For systems that require complete metallic enclosures, it is impossible to power and communicate with interior electronics using conventional electromagnetic techniques. Instead, pairs of ultrasonic transducers can be used to send and receive elastic waves through the enclosure, forming an equivalent electrical transmission line that bypasses the Faraday cage effect. These mechanical communication systems introduce the possibility for electromechanical crosstalk between channels on the same barrier, in which receivers output erroneous electrical signals due to ultrasonic guided waves generated by transmitters in adjacent communication channels. To minimize this crosstalk, this work investigates the use of a phononic crystal/metamaterial machined into the barrier via periodic grooving. Barriers with simultaneous ultrasonic power and data transfer are fabricated and tested to measure the effect of grooving on crosstalk between channels.
For systems that require complete metallic enclosures, it is impossible to power and communicate with interior electronics using conventional electromagnetic techniques. Instead, pairs of ultrasonic transducers can be used to send and receive elastic waves through the enclosure, forming an equivalent electrical transmission line that bypasses the Faraday cage effect. These mechanical communication systems introduce the possibility for electromechanical crosstalk between channels on the same barrier, in which receivers output erroneous electrical signals due to ultrasonic guided waves generated by transmitters in adjacent communication channels. To minimize this crosstalk, this work investigates the use of a phononic crystal/metamaterial machined into the barrier via periodic grooving. Barriers with simultaneous ultrasonic power and data transfer are fabricated and tested to measure the effect of grooving on crosstalk between channels.
Several applications, such as underwater vehicles or waste containers, require the ability to transfer data from transducers enclosed by metallic structures. In these cases, Faraday shielding makes electromagnetic transmission highly inefficient, and suggests the employment of ultrasonic transmission as a promising alternative. While ultrasonic data transmission by piezoelectric transduction provides a practical solution, the amplitude of the transmitted signal strongly depends on acoustic resonances of the transmission line, which limits the bandwidth over which signals are sent and the rate of data transmission. The objective of this work is to investigate piezoelectric acoustic transducer configurations that enable data transmission at a relatively constant amplitude over large frequency bands. This is achieved through structural modifications of the transmission line, which includes layering of the transducers, as well as the introduction of electric circuits connected to both transmitting and receiving transducers. Both strategies lead to strong enhancements in the available bandwidth and show promising directions for the design of effective acoustic transmission across metallic barriers.
This work provides the first demonstration of vertical GaN Junction Barrier Schottky (JBS) rectifiers fabricated by etch and regrowth of p-GaN. A reverse blocking voltage near 1500 V was achieved at 1 mA reverse leakage, with a sub 1 V turn-on and a specific on-resistance of 10 mΩ-cm2. This result is compared to other reported JBS devices in the literature and our device demonstrates the lowest leakage slope at high reverse bias. A large initial leakage current is present near zero-bias which is attributed to a combination of inadequate etch-damage removal and passivation induced leakage current.