EMC and Functional Safety of Automotive Electronics by Kai Borgeest;

Author:Kai Borgeest; [Неизв.]
Language: eng
Format: epub
ISBN: 9781785614088
Publisher: Institution of Engineering & Technology
Published: 2018-06-21T21:00:00+00:00

Figure 4.8 Principal idea of the transfer impedance

4.5 Sources

One common criterion to categorise sources of EMI is to distinguish between intentional sources (wireless signal transmitters) and unintentional sources. Although their physical effect is the same, problems with unintentional sources can be solved at the source, the coupling path or the sink, whereas intentional sources (and unintentional sources outside the car) usually cannot be modified, so only the coupling path and the sink can be considered for solution. Intentional sources must be distinguished from intentional electromagnetic interference (IEMI), where EMI is not a side effect of an intentional use, but the desired principal effect for criminal or military purposes. During design, most unintentional sources can be identified easily where high current or voltages are switched quickly or high-frequency signals are processed. On the other hand, in practice, if problems occur, the search for sources in an unknown environment can be very laborious.

Another criterion is the kind of signal. It can be continuous or transient. Continuous signals can carry a digital, analogue or no modulation.

A further criterion is the frequency. Table 4.2 lists some typical sources. For narrow-band sources (very often intended sources), the frequency range is given, and for broadband sources the spectrum may reach to infinite and it is not reasonable to give a limit.

The radiation intensity of a source can be given as a power or a field strength. Sometimes the effective isotropically radiated power (EIRP) is given. The power P fed into an isotropic radiator distributes in all directions with the same intensity. So the power density Sm at a given distance r from the radiator is the power divided by the surface area of a sphere with radius r.

Table 4.2 Interference sources. n is the revolution speed of the generator and p, the number of pole pairs. There are non-public GSM applications with frequencies below 850 MHz. Amateur radio uses many different bands with different modulations; in a vehicle operation, the 2-m or 77-cm bands are most likely, other bands have been omitted. For poor channel quality, LTE falls back from QAM to QPSK

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.