spike suppressor
any of several devices
e.g., metal-oxide varistors that clamp short-
duration power line overvoltages to an ac-
ceptable level.
spillover
phenomenon that occurs when
radiation from a feed extends past the reflec-
tor edges and is not intercepted by the reflec-
tor.
spin echo
an oscillating electromagnetic
field emitted by a macroscopic orientation of
atomic or nuclear spins, generated by revers-
ing the dephasing process in an inhomoge-
neously broadened material.
spin coating
the process of coating a thin
layer of resist onto a substrate by pouring a
liquid resist onto the substrate and then spin-
ning the substrate to achieve a thin uniform
coat.
spin lock
a mutual exclusion mechanism
where a process spins in an infinite loop wait-
ing for the value of a variable to indicate a
resource availability.
spindle
See
disk spindle
.
spiral computed tomography (CT)
an
imaging modality that uses a rotating X-ray
source and detector revolving around a con-
tinuously moving gantry. As viewed from
the gantry, the X-ray source appears to travel
in a spiral. A continuous set of projection
images is gathered around the spiral and is
interpolated to obtain traditional transverse
cross-section images. Also known as helical
CT.
spiral CT
See
spiral computed tomography
.
spiral inductor
an integrated circuit im-
plementation of a common electrical element
that stores magnetic energy. Two extreme be-
haviors of an inductor are that it will act as a
short circuit to low frequency or DC energy,
and as an open circuit to energy at a suffi-
ciently high frequency (how high is deter-
mined by the inductor value). In an MMIC,
a spiral inductor is realized by a rectangular
or circular spiral layout of a narrow strip of
metal. The value of the inductance increases
as the number of turns and total length of
the spiral is increased. Large spiral induc-
tors are very commonly used as “bias chokes”
to isolate the DC input connection from the
RF circuit. Since a large valued inductor es-
sentially looks like an open circuit to high
frequency RF/microwave energy, negligible
RF/microwave energy will leak through and
interact with the DC bias circuitry.
splice
a permanent connection between
two fibers made by melting or fusing the two
fibers together in an electric arc or gas flame.
Or they may be held together in a variety of
mechanical devices that align the two fiber
cores. In fusion splicing, connections can be
achieved with losses
< 0.1 dB.
spline
(1) a continuous function, interpo-
lating a set of data points
p
i
, that is com-
posed of segments, having
p
i
and
p
i+k
as
extremes. The segments are linked together
in such a way that the continuity constraint is
satisfied.
(2) piecewise polynomial, with a smooth
fit between the pieces.
spline wavelet
wavelet that is in the form
of a spline.
split and merge
procedure often used in
image or signal segmentation. The proce-
dure involves splitting, iteratively applied if
needed, the inhomogeneous regions of an im-
age or sections of a discrete signal and fol-
lowed by merging similar regions or sections
is a split and merge.
split transaction
a bus transaction (e.g.,
memory read or write) in which a request and
the corresponding response are sent in two
different bus transactions.
c
2000 by CRC Press LLC