Page 74 - Electrical Engineering Dictionary

backpropagation the way in which error (as opposed to the frontside bus connecting
terms are propagated in a multilayer neural to the main memory).
network. In a single layer feedforward net-
work, the weights are changed if there are dif- backward error recovery a technique of
ferences between the computed outputs and error recovery (also called rollback) in which
the training patterns. For multiple layer net- the system operation is resumed from a point,
works, there are no training patterns for the prior to error occurrence, for which the pro-
outputs of intermediate (‘hidden’) layer neu- cessing was backed up.
rons. Hence the errors between the outputs
and the training patterns are propagated to backward wave interaction interaction
the nodes of the intermediate neurons. The between backward propagating microwave
amount of error that is propagated is propor- electric fields against an electron stream and
tional to the strength of the connection. the electron in the electron beam. The di-
rection of propagating microwaves and the
backpropagation algorithm a super- direction of motion of electrons in the beam
vised learning algorithm that uses a form are opposite each other.
of steepest descent to assign changes to the
weights in a feedforward network so as to re- backward wave oscillator (BWO) a mi-
duce the network error for a particular input crowave oscillator tube that is based on a
or set of inputs. Calculation of the modifica- backward wave interaction.
tions to be made to the weights in the output
layer allows calculation of the required mod- balanced See balanced line.
ifications in the preceding layer, and modi-
fications to any further preceding layers are balanced amplifier an amplifier in which
made a layer at a time proceeding backwards two single-ended amplifiers are operated in
toward the input layer; hence the name of the parallel with 90 degree hybrid. Balanced am-
algorithm. plifiers feature a low voltage standing wave
ratio because of an absorption of reflected
power at the terminating resistor of the hy-
backscatter energy from a reflected elec-
brids.
tromagnetic wave. In optics, the optical en-
ergy that is scattered in the reverse direction
balanced code a binary line code that
from the transmitted optical energy in an op-
ensures an equal number of logic ones and
tical fiber transmission link or network. The
logic zeros in the encoded bit sequence. Also
backscattered energy comes from impurities
called a DC-free code because the continuous
in the fiber; mechanical or environmental ef-
component of the power spectral density of
fects that cause changes in the attenuation
a balanced encoded sequence falls to zero at
in the fiber; connectors, splices, couplers,
zero frequency.
and other components inserted into the op-
tical fiber network; and faults or breaks in
balanced line symmetric multiconduc-
the optical fiber.
tor transmission line in which the voltage on
each conductor along the transmission line
backscattering the reflection of a por- has the same magnitude, but the phases are
tion of an electromagnetic wave back in such that the voltage would sum to zero. In
the direction of the wave source. See also a two conductor transmission line, the volt-
backscatter. ages would be equal and 180 degrees out of
phase. This is the equivalent of a virtual
backside bus a term for a separate bus ground plane or zero E-field plane at the ge-
from the processor to the second level cache ometric center plane of the transmission line

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2000 by CRC Press LLC