Information

EMI Pre-Compliance Guide RIGOL Technologies
RIGOL Technologies CO., LTD. 09.09.2021
be blocked on the way to SA (via a capacitance) but the DUT disturbances won’t be blocked
and transferred to the SA. The impedance at SA connection is 50 Ω.
Two security mechanisms are important using a LISN. When a LISN or a DUT will be
activated, then the electric charge of capacitance changing and current flows for a short
period. This transient current can destroy the first mixer diode in a spectrum analyzer. It is
recommended to use a transient limiter between LISN and SA, to protect the analyzer
5
. For
the first test it is also recommended to use an external attenuator for the test to see if high
disturbances will be occur from DUT. The attenuator can be removed after first test, when
the user be sure, that the disturbance peaks are at a normal level.
In each standard it is defined how the test setup has to be performed. In figure 6 there is the
physical connection of a test setup displayed:
5
Several LISN already have a transient limiter integrated. Please check data sheet of a LISN for more information
Figure 5: Block Diagram of an AC LISN