The Sentinel diver detection sonar head comprises a combined transmit and receive array along with the required electronics to transfer raw data to the Sentinel Sonar Processor.
The Sonar Head has a wide bandwidth transmission capability, centred by default on 70 kHz with a bandwidth in excess of 20 kHz. Source level for the default transmission is 206 dB re 1 µPa @ 1 m. 8 separate 45° transmit sectors are used, which are individually addressable, allowing any segment to be disabled to reduced nuisance acoustic returns from close in objects such as harbour walls or jetties.
The transmitters themselves are fully programmable and supplied with a number of frequency modulated Doppler tolerant pulses that can be selected via the Sentinel system configuration file.
The compact 1:3 piezo-composite transducer array has 128 separately wired elements, which are used to form 256 equally spaced, receive beams – each with a 1.4° (3.5m) horizontal beam width. Software further interpolates these beams to provide highly accurate bearing estimation for the target.
The sonar head also contains the electronics to digitise, baseband, multiplex and transfer the signals received by the transducer, along with control and monitoring software that performs constant built-in-testing to verify the health of the transducer elements and front-end electronics.
Efficient electronics and transducer arrays result in a total power budget of less than 70 W.
Data is transferred to the surface via either 65 m copper or 300 m or greater fibre-optic cable.
An attitude and heading reference sensor is included in the sonar to compensate for orientation and motion of the sensor. This also allows the sonar to be mounted either way up.
The Sentinel sonar head is available in both a lightweight aluminium housing, suitable for expeditionary use, and in an super duplex housing for permanent installations.