Atek HP 8753D, Руководство пользователя, Страница: 157 / 677

Isolation Example Measurements
Isolation is the measure of signal leakage in a mixer . F eedthrough is specically 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
oset mode . Figure 3-24 illustrates the signal ow in a mixer .
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 4
PRESET
5 .
2. T o select the analyzer frequency range and source power , press:
4
ST ART
5 4
10
5 4
M/
5
4
STOP
5 4
3000
5 4
M/
5
4 MENU 5
N NNNNNNNNNNNNNNNN
POWER
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
PWR RANGE MAN 4 0 5 4 x1 5
This source stimulates the mixer's LO port.
3. T o select a ratio B/R measurement, press:
4 MEAS 5
NNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNNN
INPUT PORTS
NNNNNNNNNNN
B/R
4. Make the connections as shown in Figure 3-25.
Making Mixer Measurements 3-33