Title
Razvoj i primena postupaka za efikasnu karakterizaciju elektromagnetske sprege ostvarene posredstvom otvora u oklopljenim kućištima
Creator
Milutinović, Vesna M.
Copyright date
2014
Object Links
Select license
Autorstvo-Nekomercijalno-Bez prerade 3.0 Srbija (CC BY-NC-ND 3.0)
License description
Dozvoljavate samo preuzimanje i distribuciju dela, ako/dok se pravilno naznačava ime autora, bez ikakvih promena dela i bez prava komercijalnog korišćenja dela. Ova licenca je najstroža CC licenca. Osnovni opis Licence: http://creativecommons.org/licenses/by-nc-nd/3.0/rs/deed.sr_LATN. Sadržaj ugovora u celini: http://creativecommons.org/licenses/by-nc-nd/3.0/rs/legalcode.sr-Latn
Language
Serbian
Cobiss-ID
Theses Type
Doktorska disertacija
description
Datum odbrane: 29.06.2015.
Other responsibilities
mentor
Milovanović, Bratislav
član komisije
Dončov, Nebojša 1970-
član komisije
Marković, Vera 1956-
član komisije
Radunović, Jovan 1949-
član komisije
Pronić Rančić, Olivera 1969-
član komisije
Maleš Ilić, Nataša 1968-
Academic Expertise
Tehničko-tehnološke nauke
University
Univerzitet u Nišu
Faculty
Elektronski fakultet
Group
Katedra za telekomunikacije
Alternative title
Development and application of methods for effective characterization of electromagnetic coupling achived through apertures in shielded enclosures
Publisher
[V. M. Milutinović]
Format
[14], 139 listova
description
Telecommunications
Abstract (en)
Electromagnetic compatibility (EMC) is essential for the design and operation of
electronic systems in real time, as a form of equipment behavior in such a way that it is
resistant to a certain level of interference from the environment, and which at the same time
emits an acceptable level of EM radiation. From EMC point of view performance of
electronic systems dominantly depend on the existence and nature of interconnecting paths,
through which the coupling between EM energy sources and sensitive electronic systems is
achived dominantly, in addition to the character of excitated EM radiation and configuration
of wire and dielectric structures within the system. Major role in the elimination or reduction
of these interconnecting paths have shielded enclosures. This enclosures, made of conductive
material with adequate thickness and with different EM characteristics, affect on the level of
EM radiation that reaches the electric circuit from the environment, but also determine how
much energy is radiated by the circuit to the environment. Because enclosures have
individual apertures inevitably, which are commonly used to access the system (connectors,
power supply/shortening cables, CD/DVD-ROM, and others), and/or more apertures of the
same shape for cooling and removal of excess heat from the system (e.g. air-vent apertures),
EM radiation penetrates through the apertures in the space inside and outside the enclosure,
degrading the basic function of shielding.
The role of the shielded enclosure is that depending on the frequency, thickness and EM
material characteristics of which is made, reduces the amount of EM energy which penetrates
into the space inside and outside the enclosure and is usually expressed in term, which is
called the shielding effectiveness (SE). This measure is usually defined as the ratio in dB
between the level of the incident field in the corresponding point in the system in the absence
of enclosure and in the presence of enclosure and it can be defined as well as for the electric
(the so-called electric shielding effectiveness) and for the magnetic field (the so-called
magnetic effectiveness).
The aim of the doctoral dissertation is to analyze the influence of different effects such
as: increasing the thickness of the front metal wall with apertures, a number of apertures,
changing the shape and size of apertures, as well as their mutual distance on the shielding
effectiveness of enclosure, on the example of enclosure of certain size in a certain frequency
range. Accordingly, both individual apertures and air-vent apertures were considered with
different shapes (rectangular, circular and square), which are usually located on the walls of
shielded enclosures. In addition to the incident plane wave, an oblique wave in which the
angle of polarization, azimuth and elevation is changed, was discussed also, as well as
calculated values for SE in the different observation points within the enclosure. For most
practical EMC issues, excitation in the form of a plane wave is only an approximation of the
real excitation and is mainly used for the calculation of the shielding effectiveness. An
excitation is placed inside the enclosure, when it is necessary to estimate the level of EM
emissions, using numerical simulation, which is radiated from the shielded enclosure and the
degree of its impact on other electronic systems in the environment. The internal excitation in
enclosure, in the form of wire, was examined in the doctoral dissertation and how it affects on
the external environment for the different shape of the apertures on the front wall calculating
the electric field in the far field.
Considering that for the purposes of conducting measurement a receiving antenna is
being used, which is located inside the enclosure, it is necessary to take into account the
impact of receiving antenna on the SE. The receiving antenna of finite size can significantly
change the propagation of EM fields inside the enclosure and thus affects on the result of the
SE. The effect of the presence of the receiving dipole, as well as monopole antenna on the SE
was examined in this doctoral dissertation, in terms of how changes in antenna parameters,
such as the radius and the length of the antenna position within the enclosure and its
orientation, affect on the enclosure SE.
