Technology
ISSN : 0971-4413
BULLETIN OF DEFENCE RESEARCH AND
DEVELOPMENT ORGANISATION
Vol. 18 No. 4 August 2010
TECHNOLOGIES FOR SONAR SYSTEMS
Sonar systems have undergone evolutionary changes from
unitary systems to composite systems where fusion of data from
multiple sensors makes sonar displays highly user-friendly.
Over the last three decades, DRDO has designed, developed and
inducted several sonar systems for the warships and
submarines of the Indian Navy to enhance its capabilities.
S
onar is basically a remote sensing technique that uses sound waves to detect, locate and identify objects in water. The
term sonar is an acronym for Sound Navigation and Ranging. Sonars are the eyes and ears of ships or submarines in water
and are mainly used for underwater navigation and surveillance. Civilian uses of sonar include determination of water
depth, mapping the ocean floor, locating various objects in the ocean, determining the characteristics of ocean bottom, and
even fish finding. Sonar system consists of underwater transducers, front-end signal conditioning units, signal processors, and
displays. Sonar transducers transmit acoustic power and pick up the echo returns or merely listen to the underwater sounds,
process the signal and provide information about targets on the display units.
High Bandwidth Real-time
Sensor Data
Real-time Information and
Control Data
Raw Data Bus
FE Front-end
Hardware
Gigabit Ethernet
Transducers
Display Data Bus
Signal Processing
and Post Processing
Sub-systems
Gigabit Ethernet
Raw Data
Processed Data
Data Recorder
Functional Layout of a typical Sonar System
Display
MESSAGE
SONAR systems still remain the primary surveillance technique for ships and
submarines in naval warfare. In the case of submarines, SONARs are the eyes and ears
underwater. Ocean going platforms being relatively slow moving, airborne
surveillance SONARs play a key role in early warning. Naval Physical and
Oceanographic Laboratory has been the pioneering R&D establishment in the country
responsible for near-total self-reliance in airborne, surface ship-mounted as well as
submarine-borne SONAR systems of the Indian Navy. The technologies associated
with SONAR systems, viz., signal processing, power amplifiers, transducers, handling gears,
hydrodynamics, oceanographic, etc., are complex and multidisciplinary. This issue of Technology Focus
lucidly brings out the cutting-edge accomplishments of DRDO, in various enabling technologies that
makeup the three-dimensional world class SONARs. I am sure this effort would go a long way in
providing the readers, a quick awareness in this specialised area.
Dr J Narayana Das
OS & Chief Controller R&D (NS, M & HR)
MESSAGE
Vol. 18 No. 4 August 2010 02
The SONAR systems being the only sensor system that has the capability to overcome the
limitations of the underwater environment, it provides the capability for surveillance of undersea
situation by naval platforms and ultimately provides inputs for launch of weapons to neutralise
opposing forces. It also enables safe navigation, obstacle avoidance and underwater
communication. Considering its strategic utility for the underwater vessels, availability of
indigenously developed technology in SONAR systems is critical to our Navy.
It is a matter of great pride that various SONAR systems developed by DRDO have been inducted into Naval
platforms and their operational utility has provided impetus for further improvement/upgradation and
development of new configurations of underwater systems in tune with global standards. Some of the recent
developments of DRDO pertaining to this technology have been summarised in this Special Issue of Technology
Focus. These will augur excellence in indigenous developments in this area and further optimise the configuration
of the systems.
Commodore PK Mishra
Director Naval R&D and
Member Editorial Board Technology Focus
From the Desk of Special Editor
For an emerging economic power like India with 7600 km long coastline, 12 major and
184 minor ports, and 90 per cent of its international trade through sea routes, the
importance of defending its coastline against threats through superior underwater
surveillance capability needs no emphasis. Over the last three decades, DRDO has
designed, developed and inducted several sonar systems for the warships and
submarines of the Indian Navy to enhance this capability. Surface ship sonars like APSOH,
HUMSA, and HUMSA NG, submarine sonars like PANCHENDRIYA and USHUS, TADPOLE
sonobuoys for airborne applications are some of the major systems delivered by DRDO
and exploited by Navy. Several technologies for the towed array sonar and airborne
dunking sonar have also been developed by DRDO during this period.
DRDO has been working very closely with PSUs, private sector industries, and academic institutions for the
design, development, production, and induction of sonar systems. With the increasing requirement for sonar
systems for the new platforms being acquired by the Indian Navy, the industry has evinced keen interest in
absorbing the complex sonar technologies. Moreover, the sonar systems have undergone evolutionary changes
from unitary systems to composite systems where fusion of data from multiple sensors makes sonar displays
highly user-friendly. Riding on the revolutionary changes offered by the computation and communication
technologies, and the indigenously developed models for prediction and interpretation of sonar performance in
Indian waters, user has gained more confidence in exploitation of these sonar systems. The large number of
unique testing facilities established under DRDO for evaluation of sonars have been gainfully utilised by both Navy
and industry alike.
This issue of Technology Focus gives a summary of various technologies that are at work in the development
and induction of sonar systems. New sonar technologies are under development in DRDO in consonance with the
advances in commercial technologies and increasing demands on performance and reliability of sonar systems.
induction of advanced sonar systems.
S Anantha Narayanan
OS & Director
Naval Physical & Oceanographic Laboratory (NPOL), Kochi
Vol. 18 No. 4 August 2010 03
We are confident that these will further strengthen the surveillance capability of our naval forces through
Sonar for naval applications
broadly falls into two categories:
active and passive. Active sonar
emits pulses of sound waves that
travel through the water and
processes the received target echo to
estimate the range, bearing, and
Doppler of the target. Passive sonar
involves processing the sound signal
generated by the target for
estimating the bearing and target
characteristics through spectrum
analysis. The information gathered
by the sonar is fed to the Fire Control
Systems to compute other target
parameters like speed, course, and
range.
Intercept sonars are early warning
systems aiding classification of
targets by processing the
transmitted signals of other
platforms. Obstacle-avoidance
sonars are high frequency active
sonars for submarines to aid safe
surfacing operations. Underwater
communication systems permit
communication between platforms
through acoustic means in different
modes including voice, telegraph,
and data. For submarines, the sonar
is also the navigation equipment.
Sonar systems can also be used to
realign inertial navigation systems by
identifying known ocean floor
features.
The performance of a sonar
system is strongly influenced by the
ocean environment, which is highly
unpredictable, thereby making the
development of a sonar system a
challenging task. Continued ocean
studies for better understanding of
Algorithm
To offset the adverse effects on
detection by the bathymetric profile
of the ocean and self-noise of the
platform, the deployment
mechanisms of sonar transducers
have undergone changes to
maximise the detection range.
