HP 8753D - Page 420

Frequency
Selection
By
choosing test
frequencies
(frequency
list
mode),
you
can
reduce
the
eect
of
spurious
responses
on measurements
by
avoiding
frequencies
that
produce
IF
signal
path
distortion.
LO
Frequency A
ccuracy
and
Stability
The
analyzer
source
is
phaselocked
to
its
receiver
through
a
reference
loop
.
In
the frequency
oset
mode
,
the
mixer
under
test
is
inserted
in
this
loop
.
T
o ensure
that the
analyzer
phaselocks
correctly
,
it
is
important
that
you
use
an
LO
source
that
has
frequency
accuracy
better
than
6
1
MHz
and
residual
FM
<
20
kHz
RMS.
Up-Conversion
and
Down-Conversion
Denition
When you
choose
between
NN
NN
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
NN
RF <
LO
and
NN
NN
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
NN
RF >
LO
in
the
frequency
oset
menus
,
the
analyzer
determines
which
direction the
internal source
must sweep
in order
to
achieve
the
requested
IF
frequency
.F
or example
,to
measure the
lower
sideband
of
a
mixer
,
where
the
RF
signal
is
below
the LO
(RF <
LO), the
internal source
must
sweep
backwards
.
See
the
examples
in
Figure 6-91
.
Figure 6-91.
Examples of Up Converters and Down Converters
In standard mixer measurements, the input of the mixer is always connected to the analyzer's
RF source, and the output of the mixer always produces the IF frequencies that are received by
the analyzer's receiver.
Application and Operation Concepts 6-153