Information

EMI Pre-Compliance Guide RIGOL Technologies
RIGOL Technologies CO., LTD. 09.09.2021
definition. Furthermore EMC should protect the recourse “electromagnetic spectrum”. Three
main elements are defined in EMI (see figure 1)
The source of interference could come from e.g. parasitic back coupling effects from an
amplifier or an electromagnetic transmission of an electric / electronic facility. Due to
different coupling path the disturbance will be coupled to the susceptible device. This
interference could cause different failure rates in functionality at the EMI receptor
(susceptible device):
1.) Performance degradation
2.) Function failure
3.) Equipment damage (worst case)
To avoid such kind of scenario it is important to detect the root cause including coupling
mechanism at DUT. The EMI interferences could be transmitted via different coupling path.
For lower frequency ranges the interferences are mainly transmitted via line connection (like
for power, data bus, analog lines, RF connection) because the wavelength (λ)
3
is bigger than
the geometry and electrical and magnetically field are independent. Both fields don’t
propagate and a quasi-static approach is necessary (analysis of inductive / capacitive
elements). The line connections need to be tested if unwanted interferences occurring during
/ after activation of DUT at these lines. This kind of test is named conducted emission.
When the wavelength of a DUT is equal or smaller than its frame, then magnetic and electric
field are no longer independent and they start to combine to an electromagnetic field (EM).
If e.g. the geometry has 6 * λ then the EM field is no longer only at the source, propagation
happens and the DUT start to send out an EM wave (its acting as an antenna). Unwanted
interferences with EM waves are named radiated emission. In the near field of the EM source
a quasi-static approach is necessary.
The occurrence of interferences is in most cases unforeseen and difficult to detect because
different coupling effects could be root cause of interferences. For a device under test there
are two main influences of interferences. First one is an interference which is related within
one DUT and has an influence of functionality within the device under design. These
interferences are intra-system disturbances which will be occurred e.g. crosstalk effects.
3
Wavelength (λ) of a frequency (f) is defined with the speed of light (C = 3*10
8
m/sec.): λ = C / f. For example the
wavelength of 1 GHz: λ = 0,3 m (30 cm). With e.g. geometry of 1.2 m a 1 GHz wave (or higher frequencies) will be
propagated.
Source of
Interference
Coupling Path Susceptible
Device
Figure 1: Elements of EMI