Specifications

54 Chapter 7
Measuring Noise
Measuring Noise-Like Signals Using the Channel Power Measurement
Measuring Noise
Measuring Noise-Like Signals Using the
Channel Power Measurement
You may want to measure the total power of a noise-like signal that
occupies some bandwidth. Typically, channel power measurements are
used to measure the total (channel) power in a selected bandwidth for a
modulated (noise-like) signal. Alternatively, to manually calculate the
channel power for a modulated signal, use the noise marker value and
add . However, if you are not certain of the
characteristics of the signal, or if there are discrete spectral components
in the band of interest, you can use the channel power measurement.
This example uses the noise of the analyzer, adds a discrete tone, and
assumes a channel bandwidth of 50 kHz. If desired, a specific signal
may be substituted.
Step 1. Preset the analyzer:
Press
Preset, Factory Preset (if present).
Step 2. Set the center frequency:
Press
FREQUENCY Channel, Center Freq, 50, MHz.
Step 3. Start the channel power measurement:
Press
MEASURE, Channel Power.
Step 4. Configure the display to show the combined spectrum view with
channel power limits (span highlighted in blue):
(ESA) Press
View/Trace, Combined.
(PSA) Press
Trace/View, Combined.
Step 5. Turn averaging on:
Press
Meas Setup, Avg Number (On).
Step 6. Add a discrete tone to see the effects on the reading. Enable the internal
50 MHz amplitude reference signal of the analyzer as follows:
(PSA)
Press
Input/Output, Input Port, Amptd Ref.
(ESA E4401B and E4411B)
Press
Input/Output, Amptd Ref (On).
(ESA E4402B, E4403B, E4404B, E4405B, E4407B and E4408B)
Connect a cable from the front panel AMPTD REF OUT to the analyzer
RF input:
Press
Input/Output, Amptd Ref Out (On).
10 log channel BW()×