Though the hull-mounted and bowmounted transducers are the most
common approaches, the variabledepth towed array sonars also help in
detection of targets and torpedoes
below the surface-sound channel.
Dunk bodies housing transducers
and associated electronics are
dipped from helicopters for
ASW
Oceanography
Design
Vol. 18 No. 4 August 2010 04
the ocean are being pursued and
better acoustic propagation models
are being developed for accurate
estimation of predicted ranges.
Modelling & Simulation
MMI/Display
Materials
Transducers
Signal Processing
Signal Conditioning
Sensor Structures/Handling Systems
Advanced Sonar Systems Technologies
DRDO has been striving to meet
the aspirations of the Indian Navy
on sonar systems through the
technologies and systems developed by the Naval Physical and
Oceanographic Laboratory (NPOL) at
Kochi. During the last four decades
DRDO has delivered various types of
sonar systems for ships, submarines,
and airborne platforms of Indian
Navy, and thereby NPOL has matured
as a System Laboratory of DRDO.
Keeping in view the growing
strategic requirements of the Indian
Navy, the Laboratory is focusing on
developing advanced sonar systems
technologies.
Over the years, Advanced Sonar
Systems technologies being
developed by NPOL have made an
impressive growth in the research
and development in all the above
areas. This special issue of
Technology Focus highlights the
technologies developed and
implemented into various subsystems and the technologies
transferred to production agencies
for realising the sonar systems
inducted in various Naval platforms.
Sonar systems rely on acoustics
and a suitable transduction of the
acoustic energy to electrical energy.
NPOL has pioneered the designing of
transducer using finite element
analysis. The designs have been
prototyped and engineered for use
in ship, submarine, and helicopterborne sonar systems. Their detailed
acceptance tests and characterisation have also been done using the
unique test facilities available at
NPOL. Usually these acoustic
transducers are made of piezoelectric materials; their working
principle is based on piezoelectric
effect.
Acoustic transducers are mainly
of two types—projector for
underwater transmission and
hydrophone for reception. The
piezoelectric ceramics used in these
transducers are indigenously
manufactured at a cost that is
comparable to that of imported
Single Stave
components but meet tighter
tolerances. The technology for
manufacturing the transducers has
been transferred to production
agencies. There are mainly four
different types of designs for
underwater projectors.
Tonpilz (German for “singing
mushroom”) transducers are used in
active sonar systems to radiate high
levels of directional acoustic
pressure. The echo is received
through a hydrophone array and
processed to detect, track, and
classify targets. Members of this
family of transducers have been used
in active submarine sonar, active ship
sonar, underwater communication,
and obstacle-avoidance systems.
Several Tonpilz transducers have
been designed and developed with a
high transmitting voltage response,
a 3 dB bandwidth of more than one
octave, and a power-to-weight ratio
much higher than that achieved
Circular Array
Vol. 18 No. 4 August 2010 05
detection of sub-surface targets.
These requirements have posed new
challenges in sonar technology
development related to winches and
towed bodies. Development and
characterisation of exotic materials
for sonar systems in various areas like
composite materials, nanomaterials,
baffles, encapsulants, etc., are
important for improved reliability
and enhanced life of transducers and
interconnect materials.
earlier. Transducers, in this family,
with resonance frequencies ranging
from 1.5 kHz to 25 kHz are
individually encapsulated, are
capable of operating at a depth of
300 m for more than 10 years, and
have been extensively tested and
characterised. Tests with specially
tuned transducers and indigenous
power amplifiers have demonstrated
very high source level over
reasonably large bandwidth.
Vol. 18 No. 4 August 2010
06
Most of these transducers are also
used as hydrophones to receive the
echo. In addition, these are also used
in passive sonar operations where
the usable bandwidth is much higher
as the receiving sensitivity has a rolloff below resonance and, therefore,
reduces the high and low frequency
ambient noise.
The flextensional transducer has a
shell that is driven by piezoelectric
ceramic stacks. The extensional
vibration of the electrically-excited
stack causes the shell to flex, giving
the transducer its name. These
transducers are well suited for low
frequency sonar applications
because these are omni-directional.
These have better power handling
capacity, and power-to-weight and
power-to-size ratios much higher
than those of Tonpilz transducers.
The shape of the shell determines
the class of the transducer. A family of
class IV transducers has been
designed using finite element
analysis. These transducers have
elliptical cylindrical shells, made of
transducers have been indigenously
developed. The technology for
manufacturing these transducers has
been transferred to industrial
partners.
Flextensional Transducer
aluminium, that are excited by stacks
of piezoelectric ceramics.
Flextensional transducers with
low resonant frequencies have been
designed and developed for use in
helicopter-borne dunking sonar
systems and ship-borne towed sonar
systems. The arrays have been
pressure tested to operate at depths
up to 300 m. Efforts are on to further
achieve lower frequencies.
Piezoceramics used in these
Hydrophones are broadband
receivers used in passive
surveillance, intercept, and towed
array sonars with very good free-field
receiving sensitivity and effective
acceleration compensation. These
devices are designed for deep water
applications with long operational
life for submarine sonar systems.
Hydrophones have omnidirectional response in the radial
direction in desired frequency range.
Mainly there are three different
kinds of acceleration-balanced
hydrophones: Passive Surveillance
Array (PSA) hydrophones; Medium
Frequency (MF) intercept
hydrophones; and towed array
hydrophones.
The PSA hydrophone is one of the
broadband hydrophones operating
in the frequency range up to 10 kHz
without any baffles. The hydrophone
is capable of operating up to a depth
of 600 m and has an operational life
of more than 7 years. It has omnidirectional response in radial
direction up to 10 kHz within 1dB. Its
specially designed mounts at the
ends, with central spacer design,
provide low acceleration sensitivity.
Low Frequency Flextensional Transducer Array
The MF intercept hydrophone is a
wideband hydrophone used in the
PSA Hydrophone
frequency above 10 kHz. This is
capable of operating up to a depth of
450 m. Two piezoelectric ceramic
tubes have been assembled with
passive components and encapsulated using PV bonding technology.
DRDO has excelled in developing
different types of towed array
hydrophones with a wide
operational frequency range. These
hydrophones are small in size and
moulded with oil-compatible rubber
encapsulant. The technology has
been transferred to production
agency for the bulk fabrication of the
hydrophones.
Intercept Hydrophone for MF Band
Electro-acoustic reference
transducers of two different types
have been designed for underwater
acoustic measurements and
calibration to work over different
Reference Transducers: NP 20 and NP 30 (top)
Towed Array Hydrophone
operating bands. These transducers
work as a projector as well as a
hydrophone. As a projector, it
operates over a wide frequency band
and is capable of providing high
acoustic source level. As hydrophones, these provide flat frequency
response. The transducer technology
has been transferred to production
agency.
