Echo Repeating Acoustics Source System (ERAS)

Echo Repeating Acoustics Source System (ERAS) - calibration, test and performance evaluation of airborne, surface ship and submarine sonarsChelsea Technologies Group manufactures a wide range of state of the art equipment and systems for calibration, test and general performance evaluation of airborne, surface ship and submarine sonars. The core technology has developed over a number of years and now includes the ERAS, PERS and VASS range of products. Echo Repeater Acoustics 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.

 

Existing users of these systems include UK QinetiQ, UK Director of Submarines, NATO SACLANT Undersea Research Centre, La Spezia, Italy, the Belgian Navy, and Exelis Inc, USA.

 

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Applications

  • Sonar test and calibration
  • Underwater target detection
  • Sonar operator training
  • Surveillance
  • Noise signature simulation
  • Sea acceptance trials

Features

  • Broad band operation
  • Operator control via computer
  • Self contained and transportable
  • Small and lightweight
  • Easily deployed from a range ocean going vessels
  • Advanced, acoustic source and echo repeatfunctions

Operating Modes

  • Complex Signal Source
  • Sequence
  • Echo Repeater
  • Transponder
  • Received Signal Monitor
  • Slant Range Measurement

Introduction

Chelsea Technologies Group manufactures a wide range of state of the art equipment and systems for calibration, test and general performance evaluation of airborne, surface ship and submarine sonars. The core technology has developed over a number of years and now includes the ERAS, PERS and VASS range of products. Existing users of these systems include UK QinetiQ, UK Director of Submarines, NATO SACLANT Undersea Research Centre, La Spezia, Italy, the Belgian Navy, and Exelis Inc, USA. 

 

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 This e-mail address is being protected from spambots. You need JavaScript enabled to view it 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.

Operating Modes

The ERAS System operates in three modes:

 

Echo Repeat Mode

In Echo Repeat mode, ERAS can repeat signals 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.

 

Transpond Mode

In Transpond mode, ERAS can transmit a user defined acoustic signal 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.

Typical Source LevelERAS Typical Source Level

 

Source and Sequence Mode

As a calibrated acoustic transmitter (source mode) ERAS can generate complex test signals. 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 and source level of each tone (and noise band) may be controlled independently and each selected as CW (Continuous Wave) or pulsed. ERAS can also generate LFM (Linear Frequency Modulation) or LPM (Linear Period Modulation) sweeps and other complex modulated transmissions. The system allows pulse trains up to 1,000 pulses with stepped source level.

Versatile

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. At the surface, the system includes a rugged, portable, power amplifier unit and a portable computer. 

 

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 tonnes 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, ERAS allows desktop set-up of complete trials’ programs in advance hence avoiding potential errors in signal definition during calibration trials.

Specification

Specification for a typical ERAS system used for test and calibration of a surface ship sonar suite.

General

Modes Source, Echo Repeat, Transpod
Transmit bandwidth User definable
Horizontal beam pattern Omni-directional
Vertical beam pattern +30°

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 +10 dB
Tones Up to 24 (each with definable source levels & 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 Laptop
Power amplifier 4U 19" case
Transducer 260 outer diameter x 608mm length, 8.3kg (example)
Cable length 50m
Computer power requirment 90 to 250V AC auto swtiching 50/60 Hz
PA power requirement 95 to 130V or 185 to 260VAC auto switching 50/60 Hz

Transpond Mode

Frequency range User definable
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 User definable
Trigger types Acoustic, TTL pulse or manual
Trigger level & averaging Fully user deinfable
Echo length 10ms to 5s
Added doppler -40 to +40 knots
Added echo strength -30 to +40 dB
Echo delay Up to 60 s
Highlights Up to 5
Hightlight strength -30 to +30 dB
Highlight offset Up to 200ms
moving track target Velocity -40 to +40 knots
Tag on trasnpond User configurable

In view of our continual improvement, the designs and specifications of our products may vary from those described.