The Navy Vol_73_No_3 Jul 2011 - Navy League of Australia

NAVAL ELECTRONIC WARFARE . . . CONTINUED
available to the command in a ship and so this contribution of EW
is of vital importance in many tactical situations. Techniques for the
rapid and accurate measurement of radar signal characteristics have
been developed to a considerable degree of sophistication together
with software-aided methods of comparing these characteristics
with a library of known radar parameters, even to the point of
‘fingerprinting’ individual transmitters for greater identification, such
as the ship’s name. The result of this analysis, either in the form of a
positive or probable identification, is then associated with the bearing.
It is available to the command as a valuable addition to the threat
picture and perhaps also for correlation with contacts obtained by
other means. The EW analysis equipment can also be programmed
to recognise and give immediate warning of nominated, specific
threat radars, which pose potential dangers that require a very quick
reaction, such as Exocet.
Since the USN phased out the Mk-13 launcher, along with SM-1 anti-air missiles and rail
launched Harpoon, the Oliver Hazard Perry class have undergone an EW re-birth and are now
the EW specialist platforms for the USN. Seen here in the circle is the Sidekick ECM jammer.
Above it, the SLQ-32 ESM receiver array. To the right rear of the SLQ-32 are two two-barrel
Nulka expendable hovering rocket ECM jammer/decoy launchers. (USN)
SIGNAL ANALYSIS
Probably the most important tactical information obtained from
the interception of enemy signals is that relating to target identity,
which comes from analysing the signal characteristics. The radio
frequency, pulse width, pulse repetition rate and the aerial rotation
rate of a radar signal constitute a form of signature to identify the
radar when compared with intelligence information on enemy radar
characteristics.
With the radar identified the ship or aircraft carrying it can be
determined and so the threat posed may be assessed. No other
means, apart from visual observation, of identifying a target are
THE ROLE OF ECM
To appreciate what ECM (Electronic Counter Measures) are attempting
to achieve by the use of a large and varied array of quite different
devices, it is helpful to understand that only two main objectives are
involved. One is to disrupt surveillance and communication, so that an
enemy is unable to achieve, totally or partially, what he hopes to from
his electronic information gathering sensors, such as surveillance
radar, or from his radio communication, equipment, which serve his
command and control requirements.
The other is to reduce the lethality of his weapons, guns and missiles,
which depend on electronics for aiming, guidance or homing, by
making some or all of his shots miss their ship targets. There are many
ways in which these two objectives are pursued in the practice of ECM
and a number of them will be discussed below. Frequently, there are
complications, such as the effect of ECM, on own ship’s weapons.
These can involve considerable complexity in the precautions taken
in using ECM.
Mounted on top of the periscope of HMS ASTUTE is an advanced ESM receiver. Submarines
with some part of their structure exposed rely strongly upon EW intercept equipment for
warning of approaching search radars. (BAE Systems)
06 THE NAVY VOL. 73 NO. 3