DRDO has designed and
developed high frequency transducers using 1-3 piezocomposites.
Specifications: Reference Transducers
NP 30
NP 20
Resonance frequency
30 + 1 kHz
21 + 1 kHz
Usable frequency
frequency range
range
Usable
3-60 kHz
kHz
3-60
1-50 kHz
kHz
1-50
Beam pattern
Omni (horizontal)
Toroid (vertical @ 12 kHz)
Omni (horizontal)
Toroid (vertical @ 10 kHz)
Operating depth
0-300 m with + 1.5 dB
variation
0-300 m with + 1.5 dB
variation
Input power
400 W
400 W
Cable length
30 m
30 m
Vol. 18 No. 4 August 2010 07
Parameters
The design is basically different from
that of conventional low frequency
transducer arrays. An array of 1-3
piezocomposite was first fabricated
and the individual transducer
elements were defined later by
applying patterned electrodes on
the major surfaces.
A few prototypes of 150 kHz
transducer arrays have been
eva lua ted under wa ter . The se
transducers are useful for high
resolution underwater imaging
applications such as Mine Hunting
Sonar and Diver Detection Sonar.
Vol. 18 No. 4 August 2010 08
Transducers with Micro-ElectroMechanical Systems (MEMS)
technology are being developed at
NPOL for miniature sensor array
system especially for thin-line towed
arrays (TLTA). MEMS are miniature
devices or systems that combine
electrical and mechanical components fabricated using IC batch
processing technology. In MEMS,
sensors and actuators are monolithically integrated with signal
conditioning, interface circuits and
1-3 Piezocomposite Transducer Arrays Receiver. Inset: Projector
electronics to generate intelligent
microsystems that perform superbly
at a reduced cost.
MEMS hydrophone is one of the
devices developed by DRDO. It
comprises an extended gate MOSFET
(Metal-Oxide-Semiconductor FieldEffect Transistor) and a piezoelectric
sensor. The piezoelectric material
senses the acoustic pressure
fluctuation and an on-chip N–type
depletion mode MOSFET amplifies
the signal. It also acts as an
impedance matching device.
Five-element TLTA using MEMS Hydrophone
Silicon MOSFET was fabricated
using MOS process technology.
MOSFET hydrophone has been
mounted on a PCB (21mm x 14 mm)
with a pre-amplifier. These hydrophones are encapsulated in
acoustically transparent potting
material. Dimension of individual
hydrophone after encapsulation is
35 mm x 25 mm x 5 mm.
These miniature sensors find
applications in TLTA for submarines,
surface ships, and Unmanned
Surface Vessels (USV).
Power Amplifier (PA) is an integral
part of active sonar systems, and
amplifies the sonar signal to the
Switched Mode Power
Amplifier
Linear Power
Amplifier
Type
levels required by the transducer
element. NPOL has developed
compact and energy-efficient power
amplifier plug-in modules of
different power handling capacities
Technology
in both linear and switched modes
for use in several sonar systems.
Major types of power amplifiers
designed by the Laboratory are:
Application
(a) Quad wideband
linear power
amplifier
MOSFET-based
linear class AB
Mine hunting sonar, obstacle avoidance
sonar, echo sounder and side-scan sonar
multichannel wideband ac source and
fishing sonar
(b) Wideband high power
linear amplifier
Power BJT-based
linear class AB
PA for broadband active sonar and
broadband underwater communication
systems and wideband ac source and
audio power amplifier
(c ) Energy efficient
class S digital power
amplifier
Power MOSFETbased class S
Diver deterrence sonar and low
frequency echo sounder
(d) IGBT-based
class D high power
amplifier
Power IGBTbased class D
Low frequency active sonar
(e) MOSFET-based
class D high power
amplifier
Power MOSFETbased class D
Low frequency active sonar
Quad Wideband Linear Power Amplifier (NP-LAQ-HF-0050)
Configuration
Power output/Amplifier
Duty cycle
Distortion at full load
Frequency band
Load impedance
Dimensions (W x H x D)
Weight
:
:
:
:
:
:
:
:
Quad, linear class AB
50 W rms
10 %
< 0.5 %
10 kHz to 100 kHz
500 Ω; Cane tailored to any load
21TE x 3U x 235mm
< 4 kg
Wideband High Power Linear Amplifier NP-LAS-WB-1000)
Specifications
Configuration
Power output
:
:
Linear class AB, bridge
1000 W rms
Vol. 18 No. 4 August 2010 09
Specifications
Duty cycle
Distortion at full load
Frequency band
Load impedance
Dimensions (W x H x D)
Weight
:
:
:
:
:
:
10 %
<2%
1 kHz to 12 kHz
125Ω; can be tailored to any load
21TE x 3 x 235 mm
< 5 kg
Energy Efficient Class S Digital Power Amplifier (NP-SAS-LF-3000)
Specifications
Type
Configuration
Power output
Duty cycle
Power control
Operating frequency
Load impedance
Dimensions (W x H x D)
Efficiency
:
:
:
:
:
:
:
:
:
Plug in, Blind mate type
Full bridge class S switching
3000 W rms
10 %
0 to -9 dB in 3 steps
1 kHz to 10 kHz
100 - 400 Ω
10 %
21TE x 3U x 220 mm
> 90 %
IGBT-based Class D High Power Amplifier (NP-SAS-LF-5000)
Specifications
Configuration
Switching technique
Input
Power output
Duty cycle
Power control
Operating frequency
Load impedance
Efficiency
Dimensions (W x H x D)
:
:
:
:
:
:
:
:
:
:
IGBT full bridge
PWM, class D
Pulse width modulated signal
5000 W rms (max.)
10 %
0 to -6 dB in two steps
2.5 kHz to 6.5 kHz
200 Ω + 10 %
>80 %
135 mm x 6U x 230 m
MOSFET-based Class D High Power Amplifier (NP-SAD-LF-2000)
Vol. 18 No. 4 August 2010 10
Specifications
Configuration
Switching technique
Input
Power output
Duty cycle
Power control
Distortion at full load
Operating frequency
Load impedance
Efficiency
Dimensions (W x H x D)
:
:
:
:
:
:
:
:
:
:
:
Power MOSFET full bridge
Uni-polar PWM, class D
Pulse width modulated signal
2000 W rms (max.)
10 % duty cycle
0 to -42 dB (linear)
< 0.5 %
2.5 kHz to 6.0 kHz
200 Ω + 10 %
> 90 %
21TE x 3U x 220 mm
Towed Array Electronics
Specifications: Towed Array Data Acquisition System
Output
Acoustic sensors
Serial data rate
Power
Dimension
Length
Outer diameter
:
:
:
:
2 x 160 channel/12 bit
96 + 128
24 Mbps + 24 Mbps
1 A at 300 V dc
:
:
200 m
80 mm
transmission through a serial fibreoptic link is a challenging task.
