HP 8753E manual Isolation Example Measurements, LO to RF Isolation

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