This project was initiated to evaluate appropriate microprocessor and
digital logic techniques that could increase the flexibility and effectiveness of
a sonar transmitter. The study led to a multi-channel signal synthesis concept
designed to exploit 'phased array' steering techniques. Two versions of the
equipment have now been built and evaluated. Mk.I is a relatively low power
15 channel system with 2 kilowatts total electrical power using a 40 kHz
15 λ x 1 line array. This system proved the practicability of the basic concept
and its success led to the 16 kilowatt Mk2 high power version which
drives a 16λ x 16 λ wideband transducer array.
The study included:
The design and construction of a multi-channel signal generator.
The writing of control and signal synthesis software.
The design, evaluation and commissioning of suitable linear power
amplifiers .
Investigations into suitable transducers and phased array design, leading
to the manufacture of suitable matched wide band multi-channel 'staved'
transducer arrays.
Finally, a series of trials were made in a variety of open water conditions
to evaluate the systems performance and investigate the multiple modes
of operation that have been developed.
The system has successfully demonstrated that transmitter beam steering
is both practical and flexible. The techniques implemented permit sector
interrogation by 'within-pulse' type sweeps, by 'Ripple-fire' and by transmitting
steered 'Pings' sequentially on prededermined bearings. Each mode allows
considerable flexibility in the generated waveform shape and frequency.
The 'Multi-Mode' capability of this approach was conceived primarily
as a research tool but many of the modes can be isolated and exploited in
dedicated applications