Fibre-optic data telemetry system
has been developed for use in towed
array sonar. The towed array
electronics is a distributed multichannel real-time digital data
acquisition system. The major
challenges involved in it are:
simultaneous acquisition of data
from multiple channels, transmission
of the data over tow cable of over
1 km length, and synchronisation of
transmitter with the onboard
receiver for accurate reconstruction.
The acoustic and environmental
sensors operate at different
amplitude levels and frequency
bands with analog and digital
outputs in serial/parallel format.
Acquisition of information from
these varying sources distributed in
an elongated towed body (which can
be up to 1 km long) and combining
these into a common interface for
The realisation of the multichannel signal conditioning and data
telemetry function has been
achieved in a compact hardware
form (housed in a polyurethane tube)
for operations in high pressure and
harsh dynamic conditions. The
realisation of data in digital form has
distinct advantages over analog
systems. The entire hardware has
been realised in multiple modules
interfaced with water-blocked
electromechanical connectors to
enable easy repair and maintenance.
This technology has been successfully demonstrated and used in
towed array sonars.
Coastal Surveillance Systems are
essential to counter the asymmetric
threats posed by hostile submarines,
boats, and divers.
DRDO has developed two core
technologies̶ Seabed Arrays
Technology and Diver Deterrence
System—as part of a coastal
surveillance system.
Seabed arrays are off-board
passive sonars, which can be
deployed on the seabed for monitoring strategic locations at sea on
a continuous basis to assess the
threats from submarines and submersibles . A seabed system with
capability to detect multiple targets
around 360 without any left/right
ambiguity and end-fire anomaly, has
been developed and proven for performance. Multiple-arrays deployed
with appropriate spatial separation
will facilitate the passive range
estimation of the target too. The
system consists of multiple linear
hydrophone arrays with a data
acquisition system. The data can be
transferred to a processing station at
the coast.
Vol. 18 No. 4 August 2010 11
Towed arrays are one of the well
sought out technologies meant for
getting better immunity from own
ship noise because of towing the
array far behind the towing ship.
Also, the large aperture possible with
large number of sensors assembled
at relatively larger l/2, promises
better range. Towed array combines
a host of technologies, viz.,
packaging large number of sensors
into a proper deployable casing,
deployment from a moving platform,
and digitisation and telemetry of
acoustic and non-acoustic sensor
data.
Solid Linear Acoustic Sensor
(SOLASE) array is the latest addition
to the family of underwater acoustic
surveillance arrays for seabed
applications. It is designed and
developed to alleviate the inherent
problems of puncture damages and
oil leakages associated with the
manufacture and operation of the
oil-filled version. SOLASE is a
polymer-based monolithic flexible
solid structure that embeds the
sensors and allied electronics. It is a
multi-channel linear passive acoustic
receiver array and offers improved
underwater surveillance capability
through a new design of premoulded hydrophones, preamplifier PCB, and power supply
unit,which are assembled on
a Kevlar strength member that runs
through the entire length of the
array in a closed loop.
Solid Linear Acoustic Sensor
sonobuoys. RF communication
devices using commercial-of-theshelf (COTS) components with
duplex communication have been
developed and used in sonar
systems.
programmable gain amplifier, and a
digitally programmable anti-aliasing
filter. The system can accept either
single-ended or differential inputs.
The PCB accommodating the design
also supports two RS-422/485 serial
ports. The time division multiplexed
data is sent through a 100 Base TEthernet. In addition, there is a
provision to send this TDM data over
a fibre-optic link.
A 32-channel data acquisition
system with a facility to programme
various functions has been
developed. It incorporates a digitally
Notable features of the design are
the excellent phase matching and
commendable high isolation
between the channels. The data
acquisition system is housed in a
watertight unit making it readily
deployable for underwater
applications. A long-range singlemode fibre-optic communication
over 100 km distance for the transfer
of serial data has been designed and
developed with COTS components.
Alternately, RF communication of
10 km with COTS components with
Duplex communication has been
DRDO has developed a Diver
Deterrence system, which can be
deployed around high value assets
and at harbor mouths. On activation
under Command Control, the system
emits high decibel acoustic pulses to
deter the divers from executing their
mission.
Vol. 18 No. 4 August 2010
12
32-channel Data Acquisition Module
Specifications: 32-channel Data Acquisition System
Several technologies have been
developed to handle low level
signals picked up by multichannel
sonar arrays, and to condition these
signals in amplitude and signal
bandwidth to digitise the signals for
data telemetry, either through
copper or fibre-optic medium. VHF
receivers have been developed to
receive the data transmitted from
Number of analog input channels
PGA
:
:
Anti-aliasing filter
:
ADC
Sampling frequency
Output
:
:
:
32 max.
Digitally programmable
1 per channel
Digitally programmable
up to 10 kHz
SAR type, 12 bits resolution
Programmable
Ethernet 100 baseT and fibre
optic Ethernet link
designed and developed. The
wireless channel utilises IEEE 802.11g
standard at a frequency of 2.4 GHz,
capable of providing a data rate up to
54 Mbps. The transmitter uses 1 W
(30 dBm) power through a 3-sector
antenna with gain of 14 dB. The
systems are extensively used for
transferring both acoustic and
telemetry data.
from an inline aerial array by
comparing the outputs from a phasesensitive detector alternatively
driven by each element. The signals
from the left/right and fore/aft aerials
are sampled to provide a continuous
indication of the buoy's position.
This system is designed for
operation in helicopters for homing
on to sonobuoys. The left/right
position of the sonobuoy, with
respect to the aircraft, is derived from
a phase comparison of the signals
received from two-directional aerials
designed to operate in the VHF
frequency range.
The VHF receiver, onboard ASW
aircraft, is the communication link
between the sonobuoy and the
processor. The sonobuoy picks up
the acoustic noises in the desired
frequency band and modulates the
carrier frequency (FM) of a VHF
transmitter in any one of the 99 VHF
channels. The receiver is capable of
receiving eight sonobuoy channels
simultaneously. The processed data
go to the Signal Processor for LOFAR
and DEMON processing and
displaying.
The fore/aft position of the buoy
with respect to the aircraft is derived
Specifications: 32-channel Sensor Data Recorder
Number of analog input
Signal bandwidth
Dynamic range
Gain control
Sampling frequency
ADC resolution
Output data format
:
:
:
:
:
:
:
32 max
100 Hz to 12 kHz
80 dB
Programmable
31.25 kHz
12 bits
100 Mbps Ethernet
VHF Receiver
The sonar signal processing and
display system extracts information
from the data sensed by the sensors.
