HP 8753D - Fixed IF Mixer Measurements

Fixed IF
Mixer Measurements
A
xed
IF
can
be produced
by using
both a
swept RF
and LO
that are
oset by
a
certain
frequency
.
With
proper
ltering,
only
this oset
frequency will
be present
at the
IF port
of the
mixer
.
This
measurement
requires
two
external
RF
sources
as
stimuli. Figure
3-15 shows
the hardware
conguration
for
the
xed
IF conversion
loss measurement.
This example
measurement
procedure
uses
the
analyzer's
test
sequence
function for
automatically controlling
the two
external
synthesizers
(with
SCPI
commands),
and
making a
conversion loss
measurement in
tuned
receiver
mode
.
The
test
sequence function
is an
instrument automation
feature
internal
to
the
analyzer
.
F
or
more information
on the
test sequence
function
refer
to
\T
est
Sequencing"
located
in
Chapter 2.
Tuned
Receiver
Mode
The
analyzer's
tuned
receiver
mode
allows
you
to
tune
its
receiver
to
an
arbitrary
frequency
and
measure
signal
power
.
This
is
only
possible
if
the
signal
you
wish
to
analyze
is at
an exact
known
frequency
.
Therefore
,
the
RF
and
LO
sources
must
be
synthesized
and
synchronized
with
the
analyzer's
time
base
.
Sequence
1Setup
The
following
sequence
initializes
and
calibrates
the
network
analyzer
.
It
then
initializes
the
two
external
sources
prior
to
measurement.
This
sequence
includes:
putting
the
network
analyzer
into
tuned
receiver
mode
setting
up
a
frequency
list
sweep
of
26
points
performing
a
response
calibration
prompting
the
user
to
connect
a
mixer
to
the
test
set
up
initializing
a
loop
counter
value
to
26
addressing
and
conguring
the
two
sources
calling
the
next
measurement
sequence
1.
Make
the following
connections as
shown in
Figure 3-14
.
Set
the
HP-IB
address
of
the
external
RF
source
to
19 and
the external
LO source
to
21.
2.
Conrm
that
the
external sources
are congured
to receive
commands
in
the
SCPI
programming
language
and
that
their output
power is
switched on.
Note
Y
ou
may
have to
consult the
User's Guide
of the
external source
being used
to
determine
how
to
set
the
source
to
receive SCPI
commands
.
3. Be sure to connect the 10 MHz reference signals
of the external sources to the EXT REF
connector on the rear panel of the analyzer (a BNC tee
must be used).
Note
If the 10 MHz reference
signals of the external sources are connected together
,
then it will only be necessary to connect one reference signal from one of the
sources to the EXT REF connector of the analyzer
.
Making Mixer Measurements 3-17