HP 8753D - Page 417

Mixer
P
arameters
That
Y
ou
Can
Measure
Figure 6-87.
Mixer P
arameters
Transmission
characteristics
include
conversion
loss
,
conversion
compression,
group
delay
,
and
RF
feedthru.
Reection characteristics
include return
loss,
SWR
and
complex
impedance
.
Characteristics of
the signal
at the
output port
include
the
output
power
,
the
spurious
or
harmonic content
of the
signal, and
intermodulation distortion.
Other
parameters
of
concern
are
isolation
terms
,
including
LO
to
RF
isolation
and
LO
to
IF
isolation.
A
ccuracy
Considerations
In
mixer
transmission
measurements
,
you
have
RF
and
LO
inputs
and
an
IF
output.
Also
emanating
from
the
IF
port
are
several
other
mixing
products
of
the
RF
and
LO
signals
.In
mixer
reection
measurements
,
leakage
signals
from
one
mixer
port
propagate
and
appear
at
the
other
two
mixer
ports
.
These
unwanted mixing
products or
leakage
signals
can
cause
distortion
by
mixing
with
a
harmonic
of
the
analyzer's rst
down-conversion stage
.
T
o
ensure
that
measurement
accuracy
is
not
degraded,
you must
lter certain
frequencies or
avoid them
by
frequency
selection.
If
you
place
attenuators
at
all mixer
ports,
you can
reduce
mismatch
uncertainties
.
6-150 Application and Operation Concepts