The Spectrum Application (RF Measurements)
R&S
®
FPL1000
238
User Manual 1178.3370.02 ─ 09
7.2.12.1
About the TOI Measurement
If several signals are applied to a transmission two-port device with nonlinear charac-
teristic, intermodulation products appear at its output at the sums and differences of
the signals. The nonlinear characteristic produces harmonics of the useful signals
which intermodulate at the characteristic. The intermodulation products of lower order
have a special effect since their level is largest and they are near the useful signals.
The intermodulation product of third order causes the highest interference. It is the
intermodulation product generated from one of the useful signals and the 2nd harmonic
of the second useful signal in case of two-tone modulation.
In order to measure the third order intercept point (TOI), a two-tone signal with equal
carrier levels is expected at the R&S
FPL1000 input. Marker 1 and marker 2 (both nor-
mal markers) are set to the maximum of the two signals. Marker 3 and marker 4 are
placed on the intermodulation products.
The R&S
FPL1000 calculates the third order intercept point from the level difference
between the first 2 markers and the markers 3 and 4 and displays it in the marker
table.
7.2.12.2
TOI Basics
If several signals are applied to a transmission two-port device with nonlinear charac-
teristic, intermodulation products appear at its output at the sums and differences of
the signals. The nonlinear characteristic produces harmonics of the useful signals
which intermodulate at the characteristic.
The frequencies of the intermodulation products are above and below the useful sig-
nals. The
shows intermodulation products P
S1
and P
S2
generated by the
two useful signals P
U1
and P
U2
.
Measurements and Results
