Spectrum Analyzer
R&S FS300
E-1007.9900.15
6-150
Operating manual, 02/2006
6.2.7.2
Measuring the Third-Order Intercept Point
Use
If two signals with different frequencies are applied to a DUT with non-linear
characteristic, intermodulation products occur at the output. Third-order mix-
ture products are of particular importance since they are close to the useful
signals.
The frequencies of the noise products f
s1
and f
s2
are located above and below
the frequencies of the input signals f
n1
and f
n2
:
F
s1
= 2 x f
n1
- f
n2
F
s2
= 2 x f
n2
- f
n1
A third-order intercept point can be easily calculated with the input signals at
the same level P
n
plus the measured value of an intermodulation product:
IP3 = a
d3
/2 + P
n
When the TOI function is set and the markers are set to the input signals, the
R&S FS300 automatically measures the intermodulation products and dis-
plays the value calculated for the intercept point.
Setting the
markers to the
input signals
1.
Set markers 1 and 2 to the two input signals ( 6-98, 6-102).
Activating the
measurement
2.
Press the
function key
in the
submenu.
The TOI measurement is activated and the function key is highlighted.
The value calculated for the TOI is displayed in the parameter field.
Deactivating the
measurement
•
Press the
function key
in the
submenu.
The TOI measurement is deactivated and the function key is no longer
highlighted.
Summary of Contents for FS300
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