Page 208 - Electrical Engineering Dictionary

depth of field the range of depths over descriptor an object describing an area of
which objects in the field of vision are in ac- space within memory. A descriptor contains
ceptable focus. information about the origin and length of the
area.
depth of focus (DOF) the total range of
focus that can be tolerated; that is, the range desensitization a reduction in a device
of focus that keeps the resulting printed fea- output signal power due to one or more addi-
ture within a variety of specifications (such as tional signals that compress the device out-
critical dimension, photoresist profile shape, put, expressed as a negative ratio of the de-
and exposure latitude). sensed signal output power to the output
power without the additional signals, in deci-
bels.
depth of penetration distance inside a
material interface that an impinging wave has

attenuated by 1/e where e = 2.7183 (Euler’s p desensed
D =−10 log 10
constant). p undesensed

depth-first search a search strategy for
tree or trellis search where processing is per- design for testability designing a semi-
formed depth first, i.e., a particular path is conductor component such that it is easier
processed through the depth of the tree/trellis to feed it a set of test vectors that guaran-
as long as it fulfills a certain threshold crite- tees, or provides sufficient reassurance, that
rion (e.g., based on the Fano metric). If a path the component was manufactured (and de-
fails the threshold test, a new path is consid- signed) correctly.
ered. Also known as sequential search.
design model a mathematical model that
derating factor the fraction (or percent) is used to design a controller. The design
of nominal rating to which a specified quan- model may be obtained by simplifying the
tity must be reduced due to unusual operat- truth model of the process. The truth model
ing conditions. Examples of conditions that is also called the simulation model. The truth
may require application of a derating factor model is usually too complicated for con-
are high altitude, high ambient temperature, troller design purposes. The controller per-
frequent motor starting, and “plugging” op- formance is tested using the truth model. See
eration of a motor. also truth model.

derivative control control scheme where- designed distance the guaranteed mini-
by the actuator drive signal is proportional to mum distance of a BCH forward error con-
the time derivative of the difference between trol code that is designed to correct up to t
the input (desired output) and the measured errors.
actual output.
destination operand where the results of
descrambling the process of restoring a an instruction are stored, e.g., the instruc-
transmitted signal to its original form com- tion MOV AL,7 uses AL as the destination
monly used in CATV systems. The positive- operand (7 is the source operand).
trap, negative-trap, and baseband are com-
mon methods of scrambling requiring such destructive physical analysis (DPA) de-
a means to restore the signal to its original vices are opened and analyzed for process
form. integrity and workmanship.

c
2000 by CRC Press LLC