Electrical Engineering Dictionary - part 150

capacitor,

, are equal.

= 2πf

= 1/(2πf

)

resonance fluorescence

the modified flu-

orescence produced when a quantum me-
chanical system is strongly driven by one or
more near-resonant electromagnetic fields.

resonance Raman system

Raman sys-

tems that have a near-resonant intermediate
state. Resonance Raman systems are some-
times referred to as lambda systems and can
exhibit coherent population trapping.

resonant

in any circuit or system under

excitation, the frequency at which a pair of
reactive components cancels (pole or zero)
resulting in a natural mode of vibration.

resonant antenna

linear antennas that ex-

hibit current and voltage standing wave pat-
terns formed by reflections from the open end
of the wire.

resonant cavity

cavity with reflecting sur-

faces or mirrors that can support low-loss os-
cillations. By closing a metallic waveguide
by two metallic surfaces perpendicular to its
axis, a cylindrical cavity is formed. Resonant
modes in this cavity are designated by adding
a third subscript so as to indicate the num-
ber of half-waves along the axis of the cav-
ity. When the cavity is a rectangular paral-
lelepiped, the axis of the cylinder from which
the cavity is assumed to be made should
be designated, since there are three possible
cylinders out of which the parallelepiped may
be made. More generally, each closed cav-
ity may sustain a discrete infinity of resonant
field distributions.

resonant frequency

(1) a frequency at

which the input impedance of an device is
nonreactive, since the capacitive and induc-
tive stored energy cancel each other.

(2) an oscillation frequency of the modes

of a resonator.

resonant link inverter

an inverter that

uses a resonant circuit to convert a constant
DC voltage to a pulsating DC voltage. The
switching elements in the inverter are then
turned off during the times that the input volt-
age is zero, a technique referred to as soft-
switching. Resonant switching techniques
reduce the switching losses and allow high
switching frequency operation to reduce the
size of magnetic components in the inverter
unit.

resonant tunneling

refers to the process

of resonant enhancement of electron tunnel-
ing by intermediate energy states. In the sim-
plest case, it occurs when incoming electrons
coincide in energy with the states created in
the well.

resonator

(1) circuit element or combina-

tion of elements, which may be either lumped
or distributed, that exhibit a resonance(s) at
one or more frequencies. Generally, a reso-
nant condition coincides with the frequency
where the impedance of the circuit element(s)
is only resistive.

(2) cavity with reflecting surfaces de-

signed to support low-loss oscillation modes.
See also bi

-directional resonator,

plane-parallel resonator

unidirectional resonator

unstable resonator

resonator stability

perturbation stability

of an axial light ray in a resonator; bounded-
ness of ray trajectories; corresponds to con-
finement of the resonator modes; not the
same as mode stability (unstable resonators
have stable modes).

resource auction multiple access (RAMA)

a multiple access protocol that stipulates

part of the frame for contention.

Unlike

PRMA and D-TDMA, the contention is not
performed by an ALOHA-type of protocol
but by an auction — a tree-sorting type of
algorithm.

2000 by CRC Press LLC

resource conflict

the situation when a

component such as a register or functional
unit is required by more than one instruc-
tion simultaneously. Particularly applicable
to pipelines.

response formula for general 2-D model
the solution to the general 2-D model

i+1,j+1

= A

+ A

i+1,j

+ A

i,j+1

+ B

i+1,j

+ B

i,j+1

(1a)

= Cx

+ Du

(1b)

i, j ∈ Z

(the set of nonnegative integers)

with boundary conditions

, i ∈ Z

and

, j ∈ Z

is given by

p=1

q=1

i−p−1,j−q−1

+ T

i−p,j−q−1

+ T

i−p−1,j−q

p=1

i−p,j−1

[

]

+ T

i−p−1,j−1

[

]

(2)

q=1

i−1,j−q

[

]

+ T

i−1,j−q−1

[

]

+ T

i−1,j−1

[

]

where

∈ R

is the local state vector,

∈

is the input vector,

(k = 0, 1, 2)

are given real matrices, and the transition ma-
trix

is defined by












I for p = q = 0

p−1,q−1

+ A

p,q−1

p−1,q

for

p, q ≥ 0

(p + q 6= 0)

0 for

p < 0 or/and q < 0

Substitution of (2) into (1b) yields the re-
sponse formula.

restart

the act of restarting a hardware or

software process.

restoration

the act of restoring electric

service to a consumer’s facility.

A dis-

tinction is made between restoration and
repair as repair implies that whatever was
the cause of the outage has been corrected,
whereas restoration implies that the power
was restored but it may have been through
some means other than a repair, for ex-
ample through switching. See also

image

restoration

restore instruction

an assembly language

instruction that restores the machine state of
a suspended process to the active state.

retentivity

See

remanence

reticle

See

mask

retiming

the technique of moving the de-

lays around the system. Retiming does not
alter the latency of the system.

retire unit

in modern CPU implementa-

tions, the module used to assure that instruc-
tions are completed in program order, even
though they may have been executed out of
order.

retrace blanking

blanking of a display

during vertical retrace to prevent the retrace
line from showing on the display.

retrace switch

electronic method used to

blank a display during retrace blanking.

retrace time

amount of time that a

blanked vertical retrace takes for a display
device. Note that this time is less than the
time the display is blanked.

retrograde channel

for a MOSFET semi-

conductor device, the channel region whose
doping is less at the surface of the channel
than it is at some depth below the surface.

retry

a repetition of an operation, dis-

turbed by a transient fault, to obtain good
result.

