| This thesis describes an investigation into the design of a digital signal processing ultrasonic fish tracker. This work was initiated to overcome problems with an analog system presently used at Memorial University to track individual cod. Consisting of a local oscillator and several superheterodyne receivers, the analog system now works intermittently and gives unreliable results. A study into a more compact receiver design based on recent technological advancements was then commenced. The new receiver will connect to the existing four hydrophones, interface through a PC ISA bus, fit on a single PC proto-board, and track three frequencies simultaneously from each of the four hydrophones. Position resolution under 1 m is achievable, over a 500 m range.;For this study only passive fish tracking systems are investigated where a transmitter is attached to the fish and a grid of detecting hydrophones are placed around the area of interest. These systems are reviewed from beat frequency receivers used in the 1950's, to computer controlled superheterodyne receivers in use today. Analog designs are prevalent throughout all these systems. (Abstract shortened by UMI.). |