The information extracted includes
direction of arrival, speed of the
contact, the bearing rate, dominant
tonal frequencies, shaft rpm, and the
number of blades. For this, the data
coming from the various sensors is
subjected to a variety of signal
processing techniques. The
processing is done using high performance Digital Signal Processors
(DSP) and PowerPC-based boards.
The information is subsequently
presented to the operator through
suitable human- machine interfaces.
To meet the requirement of
processing a large number of
channels of data simultaneously to
provide all-round surveillance, sonar
systems use a high-speed signal
processing strategy. Adaptive sonar
signal processing techniques, which
form the core of the processing,
require enormous amount of
Vol. 18 No. 4 August 2010 13
Homing Receiver System
The recorder unit is used for
recording the acoustic data directly
from sensors for monitoring and
storing for further analysis. This unit
receives 32-channel sensor data,
conditions it in both amplitude and
frequency, digitises it and converts it
to Ethernet format. It incorporates
pre-amplifiers, programmable gain
amplifiers, and different types of
filters and data converters.
computational capability along with
the capacity to handle high input
data rates. The resulting signal
processing functions have been
implemented using high-speed
digital signal processor boards based
on open standards using TigerSHARC
processors. The processor board is
designed in 6U form factor plugging
on a VXS back plane.
The TigerSHARC processor-based
DSP board combines 24GFlops of
raw computing power along with a
variety of high-speed interfaces for
efficient data transfer. The design
combines a cluster of eight such high
performance processors along with a
separate communication engine
based on a dual-core BlackFIN
processor.
Vol. 18 No. 4 August 2010 14
The communication engine
connects to two Ethernet ports, each
operating at 1Gbps, and VME and
USB ports over the PCI bus. This
completely takes care of all data
interfaces and leaves the high
performance core unhindered to do
all core signal processing functions.
The board also has two audio ports, a
PMC site for PCI mezzanine boards as
well as JTAG ports for debugging.
The high computational power
provided by the design makes the
cherished dream of single-board
sonar closer to reality.
The NP-TS201-24 is complete
with a user-friendly development
support system, facilitating the
utilisation of the hardware
resources, most effectively. The
design supports software development in C language, utilising an
extensive collection of routines
developed for signal processing
applications and runs on a personal
computer. Utility software communicates with NP-TS201-24 for
downloading the compiled code,
monitoring, and debugging the
program during execution.
Together with the available
software support, the NP-TS201-24
offers significant advantages in
hardware reduction and easy system
integration. The board is being used
in the latest series of sonar systems
and was developed with the help of
reliable industrial partners.
For control, networking, and
information and display data
processing, a high-end Single Board
Computer (SBC) is essential.
Adapting open standards, an SBC in
6U VME form factor based on
PowerPC MPC7448 processor
operating at 1 GHz has been
designed and developed in close
collaboration with industrial
partners. The board combines high
processing power and IO bandwidth,
and low power dissipation.
The PowerPC has become the
most widely used new generation
Reduced Instruction Set Computer
(RISC) processor because of its
superscalar architecture, extended
temperature options, instruction set
compatibility across the entire
product line, multiprocessing
capabilities, long-term growth path,
and the wide selection of
development tools. A 128-bit
implementation of "AltiVec" SIMD
(Single Instruction, Multiple Data)
engine accelerates typical networking and information processing
functions.
The NP-PPC7488 SBC has 512 MB
DDRII SDRAM, 256 MB Flash, and two
Gigabit Ethernet ports. Real-time
Clock (RTC), high resolution timers,
and watchdog timer are also
available. The board is ported with
U-Boot and Linux kernel. The SBC
provides two PMC expansion slots for
extended flexibility and integration
of additional I/Os to the board.
Configuration of NP-TS 201-24
NP-TS 201-24 Board
Processing engine
Internal memory
Onboard memory
External interface
:
:
:
:
Communication engine
Software support
:
:
Eight TigerSHARC processor @ 500 MH z
24 Mb/processor
128 MB SDRAM; 16 MB Flash
Gigabit Ethernet; VME; Link and
Serial ports
Black FIN processor
VDSP IDE; TigerSHARC communicator;
Signal processing library
Configuration of NP-PPC7448 Single Board Computer
Processor
Memory
:
:
PMC sites
Network
USB
Backplane
Firmware
:
:
:
:
:
Power PC 7448 @ 1GHz
512 MB DDR II SD RAM; 256 MB Flash;
L2 1 MB Cache
Slot 1(64 bit/66 MHz); Slot 2 (32 bit /33 MH z)
2 channel Gigabit Ethernet
2 USB 2.0 ports
VME 64 x with 2eSST
U-Boot 1.2.0 and Linux 2.6.16 BSP
NP-PPC7448 Single Board Computer
Application
Program
Services
Utilities
Middleware
Linux OS
The middleware mainly provides
services for communication and
multi-thread management. It
presents the application program a
protocol and hardware transparent
communication interface to handle
different interfaces like Ethernet,
VME, serial port, and SDLC, channel,
etc.
For achieving protocol and
hardware transparency, a common
communication packet structure has
been defined and modules for
communicating data using different
Communication
Management
TCP
Ethernet
UDP
VME
Hardware
Communication Interface
Multithread
Management
Serial
Threads
SDLC
Queues
interfaces have been provided in the
middleware. It provides a generic
method to communicate the data
through different interfaces. Using
these services, the application
programmer is insulated from the
complexities of low-level communication.
As part of the architectural
framework, the middleware provides
a set of threads with specific
functions. These include: receive
thread (for receiving data), transmit
thread (for transmitting data),
process thread (processing of
received data), health thread (for
periodic health monitoring), and
simulation thread (for simulating
data). In addition to the major
services described above, middleware also provides several utility
services like handling of sub-system
health, maintenance of system log,
etc.
The middleware was designed
using OOD principles and is
organised as different layers of
project-independent common,
project-specific common, and subsystem-specific common along with
core functional logic required in the
core domain. This also promotes
reuse of software to a large extent
Vol. 18 No. 4 August 2010 15
Common architectural framework for applications software for
information processors of sonar
systems was achieved by developing
a middleware in-house. This, along
with the use of open standard
interfaces between sonar subsystems, helped in developing highly
maintainable, reusable software in a
short time span with lesser
manpower. The middleware
functions as a layer between the
application and the Linux operating
system. The bottom hardware layer
could be the NP-PPC7448 SBC with
necessary communication interfaces. Linux OS comes on top of the
hardware. The middleware layer is
sandwiched between the Linux and
the application program. This layer
provides a set of services, which can
be accessed by the application
program through well-defined
interfaces.
and reduces time period required for
software development .
