Page 215 - Electrical Engineering Dictionary

diffusive scattering when the photon sequence of numbers (acting as an input) is
mean free path is much smaller than the scat- transformed into a second sequence of num-
terer dimensions and then the energy is scat- bers termed the output signal. The compu-
tered uniformly in all directions. tational process may be that of low-pass fil-
tering (smoothing), bandpass filtering, high-
DigiCipher HDTV system a high-defini- pass filtering, interpolation, the generation of
tion television (HDTV) digital transmission derivatives, etc.
television system proposed to the FCC by
the American Television Alliance composed
digital halftone halftone technique based
of General Instruments and Massachusetts
on patterns of same size dots designed to sim-
Institute of Technology. The DigiCipher
ulate a shade of gray between white paper and
HDTV proposal submitted to the FCC in Au-
full colorant coverage.
gust of 1991 was the first system to provide
an all digital television system that promised
spectrum compatibility with the existing tele- digital image (1) an array of numbers rep-
vision channel allocation. The system used resenting the spatial distribution of energy in
quadrature amplitude modulation (16-QAM) a scene obtained by a process of sampling
digital transmission at a 4.88 MHz symbol and quantization.
rate.
ˆ
(2) a discrete-value function I(k, l) =
I(k1x, l1y) obtained by sampling, at equi-
digital circuitsorsystemsthatemploytwo
spaced positions, the continuous function
valued (binary) signals denoted by the digits
I(x, y) which measures image intensity at
0 and 1. Normally binary 1 is used to indicate
position x, y of the image plane. I can be
high/true and binary 0 to indicate low/false
single-valued for monochrome images or m-
(Positive Logic).
valued (usually m = 3) for color images.
digital cellular radio cellular radio prod-
uct designed to transmit its signals digitally. digital modulation signal generator an
RF signal generator capable of providing sig-
digital communications communication nals with digital modulation formats such
techniques that employs binary bits to encode as Gaussian minimum shift keying (GMSK),
information. Pi/4 differential quadrature phase shift key-
ing (DQPSK), and code division multiple ac-
digital European cordless telephone cess (CDMA).
(DECT) a digital microcell system op-
erating in the 1.88–1.90 GHz band designed
digital optical computing optical com-
to provide high-capacity wireless voice and
puting that deals with binary number opera-
data services indoors and outdoors in small
tions, logic gates, and other efforts to even-
local networks. DECT systems use a
tually build a general-purpose digital optical
TDMA/FDMA multiple access scheme, with
computer. In digital optical computing, new
10 radio frequency carriers, each 1728 kHz
opticaldevicesaresoughttoreplaceelements
wide, divided into 2 × 12 time slots. This
in an electronic computer. The digital opti-
provides a total of 120 duplex traffic chan-
cal computer may be primarily based on al-
nels, with duplexing via TDD. The carrier bit
ready known computer architectures and al-
rate is 1152 kb/s. DECT portable terminals
gorithms.
have a peak transmit power of 250 mW.
digital filter the computational process digital optics optical systems that handle
or algorithm by which a sampled signal or digital data.
c
2000 by CRC Press LLC