Keysight Technologies N9321C, User Manual

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Functions and Measurements
Making Distortion Measurements
56
Third-Order Intermodulation Distortion
Two-tone, third-order intermodulation distortion is a common
specification 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. System components such as
amplifiers and mixers contribute to the generation of these
distortion products.
This example will test a device for third-order intermodulation
through the use of 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. 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 device-under-test (DUT) (for
example, an amplifier) would be inserted between the directional
coupler output and the analyzer input.
Frequency
Enter
7 MOD
On/ Off
RF
4
1
0
2
9
6
3
On/ Off
Amplitude FM
Utility
LF Out
Preset
Local
AM I/ Q
File
Trigger Pulse M
¡¤
Sweep
8
FUNCTIONS
LF OUT RF OUT 50
Remote
Standby
On
N9310A RF Signal Generator 9 kHz - 3.0 GHz
5
REVERSE PWR
4W MAX 30VDC
Frequency
Enter
7 MOD
On/ Off
RF
4
1
0
2
9
6
3
On/ Off
Amplitude FM
Utility
LF Out
Preset
Local
AM I/ Q
File
Trigger Pulse M
¡¤
Sweep
8
FUNCTIONS
LF OUT RF OUT 50
Remote
Standby
On
N9310A RF Signal Generator 9 kHz - 3.0 GHz
5
REVERSE PWR
4W MAX 30VDC
Remote
Standby
On TG SOURCE CAL OU T
50M Hz 10dBm
7
·
4
1
0
2
5
8 9
6
3 Back
Enter
M arker
Peak
Search
M arker
Auto
Tune
Det/
Display
File/
Print
BW /
Avg
View /
Trace
Meas MODE
Sw eep/
Trig
Local
Save
N9320A SPECTRUM ANALYZER 9 kHz - 3.0 GHz
PROBE POWER
RF IN 50
50V DC M AX
30dBm 1W M AX
CAT Ⅱ
Signal Generator Signal Generator
Spectrum Analyzer
Directional Coupler
RF OUT
RF IN
300 MHz low
pass filter
300 MHz
low pass
filter
NOTE
The coupler should have a high degree of isolation between the two input
ports so the sources do not intermodulate each other.