable Internet of Underwater Things (IoUT). SEANet will be based on new software-defined platforms based on an open architecture to enable the flexibility to define, add, update, and swap new components in both hardware and software. SEANet is designed to support data rates at least one order of magnitude higher than existing commercial platforms over short and moderate range links. Moreover, the SEANet project will explore the design of new custom-designed ultra-wide band Microelectromechanical systems (MEMS) transducers that allow operating over much wider acoustic bandwidth (i.e., 0.01.-2 MHz) than possible with bulk piezoelectric transducers. We present a set of preliminary experiments showing that SEANet can outperform existing software-defined radio SDR-based acoustic modems based on a commercial off-the-shelf (COTS) SDR platforms. We also demonstrate the real-time reconfiguration capability of SEANet and preliminary performance of the MEMS transducers.

This article demonstrates, for the first time, a zero-power ultrasonic wakeup receiver for intra-body communication with Implantable Medical Devices (IMDs). The system is based on a 10 x 10 Piezoelectric Micromachined Ultrasonic Transducer (pMUT) array, a zero-power 500 nm gap MEMS plasmonic switch, a low-leakage CMOS load-switch, and an ad hoc sensing circuit. An ultrasonic signal of 10 mVpp is received by the pMUT array at a distance of 5 cm and brings the MEMS switch from the off-state (1 pA) to the on-state (20 μ A) when biased at 9.09 $V_{DC}$ . This small current then wakes up the load-switch (<10 nW when off), which powers up the sensing circuit to decode the pMUT signal. The system is demonstrated in a tissue phantom, making it ideal for intrabody communication.

This work demonstrates a low-power wake-up receiver utilizing a MEMS resonant device followed by CMOS demodulator and rectifying trigger circuits. The MEMS device is a Lamb wave piezoelectric-based acoustic resonator utilizing a thin film of lithium niobate (LN) which possess the largest reported electromechanical coupling factors (kₜ²). This parameter, in conjunction with the high Q, is of paramount importance in providing for passive voltage amplification and filtering of the input signal. The CMOS demodulator is a 9-stage differential cross-coupled passive rectifier circuit designed with a differential output. It demodulates the signal from the MEMS resonator with the same gain as that could be achieved by a single-ended rectifier, but with half the charging time for double the single-ended bit-rate. The rectifier's output is AC-coupled and fed to a two-stage differential voltage amplifier. Finally, an active latch rectifier is used to trigger a wake-up signal. The wake-up receiver is tested with an on-off keying modulated signal with carrier frequency around 400 MHz achieving a bit rate up to 100 kbps. This newly proposed system exhibits a sensitivity of -47 dBm at 3 kbps while consuming a total power of 18 nW.