2000 by CRC Press LLC

return address

the address of an instruc-

tion following a Call instruction, where the
program returns after the execution of the
Call subroutine.

return difference matrix at the input
the transfer function matrix relating the dif-
ference between the injected and the re-
turned signal in a feedback loop that has been
opened at the input. This transfer function
matrix characterizes the effect of closing the
loop and is the mathematical entity that is
central to numerous control engineering the-
ories. For a nonunity feedback configuration
with both pre- and postcompensation, it is
given by

+ F GK(s)

See also

return difference matrix at the

output

return difference matrix at the output
the transfer function matrix relating the dif-
ference between the injected and the re-
turned signal in a feedback loop that has been
opened at the output. For a nonunity feed-
back configuration with both pre- and post-
compensation, it is given by

+ GKF (s)

See also

return difference matrix at the input

return instruction

an instruction, when

executed, gets the address from the top of the
stack and returns the program execution to
that address.

return loss

usually expressed in decibels,

it is the magnitude of the reflection coeffi-
cient; the return loss is a measure of the power
reflected due to impedance mismatch of an
antenna or other device.

return stroke

in lightning, the upward

propagating high-current, bright, potential
discontinuity following the leader that dis-
charges to the ground some or all of the
charge previously deposited along the chan-
nel by the leader.

return-to-bias recording

See

magnetic

recording code

return-to-zero recording

See

magnetic

recording code

reusability

the possibility to use or easily

adapt the hardware or software developed for
a system to build other systems.

reuse

programming modules are reused

when they are copied from one application
program and used in another. Reusability is a
property of module design that permits reuse.

reuse ratio

the ratio of the physical dis-

tance between the centers of radio commu-
nication cells and the nominal cell radius.
This term is usually used with reference to
the reuse of particular radio channels (e.g.,
cochannel reuse ratio).

reverberation

inhomogeneities, such as

dust, sea organisms, schools of fish, and sea
mounds on the bottom of the sea, form mass
density discontinuities in the ocean medium.
When an acoustic wave strikes these inho-
mogeneities, some of the acoustic energy is
reflected and reradiated. The sum total of
all such reradiations is called reverberation.
Reverberation is present only in active sonar,
and in the case where the object echoes and
is completely masked by reverberation, the
sonar system is said to be “reverberation-
limited.”

reverse breakdown

the diode operating

region in which significant current flows from
cathode to anode, due to an applied voltage
exceeding the breakdown voltage.

reverse breakdown region

the region of

the I-V curve(s) of a device in which the de-
vice is operating in avalanche or zener break-
down.

reverse breakdown voltage

See

reverse

breakdown region

2000 by CRC Press LLC

reverse conducting thyristor (RCT)

variety of asymmetric silicon controlled rec-
tifier in which the diode is integrated into the
thyristor structure.

reverse engineering

the reverse analysis

of an old application to conform to a new
methodology.

reverse generation-recombination current

part of the reverse current in a diode

caused by the generation of hole-electron
pairs in the depletion region. This current
is voltage-dependent because the depletion
region width is voltage-dependent.

reverse isolation

device or circuit loss in

a path that is the reverse of the path normally
desired, expressed as the power ratio in deci-
bels of the RF power delivered to a load at
the input port versus the RF power incident
at the output port. The negative sign results
from the term “loss.”

reverse leakage current

a nondestructive

current flowing through a capacitor subjected
to a voltage of polarity opposite to that nor-
mally specified.

reverse link

See

uplink

reverse saturation current

part of the

reverse current in a diode caused by diffusion
of minority carriers from the neutral regions
to the depletion region. This current is almost
independent of the reverse voltage.

reverse translation buffer

See

inverse

translation buffer

reverse voltage

the voltage across the de-

vice when the anode is negative with respect
to the cathode.

reversible

a motor capable of running in

either direction, although it may be neces-
sary to rewire the connections to the motor
to change the direction of rotation. See also

reversing

reversible loss

a decrease in magnetic

induction (

B) of a permanent magnet when

subjected to thermal or magnetic demagneti-
zation that is fully recovered (without remag-
netization) when the detrimental conditions
are removed.

reversible temperature coefficient

for

permanent magnets, a quantity that indicates
the reversible change in magnetic induction
with temperature.

reversing

a motor that can be run in either

direction through the use of suitable switches
or contactors.

reversing motor starter

a motor con-

troller capable of accelerating a motor from
rest to normal speed in either direction of
rotation. Some reversing motor starters can
go directly from forward to reverse (or vice
versa), while others must be stopped before
a reversal of direction can take place. Both
electromechanical and electronic reversing
starters are available.

revolute joint

a joint characterized by a

rotation angle that is the relative displace-
ment between two successive links.

revolving field

the magnetic field created

by flow of a set of balanced three-phase cur-
rents through three symmetrically displaced
windings. The created field revolves in the
air-gap of the machine at an angular veloc-
ity corresponding to the synchronous speed
of the machine. The revolving field theory is
the basis of functioning of synchronous and
induction machines.

Reynolds number

a nondimensional pa-

rameter used to determine the transition to
turbulence in a fluid flowing in pipes or past
surfaces.

See

radio frequency

RF amplifier

amplifier capable of provid-

ing gain at radio frequencies.

2000 by CRC Press LLC

Content .. 148 149 150 151 ..