Multibeam Sonar Theory of Operation

Multibeam Sonar Theory of Operation Table of Contents
Table of Contents
Chapter 1 - Introduction
Organization of this Document....................................................................................................................................1-3
Scope of this Document................................................................................................................................................1-3
Chapter 2 - Sonar Concepts
The Physics of Sound in Water...................................................................................................................................2-1
The Principles of Sonar.................................................................................................................................................2-3
The Sonar Equation...............................................................................................................................................2-5
A Single-Beam Depth Sounder....................................................................................................................................2-6
Why Multibeam? The Limitations of a Single-Beam Depth Sounder....................................................................2-8
Echo Location Questions – Where is the Bottom? ..........................................................................................2-8
Survey Speed........................................................................................................................................................2-12
The Multibeam Solution .....................................................................................................................................2-13
Chapter 3 - Introduction to Multibeam Sonar: Projector and
Hydrophone Systems
Projector Arrays and Beam Forming...........................................................................................................................3-1
Hydrophone Arrays ....................................................................................................................................................3-11
Beam Steering...............................................................................................................................................................3-15
The Mills Cross Technique........................................................................................................................................3-17
The Mills Cross Applied in the SEA BEAM 2100 System ....................................................................................3-20
The SEA BEAM 2100 Projector and Hydrophone Arrays ............................................................................3-20
SEA BEAM 2100 Beam Steering........................................................................................................................3-21
Chapter 4 - Detection Processing and Range Calculations
Processing Steps............................................................................................................................................................4-1
The Steered Beam Data.................................................................................................................................................4-5
Dynamic Threshold Calculation ..................................................................................................................................4-6
Time of Arrival (TOA) and Direction of Arrival (DOA) Calculations: BDI and WMT Processing.................4-10
BDI Processing.....................................................................................................................................................4-11
High-Resolution Angle Estimation ...........................................................................................................4-11
Motion Compensation ................................................................................................................................4-12
Application of the Start and Stop Gates...................................................................................................4-16
Direction of Arrival (DOA) and Time of Arrival (TOA) Calculations..................................................4-17
WMT Processing.................................................................................................................................................4-19
Interpolating Amplitudes for Each Time Slice.........................................................................................4-20
Amplitude-Weighted Time of Arrival (TOA) Computation ..................................................................4-21
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