HP 8340B Manual page 67

4-14. PULSE MODULATION VIDEO FEEDTHROUOH TEST (Cont'd)
The test limits are derived using the following equation:
10 log (Vrms 2/R/1 inW)
P
=
Where:
P DUT RF output level —10 dBm, and,
=
R 50 Ohms.
=
Example:
For a DUT set to 0 dBin, the output of the 10 dB pad is —10 dBin.
P 10 log (Vrins2/R/1 mW)
=
—10 10 log (V2/S0/0.001) (divide through by 10)
=
—1 log (V2/50/0.001) take antilog of both sides
=
101 (V2/S0/0.001) (cross multiply)
0.1
= =
0.0001 V2/50 (cross multiply again)
=
OQOS V
=
Test Limit Vpk X S%
=
8. Repeat steps 6 and 7 for DUT output power levels of 0 and —10 dBin.
9. Repeat steps S through 8 at CW frequencies of 1,1.5, and 2 GHz.
For DUT frequencies above 2.3 GHz the video feedthrough is typically so
small that it is difficult to measure. The following steps provide a means
to verify that the video feedthrough is negligible.
Remove the 10dB pad between the DUT and the low pass filter. Press the [CW] key and enter any
10.
frequency from >2.3 GHz to the DUT's maximum frequency. Press the [POWERLEVEL] key and
enter [1] [0] [dBm].
[—]
11. Select the oscilloscope XS vertical magnifier. The test limit is now 0.2 mV or 1 minor division on the
oscilloscope.
12. Select several CW frequencies >2.3 GHz. and verify that the video feedthrough is less than 1
minor division on the oscilloscope.
4-70 Performance Tests
0.0707 ms
=
0.0707 X 1.414 )<
=
mV
S
SO/a
=
NOTE
HP 8340B/41B