Theory Of Operation; Introduction; Towfish - Klein 3900 Series Operation And Maintenance Manual

1.4

Theory of Operation

This section provides a detailed functional description of the Series 3900 Sonar
System operation.
1.4.1
The Series 3900 Sonar System is a single beam side-looking sonar intended for
high resolution survey use.
The Series 3900 departs from previous single beam systems in that the swath
forming process is implemented digitally using digital signal processing (DSP),
rather than analog delay lines, phase shifters, or multipliers and adders. The
primary advantage of this technique is a reduction in the size and weight of the
towfish. This affords a concomitant reduction in the size of the required survey
vessel and ancillary equipment, such as a winch and crane. Other advantages
include more flexibility in the swath processing, allowing software control of
operating parameters. Previously this would have required hardware changes.
The Series 3900 architecture is composed of the towfish, the tow cable, the
computer, and the TPU. The towfish contains the transducer arrays and electronic
subsystems for transmission, reception and data acquisition, and telemetry. The
towfish also includes standard and optional sensors for the monitoring of towfish
position and motion dynamics, pressure, depth and altitude (acoustically
measured), magnetometer, and other pertinent information.
The tow cable is a coaxial cable that provides power transfer and duplex
communications between the towfish and the TPU.
The TPU processes the data from the towfish and outputs this data via the local
area network (LAN). Sonar processor control of the TPU is also done via the LAN.
1.4.2
The towfish is composed of the towfish housing, which has external brackets for
cable attachment, the transducer arrays (one for each side), the nose cone, the tail
section, and a pressure housing containing optional sensors and electronics. In a
typical operation the towfish is towed behind the survey vessel by means of the
tow cable. The depth at which the towfish runs below the surface of the water is a
function of both the length of the deployed cable and the tow speed.

Introduction

Towfish

Theory of Operation
1-5