Research methods that were applied in this doctoral dissertation are: analytical method
for modeling using equivalent circuit and numerical modeling method using electrical lines
(Transmission Line Matrix - TLM). The method of equivalent circuit was used for the
analysis, in order to consider more apertures at many walls and oblique incident wave, and it
was enhanced by the author to consider the presence of the receiving antenna inside the
enclosure, which is used in the measurements process for calculating SE. Therefore, the main
subject of this doctoral dissertation is development of analytical model and the development
of equivalent model in order to calculate SE of enclosure with apertures. The basic advantage
of this improved analytical model is his ability to precisely modeling antennas inside the
enclosure. In fact, at some point within the enclosure receiving antenna was presented with
appropriate impedance in the observing point of equivalent model. From this reason, the
obtained results for the input impedance of a receiving antenna, for obtained equivalent
model, were presented in the doctoral dissertation. The TLM method with the compact wire
model was used also, for consideration of the receiving antenna presence in the measurement
process, while in the case when an enclosure have air-vents, so-called a compact TLM model
for the air vents on the metal walls, was applied, owing to calculate distribution of the EM
field around a large number of apertures. Analytical and numerical model were compared in
the dissertation in terms of their ability to calculate a different number of air-vent apertures,
with a different mutual spacing on the front wall.
A comparison of analytical and numerical results with the obtained measurement results
was presented in detail, in order to verify and investigate the possibility of applying the
proposed method for modeling the receiving antenna. The efficiency of the proposed
analytical method was discussed in the example of enclosure with apertures on the front wall
and the receiving antenna located at different points within the enlosure. The accuracy of the
method was verified by comparison with numerical values, for a different length and
diameter of the receiving antenna and with the corresponding measurement results. In this
context, to what extent there is a difference between results obtained by analytical and
numerical model, was shown in the doctoral dissertation, depending on the size of the
receiving antenna. The corresponding numerical results, which represent the shielding
effectiveness of enclosure, for a number of different wire diameters used as a receiving
antenna, were illustrated in the framework of the doctoral dissertation.
Among the expected results, which represent the original scientific contribution of the
dissertation, can be extricate as following:
computation of impact for various factors: the number and shape of apertures, their
mutual spacing, wall thickness, changes in the excitation parameters of plane EM wave, on
the SE using numerical differential method in time-domain for analysis of practical EMC
problems;
computation of excitation influence in the form of wire inside the enclosure on the
EM field in the far field using numerical method;
application of improved TLM method with compact wire model for generating a
numerical model in order to analyze the impact of the receiving dipole antenna on the SE;
application of analytical and numerical models for calculation the SE of enclosure
with apertures and receiving antenna inevitable in the measurement process especially at the
resonant frequencies;
calculation of the SE with and without receiving antenna with different diameters
using improved numerical and analytical models.
The conclusions are based on analyzes and calculations, in which it was highlight the
most important features and advantages of the proposed methods. It was indicated on the
differences of analytical and numerical models with and without receiving antenna of various
diameters, that must be taken into account during the experimental characterization, in order
to correctly calculate the level of SE and the position of resonant frequencies.
Authors Key words
oklapanje, efikasnost zaštite, kućište, elektromagnetska kompatibilnost,
sprega, otvor, analitički metod, TLM metod, prijemna antena
Authors Key words
shielding, shielding effectiveness, enclosure, electromagnetic compatibility,
coupling, aperture, analytical method, TLM method, receiving antenna
Classification
004.3:[537.81+537.531(043.3)
Type
Tekst
Abstract (en)
Electromagnetic compatibility (EMC) is essential for the design and operation of
electronic systems in real time, as a form of equipment behavior in such a way that it is
resistant to a certain level of interference from the environment, and which at the same time
emits an acceptable level of EM radiation. From EMC point of view performance of
electronic systems dominantly depend on the existence and nature of interconnecting paths,
through which the coupling between EM energy sources and sensitive electronic systems is
achived dominantly, in addition to the character of excitated EM radiation and configuration
of wire and dielectric structures within the system. Major role in the elimination or reduction
of these interconnecting paths have shielded enclosures. This enclosures, made of conductive
material with adequate thickness and with different EM characteristics, affect on the level of
EM radiation that reaches the electric circuit from the environment, but also determine how
much energy is radiated by the circuit to the environment. Because enclosures have
individual apertures inevitably, which are commonly used to access the system (connectors,
power supply/shortening cables, CD/DVD-ROM, and others), and/or more apertures of the
same shape for cooling and removal of excess heat from the system (e.g. air-vent apertures),
EM radiation penetrates through the apertures in the space inside and outside the enclosure,
degrading the basic function of shielding.
The role of the shielded enclosure is that depending on the frequency, thickness and EM
material characteristics of which is made, reduces the amount of EM energy which penetrates
into the space inside and outside the enclosure and is usually expressed in term, which is
called the shielding effectiveness (SE). This measure is usually defined as the ratio in dB
between the level of the incident field in the corresponding point in the system in the absence
of enclosure and in the presence of enclosure and it can be defined as well as for the electric
(the so-called electric shielding effectiveness) and for the magnetic field (the so-called
magnetic effectiveness).
