Electrical Engineering Dictionary - part 32

The CIE diagram shows all of the visible
chromaticity values and maps all colors with
the same chromaticity but different value (lu-
minances) onto the same points.

CIM

See

computer-integrated manufac-

turing

CIR

See

carrier-to-interference ratio

circle detection

the location of circles in

an image by a computer. Often accomplished
with the Hough transform.

circle diagram

(1) graphical representa-

tion of the operation of an induction machine.
It is based on the approximate equivalent cir-
cuit and expresses stator and rotor current re-
lations for all operating modes (motor, brak-
ing, generator) and all values of slip. Several
variations of the diagram exist.

(2) graphical representation of the power

flow through a transmission line. The maxi-
mum power flow through the line can be de-
termined by the impedance of the line.

circuit

a physical device consisting of

an interconnection of elements, or a topolog-
ical model of such a device. For example,
an electric circuit may be constructed by in-
terconnecting a resistor and a capacitor to a
voltage source. A representation of this cir-
cuit is shown by the diagram in the figure.

Circuit example.

circuit (STM)

switching technology that

provides a direct connection between two
endpoints; data is transferred directly be-
tween the endpoints of a circuit without being
stored in any intermediate nodes.

circuit breaker

a circuit breaker is a de-

vice that makes and breaks the electrical con-
tact between its input and output terminals.
The circuit breaker is capable of clearing fault
currents (tripping) as well as load currents.
The circuit breaker consists of power con-
tacts with arc clearing capability and associ-
ated control and auxiliary circuits for closing
and tripping the breaker under the required
conditions.

circuit protection

devices or control

measures used to safeguard electrical circuits
from unsafe operating regions, such as over-
currents and overvoltages.

circuit switching

a method of commu-

nication in which a physical circuit is estab-
lished between two terminating equipments
before communication begins to take place.
This is analogous to an ordinary phone call.

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circuit-set

a closed path where all vertices

are of degree 2, thus having no endpoints in
the path.

circuit-switched service

a telecommu-

nications service, where the communications
resource is retained for the whole period of
communication.

For example wired tele-

phone services or mobile telephone services
in the first- and second-generation systems
can be classified to circuit-switched services.

circulant matrix

a square

N × N

matrix

M = {m

i,j

} such that m

i,j

(i+n)

mod

N,(j+n)

mod

; that is, that each

row of

M equals the previous row rotated

one element to the right. All circulant matri-
ces are diagonalized by the discrete Fourier
transform.

circular cavity

a section of the circular

waveguide closed at both ends by conducting
plates.

circular convolution

See

periodic convolu-

tion

circular mil

the area of a circle which

measures 0.001 inch in diameter.

Used to specify the cross-sectional area of

a wire.

circular polarization

a polarization state

of a radiated electromagnetic field in which
the tip of the electric field vector traces a
circle as a function of time for a fixed po-
sition. The sense of rotation of the electric
field vector is either right-hand or left-hand
(clockwise or counter-clockwise).

circular register buffer

a set of general

purpose CPU registers organized to provide
a large number of registers, which may be ac-
cessed a few at a time. The group of registers
accessible at any particular time may be read-
ily changed by incrementing or decrementing
a pointer, with wraparound occurring from
the highest numbered registers to the lowest
numbered registers, hence the name circular

register buffer. There is overlap between the
groups of adjoining registers that are accessi-
ble when switching occurs. The overlapping
registers can be used for passing arguments
during subroutine calls and returns. The cir-
cular register buffer is a feature of the SPARC
CPU architecture. In the SPARC CPU there
are 256 registers, available 32 at a time, with
an overlap of eight registers above and eight
registers below the current group.

circular self-test path

a BIST technique

based on pseudorandom testing assured by
arranging flip-flops of a circuit (during test)
in a circular register in which each flip-flop
output is ex-ored with some circuit signal
and feeds the input of the subsequent flip-
flop. This register simultaneously provides
test pattern generation and test result com-
paction.

circularity measure

the size invariant ra-

tio of area divided by perimeter squared for
small shapes and much used as a preliminary
discriminant or measure of shape, so-called
because it is a maximum for circular objects.

circularly polarized light

light com-

posed of two orthogonal polarizations that
are 90 degrees out of phase; the resultant light
amplitude vector thus rotates about the direc-
tion of propagation at the optical frequency.

circulator

a multiport nonreciprocal de-

vice that has the property that an electromag-
netic wave incident in port 1 is coupled to port
2 only, an electromagnetic wave incident in
port 2 is coupled into port 3 only and so on.

CIRF

See

cochannel interference reduc-

tion factor

CISC processor

See

complex instruction

set computer

Citizen’s band (cb)

40 channels where

the carrier frequency is between 26.965 MHz
and 27.405 MHz established by the FCC for

2000 by CRC Press LLC

short-distance personal or business commu-
nication.

city-block distance

a distance measure

between two real valued vectors

, x

, . . . ,

) and (y

, y

, . . . , y

) defined as

city block

i=1

− y

City-block distance is a special case of
Minkowski distance when

λ = 1. See also

Minkowski distance

Also called Manhat-

tan distance.

cladding

the optical material that concen-

trically surrounds the fiber core and provides
optical insulation and protection for the core.
The refractive index of the cladding must be
lower than that of the core material so that
optical power is guided through the fiber by
total internal reflection at the core-cladding
boundary. See also

total internal reflection

Snell’s Law

clamping

the process of fixing either the

minima or maxima of a voltage.

