HP 8340B Manual

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4-14. PULSE MODULATION VIDEO FEEDTHROUGH TEST (Cont'd)The test limits are derived using the following equation:P = 10 log (Vrms2/R/1 mW)Where:P = DUT RF output level -10 dBm, and,R = 50 Ohms.Example:For a DUT set to 0 dBm, the output of the 10 dB pad is —10 dBm.P = 10 log (Vrms2/R/1 mW)-10 = 10 log (V2/50/0.001) (divide through by 10)-1 = log (V2/50/0.001) take antilog of both sides10-i =0.1 = (V2/50/0.001) (cross multiply)0.0001 = V2/50 (cross multiply again)^0^05" = V =0.0707 rmsTest Limit = Vpk X 5% = 0.0707 X 1.414 X 5% = 5 mV8. Repeat steps 6 and 7 for DUT output power levels of 0 and -10 dBm.9. Repeat steps 5 through 8 at CW frequencies of 1,1.5, and 2 GHz.NOTEFor DUT frequencies above 2.3 GHz the video feedthrough is typically sosmall that it is difficult to measure. The following steps provide a meansto verify that the video feedthrough is negligible.10. Remove the 10 dB pad between the DUT and the low pass filter. Press the [CW] key and enter anyfrequency from >2.3 GHz to the DUT's maximum frequency. Press the [POWER LEVEL] key andenter [-][1][0] [dBm].11. Select the oscilloscope X5 vertical magnifier. The test limit is now 0.2 mV or 1 minor division on theoscilloscope.12. Select several CW frequencies >2.3 GHz. and verify that the video feedthrough is less than 1minor division on the oscilloscope.4-70 Performance Tests HP 8340B/41B