Hydroacoustic sonar equipment

DETAILED DESCRIPTION We claim: 1.
In a hydroacoustic sonar system comprising transmitter-receiver means for beaming a pulse modulated radio frequency acoustic signal towards a target and receiving an echo signal reflected from the target, and means for deriving from the received echo signal a time varied gain corrected electrical signal to be demodulated and recorded, an improved means for demodulating said electrical signal comprising an input amplifier having a bandwidth of at least 500 kHz, a full wave detector means having a bandwidth of at least 500 kHz, the detector being coupled to the output of the amplifier, and an active low pass filter coupled to the output of the detector, the low pass filer having a cut off frequency of at least 50 kHz.
2.
A hydroacoustic sonar system according to claim 1, wherein the input amplifier and the full wave detector each have a bandwidth of at least 1.
2 MHz.




Description:
This invention relates to hydroacoustic sonar equipment and to the detection and examination of underwater targets by the use of such equipment.
The invention is especially applicable to the examination of fish populations in environmental studies, but is not necessarily limited to such applications.
To comply with regulatory agencies' requirements, biological studies must be conducted in the vicinity of hydroelectric, nuclear and thermal power stations.
Most studies are directed towards fish, with netting being used as the principal method of determining fish composition and abundance in each area under examination.
While netting methods cannot be dispensed with entirely, they are labour-intensive and inevitably involve destruction of fish.
Hydroacoustics may offer an alternative method for the examination of fish population and distribution which is cost-effective and non-destructive.
Considerable advances have been made in the use of hydroacoustics for fish management.
Advances have been made in the areas of developing real time data collection and analysis systems