Clapp oscillator

an oscillator whose fre-

quency is determined by a tuned parallel LC
circuit with a split capacitance, i.e., two series
capacitances, in the capacitive branch and an
additional series tuning capacitance in the in-
ductive branch. The Clapp oscillator is a vari-
ation of the Colpitts oscillator.

class

(1) in general, patterns are com-

monly discriminated into different categories
according to certain properties they share.
The categories in which a given set of patterns
are partitioned are referred to as classes.

(2) in object orientation, is an entity that

defines a set of objects which share the same
attributes and processes.

class fuse

See

UL classes

class A amplifier

an amplifier in which

the active device acts as a modulated cur-
rent source biased midway between satura-

tion and conduction cutoff. In a class A am-
plifier, as the amplitude of an applied sinu-
soidal signal is increased, the output will start
to clip at both ends simultaneously. This is
equivalent to a conduction angle of 360 de-
grees as long as the output signal is not clip-
ping, which is avoided. This term is often
used to include any amplifier operating with
signal levels low enough such that signal clip-
ping is not present (i.e., small signal condi-
tions).

class A-B amplifier

most current source

amplifiers fall into this category, which in-
cludes all amplifiers biased somewhere be-
tween class A and class B. As the amplitude
of a sinusoidal signal is increased, the output
will start to cut off first. Further increases
will cause clipping due to saturation. Thus
the conduction angle is between 180 and 360
degrees, dependent on applied signal ampli-
tude. Device saturation is usually avoided.

class B amplifier

an amplifier in which

the active device acts as a modulated cur-
rent source biased at conduction cutoff. In
a class B amplifier, an applied sinusoidal sig-
nal will result in only half of the sinusoid
being amplified, while the remaining half is
cut off. Further increases in the signal am-
plitude will eventually cause the remaining
half of the signal to saturate and clip, which
is usually avoided. This is equivalent to a
conduction angle of 180 degrees, regardless
of signal amplitude.

class B-D amplifier

switched mode am-

plifier where the device is biased at cutoff,
and the input signal is large enough to drive
the amplifier into heavy saturation such that
only a small percentage of time is spent in
transition. The amplifier is literally switched
between cutoff and saturation, and thus the
saturation angle is a significant percentage
of the conduction angle, which is 180 de-
grees. The unfiltered, broadband output cur-
rent waveform of a class B-D amplifier re-
sembles a stepped squarewave. It is impor-
tant to note that only frequency related infor-

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mation (FM) is preserved in a class B-D am-
plifier, while all amplitude information (AM)
is lost. Usually, class B-D power amplifiers
are designed in a push-pull configuration to
take advantage of both halves of a cycle.

class B-E amplifier

transient switched

mode amplifier where the device is biased
at cutoff, the input signal is large enough
to drive the amplifier into heavy saturation
such that only a small percentage of time is
spent in transition, and the design is such
that during saturation the waveform is de-
termined by the switch circuit transient re-
sponse, while the waveform during cutoff is
determined by the transient response to the
entire circuit, including the load. The ampli-
fier is literally switched between cutoff and
saturation, the transient responses are well
controlled, and thus the saturation angles ap-
proach the conduction angle, which is 180
degrees. The final tuned output current wave
form of a class B-E amplifier resembles an
ideal squarewave. It is important to note that
only frequency related information (FM) is
preserved in a class B-E amplifier, while all
amplitude information (AM) is lost.

class C amplifier

a current source ampli-

fier biased beyond the conduction cutoff such
that operation will not begin until the input
signal reaches a specific amplitude, and re-
sults in less than half of an input sinusoid
being amplified. If the signal amplitude is
increased sufficiently, saturation and the as-
sociated clipping will occur. Thus the con-
duction angle is between 0 and 180 degrees,
regardless of amplitude. Device saturation is
usually avoided.

class D amplifier

switched mode ampli-

fier where the device is biased somewhere
between class A and class B cutoff, and the
input signal is large enough to drive the am-
plifier from cut-off to heavy saturation such
that only a small percentage of time is spent in
transition. The amplifier is literally switched
between cutoff and saturation, and thus the
saturation angle is a significant percentage

of the conduction angle, which is 180 de-
grees. The unfiltered, broadband output cur-
rent waveform of a class D amplifier resem-
bles a stepped squarewave. It is important
to note that only frequency related informa-
tion (FM) is preserved in a class D ampli-
fier, while all amplitude information (AM) is
lost. Usually, class D power amplifiers are
designed in a push-pull configuration to take
advantage of both halves of a cycle.

class E amplifier

a transient switched

mode amplifier where the device is biased
somewhere between class A and class B cut-
off, the input signal is large enough to drive
the amplifier into heavy saturation such that
only a small percentage of time is spent in
transition, and the design is such that dur-
ing saturation the waveform is determined by
the switch circuit transient response, while
the waveform during cutoff is determined by
the transient response to the entire circuit,
including the load. The amplifier is literally
switched between cutoff and saturation, the
transient responses are well controlled, and
thus the saturation angles approach the con-
duction angle, which is 180 degrees. The fi-
nal tuned output current waveform of a class
E amplifier resembles an ideal squarewave.
It is important to note that only frequency re-
lated information (FM) is preserved in a class
E amplifier, while all amplitude information
(AM) is lost.

class E-F amplifier

a harmonic tuned or

harmonic reaction amplifier (HRA) in which
devices, biased for class B operation, are
arranged in a push/pull configuration, and
are utilized to inject each other with large
harmonic currents in order to modulate the
amplitude of the fundamental output current
through the device, resulting in improved
switching efficiency. The even order har-
monics must be shorted at the output, while
the odd order harmonics must be provided an
open at the output.

class F amplifier

a high-efficiency opera-

tion in amplifiers. The class F amplifier has a

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