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Conversion Loss
fl F=
fRF-fLO
iL0
’
RF
fl F=
fRF+
fLO
FREQUENCY
pg694d
Figure 6-95.
Example Spectrum of RF, LO, and IF Signals Present in a Conversion Loss Measurement
Conversion loss is a measure of how
efliciently
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
Feedthrough
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Figure 6-96. Main Isolation
‘lkrms
Isolation is the amount of attenuation provided when a signal is applied to one port of a mixer
and measured at another port. Figure 6-96 shows the three main isolation terms.
LOFeedthru/LOtoRFLedage
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.
Roth of these
LO
isolation terms are small for single and double balanced mixers. The RF signal
level applied to the mixer will have an affect on this measurement. For this reason, these
terms are usually measured with the RF port of the mixer terminated in a matched state.
6-l
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Application and Operation Concepts