HP 8753D - Page 266

Understanding
Spur
A
voidance
In
the
400
MHz
to
3
GHz
range
,
where
the source
signal is
created by
heterodyning two
higher
frequency
oscillators
,
unwanted
spurious
mixing
products
from
the source
may be
present at
the
output.
These
spurs
can
become
apparent
in
lter measurements
when lters
have greater
than
80
dB
rejection.
Spur
avoidance
slightly
moves
the
frequency
of
both
oscillators
such
that the
source frequency
remains
the
same
but
the
spurious
mixing
products
shift out
of the
measurement receiver
range
.
The
calculation
of
the
exact
frequency
points where
the shifting
must occur
(stored
in
the
sampler
oset
table)
increases
the
time
needed to
change or
recall instrument
states
.
Selecting
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SPUR
AVOID
OFF
and
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RAW
OFFSET
OFF
eliminates
this
calculation.
Optimizing Measurement Results 5-59