Using Fixed Frequency Mode; Setting The Bandwidth And Averaging; Effect Of Bandwidth And Averaging On Speed, Jitter, And Measurement Accuracy; Selecting The Resolution Bandwidth (Rbw) Value - Keysight Technologies N9040B UXA Manual

Measurement Related Tasks and Concepts
Setting the Signal Analyzer to Make a Measurement

Using Fixed Frequency Mode

The fixed frequency mode is used when you want to make a measurement at a
single frequency.
To set a fixed frequency, press FREQ, Freq Mode, Fixed, then press Fixed Freq
and enter the frequency value using the numeric keys and the unit termination
menu.
If you have not entered the noise source ENR data that you intend using for
the fixed frequency mode measurement, you may specify a spot ENR value
and set the ENR mode to Spot.

Setting the Bandwidth and Averaging

Effect of Bandwidth and Averaging on Speed, Jitter, and Measurement
Accuracy
Jitter is a natural occurrence when measuring noise. To reduce jitter you must
increase the number of averages or increase the measurement bandwidth.
If the bandwidth is reduced, you need to increase the number of averages to
maintain the same uncertainty.
The greater the number of averages chosen, the more accurate the
measurement, as this reduces jitter on the measurement. However, this must
be considered against how long it takes to complete the measurement.
There is therefore a trade off between speed and the accuracy and uncertainty
of a measurement.

Selecting the Resolution Bandwidth (RBW) Value

To set the RBW value, press BW, RBW and select whether the resolution
bandwidth is to be set automatically, or to be set manually by you.
When the resolution bandwidth is set to Auto (default setting), the bandwidth
is set automatically, and is dependent on the measurement frequency.
At measurement frequencies of 8 MHz or above, the resolution bandwidth is
set automatically to 4 MHz.
At measurement frequencies less than 8 MHz, the resolution bandwidth is set
automatically to approximately one third of the measurement frequency.
N9069C Noise Figure Measurement Guide 73