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Chapter 4 211
Key Function Descriptions
Key Descriptions
ACP COMPUTE Performs an adjacent channel power (ACP)
computation on the current trace data without
changing the instrument state settings. This
computation operates exactly the same as that of ACP
AUTO MEASURE, but ACP COMPUTE allows you to
control the instrument state settings. The peak method
or analog method must be selected to use this function.
When ACP COMPUTE is pressed and the
measurement setup is suitable for rms detection, the
same rms voltage detection message displayed when
using ACP AUTO MEASURE is displayed in the active
function area. However, if the instrument state is
unsuitable for rms detection, the following warning
message is displayed.
****WARNING****
NOT RMS DETECTOR
In addition to the warning message, the
instrument-state parameter that is causing the
warning will also be displayed. The instrument-state
messages that may be displayed are:
• RBW ≥ 300 kHz
• VBW < 10 × RBW
• DETECTOR MODE
• MIN HOLD
• MAX HOLD
• VIDEO AVERAGE
Even though a warning message with an invalid
instrument-state parameter was indicated, the
measurement is still made and the results are
displayed in the active function area. If an invalid
instrument-state parameter is suspected, the warning
message can be viewed briefly by pressing ACP
COMPUTE repeatedly. Computation results without
rms detection can be accurate if the signals in the
adjacent channels are similar to continuous wave (CW)
signals, but not if the signals are noise-like. Also, some
international standards for ACP measurementsrequire
the video bandwidth to be equal to the resolution
bandwidth, which prohibits rms detection, while
requiring the measurement to respond to the rms sum
of all signals in the passband. If the video bandwidth is
set according to this standard, the warning message
will be displayed.
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