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c)
Reduce the resolution bandwidth with the step key
【
↓
】
As shown in Fig. 3.9, the noise floor reduces and therefore we can see the signal more clearly.
Fig. 3.9 Measuring Small Signals by Reducing Resolution Bandwidth
As the reduction of resolution bandwidth will increase the sweep time, in the S3302 Spectrum Analyzer, resolution
bandwidth 1Hz - 10MHz is realized by step 1-3-10. Proper resolution bandwidth should be selected to realize
delicate compromise between sweep time and resolution bandwidth.
3.3.3 Measuring small signals by using average detection and increasing sweep time
When the noise floor of the spectrum analyzer masks small signals, the noise can be smoothed by using the
average detector and increasing the sweep time so as to improve the visibility of such signals. A slower sweep
speed can result in a better mean square error of noise.
a)
Reset the spectrum analyzer
Press
【
Preset
】
key to restart the spectrum analyzer.
b)
Set the center frequency, the span, and the reference level
Set the frequency of the external signal generator to 300MHz and set the amplitude to -80dBm, and connect the
radio frequency output end of the signal generator to the radio frequency input end of the spectrum analyzer. Set
the center frequency of the spectrum analyzer. Press
【
Freq
】
and select [Center Freq] to set the center
frequency to 300MHz, and then select
【
Span
】
to set the span to 5MHz. Press
【
Ampt
】
and select [Ref Level]
to set the reference level to -40dBm.
c)
Select the detection method of the spectrum analyzer to the average detection.
Press
【
BW
】
, [Detector] and [Average] to select the average detection method. At this time, the information
bar at the left of the display screen appears “Detection Average”, showing it is set to the mean detection
