HP 8591C User Manual page 284

We assume that the channel BW is at least 75% of the selected frequency
span.
Auto Resolution Bandwidth (RBWI and Video Bandwidth NBW selection
S P A N >- 1 2 M H z
1 2 M H z > S P A N >- 4 M H z
4 M H z > S P A N > - 1 . 2 M H z
1 . 2 M H z > S P A N >- 0 . 4 M H z
S P A N < 0 . 4 M H z
Please note the analyzer has been configured for maximum accuracy.
Adjustment of VBW or RBW may degrade measurement performance.
The following steps are performed to determine channel power:
The logarithmic trace is converted to linear units (volts) and the RMS average
is computed. The value is then converted back to logarithmic measurement
units.
The power result is then normalized to a power spectral density in a 1 Hz
bandwidth and scaled to the desired channel bandwidth.
The formula is:
Channel power = (Noise equivalent BW) x (RMS power spectral density in a
1 Hz BW)
Where:
Noise equivalent BW = IBW / 1.128 x RBW
Power spectral density in a 1 Hz BW = total power / total BW
IBW = Channel BW or integration BW
RBW = Resolution bandwidth
Digital Channel Power Measurement Description
Table 8-1.
300
100
30
1 0
3
Test Descriptions
3000
1000
300
100
8-31