A Doppler Sonar Controller

Accurate measurements of the upper ocean velocity field can now be made using Doppler sonar. Doppler measurements can be made with a wide variety of transducers provided that signal generation and echo processing techniques suitable for Doppler are applied. This paper describes a Doppler sonar controller which was designed to operate a variety of experimental Doppler systems. The controller can generate sequences of eight tones, each with independently prescribed frequency, duration and start time. The received echos are complex heterodyned and low-pass filtered to remove the carrier frequencies. The data is then passed to a computer for subsequent analysis. A simplified method of digital frequency synthesis used in the controller is described. The controller has proven to be exceptionally versatile in both oceanic and laboratory tests.