Isolation Example Measurements
Isolation is the measure of signal leakage in a mixer. Feedthrough is
specificalIy
the forward
signal leakage to the IF port. High isolation means that the amount of leakage or feedthrough
between the mixer’s ports is very small. Isolation measurements do not use the frequency
offset mode.
Figure
3-24 illustrates the signal flow in a mixer.
RF
Feedthrough
IF
Feedthrough
pg6105d
Figure 3-24. Signal Flow in a Mixer Example
The RF and
Lo
feedthrough signals may appear at the mixer IF output, together with the
desired IF signal.
The
Lo
to RF isolation and the
Lo
feedthrough are typically measured with the third port
terminated in 50 ohms. Measurement of the RF feedthrough is made as the
Lo
signal is being
applied to the mixer.
LO to
RF
Isolation
1. Initialize the analyzer by pressing
m.
2.
‘Ib
select the analyzer frequency range and source power, press:
This source stimulates the mixer’s LO port.
3.
‘lb
select a ratio B/R measurement, press:
4.
Make the connections as shown in Figure 3-25.
Making Mixer Measurements 3-33