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noise marker
A marker whose readout represents the noise level in a 1 Hz noise power
bandwidth. When the noise marker is selected, the sample display
detection mode is activated, the values of a number of consecutive trace
points about the marker (the number depends on the type of analyzer) are
averaged, and this average value is normalized to an equivalent value
in a 1 Hz noise power bandwidth. The normalization process accounts
for detection and bandwidth plus the effect of the log amplifier when we
select the log-display mode.
noise sidebands
Modulation sidebands that indicate the short-term instability of the local
oscillator (primarily the first local oscillator) system of an analyzer. The
modulating signal is noise, in the local oscillator circuit itself or in the
local oscillator stabilizing circuit, and the sidebands comprise a noise
spectrum. The mixing process transfers any local oscillator instability
to the mixing products, so the noise sidebands appear on any spectral
component displayed on the analyzer far enough above the broadband
noise floor. Because the sidebands are noise, their level relative to a
spectral component is a function of resolution bandwidth. Noise sidebands
are typically specified in terms of
dBc/Hz
(amplitude in a 1 Hz bandwidth
relative to the carrier) at a given offset from the carrier, the carrier being
a spectral component viewed on the display.
nonvolatile memory
Memory data that is retained in the absence of an ac power source. This
memory is typically retained with a battery. Refer
also
to battery-backed
RAM.
occupied bandwidth
A measure of the frequency bandwidth occupied by the carrier of a
transmitter. It is usually the bandwidth that includes 99% of the total
mean carrier power, and is equivalent to “99% power bandwidth”. It is
measured by determining the lower and upper frequency limits; where
0.5% of the total mean carrier power is below the lower frequency limit
and 0.5 % is above the upper frequency limit. Occasionally percentages
other than 99% are specified.
Glossary 18