The Human Machine Interface
(HMI) of the sonar allows the
operator to configure different sonar
functions and present the processed
information in an easily comprehensible manner. From the
conventional approach of using
custom devices, the new generation
sonar HMI uses industry standard
devices such as high resolution LCD
displays, keyboards, and tracker balls
shared through KVM switches.
Vol. 18 No. 4 August 2010 16
The data is presented in
composite pages in a Windows-like
environment. The HMI pages have all
the advanced graphics widgets like
pop-up menus, combo boxes,
command buttons, etc. Unlike
conventional sonar systems display,
where controls are selected through
a nested series of soft key operations,
in the new generation display, the
required controls are available in the
information page directly through
the above widgets. In addition, the
operator commands can be given
through the touch panels.
The HMI has been developed
using object oriented methodology
using C++/Qt over Linux operating
system on indigenously developed
NP-PPC7448 SBC with Graphics PMC.
The graphics toolkit Qt, running on X
window system, provides a lot of
flexibilities in terms of the fonts and
colours. Compared to the
conventional sonar HMIs, which used
to run on dedicated hardware with
limited graphics support, the clientserver architecture of the new
generation sonar HMIs provide much
more flexibility to meet many
requirements.
A typical sonar display is broadly
divided into video and annotations/
control areas. The video area
contains graphs and cursors, which
presents information from various
sonar sensors. The information is
presented as the amplitude and
waterfall graphs. The amplitude
graph provides the instantaneous
signal amplitude, whereas the
waterfall graph provides the history
information in the form of signal
intensities over time to the operator.
The annotation area provides all
necessary controls and status
information.
DRDO has acquired sufficient
expertise in phased array signal
processing, which forms core of the
sonar signal processing. Spatial
processing incorporating conventional and adaptive techniques are
being used extensively in all the
sonar designs. These include MVDR,
MUSIC, ESPIRIT and STAP algorithms,
which have been perfected to make
these implementable on the signal
Triplet Sensor for L/R Array
processing hardware. The standard
techniques of detection, tracking,
background normalisation, and
spectral analysis used in sonar signal
processing have also been
extensively refined to give better
performance of both active and
passive sonar systems. NPOL has
expertise to detect transient signals,
which are of short duration. Robust
techniques have been developed for
providing automatic transient alert
using both cylindrical and linear
arrays. The Laboratory has established its credibility in resolving the
left/right ambiguity—a bane for a
towed array sonar system. The
left/right ambiguity resolution is
achieved using a three-element
linear sensor assembly, supported
by powerful signal processing
algorithms.
Automatic Target Recognition
(ATR) provides early warning so as to
give sufficient reaction time for
taking counter-measures. To this
end, ATR extracts features of each of
the tracked targets. A number of
discriminatory features to distinguish different types of targets with
very low miss-classification error
have been successfully identified and
established. All algorithms of signal
processing have been subjected to
elaborate Monte Carlo simulations
for finalising the parameters
involved.
The 3-G Underwater Wireless
Acoustic Communication System (3G
UWACS) is the third generation
product in underwater communi-
cation from NPOL succeeding the
stand-alone Underwater Telephone
(UWT) and the integrated
Underwater Telephone System used
in submarines. The product has been
developed in collaboration with an
industrial partner.
In modern network-centric
warfare enabled operational
scenarios, seamless connectivity
between underwater platforms and
surface vessels is of prime importance. This calls for an advanced
wireless communication system with
ability to cater to a variety of
operational modes like multiband
voice and robust data transfer. The
3-G UWACS has been developed
with such an operational framework
in view. It is a state-of-the-art system
based on Software Defined Radio
(SDR) Architecture.
The 3-G UWACS has several new
features in comparison with the
earlier underwater communication
products. This system incorporates
advanced modulation and coding
techniques in addition to data
recording and analysis features. It
offers the user enormous flexibility in
materials without compromising
strength and safety. The above subsystems have been designed and
developed with the state-of-the-art
technology in collaboration with
industrial partners and inducted in
several sonar systems used by the
Navy.
Air Transport Rack (ATR) is a
ruggedised enclosure used for
packaging of electronics and
electrical items onboard airborne
platforms. The ATR is designed as per
military standards MIL-STD-810F for
environmental testing , MIL - STD 461E for EMI/EMC compliance, MILSTD-704D for qualification of brick
The various sub-components in a
sonar system are sensor arrays, winch
and handling systems, system
electronics, and display units. The
packaging of system electronics is
done in compact enclosures with
efficient thermal management and
with EMI/EMC compatibility. In
towed sonar systems the deployment and retrieval of sensor arrays
with very long cables and separate
transmitter bodies are handled by
complex winch and handling
systems.
Winches for airborne applications
are designed using lightweight
Display Processor ATR Card Cage Assembly
Salient Features: Air Transport Rack
Backplane
Heat load
Cooling method
Cooling fans
Power supply unit
I/O connection
:
:
:
:
:
:
12 slots, 6U-VME64x
300 W
Forced convection using ambient air
Two ebm-NADI axial fans
115 V ; 400 Hz- brick type, integrated
MIL-C-38999 connector on
frontal panel
Vol. 18 No. 4 August 2010 17
3-G Underwater Communication System
operation, easier maintenance, and a
host of additional features through a
comprehensive GUI. Besides, it
supports remote operation and
monitoring through standard
networking technologies critical for
platform-level integration. The
system has been designed with a
view to make it backward compatible
with the earlier versions of UWT to
facilitate operational requirements
with platforms equipped with the
earlier product. The system can be
utililsed in stand-alone or integrated
mode of operation.
side panels. The temperature
throughout the cabinet is maintained to be within limits.
type power supply unit, and IEEE
standard 6U VME card cages. The rack
developed is a display processor card
cage assembly of standard one ATR
long dimensions and fabricated
using airworthy aluminium alloy.
DRDO has designed and
developed a winch (ASW 4001) for
lowering and hoisting the dipping
sonar dome into the sea for underwater surveillance operations. The
winch has been installed on
platforms after obtaining flight
clearance certification. It has the
facility to display cable paid out
length, cable angle and has
automatic speed control with
respect to sonar dome position while
lowering as well as hoisting. The
winch has been fabricated using
aluminium alloy based on an
optimum design for strength and
safety, and has got a cable spooling
mechanism.
The unit is fully integrated and
has successfully completed all the
environmental tests as per the
specifications. Heat generated by
PCBs is removed by forced
convection of air. The cooling design
is such that it maintains a positive
pressure in the enclosure to keep
dust ingression to minimal. The unit
is mounted on an ARINC tray for easy
maintenance and installation, and
provided with shock mounts (Barry
controls) for isolating the ATR from
the shock and vibration of the
platform.
