HP 8924E, Сборка

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Chapter 14, Diagnostics Descriptions
Description of RF Diagnostics (RFDIAGS3)
N:\mkt\MANUALS\HP8924C\ALR\diagnos.fb
Spectrum Analyzer Tests A32
Table 127 A32 Spectrum Analyzer Tests
Measurement Explanation and Suggestions Measurement Point
Detector
Output,
No Signal The signal generator’s signal is routed to the spectrum
analyzer, but the level is set to
−
100 dBm at the RF
IN/OUT connector which produces a very small sig-
nal at the spectrum analyzer. The spectrum analyzer’s
detector should produce just an off-set voltage.
DVM:SCOPE2
Stepped Gain Using the spectrum analyzer’s internal calibration sig-
nal (110 MHz), the stepped-gain amplifiers are
checked. Each gain step is turned on one step at a
time. The sensitivity of the detector varies from
24 mV/dB to 6 mV/dB at the levels where the internal
calibration signal could be. 3 dB of gain error is
allowed for the steps. If this measurement fails, trace
the 20 MHz signal from P3-9 of the A27 Reference to
P1-3 of the A32 Spectrum Analyzer. DVM:SCOPE2
IF Band Width The IF bandwidth is set to all possible values. The
spectrum analyzer LO is moved in increments of 10%
of the bandwidth of the filter being tested to find a
signal within each filter. The voltage read by the
detector should be basically the same as the full scale
reading (0 dB) in the stepped gain test above. DVM:SCOPE2
Filter Rejection The LO’s frequency is set 10
×
BW away from the
normal center of each filter. Then the detector is read.
The level at the detector should be low. A 0.55 V
change is equivalent to a 27.5 dB change in signal
level.
DVM:SCOPE2
Variable Gain
IF Amplifier The variable-gain IF amplifier is checked by turning
on one bit at a time, the DAC which controls it. The
least-significant bit is turned on first. DVM:SCOPE2