Agilent Technologies E7405A User Manual
Chapter 1
45
Making Basic Measurements
Identifying Distortion Products
Figure 1-37
No Harmonic Distortion
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 can interact and create third-order intermodulation
distortion products that are located close to the original signals. These
distortion products are generated by system components such as
amplifiers and mixers.
communication systems. When two signals are present in a non-linear
system, they can interact and create third-order intermodulation
distortion products that are located close to the original signals. These
distortion products are generated by system components such as
amplifiers and mixers.
Identifying TOI Distortion Example:
Test a device for third-order intermodulation. This example uses two
sources, one set to 300 MHz and the other to approximately 301 MHz.
(Other source frequencies may be substituted, but try to maintain a
frequency separation of approximately 1 MHz.)
sources, one set to 300 MHz and the other to approximately 301 MHz.
(Other source frequencies may be substituted, but try to maintain a
frequency separation of approximately 1 MHz.)
1.
Connect the equipment as shown in
. 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 and another measurement
would be made.
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 and another measurement
would be made.