The aim of the doctoral dissertation is to analyze the influence of different effects such
as: increasing the thickness of the front metal wall with apertures, a number of apertures,
changing the shape and size of apertures, as well as their mutual distance on the shielding
effectiveness of enclosure, on the example of enclosure of certain size in a certain frequency
range. Accordingly, both individual apertures and air-vent apertures were considered with
different shapes (rectangular, circular and square), which are usually located on the walls of
shielded enclosures. In addition to the incident plane wave, an oblique wave in which the
angle of polarization, azimuth and elevation is changed, was discussed also, as well as
calculated values for SE in the different observation points within the enclosure. For most
practical EMC issues, excitation in the form of a plane wave is only an approximation of the
real excitation and is mainly used for the calculation of the shielding effectiveness. An
excitation is placed inside the enclosure, when it is necessary to estimate the level of EM
emissions, using numerical simulation, which is radiated from the shielded enclosure and the
degree of its impact on other electronic systems in the environment. The internal excitation in
enclosure, in the form of wire, was examined in the doctoral dissertation and how it affects on
the external environment for the different shape of the apertures on the front wall calculating
the electric field in the far field.
Considering that for the purposes of conducting measurement a receiving antenna is
being used, which is located inside the enclosure, it is necessary to take into account the
impact of receiving antenna on the SE. The receiving antenna of finite size can significantly
change the propagation of EM fields inside the enclosure and thus affects on the result of the
SE. The effect of the presence of the receiving dipole, as well as monopole antenna on the SE
was examined in this doctoral dissertation, in terms of how changes in antenna parameters,
such as the radius and the length of the antenna position within the enclosure and its
orientation, affect on the enclosure SE.
Research methods that were applied in this doctoral dissertation are: analytical method
for modeling using equivalent circuit and numerical modeling method using electrical lines
(Transmission Line Matrix - TLM). The method of equivalent circuit was used for the
analysis, in order to consider more apertures at many walls and oblique incident wave, and it
was enhanced by the author to consider the presence of the receiving antenna inside the
enclosure, which is used in the measurements process for calculating SE. Therefore, the main
subject of this doctoral dissertation is development of analytical model and the development
of equivalent model in order to calculate SE of enclosure with apertures. The basic advantage
of this improved analytical model is his ability to precisely modeling antennas inside the
enclosure. In fact, at some point within the enclosure receiving antenna was presented with
appropriate impedance in the observing point of equivalent model. From this reason, the
obtained results for the input impedance of a receiving antenna, for obtained equivalent
model, were presented in the doctoral dissertation. The TLM method with the compact wire
model was used also, for consideration of the receiving antenna presence in the measurement
process, while in the case when an enclosure have air-vents, so-called a compact TLM model
for the air vents on the metal walls, was applied, owing to calculate distribution of the EM
field around a large number of apertures. Analytical and numerical model were compared in
the dissertation in terms of their ability to calculate a different number of air-vent apertures,
with a different mutual spacing on the front wall.
A comparison of analytical and numerical results with the obtained measurement results
was presented in detail, in order to verify and investigate the possibility of applying the
proposed method for modeling the receiving antenna. The efficiency of the proposed
analytical method was discussed in the example of enclosure with apertures on the front wall
and the receiving antenna located at different points within the enlosure. The accuracy of the
method was verified by comparison with numerical values, for a different length and
diameter of the receiving antenna and with the corresponding measurement results. In this
context, to what extent there is a difference between results obtained by analytical and
numerical model, was shown in the doctoral dissertation, depending on the size of the
receiving antenna. The corresponding numerical results, which represent the shielding
effectiveness of enclosure, for a number of different wire diameters used as a receiving
antenna, were illustrated in the framework of the doctoral dissertation.
Among the expected results, which represent the original scientific contribution of the
dissertation, can be extricate as following:
computation of impact for various factors: the number and shape of apertures, their
mutual spacing, wall thickness, changes in the excitation parameters of plane EM wave, on
the SE using numerical differential method in time-domain for analysis of practical EMC
problems;
computation of excitation influence in the form of wire inside the enclosure on the
EM field in the far field using numerical method;
application of improved TLM method with compact wire model for generating a
numerical model in order to analyze the impact of the receiving dipole antenna on the SE;
application of analytical and numerical models for calculation the SE of enclosure
with apertures and receiving antenna inevitable in the measurement process especially at the
resonant frequencies;
calculation of the SE with and without receiving antenna with different diameters
using improved numerical and analytical models.
The conclusions are based on analyzes and calculations, in which it was highlight the
most important features and advantages of the proposed methods. It was indicated on the
differences of analytical and numerical models with and without receiving antenna of various
diameters, that must be taken into account during the experimental characterization, in order
to correctly calculate the level of SE and the position of resonant frequencies.
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