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Making Measurements 3
N9340A User’s Guide 31
Measuring a Low-Level Signal
This section provides information on measuring
low-level signals and distinguishing them from
spectrum noise. There are four main useful
techniques as follows to measure a low-level signal.
Reducing Input Attenuation
The ability to measure a low-level signal is limited
by internally generated noise in the spectrum
analyzer.
The input attenuator affects the level of a signal
passing through the analyzer. If a signal is very
close to the noise floor, reducing input attenuation
will bring the signal out of the noise.
1 Preset the analyzer:
2 Input a signal (1 GHz, –80 dBm) to the analyzer
RF input connector.
3 Set the center frequency, span and reference
level:
• Press [FREQ] > {Center Freq} > 1 > {GHz}
• Press [SPAN] > 5 > {MHz}
• Press [AMPTD] > {Ref Level} > –40 > {dBm}
4 Move the desired peak (in this example, 1 GHz)
to the center of the display:
• Press [MARKER] > {Peak Search}
• Press [MARKER] > {Marker To} > {To Center}
Figure 6 A signal closer to the noise level (Atten:10 dB)