HP 8753D - Page 423

Conversion
Loss
Figure
6-94.
Example
Spectrum
of
RF
,
LO
,
and
IF
Signals
Present
in
a
Conversion
Loss
Measurement
Conversion
loss
is
a
measure
of
how
eciently
a
mixer
converts
energy
from
one
frequency
to
another
.
It
is
the
ratio
of
the
sideband
output
power
to
input
signal power
and is
usually
expressed
in
dB
.
Since
the
frequency
response
of
the
test
system
gets measured
with the
mixer's
response
,
you
can
perform
a
frequency
response
calibration
to
remove
this group
of errors
.
Isolation
Figure
6-95.
Main
Isolation
T
erms
Isolation is the amount of attenuation provided when a
signal is applied to one port of a mixer
and measured at another port. Figure 6-95 shows the three
main isolation terms
.
LO F
eedthru / LO to RF Leakage
LO feedthru, or LO-to-IF isolation, is the amount the LO signal that is attenuated when it
reaches the IF port.
LO to RF isolation is the amount the LO power is attenuated when it appears directly at the RF
port.
Both of these LO isolation terms are small for single and double balanced mixers. The RF signal
level applied to the mixer will have an aect on this measurement. For this reason, these
terms are usually measured with the RF port of the mixer terminated in a matched state.
6-156 Application and Operation Concepts