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MS278XB OM 5-31
Channel Power Measurement
The Channel Power (CP) measurement is similar to a power meter. It shows the total power from a
transmitter, but the measurement is more accurate than a power meter as it is frequency selective and can be
made on lower amplitude signals.
The channel power measurement is made by integrating the power reading from multiple pixels on the display
and making various corrections to this result.
The measurement is made by setting the span to be somewhat larger than the channel width of interest.
Markers are used to indicate the channel width and the power from all of the display points within the
markers are integrated to obtain the channel power. RMS detection is used to ensure accurate readings for
digital modulation with any amplitude statistics. A correction is then applied to account for the noise
bandwidth of the RBW filter, along with the channel bandwidth and the number of data points.
The following is the equation used to calculate the Channel Power:
Where:
CP = Channel Power in dBm
CHBW = Channel bandwidth in kHz
RBW = Resolution bandwidth used for measurement in kHz
kn = RBW filter noise bandwidth correction factor
kn = NBW/RBW
N = Number of data points within the channel
Pi = Level represented by data point i of the trace in dBm