Measuring Signals in the Vicinity of Noise R&S FSL
1300.2519.12 2.14 E-11
Measurement example – Measuring level at low S/N ratios
The example shows the different factors influencing the S/N ratio.
S
ignal generator settings (e.g. R&S SMU):
Frequency: 128 MHz
Level: – 80 dBm
Procedure:
1. Set the R&S FSL to its default state.
Press the PRESET key.
The R&S FSL is in its default state.
2. Set the center frequency to 128 MHz and the frequency span to 100 MHz.
Press the FREQ key and enter 128 MHz.
Press the SPAN key and enter 100 MHz.
3. Set the RF attenuation to 60 dB to attenuate the input signal or to increase the intrinsic noise.
Press the AMPT key.
Press the RF Atten Manual softkey and enter 60 dB.
The RF attenuation indicator is marked with an asterisk (*Att 60 dB) to show that it is no longer
coupled to the reference level. The high input attenuation reduces the reference signal which
can no longer be detected in noise.
Fig. 2-10 Sinewave signal with low S/N ratio. The signal is measured with the auto peak
detector and is completely hidden in the intrinsic noise of the R&S FSL.
4. To suppress noise spikes the trace can be averaged.
Press the TRACE key.
Press the Trace Mode key.
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