Model 8640B TM 9-4935-601-14-7&P
PERFORMANCE TESTS
4-24. OUTPUT LEVEL ACCURACY TEST (Complete)
SPECIFICATION:
Range: 10 dB steps and 18 dB vernier provide output power settings from +19 to -145 dBm (2V to 0.013 µV) into 50Ω.
Using Top 10 dB of Using Full
Vernier Range Vernier Range
Output Level (dBm) +19 to -7 -7 to -47 -47 to -137 +19 to -145
Total Accuracy as
Indicated on Level Meter
±1.5 dB ±2.0 dB ±2.5 dB Add ±0.5 dB
DESCRIPTION:
RF output level accuracy above -7 dBm is measured with a power meter; below -7 dBm, cumulative error is measured
against a lab calibrated step attenuator using an IF substitution technique. The test Signal Generator's output is down-
converted to 3 MHz (the IF) using a mixer and a reference signal generator. The 3 MHz IF is fed through the calibrated
step attenuator to a spectrum analyzer. A reference level is established on the analyzer, and the step attenuator and the
test generator's OUTPUT LEVEL switch are stepped together. Any amplitude variations are measured with a DVM
connected to the analyzer's vertical output.
A spectrum analyzer tracking generator is connected, with the two signal generators, in a phase lock loop that prevents
relative drift between the units.
NOTE
This procedure allows the output level accuracy to be verified down to -145 dBm. Care must be
taken to ensure that leakage signals do not reduce the dynamic range of the test setup (use
double-shielded coaxial cable, HP 08708-6033). Keep cables in the phase lock path away from
cables in the measurement path.
EQUIPMENT:
Reference Signal Generator.................................................................HP 8640A
20 dB Amplifier (3 required) .................................................................HP 8447A
10 dB Step Attenuator............................................................................HP 355D
Calibrated Step Attenuator.....................................................HP 355D OPT H36
Digital Voltmeter ........................................................HP 3480B/3484A OPT 043
Spectrum Analyzer...........................................................HP 141T/8552B/8553B
Tracking Generator ..............................................................................HP 8443B
Mixer (3 required) ..............................................................................HP 10514A
4 MHz Low Pass Filter (2 required) ......................................... CIR-Q-TEL 3 Pole
4-29
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