Page 211 - Electrical Engineering Dictionary

of the response of a dielectric to an applied dielectric waveguide a waveguide that re-
electric field. lies on differences in permittivity among two
(4) an electric property of an insulator or or more materials to guide electromagnetic
semi-conducting material, which describes energy without the need for ground planes or
how differently electric fields will behave in- metallic strips. Such guides of rectangular,
side of the material as compared to air. As circular, elliptical, and other cross sections
an example, e r = 12.9 for GaAs as com- are made of dielectric materials and used for
pared to e r = 1 for air. In integrated circuits, transmitting signals. Transmission is accom-
an effective dielectric constant (e eff ) is used, plished by the total internal reflection mech-
since the electric fields supported by the sig- anism inside the waveguide.
nals traveling through the conductors on the
circuit flow through both air and the insulator difference amplifier See differential
or semiconductor simultaneously. amplifier.
differenceengine amechanicalcalculator
dielectric discontinuity interface be-
developed by Babbage in 1823.
tweentwomediawithdifferentdielectricper-
mittivity properties.
difference equation the mathematical
model of a LTIL discrete time system. See
dielectric medium medium that is polar-
also discrete time system, LTIL system.
izable but relatively nonconducting.
difference of Gaussian filter a bandpass
dielectric resonator an unmetallized di-
filter whose point spread function is the dif-
electric object of high dielectric constant and
ference of two isotropic Gaussians with dif-
high quality factor that can function as an en-
ferent variances. The result is a “Mexican
ergy storage device.
hat” shape similar to the Laplacian of a Gaus-
sian (See Marr-Hildreth operator). Various
dielectric resonator [stabled] oscillator
physiological sensors, including some filters
(DRO) a dielectric resonator is a cylindri-
in early vision, appear to have DOG point
cally shaped piece of material, or “puck,” that
spread functions.
hasthepropertiesofhavinglow-lossresonant
frequencies that are determined primarily by
difference-frequency generation a sec-
the size of the cylinder. Placing a dielectric
ond-order nonlinear optical process in which
resonator near a microstrip line can form a
two input beams are applied to a nonlinear
resonant circuit that will frequency stabilize
optical material and an output is produced at
a voltage-controlled oscillator.
the difference of the frequencies of the two
input beams.
dielectric resonator antenna (DRA) an
antenna where a dielectric resonator is used difference-mode signal if two arbitrary
as the radiation element. signals v 1 and v 2 are applied to the inputs
of a differential amplifier, then the common-
dielectric slug tuner system of two mov- mode signal is the arithmetic average of the
able dielectric pieces of material placed on a two signals. That is,
transmission line for the purpose of matching
a wide range of load impedances by means (v 1 + v 2 )/2
of placing the dielectrics in proper positions.

dielectric step discontinuity the junction differential amplifier an amplifier in-
between different dielectric waveguides. tended to respond only to the difference be-

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