Frequency range: The minimum to maximum
frequencies over which a spectrum
analyzer can tune. While the maximum
frequency is generally thought of in terms
of an analyzer’s coaxial input, the range of
many microwave analyzers can be extended
through use of external waveguide mixers.
Frequency resolution: The ability of a spectrum
analyzer to separate closely spaced
spectral components and display them
individually. Resolution of equal amplitude
components is determined by resolution
bandwidth. The ability to resolve unequal
amplitude signals is a function of both resolution
bandwidth and bandwidth selectivity.
Frequency response: Variation in the
displayed amplitude of a signal as a function
of frequency (flatness). Typically specified in
terms of ± dB relative to the value midway
between the extremes. Also may be specified
relative to the calibrator signal.
Frequency span: The frequency range
represented by the horizontal axis of the
display. Generally, frequency span is given as
the total span across the full display. Some
earlier analyzers indicate frequency span
(scan width) on a per-division basis.
Frequency stability: A general phrase that
covers both short- and long-term LO instability.
The sweep ramp that tunes the LO also
determines where a signal should appear
on the display. Any long term variation in LO
frequency (drift) with respect to the sweep
ramp causes a signal to slowly shift its horizontal
position on the display. Shorter-term
LO instability can appear as random FM or
phase noise on an otherwise stable signal.
Full span: For most modern spectrum
analyzers, full span means a frequency span
that covers the entire tuning range of the
analyzer. These analyzers include single
-band RF analyzers and microwave analyzers
such as the ESA, PSA and X- Series that use
a solid-state switch to switch between the
low and preselected ranges.
NOTE: On some earlier spectrum analyzers,
full span referred to a sub-range. For example,
with the Agilent 8566B, a microwave
spectrum analyzer that used a mechanical
switch to switch between the low and preselected
ranges, full span referred to either
the low, non-preselected range or the high,
preselected range.