photovoltaic effect
a photoelectric phe-
nomenon in certain photorefractive crystals,
for example, LiNbO
3
, BaTiO
3
, LiTaO
3
, in
which the illumination of light leads to the
generation of electric current along certain
direction in the crystals. This leads to the ac-
cumulation of charges on the surfaces of the
crystals, causing an open circuit voltage.
photovoltaics
conversion of insolation
into DC electricity by means of solid state
p-n junction diodes.
PHPS
See
personal handy phone system
.
PHS
See
personal handy phone system
.
physical address
See
real address
.
physical medium
the communication
channel over which signals are transmitted.
Broadcast media, in which all stations re-
ceive each transmission, are primarily used
in local-area networks. Common media are
optical fibers, coaxial cable, twisted copper-
wire pairs, and airwaves.
physical model
a mathematical model
based on device physics. Physical models
generally have a mid-range to high modeling
valuation coefficient.
physical optics
a high-frequency tech-
nique to approximate electromagnetic scat-
tering from an object by representing the
smooth, electrically large parts of the object
by equivalent currents at the object’s surface.
physical page number
the page-frame
address (in main memory) of a page from
virtual memory.
physical placement of logic (PPL)
a de-
sign entry method between full custom and
standard cell. It begins at the block diagram
level where the detailed block specification
and the corresponding layout are done simul-
taneously. PPL is targeted at the occasional
designer.
physical sensor
an interface device at the
input of an instrumentation system that quan-
titatively measures a physical quantity such
as pressure or temperature.
physical theory of diffraction
a correc-
tion to physical optics that includes diffracted
fields due to edges and corners.
physical vapor deposition
a process in
which a conductive or insulating film is de-
posited on a wafer surface without the as-
sistance of chemical reaction. Examples are
vacuum evaporation and sputtering.
pickup current
the specified value that, if
exceeded, causes the relay to act on its con-
tact and cause a circuit breaker action. It is
the threshold current for system protection,
and a magnitude above this is considered a
fault or abnormal condition.
pickup voltage
See
pickup current
.
picocell
cell with radius of a few meters.
See also
cell
.
picture description language
a language
in which parts of scenes are labelled and
their relative positions are described in a spe-
cial symbolic form.
Typical relationships
between objects are “inside,” “adjacent to,”
“underneath,” and so on. Such a language
can be parsed and interpreted symbolically
to build up a meaningful understanding of
the picture.
picture–carrier
the carrier frequency of
1.25 MHz above the lower frequency limit
of a standard NTSC television signal (lumi-
nance carrier in color TV).
PID control
See
proportional-integral-
derivative control
.
piecewise deterministic process (PDP)
a
class of Markov stochastic processes that fol-
low deterministic dynamics between random
jumps. A generator of piecewise determin-
c
2000 by CRC Press LLC