Chelsea Technologies Group - Echo RepeaterAcoustics Source

ERAS is a compact and versatile system for the performance evaluation of a wide range of active and passive sonar. It has been designed to be hand-deployed from small vessels with few facilities - the transducer assembly is a small lightweight unit containing both projector and hydrophone. At the surface, the system includes a rugged, portable, power amplifier unit and a controlling computer.

ERAS has been designed to be hand-deployed from small vessels with few facilities - the transducer assembly is a small lightweight unit containing both projector and hydrophone.

Applications	Operating modes	Features
• Sonar test and calibration • Underwater target detection • Sonar operator training • Surveillance • Noise signature simulation • At sea, acceptance trials	• Complex Signal Source • Sequence • Echo Repeater • Transponder • Received Signal Monitor • Slant Range Measurement	• Broadband operation • Operator control via computer • Self contained and transportable • Small and lightweight • Easily deployed from a range of ocean going vessels • Advanced, acoustic source and echo repeat functions

The initial function of ERAS was to act as a very low frequency acoustic source with an echo repeating capability for at sea, customer acceptance of a shipborne, active and passive sonar suite. Whilst its frequency range of operation is specific to these target sonars it can easily be tailored to the specific needs of any user. Please contact our sales department with your requirements.

When compared to alternative systems, ERAS is extremely attractive to a user due to its relatively low cost, small size and light weight. It can be deployed easily from a small boat, if required, but still offers a very sophisticated suite of signal source and echo repeating capabilities.
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ERAS retains many of the powerful features of the Chelsea Technologies Group Versatile Acoustic Source System (VASS) but without the complexity of a towed format obviating the need for larger vessels. ERAS is controlled by an easy-to-use Graphical User Interface commanding the Digital Signal Processor which is used to Echo Repeat, Transpond, and produce calibrated transmissions with up to 24 tones simultaneously. ERAS provides a highly versatile and flexible sonar test system that is configured by simple mouse or keyboard selections. In addition to instant configuration changes, via its Graphical User Interface run from Windows XP Professional, ERAS allows desktop set-up of complete trials’ programs in advance hence avoiding potential errors in signal definition during calibration trials.


Echo Repeat Mode	Transpond Mode
In Echo Repeat mode, ERAS can repeat signals (between 2000Hz and 2600Hz) received from a hydrophone contained in the hand-deployable, transducer head. It does this in response to a trigger event, based either on the incoming acoustic signal, an external input, or under operator control. The repeated signal can have a highlight structure imposed upon it to mimic the reflections from a target. The many configurable parameters are controlled via an easily operated Graphical User Interface. Within this interface, the user can add Doppler, target strength and signal highlights to the echo repeated acoustic signal. A programmed sequence of echo repeated signals can be configured to simulate a moving target by appropriate addition of Doppler frequency shift and monotonically changing time delay. .	In Transpond mode, ERAS can transmit a user defined acoustic signal (between 280Hz and 2600Hz) in response to a trigger event which can be either acoustic, from an external input or under operator control. The transpond signal can be defined as a single pulse, or a ramp of pulses, either of a monotone or LFM or LPM sweeps, with selectable frequency and source level. In addition, any selection within the Source Mode can be transponded.

Source & Sequence Mode
As a calibrated acoustic test, signal transmitter (source mode) ERAS can generate complex acoustic test signals (between 280Hz to 2600Hz). It is capable of concurrently generating up to 24 tones. The system also allows up to five noise bands (selectable from white, pink or PRN (Pseudo Random Noise)) and 5 bands of Band Limited noise (White, Pink or PRN) to be generated with the tones. The frequency & source level of each tone (&noise band) may be controlled independently &each selected as CW (Continuous Wave) or pulsed. ERAS can also generate LFM (Linear Frequency Modulation) or LPM (Linear Period Modulation) sweeps and complex modulated transmissions. The system allows pulse trains up to 1,000 pulses with stepped source level.

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General Specification
Modes:	Source, Echo Repeat, Transponder
Transmit Bandwidth:	280Hz to 2600Hz (user definable)
Horizontal Beam Pattern:	Omni-directional
Vertical Beam Pattern	+30^o
Source Mode
Pulse Lengths:	3ms to 10s or CW
Number of Pulses:	Up to 1000
Pulse Intervals:	Up to 60s
Variable Step Levels:	-10 to +10dB
Tones:	Up to 24 (each with definable source levels and frequencies - CW or pulsed)
Sweeps:	LFM or LPM
Noise:	Either broadband or up to 5 user definable bands
Noise types:	White, Pink or Pseudo-Random
Modulated Signal:	AM or FM, user definable carrier and modulating signal

Mechanical
Computer:	405 x 225 x 205mm, 10kg
Power Amplifier:	445 x 220 x 538mm, 15kg (splashproof)
Transducer:	260 outer diameter x 608mm length, 8.3kg
Cable length:	50m
Computer Power Requirement:	90 to 250V AC auto switching 50/60 Hz
PA Power Requirement:	95 to 130V or 185 to 260VAC auto switching 50/60 Hz

Transponder Mode
Frequency Range:	280Hz to 2600Hz
Pulse Length:	10ms to 10s
Variable Step Levels:	-10 to +10 dB
Trigger Types:	Acoustic, TTL pulse or manual
Trigger Level & Averaging:	Fully user definable
Transpond types:	LFM or LPM sweep, Monotone or Source Mode (see above)

Echo Repeat Mode
Echo Frequency:	2000Hz to 2600Hz
Trigger Types:	Acoustic, TTL pulse or manual
Trigger Level and Averaging:	Fully user definable
Echo Length:	10ms to 5s
Added Doppler:	-40 to +40 knots
Added Echo Strength:	- 30 to +40dB
Echo Delay:	Up to 60s
Highlights:	Up to 5
Highlight Strength:	-30 to +30dB
Highlight Offset:	Up to 200ms
Moving Track Target :	Velocity –40 to +40 knots
Tag on Transponder:	User configurable

Back Sonar Test & Evaluation Page	Download ERAS brochure (pdf)


Transducer Deck Cable	Power Amplifier Unit	ERAS Computer