Measuring the Spectra of Complex Signals R&S FSL
1300.2519.12 2.10 E-11
5. Measuring intermodulation by means of the 3
r
d
order intercept measurement function
Press the MEAS key.
Press the TOI softkey.
The R&S FSL activates four markers for measuring the intermodulation distance. Two markers
are positioned on the useful signals and two on the intermodulation products. The 3
r
d
order
intercept is calculated from the level difference between the useful signals and the
intermodulation products. It is then displayed on the screen:
Fig. 2-6 Result of intrinsic intermodulation measurement on the R&S FSL. The 3
rd
order
intercept (TOI) is displayed at the top right corner of the grid.
The level of a spectrum analyzer's intrinsic intermodulation products depends on the RF level of the
useful signals at the input mixer. When the RF attenuation is added, the mixer level is reduced and
the intermodulation distance is increased. With an additional RF attenuation of 10 dB, the levels of
the intermodulation products are reduced by 20 dB. The noise level is, however, increased by 10
dB.
6. Increasing RF attenuation to 10 dB to reduce intermodulation products.
Press the AMPT key.
Press the RF Atten Manual softkey and enter 10 dB.
The R&S FSL's intrinsic intermodulation products disappear below the noise floor.
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