Display-cum-Processor Cabinet
Vol. 18 No. 4 August 2010 18
Display-cum-Processor cabinet is
intended to integrate display
processing and signal processing
functions of a sonar system. The
cabinet comprises five levels where
each level is a standard subrack
stacked one over the other. IEEE
standard 6U form factor subracks
along with VME backplane have
been incorporated in this cabinet. In
addition, VME standard plug-in units
such as PCB and power supply
including injector and extractor
handles have also been used. The
cooling design of the cabinet is a
combination of series and parallel
flow types. Cooling is achieved by
lateral entry of fresh air at each level
through a double-walled duct at the
The winch is driven by a main
hydraulic motor capable of developing 10 HP at 4000 rpm. Its speed is
controlled by an electrical servo valve
and a hydraulic circuit. It also has an
auxiliary electrical back up motor and
a manual cranking device for
redundancy, and a pyrocutting
device for emergency. The winch is
software-driven in the lines of latest
state-of- the- art technology .
Salient Features: DCP Cabinet
Backplane
Packaging capacity
Heat load
Cooling method
Cooling fans
No. of displays
Keyboard
EMI/EMC protection
:
:
:
:
:
:
:
:
18 slots, 6U-VME64x
90 PCBs and 5 power supply units
1200 W
Forced convection using ambient air
Two centrifugal fans
Two
Foldable
Using EMI fingers and honeycomb
ASW 4001
Salient Features: Airborne Hydraulic Motor
:
:
:
:
:
:
:
:
:
Axial piston
Fixed
Bend axis
30o
6 + 0.1 cc/rev
MIL-H-5606 or its equivalent
2 kg (max.)
9 with fixed strokes
38.5 + 0.1 lpm
:
:
:
207 bar (continuous)
210 bar
6400 + 100 rpm (at 38.5 lpm)
Low frequency dipping sonar,
deployed from a helicopter to detect
underwater targets in the sea has
been developed. The dipping sonar
utilises a dunk body (NP-DB-214)
lowered from the helicopter for ASW
operations. The body consists of an
electronic unit, drive assembly, active
and passive transducer array
assembly, and non-acoustic sensors
unit. The dunk body is connected to
the winch by means of an
Dunk Body Dome with extended arms
electromechanical (EM) connector
using high strength multi-core EM
cable. It has a high-power active
transducer array to transmit sound
signals underwater to detect longrange targets.
The drive assembly comprises
mechanism for the foldable and
unfoldable passive transducers array
fixed in vertical staves and is actuated
by an actuator. The array fold and
unfold mechanism can be remotely
operated from the platform during
sonar deployment. The complete
control of the dunk body deployment along with winch operation
can be carried out from the operator
console unit installed in the platform.
The dunk body has been designed
keeping in view the hydrodynamic
aspects during the deployment. All
the mechanical components have
been manufactured using airborne
quality aluminium alloy and GFRP.
The components that will be
exposed to seawater during
deployment have been anodized to
withstand corrosion.
Vol. 18 No. 4 August 2010 19
Type
Displacement
Axis of rotation
Bend angle
Displacement volume
Fluid
Weight
No. of cylinders
Theor tical flow rate at max.
continuous speed
Pressure rating
Maximum pressure
Max. continuous speed
Hydraulic Ship-borne Sonar Winches
NPOL has developed ship-borne
winches (SSW 5 H and SSW 7 H) for
onboard installation on Naval
platforms. Winches have proven
seaworthiness by undergoing
several sea trials, and are been used
for deployment, retrieval, spooling,
and stowage of the wet-end sonar
systems.
Vol. 18 No. 4 August 2010 20
The systems are electrohydraulic
with stand-alone power packs and
are controlled by microprocessors.
Dedicated sensors and ergonomic
displays help in online monitoring of
critical system parameters like cable
paid out length, cable tension, speed
of operation, etc. Safety interlocks
(software and hardware controlled)
have been integrated into the system
for safeguarding the system as well
as the operator. These winches are
driven by hydraulic motors through
SSW 5 H
compact planetary gearboxes with
provision for redundant electric drive
and manual drive for maintenance
purposes.
SSW 5 H can accommodate 500 m
of tow cable, 30 m passive array, and
is designed for 5 ton. SSW 7 H system
is capable of handling 1300 m of tow
cable and 200 m towed array,
comprises a dedicated handling
system for deployment and retrieval
of underwater towed body and is
designed for survival load of 7 ton.
Electric Ship-borne Sonar Winch
Electric Ship-borne Sonar Winch
(SSW 5 E) is an electric winch
developed to deploy, retrieve, and to
store 1500 m of electromechanical
optical cable and sensor array. The
system consists of a drum with
flanges on both sides over which the
cable is wounded. The drum is driven
by a 3-phase 25 hp induction motor
controlled by Variable Frequency
Drive (VFD) through a reduction
gearbox. A constant-speed, 3-phase
5 hp electrical motor drives the drum
at constant speed in redundant
mode. Dog clutch mechanism has
been provided for change of
'operation mode' to 'redundant
mode'.
Operational speed of SSW 5 E is
between 0 and 25 rpm in VFD mode.
Operator console has a joystick for
speed control. The control console
consists of a variable frequency drive
and an overload trip device. The
system is built-in with strain gauge
and encoder assembly for online
cable tension and the cable length
pay out measurement.
The system is also fitted with failsafe electrically operated thruster
brakes. Overall size of the system is
2150 mm x 2100 mm x 2000 mm and
the weight is approximately 5 ton.
SSW 7 H
cable (LTC) through flexible link. TTB
handling system caters for the safe
deployment and recovery of the
towed body from a moving ship. A
pair of hydraulically operated robotic
arms facilitates the purpose. The
mode of operation of the entire
system is electrohydraulic.
Underwater Electromechanical
Connector
The compact and lightweight
connector provides mechanical as
well as electrical connections
between the different functional
modules of a towed sensor array. The
unique features of the connector
include sealing against seawater,
high axial load-bearing capacity,
automatic polarisation, quick
assembly/disassembly, and
streamline shape. The connector is
designed to withstand harsh
The transducer is powered by a
tuning coil unit, which is also housed
inside the TTB. The sub-systems are
integrated with titanium grade five
fasteners. The bridle is connected to
the pivot axis of the body using two
fulcrum pins. The TTB fore-end is
connected to the heavy tow cable
using a U-shaped bridle assembly
through an electrooptic mechanical
interconnector.
Salient Features: Strength Member
A swivel hub, provided at the rear
end of the TTB, connects light tow
Material
Cross-section (mm)
Breaking Strength ( kN)
Kevlar
13 x 2
21
Spectra 1000
13 x 3.5
40
Spectra 1000
dia: 10
13
21
A Towed Transmitter Body (TTB)
and handling system has been
developed by NPOL in collaboration
with an industrial partner. TTB is a
hydrodynamically shaped towed
underwater body and has got an
elliptical cross-section. The body is
used to house flextensional
transducer and serves as an acoustic
source for towed array sonar system.
