Page 164 - Radar Technology Encyclopedia

154 eclipsing, deterministic ECCM, antenna related

eclipsing of radar returns will occur. Sometimes eclipsing is EFFICIENCY
also termed an eclipsing effect or an eclipsing loss.
antenna aperture efficiency (see APERTURE).
Ref.: IEEE (1993), p. 403; Hovanessian (1984), pp.147–150.
integration efficiency (see LOSS, integration).
ELECTROMAGNETIC COMPATIBILITY (EMC) is
“the capability of electronic equipment or systems to be oper-
ated in the intended operation electromagnetic environment at
designed levels of efficiency.” While operating a radar, it
must not have a harmful effect on the operation of other elec-
tronic equipment and it must be protected from the harmful
influence of this equipment. Typically, the electromagnetic
environment in which a radar operates is characterized by
radiation of neighboring radars, other electronic equipment,
and natural and industrial interference sources.
The main measures to control mutual interference are
using different frequencies, choosing appropriate antenna
locations for interfering equipment, reducing spurious radia-
tion levels of transmitters, and using waveform coding, pulse-
repetition-frequency agility, polarization selection, and other
special measures. Usually, none of these measures is able to
ensure the required level of electromagnetic compatibility by
itself. The combination of technical and organizational mea-
sures must be undertaken. AIL, SAL
Ref.: IEEE (1978), p. 222; Maksimov (1976), p. 96-108; White (1971, 1973);
Figure E1 Eclipsing of radar return (from Hovanessian, 1984,
Finkel’shteyn (1983), pp. 351–354.
p. 149).
ELECTRONIC COUNTER-COUNTERMEASURES
Average eclipsing is an average power loss due to the eclips-
(ECCM) are “actions taken to ensure friendly use of the elec-
ing effect. Practically it can be represented by the area under
tromagnetic spectrum against electronic warfare.” Their main
the curve of Fig. E1(c).
objective is to eliminate or reduce the efficiency of the
Ref.: Hovanessian (1984), p. 148.
enemy’s ECM. They fall into two broad classes: electronic
Deterministic eclipsing is the amount of power loss due to ECCM and operational ECCM. Electronic techniques are
eclipsing that can be calculated in a deterministic fashion. included in the main radar subsystems and are typically
The simplified series of eclipsing diagrams is cited on Fig. described, following the usage of Johnston (1979), as
E2. Typically, using the deterministic eclipsing calculation antenna-related ECCM, transmitter-related ECCM, and
receiver- and signal-processing ECCM. From the point of
view of radar types where these techniques are implemented,
search (surveillance) radar ECCM and tracking radar ECCM
are distinguished. SAL
Ref.: Johnston (1979), p. 58; Schleher (1986), pp. 199–301; Barton (1991),
p. 12.11; Skolnik (1990), pp. 9.7–9.35; Neri (1991), pp. 417–453; Farina
(1992).
Figure E2 Deterministic eclipsing calculation (from Hovanes-
Antenna-related ECCM are ECCM techniques based on the
sian, 1984, p. 151).
properties of antenna systems to reduce the effectiveness of
method, the amount of power loss due to eclipsing can be ECM. Space selection based on antenna directivity and polar-
determined by dividing the radar-target range during each tar- ization selection based on the polarization properties of elec-
get illumination by DR = ct/2, where DR is the distance tromagnetic waves are the main ECCM strategies of
between successive uneclipsed periods, and calculating the discrimination the useful signals and interference.
signal power loss from the decimal fraction portion of this The main techniques for antenna-related ECCM based on
ratio. SAL spatial selection are coverage and scan control, reduction of
Ref.: Hovanessian (1984), p. 150. main-beam width, reduction of sidelobe level, and employing
of adaptive antennas. The first group of methods based on
eclipsing loss (see LOSS, eclipsing).
antenna pattern and scan control may include blanking or
EFFECTIVE ECHOING AREA is the same as radar cross turning of the receiver while the radar is observing the part of
section. space containing a jammer, using multiple-beam configura-
Ref.: IEEE (1990), p. 15. tion to detect a target by a beam not afflicted by jammers, ran-