Editing Kolchuga passive sensor (section)

==Mode of operation==
Kolchuga is an [[electronic support measures]] system that employs two or more sites to locate emitters by [[triangulation]].  The system is vehicle mounted and comprises a large vertical meshed reflector, with two smaller circular parabolic dishes beneath and a pair of VHF-to-microwave [[log-periodic antenna|log periodic antennas]] above.  The dishes may exploit [[amplitude monopulse]] techniques for improved direction finding, whilst the angled spacing of the log-periodic antenna suggests that they may use [[phase interferometry]] to improve angle measurements.  Various smaller antennas, presumably for inter-site communications are to the side and rear of the dish.

The detection range is one of the best in its class, but it is highly dependent on the emitted power of the transmitter being tracked, and requires satisfaction of the [[Line-of-sight propagation|line of sight]] condition to at least two receiving sites for [[triangulation]] (compared with three sites for a multilateration system such as the [[VERA passive sensor]]).  A Kolchuga complex can detect and locate air and surface targets and trace their movement to a range generally limited only by the ''common'' line-of-sight of the stations.  Assuming no terrain masking, the line-of-sight range of a single Kolchuga station (in km) is approximately:<ref>{{cite book
  | last = Skolnik
  | first = Merrill
  | authorlink = Merrill Skolnik
  | title = Introduction to Radar Systems
  | publisher = [[McGraw-Hill]]
  | year = 1981
  | isbn = 0-07-057909-1 }}</ref>
:<math>d(km) =130(\sqrt{hr(km)}+\sqrt{ht(km)})</math>

where ''hr(km)'' is the height of the radar in km, and ''ht(km)'' is the height of the target in kilometres, and assuming standard atmospheric radio refraction.  Thus, for a Kolchuga at 100 m altitude (above local terrain) and a target at 10&nbsp;km (30 kft), the range of the system would be approximately 450&nbsp;km.  For targets at altitudes of 20&nbsp;km (60 kft) the line of sight limitation would be 620&nbsp;km&mdash;but few targets fly at such altitudes.  Being line-of-sight limited, the system is an effective [[early warning]] [[air defense]] system against high power emitters.

===System parameters===
According to the manufacturer's brochure (from AIDEX 1997), the upgraded Kolchuga-M is equipped:

<blockquote>
*With four antennas in the VHF, UHF and SHF radio bands with narrow and wide beams
*With parallel receivers allowing the instant discovery and analysis of signals of radio technical equipment (RTE) in the range 100&nbsp;MHz -18&nbsp;GHz and continual tracking across the entire band.  [Other sources claim from 130MHz to 18GHz, and a 36 channel preset receiver].
*With sensitivity of approximately -145 [[dBW]]
*With equipment for the analysis, processing and continual calculation and tracking of coordinates by triangulation and chronometrical-hyperbolic method.
*With equipment for the identification, operative displaying of information, long term memory and recording of the results of processing.
 </blockquote>

The brochure also claims that the system provides:
<blockquote>
*The detection, analysis of signals with pulsed and continuous waves and resolution of practically all known radio technical equipment (RTE) deployed on ground, sea and air platforms, including radar units of all classes, identification systems, air traffic control system and navigation systems
*The composition, character of operation and flight paths of RTE in a zone 600&nbsp;km deep with complete exception of blind zones and continual high accuracy
*The detection of take-off of aerial targets and their formation in groups at a distance exceeding that of modern radars.
*The direction of arrival of solitary and group targets and target indication to active facilities of anti-aircraft systems
</blockquote>

Special inhibitory sorters omit up to 24 interfering signals, and tracking sorters make it possible to synchronously sort out and track signals from 32 targets;

===Target identification===
Kolchuga is able to detect and identify many types of radio devices mounted on ground, airborne, or marine objects.  Target detection relies only on an emitter having sufficient power and being within Kolchuga's frequency range.  Target identification, however, is more complex and is based on the measurement of different parameters of the transmitted signal&mdash;such as its frequency, bandwidth, pulse width, pulse repetition interval, etc.  Kolchuga has been reported to use around forty different parameters when identifying a target.  These parameters are compared to a database in order to identify both the type of emitter and, in some cases, even the specific piece of equipment (by identifying the unique signature or "fingerprint" that most transmitters have, due to the variations and tolerances in individual components).  The database within Kolchuga is said to have the capacity to store around three hundred different types of emitter and up to five hundred specific signatures for each type.