The major sub-systems of TTB are:
shell assembly, ballast, splitter plates,
wing, bridle, and flextensional
transducer.
Towed Transmitter Body and Handling System
Vol. 18 No. 4 August 2010
SSW 5 E
operating conditions including
dynamic towing loads and
hydrostatic pressure. The connector
is dry-mateable. Mating and demating is carried out using a portable
assembly fixture.
Electro-Opto-Mechanical Inter
Connector
It is a flexible pressure-balanced
module of towed array system that
performs the following functions in a
field environment with dynamic
tension:
Electrical, optical and mechanical
inter-connection between Heavy
Tow Cable (HTC) and LTC.
Mechanical engagement and
electrical powering of TTB.
Vol. 18 No. 4 August 2010 22
Transfer of towing loads from LTC
to HTC.
Electro-Opto-Mechanical Inter
Connector (EOMIC) assembly is
encapsulated with polyurethane
(PU) hose and filled with gel under
pressure to block water seepage into
the assembly. It maintains a pressure
difference of zero making it a
pressure-balanced design. Enough
slackness has been provided for tow
cable core sheath, electric and fibreoptic lines to compensate relative
elongation. A loop of strength
member (SS wire rope) takes the
dynamic load acting on EOMIC. It is
designed to withstand a pressure of
30 bars and can take an axial load of
30 kN. The outer diameter of EOMIC
assembly is 80 mm.
Rubber-based encapsulants are
used for protecting the electroacoustic transducers from the marine
environment. The need for long
shelf-life of rubber encapsulants has
been addressed leading to
development of new encapsulants.
Adhesives have been used widely for
development of underwater components meant for sonar systems.
Underwater cable junction boxes are
necessary especially for submarine
sonar systems to route multichannel
sensor array data to the electronic
hardware kept inside a pressure hull
compartment. Adhesive-free cold
moulded PU underwater junction
box and cable splicing technology
have been used for realising the
same.
Encapsulants based on thermoplastic polyolefine elastomers have
been developed. The encapsulants
have shelf-life of 25–30 years and
possess better electrical resistivity.
Electro-Opto-Mechanical Inter Connector
Transducers with Long-life Enhancement
Colourants can be added to the
encapsulants for enabling colour
coding and easy traceability of
encapsulated sensors.
A new indigenous adhesive (NP
235) has been used for fabrication of
molded Rubber Junction Boxes
(RJBs), cable splicing, and
transducers encapsulation . The
adhesive is flexible with good peel
strength, seawater compatibility,
and insulation resistance. The
adhesive bonds vulcanised rubber to
either vulcanised rubber or primed
metal substrates. It is well-suited for
producing and bonding of
transducer electrical components
because of its better insulation
properties and durability in
underwater marine environments.
Underwater cable junction boxes
are used to connect multiple singlecore neoprene cables to a multi-core
cable to be used in deep sea
The sealing material employed is
a two-part PU system having
excellent bonding with varieties of
substrates. Higher water impermeability, stability, and improved
mechanical and electrical properties
are additional advantages of the
material employed.
Ocean has a complex environment in which sonar system has to
perform to the needs of the Navy, the
end user. Since the sonar performance is largely influenced by the
ocean behaviour, a proper understanding of the ocean environment is
most imperative for optimum
performance. Oceanographic
studies are concentrated towards
this end to know the environment
and the acoustic propagation in a
better way by modelling and
validation of the model by data
collection.
comprehensive data available till
today. The other model is a unique
package, to simulate 3-D structure of
temperature, salinity, current fields
and to estimate the sound velocity
structure off the west coast of India
for any desired month, both on
climatologically and daily scales,
using a 3-D circulation model.
A sonar performance modelling
tool has been developed and
implemented by DRDO. It is a generic
model catering to the modelling
requirements of a wide range of
active and passive sonars. This is
implemented as a PC-based menudriven program with user-friendly
interface. It is being used extensively
within the Laboratory for modelling
the performance of various types
of sonars during the design, development, and evaluation phases.
Two other software packages
have been developed to understand
and visualise the ocean environment
and to support the above modelling
tool. Complete with a user-friendly
interface, one model visualises the
environment, i.e., temperature,
salinity, and velocity up to the water
column depth using the best
23
environment. Adhesive-free cold
molded PU underwater junction box
and cable splicing technology have
been developed in collaboration
with industrial partner. To obtain
better mechanical strength and
avoid contamination of soldering
slag, connectorisation of the cables
has been achieved by crimping with
tinned copper tubes in place of
soldering. The technology avoids the
problems associated with fabrication
at higher temperature, and hence
can be extended to thermallysensitive cables and sensors.
Cold Moulded Underwater PU Junction Boxes
in situ
Vol. 18 No. 4 August 2010
Spliced Cable using NP-235
airborne, and submarine applications.
A large number of technologies as
described above have found
applications in the large number of
sonar systems developed and
delivered by DRDO and fitted on
Naval platforms for ship-borne,
The technology roadmap for
futuristic sonar systems envisage
development of high power and low
frequency transducers, efficient
compact power amplifiers, highspeed high-resolution multichannel
data acquisition systems, high performance computing engine for
gleaning out sonar information and
fusion of data, thin-line towed array
for submarine sonar applications,
lightweight compact sonar winches,
and more accurate sonar rangeprediction models.
Editors thank Letha MM, Scientist D and Local Correspondent of
Technology Focus for helping in bringing out this Special Issue.
lEikndh; eaMy
Editorial Committee
ºÉàÉx´ÉªÉBÉE
Coordinator
Dr AL Moorthy, Director, DESIDOC, Metcalfe House, Delhi
Members
Dr Sudarshan Kumar, Director of Materials, DRDO Bhavan, New Delhi
Shri R Shankar, Director of CV&E, DRDO Bhavan, New Delhi
Cmde PK Mishra, Director of Naval Research & Development
DRDO Bhavan, New Delhi
Shri Sudhir K Mishra, Director of Missiles, DRDO Bhavan, New Delhi
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Vol. 18 No. 4 August 2010 24
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Editor-in-Chief
AL Moorthy
Assoc. Editor-in-Chief
Shashi Tyagi
Editors
B Nityanand
Manoj Kumar
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Editorial Assistant
Dipti Arora
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Pre-press Coord.
SK Tyagi
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Printed & published by Director, DESIDOC, on behalf of DRDO
RNI No. 55787/93
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SK Gupta
Hans Kumar
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Distribution
RP Singh