R&S ESU Series Operating Manual page 243

R&S ESU
Level
Fig. 4.14 Intermodulation products P
The intermodulation product at f
signal P
monic of useful signal P
f = 2 × f
I1
f = 2 × f
I2
The level of the intermodulation products depends on the level of the useful signals.
If the two useful signals are increased by 1 dB, the level of the intermodulation prod-
ucts increases by 3 dB, which means that spacing a
nals and useful signals is reduced by 2 dB. This is illustrated in
Dependence of intermodulation level on useful signal
O utput
level
Fig. 4.15 Dependence of intermodulation level on useful signal level
The useful signals at the two port output increase proportionally with the input level
as long as the two port is in the linear range. A level change of 1 dB at the input
causes a level change of 1 dB at the output. Beyond a certain input level, the two
port goes into compression and the output level stops increasing. The intermodula-
tion products of the third order increase three times as much as the useful signals.
4.212
P
U1
P I1
f ∆
f
f
I1
U1
U1
and signal P , the intermodulation product at f
U2 U1
and signal P
U1
- f
U1 U2
- f
U2 U1
Com pression
Useful signal
1
1
P
U2
a D3
P I2
f ∆ f ∆
f
f
I2
U2
and P
U2
is generated by mixing the 2nd harmonic of useful
I2
.
U2
between intermodulation sig-
D3
level.
Intercept point
Intermodulation
product
3
1
Operating Manual 1302.6163.12 - 03
Instrument Functions
Analyzer Mode
Frequency
by mixing the 2nd har-
I1
Fig. 4.15
Input level
(37)
(38)