Passive and Active Sonar – Fundamentals

This three-day course is designed for SONAR systems engineers, combat systems engineers, undersea warfare professionals, and managers who wish to enhance their understanding of passive and active SONAR or become familiar with the “big picture” if they work outside of either discipline. Each topic is presented by instructors with substantial experience at sea. Presentations are illustrated by worked numerical examples using simulated or experimental data describing actual undersea acoustic situations and geometries. Visualization of transmitted waveforms, target interactions, and detector responses is emphasized.

• The differences between various types of SONAR used on Naval platforms today.
• The fundamental principles governing these systems’ operation.
• How these systems’ data are used to conduct passive and active operations.
• How to avoid previous mistakes revealed when systems were taken to sea.
• Signal acquisition and target motion analysis for passive systems.
• Waveform and receiver design for active systems.
• The major cost drivers for undersea acoustic systems.

1. Sound and the Ocean Environment: Conductivity, temperature, depth (CTD), sound velocity profiles, refraction, decibels, transmission loss, and attenuation. Source reference levels in air and water.
2. SONAR System Fundamentals. Major system components in a SONAR system (transducers, signal conditioning, digitization, signal processing, displays and controls). Various SONAR systems (hull, towed, side scan, multibeam, communications, navigation, etc.). Calculation of source level (dB) as a function of acoustic power output (watts) and source directivity index. Measurement of target strength at sea, echo energy splitting.
3. Array Gain and Beampatterns. Calculation of beam patterns for line arrays, directional steering, shading for sidelobe control. Directivity index of an array and array grating lobes.
4. SONAR Equations. Passive and active SONAR equations. Probabilities of detection and false alarm. Relationship between energy, intensity, and spectrum height. Alternative active SONAR equations when working against noise or reverberation. Limitations of these equations in deep and shallow water.
5. Target Motion Analysis (TMA). What it is, why it is done, how SONAR is used to support it, what other sensors are required to determine the motion of passive targets.
6. Time-Bearing Analysis. How relative target motion affects bearing rate, ship maneuvers to compute passive range estimates (Ekelund Range). Use of time-bearing information to assess passive target motion.
7. Waveform and Receiver Design. Traditional and novel waveform alternatives. Replica correlation and convolution. Discrete Fourier transform. Narrowband and wideband ambiguity functions. Accounting for real medium effects.

Dr. Harold “Bud” Vincent, Research Associate Professor of Ocean Engineering at the University of Rhode Island and President of DBV Technology, LLC is a U.S. Naval officer qualified in submarine warfare and salvage diving. He has over twenty years of undersea systems experience working in industry, academia, and government (military and civilian). He served on active duty on fast attack and ballistic missile submarines, worked at the Naval Undersea Warfare Center, and conducted advanced R&D in the defense industry. Dr. Vincent received the M.S. and Ph.D. in Ocean Engineering (Underwater Acoustics) from the University of Rhode Island. His teaching and research encompass underwater acoustic systems, communications, signal processing, ocean instrumentation, and navigation. He has been awarded four patents for undersea systems and algorithms.