Page 254 - Electrical Engineering Dictionary

electrostatic discharge (ESD) the dis- ellipse detection the detection of ellipses
charge of a body through a conducting path in digital images, often with a view to lo-
between two pins of an IC. Circuits located cating elliptical objects or those containing
at the inputs and outputs of ICs protect the ellipses; ellipse detection is also important
internal devices from ESD events. for the location of circular features on real
objects following orthographic projection or
electrostatic precipitator a method of ex- perspective projection.
tracting dust from stack gases or ventilating
systems in which ions are laid on the dust ellipsometry measurement of the changes
particles by high-voltage electrodes and then of light polarization produced by scattering.
attracted electrostatically into a trap.
elliptic See elliptic filter.
electrostatic voltmeter a voltmeter, typ-
ically used for voltages in the kilovolt range, elliptic filter (1) filter with an equal ripple
in which the pointer is moved by the elec- passband frequency response, but in which
trostatic attraction of a pair of metal plates the stop band also exhibits an equal ripple
across which the voltage to be measured is (peaks) stopband response. Also known as a
applied. Caurer filter.
(2) member of a class of low pass, high
electrostriction the tendency of materials pass, band pass and band stop filters with an
to become compressed in the presence of an equiripple characteristic, designed to achieve
applied electric field. The change in density optimally rapid rollof rates near cutoff fre-
is proportion to the square of the electric field quencies ( See also Butterworth filter and
strength. This process leads to an increase in Chebyshev filter) at the expense of a loss
the refractive index of the material, describ- of monotonicity in both the passbands and
able by δn = n 2 I, where n 2 is the (positive) the stopbands. For example, an elliptic low
coefficient of the nonlinear refractive index pass filter design is equiripple in the passband
and I is the intensity of the field in units of and stopband, and has a squared magnitude
power per unit area. For condensed matter, a response of the form
2
typical value of n 2 is 10 −20 m /W.
1
2
|H(jw)| = 2 ,
2
element factor in antenna theory, that part 1 + U (w/w c )
N
of the radiation pattern that is governed by the where U N (w) is a Jacobian elliptic function.
geometrical shape of the antenna that con-
strains the current. elliptical polarization the polarization
state of a radiated electromagnetic field in
Elias’ upper bound for any (n, k) block which the tip of the electric field vector traces
code, the minimum distance is bounded an ellipse as a function of time for a fixed po-
asymptotically as sition. The sense of rotation of the electric
field vector is either right-hand or left-hand
d min (clockwise or counter-clockwise). Circular
≤ 2A(1 − A)
n polarization and linear polarization are spe-
where the parameter A is related to the code cial cases of elliptical polarization.
rate through the equation
embedded computer (1) a computing
k machine contained in a device whose pur-
= 1 + A log A + (1 − A) log (1 − A) pose is not to be a computer. For example,
2
2
n
1 the computers in automobiles and household
0 ≤ A ≤ appliances are embedded computers.
2
c
2000 by CRC Press LLC