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4
Making Measurements
Third-Order Intermodulation Distortion
Two- tone, third- order intermodulation distortion is
a common test in communication systems. When
two signals are present in a non- linear system,
they may interact and create third- order
intermodulation distortion (TOI) products that are
located close to the original signals. These
distortion products are generated by system
components such as amplifiers and mixers.
This example tests a device for third- order
intermodulation using markers. Two sources are
used, one set to 300 MHz and the other to 301
MHz.
1 Connect the equipment as shown in figure below.
Signal generator
Signal generator
This combination of signal generators, low pass
filters, and directional coupler (used as a
combiner) results in a two- tone source with very
low intermodulation distortion.
Although the distortion from this setup may be
better than the specified performance of the
analyzer, it is useful for determining the TOI
performance of the source/analyzer combination.
After the performance of the source/analyzer
combination has been verified, the DUT (Device
Under Test, for example, an amplifier) would be
inserted between the directional coupler output
58
N 9310A
FUN C TI O N S
R F Si g na l G en era t o r
9 kHz - 3.0 G Hz
F r eque nc y
A M
I / Q
U ti li t y
Pre s et
A m p li tude
F M
Sw eep
F i l e
L o c a l
E nter
M
Pu ls e
Tri g ger
L F O ut
7
8
9
MO D
O n/ O f f
4
5
6
1
2
3
0
·
RF
O n/ O f f
R e m o t e
St a n db y
L F O U T
R F O UT 50
O n
R E VE R S E PW R
4W M A X 30VD C
FU N C TI O N S
N 9310 A
RF Signa l G ener a to r
9 kH z - 3 .0 G H z
Fr equ enc y
AM
I / Q
U ti li ty
Pr es et
Am p li tud e
FM
Sw eep
Fi le
Lo ca l
E nter
M
Pul s e
T rigger
LF O u t
7
8
9
MO D
O n/ O f f
4
5
6
1
2
3
·
0
R F
Rem o te
O n/ O f f
Sta ndb y
L F O U T
RF O U T 50
O n
RE VE RSE PW R
4 W M A X 3 0 VD C
Directional
coupler
N9340A User's Guide
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