Available at: https://digitalcommons.calpoly.edu/theses/3000
Date of Award
6-2025
Degree Name
MS in Electrical Engineering
Department/Program
Electrical Engineering
College
College of Engineering
Advisor
Dennis Derickson
Advisor Department
Electrical Engineering
Advisor College
College of Engineering
Abstract
There is a growing market for compact, power-efficient underwater communication technology. Due to the limited propagation of electromagnetic waves through water, modulated acoustic waves have emerged as an effective means of wireless communication underwater. In decades past, many acoustic modems had been developed primarily for defense customers in larger systems functioning at high power. In recent years, smaller, relatively inexpensive acoustic modems have become available on the market—but data on their performance in a real-world environment is scarce. Companies such as OWL Integrations are interested in employing such acoustic modems as part of sensing networks across multiple mediums. For such applications, data on maximum distance, directivity, and adjacent channel interference are valuable. Developing a demonstration underwater sensing node with hardware amenable to hosting an RF transceiver is a key step towards the integration of air-sea boundary nodes and subsea sensing nodes into an underwater sensing network. In this work, the performance of the Waterlinked Modem M16 is tested in the harbor environment of Morro Bay, California. The testing revealed a maximum measured range of 521 meters, with some multipath propagation ability observed; a front-to-back difference of 21.8 in relative signal strength on a logarithmically scaled 0-255 scale, comparable to a distance change of 100 meters; and adjacent channel interference sufficient to decrease the signal-to-noise metric by 5 on the same scale. Throughout the tests, the modem consumed less power than its stated maximum values. Ocean pH data was collected and transmitted over the link, and the modem, sensor, and microcontroller boards were all powered from OWL’s QuAD-RC1 power board. The practical testing quantified the modem’s limitations, and the success of the overall integrated testing showed that compact, low-power modems like the Modem M16 are strong candidates for underwater sensing, communication, and control networks.