Model 8640B
TM 9-4935-601-14-7&P
PERFORMANCE TESTS
4-27. OUTPUT IMPEDANCE TEST (Out of Band) (Cont'd)
Figure 4-14. Output Impedance Test Setup (Out of Band).
EQUIPMENT:
Tracking Generator ............................................................................. HP 8444A
Spectrum Analyzer........................................................... HP 8554B/8552B/141T
VSWR Bridge ............................................................................... Wiltron 60N50
Coaxial Short ..................................................................................... HP 11512A
10 dB Attenuator .................................................................... HP 8491A OPT 10
PROCEDURE:
1. Connect equipment as shown in Figure 4-14 after setting Signal Generator's controls as follows:
AM ...............................................................................................................OFF
FM ................................................................................................................OFF
RANGE ......................................................................................... 256 - 512 MHz
FREQUENCY TUNE ................................................................................ Full cw
OUTPUT LEVEL ....................................................................................+19 dBm
RF ON/OFF ..................................................................................................OFF
2. Set spectrum analyzer for a frequency span of 50 550 MHz, 300 kHz resolution bandwidth, and 20 dB input
attenuation. Set tracking generator output level to 0 dBm.
3. To establish a reference level, connect coaxial short to bridge output port. Use the spectrum analyzer's vertical
scale, logrithmic level controls to set the reference level trace to the top of the analyzer display.
4. Remove coaxial short and couple bridge output port to Signal Generator's RF OUTPUT connector. The
difference, in dB, from the reference level established in step 3 to the level now visible on the display is the
return loss of the generator's output port. The return loss should be >9.5 dB from 50 to 512 MHz (VSWR <2.0:1).
9.5 dB________________
4-40
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