The Navy Vol_73_No_3 Jul 2011 - Navy League of Australia

NAVAL ELECTRONIC WARFARE . . . CONTINUED
the electronic false targets do not affect it at
all. Thus, in theory, the electronic false target
generator alone is not always of prime naval
significance, mainly because it has only a
limited potential for reducing missile lethality,
which is the prime requirement of the ship
being attacked.
Nevertheless, in practice, false target
generators have proved to be a serious
embarrassment to attackers launching
missiles against ships and it seems that their
tactical value is, currently, quite considerable.
Commercial equipment combine false target
generation with other jamming modes and
collectively these are effective in reducing the
lethality of attacks.
BREAK-LOCK DEVICES
If a missile has locked on to a ship, it is
possible by electronic means to break the lock
in range and also, with some types of missile
homing, to break the lock in angle as well.
This is achieved by electronically creating
in the missile’s radar a strong false target
greater than that of the ship and ‘capturing’
the lock. The false target is moved away in
range or angle with the missile following, and
then switched off. The missile is left without a
target and is forced to search again. If there
is a strong decoy target placed nearby, the
missile has a high probability of locking on
to this, provided it is a real physical object
in space, and so missing the ship. This
combination of a break lock device and
decoys is effective in reducing lethality when
The South Korean Navy SLQ-200 Sonata
EW system. The horizontal radome is for
ECM while the smaller radome atop is the
EW receiver. The SLQ-200 system is fitted
to the KDX-II destroyers.
a ship has actually been selected as a target
and a missile is homing to it.
It is rather more difficult to break lock in
angle than in range, especially, if the missile
is using a simultaneous lobing method of
guidance for homing. If sequential-lobing,
such as the well known conical scanning
technique is used, a missile can be pulled off
in angle. This is not so good as range break
lock since the angle pull-off may result only
in the missile reaching its target by a curved
rather than a straight line.
DECOYS
Decoys, real rather than false electronic
targets, are by far the most potent form of
ECM in providing protection to ships through
reducing the lethality of missiles and causing
them to miss. If a ship receives warning,
including target identity, from its ESM
equipment that a missile attack is imminent,
its course of action is to lay down a pattern
of decoys around itself. The attacking aircraft
then sees a number of radar contacts in a
group; these are all ‘real’ targets in that they
provide a radar echo from a point in space
and they are capable of being locked onto. If
the aircraft selects any of the decoys for its
missiles, and the missiles home to these, then
dilution of the attack occurs because some or
all of the missiles are wasted. If a missile is
approaching the real ship and would acquire
it, but is seeing also close to the ship a bigger
decoy target, it will select the bigger target
and is, thereby, distracted. If the real ship is
actually selected by the missile, which the
ship can know from the pattern of behaviour
of the intercepted missile signal, it can deploy
a decoy above or beside itself, which the
missile will see as part of the ship echo. The
ship then moves away from the decoy and
the missiles stays locked to the bigger decoy;
this is known as seduction. In all of these
cases the attack lethality can be substantially
reduced and the chance of the ship’s survival
increased in a very cost-effective manner.
ECCM
EW is essentially a conflict between devices
which ‘attack’ and deceive the electronic
sensors used in naval weapons, and the
features in design of these sensors, which
make them less prone to, or immune from
electronic interference and deception. A
step taken by ESM and ECM designers
creates a response from ECCM designers.
In this escalating battle of electronic design
much ingenuity, complexity and subtlety is
employed to an increasing extent because
the advantages to be gained can be very
A Nulka hovering rocket decoy developed by Australia and
the US. Nulka is fired from the ship and hovers away from
the ship moving slightly towards the incoming missile.
It can deploy either an EW or IR countermeasures payload
significant in both tactical and costeffectiveness
terms.
For obvious reasons ECCM is the most
sensitive and secret aspect of EW because,
to reveal the actual ECCM measures
incorporated in the design of a weapon or
sensor is to reveal its degree of vulnerability
to ESM or ECM. From the point of view of
08 THE NAVY VOL. 73 NO. 3