Glossary—492/492P Service Vol. 1
TERMS RELATED TO FREQUENCY
TERMS RELATED TO AMPLITUDE
Display Frequency.
The input frequency as indicated by
Deflection Coefficient.
The ratio of the input signal mag-
the
spectrum analyzer and expressed in hertz.
nitude to the resultant output indication.
Frequency Span (Dispersion).
The magnitude of the
frequency band displayed, expressed in hertz or hertz per
division.
Frequency Linearity Error.
The error of the relationship
between the frequency of the input signal and the frequency
displayed (expressed as a ratio).
Frequency Drift.
Gradual shift or change in dispiayed fre
quency over the specified time due to internal changes in the
spectrum analyzer, and expressed in hertz per second,
where other conditions remain constant.
Residual FM (Incidental FM).
Short term displayed fre
quency instability or jitter due to instability in the spectrum
analyzer local oscillators, given in terms of peak-to-peak fre
quency deviation and expressed in hertz or percent of the
displayed frequency.
Impulse Bandwidth.
The displayed spectral level of an
applied pulse divided by its spectral voltage density level
assumed to be flat within the pass-band.
Static (Amplifier) Resolution Bandwidth.
The specified
bandwidth of the spectrum analyzer’s reponse to a cw sig
nal, if sweep time is kept substantially long.
NOTE
This bandwidth is the frequency separation of two
down points, usually 6 dB, on the response curve, if it
is measured either by manual scan (true static meth
od) or by using a very low speed sweep (quasi-static
method).
Shape Factor (Skirt Selectivity).
The ratio of the fre
quency separation of the two (60 dB/6 dB) down points on
the response curve to the static resolution bandwidth.
Zero Pip (Response).
An output indication which corre
sponds to zero input frequency.
NOTE
The ratio may be expressed in terms of volts (rms) per
division, decibels per division, watts per division, or
any other specified factor.
Display Reference Level.
A designated vertical position
representing a specified input level.
NOTE
The level may be expressed in decibels (e.g., 1 mW),
volts, or any other units.
Sensitivity.
Measure of a spectrum analyzer’s ability to
display minimum level signals, at a given IF bandwidth, dis
play mode, and any other influencing factors, and expressed
in decibels (e.g., 1 mW).
Equivalent Input Noise Sensitivity.
The average level of
a spectrum analyzer’s internally generated noise referenced
to the input.
Display Flatness.
The unwanted variation of the dis
played amplitude over a specified frequency span, ex
pressed in decibels.
Relative Display Flatness.
The display flatness mea
sured relative to the display amplitude at a fixed frequency
within the frequency span, expressed in decibels.
NOTE
Display flatness is closely related to frequency re
sponse. The main difference is that the spectrum dis
play is not recentered.
Frequency Response.
The unwanted variation of the
displayed amplitude over a specified center frequency
range, measured at the center frequency, expresed in
decibels.
A-2
REV AUG 1981