Isolation Example Measurements; Lo To Rf Isolation - HP 8753E User Manual

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.
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:
Make the connections as shown in Figure 3-25.
4.
Figure 3-24. Signal Flow in a Mixer Example
RF
Feedthrough
IF
Feedthrough
Making Mixer Measurements 3-33