whole chip is scaled down. As the length
of a wire shrinks by a factor of
k and the
cross-sectional area of the wire is reduced by
a factor of
k
2
, the capacitance of the wire de-
creases by a factor of
k while the resistance
increases by a factor of
k. The RC time re-
mains constant, and thus the input charging
time remains the same, independent of scal-
ing. Consequently, the scaling down of the
chip cannot increase the speed of the chip if
wire is used. Optical interconnects can speed
up the chip.
RCPC code
See
rate-compatible punctured
convolutional code
.
RCS
See
radar cross section
.
RCT
See
reverse conducting thyristor
.
RDSL
See
rate-adaptive digital subscriber
line
.
re-entrancy
term describing the number
of times that a multiplex armature winding
of a commutated machine closes upon itself
via the commutator ring. For example, du-
plex windings can be either singly or dou-
bly re-entrant. In a doubly re-entrant du-
plex winding, the ends of the two winding
circuits close only on themselves and not
on each other, creating two distinct circuits
through the commutator and two distinct cir-
cuit closures.
Conversely, in a singly re-
entrant duplex winding, the two windings are
connected in series through the commutator
ring creating only a single circuit closure.
reachability
a term that indicates that a
dynamical system can be steered from zero
initial state to any final state in a given time in-
terval. For many dynamical systems, reach-
ability is equivalent to controllability. This
is always true for linear finite-dimensional
continuous-time dynamical systems. How-
ever, in discrete case, controllability may be
the stronger notion than reachability. In this
case, the two concepts are equivalent if and
only if rank
A = n. For dynamical systems
with delays, these two notions are essentially
different. For infinite-dimensional systems,
the relations between reachability and con-
trollability depend on the properties of the
semigroup
S(t) generated by the operator A.
reactance grounded
an electrical system
in which the neutral is intentionally grounded
through a reactance.
Frequently used in
the neutral of generators and transformers to
limit the magnitude of line to ground fault
currents.
reactance modulator
modulator nor-
mally using phase or frequency modulation
where the reactance of the circuit is depen-
dent on changes in the input modulating volt-
age.
reaction
a functional in electromagnetics
that relates a set of fields and sources to one
another. Reaction concepts are often used in
the discussion of field reciprocity.
reaction range
sum of end-to-end round-
trip delay and processing time.
reactive compensation
process of coun-
teracting the reactive component of a device
by means of capacitors and inductors. Both
series and shunt compensation are prevalent.
reactive congestion control
in packet net-
works, a congestion control system whose
actions are based on actual congestion oc-
currence.
reactive ion etching
the process of etch-
ing materials by the use of chemically reac-
tive ions or atoms. Typically, the reactive
ions or atoms are generated in a RF plasma
environment or in a microwave discharge.
reactive load
a load that is purely capac-
itive or inductive.
reactive matching
impedance transfor-
mation achieved by employing a matching
c
2000 by CRC Press LLC