Specifications

76 Chapter 9
Measuring Digital Communications Signals
Making Adjacent Channel Power (ACP) Measurements
Measuring Digital Communications
Signals
Figure 9-7 Measuring a Third Adjacent Channel
Step 8. Set pass/fail limits for each offset:
Press
Meas Setup, Offset/Limits, Offset (A), Neg Offset Limit, −55, dB, Pos
Offset Limit
, −55, dB, Offset (B), Neg Offset Limit, −65, dB, Pos Offset Limit,
−65, dB, Offset (C), Neg Offset Limit, −65, dB, Pos Offset Limit, −65, dB.
Step 9. Turn the limit test on:
Press
Meas Setup, More, Limit Test (On).
In Figure 9-8 notice that offset A has passed, however offsets B and C
have failed. Power levels that fall below our specified
−65 dB for offsets
B and C, fail. Failures are identified by the red letter “F” next to the
levels (dBc and dBm) listed in the lower portion of the window called,
“RMS Results”. The offset bar graph is also shaded red to identify a
failure.
Figure 9-8 Setting Offset Limits
NOTE You may increase the repeatability by increasing the sweep time.