Keysight N9927-90001 User’s Guide 231
RTSA (Real-Time Spectrum Analyzer) Mode—Option 350 (CPU2 Only)
RTSA Mode Settings
— Auto When Auto is selected, the preamp setting is coupled to the RF
attenuation and to the acquisition. When the acquisition reaches a certain
value, the preamp is turned on and PA is shown to the left of the graticules
on the display.
Check for Compressed Measurements
Compression occurs when too much power into an amplifier causes it to no
longer amplify in a linear manner. When too much power goes into the
FieldFox RF Input connector, the amplifiers in the RTSA receiver compress and
signal power will not be displayed accurately. This can occur even if ADC Over
Range is not displayed because devices other than the ADC, such as the mixer,
might be compressed. Increase the RF Attenuation value to prevent the RTSA
receiver from being compressed.
How to Check for a Compressed Measurement
— Using a marker at the signal peak, make note of the signal power level.
— Increase the RF Attenuation level by 5 dB.
—If the signal level does NOT change, then NO compression exists. This
indicates that the signal is in the linear region of the FieldFox
receiver.
—If the signal level DOES increase, then the receiver was compressed.
Set the RF Attenuation value at the setting when further increases no
longer result in an increase in the displayed power level.
Spectrum Selection
To select the spectrum-type for your measurement:
How to make Spectrum Settings
—Press Measure 1
—Then Press:
— Density Spectrum
The signal displayed is a real-time spectrum with
a histogram bitmap. Refer to Figure on page 232 and Figure 10-2 on
page 233.
— Spectrogram
The signal is displayed is a real-time spectrum with a
spectrogram bitmap. Spectrogram views are valuable in capturing
signals that include both time and frequency variations. Refer to
Figure 10-3 on page 233.
Density Spectrum and Spectrogram data is lost when you change modes,
because the FieldFox optimizes the instrument’s resources during mode
changes.
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