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This material is intended for education purposes only
Cap for
EMF
protection (ideal material)EMF
). Do they work? As I am not electromagnetic field sensitive and I am not good enough situated to buy and test these clothes, I cannot answer this question for sure with100
% certainty.EMC
) involved in testing of shielding materials, measurements of electromagnetic devices,3
D modelling of complex electromagnetic situations, I’ve knowledge to measure and model. In this case, to evaluate cap it is necessary to have couple of them for measurements. None ofEMF
clothes manufacturers and sellers wanted to contribute to this article by lending some caps for measurements and tests. And it is understandable– not all the facts written in item characterization is true.EMF
) protection. I’m curious by myself– can cap made of special conductive textiles protect humans. I’m using3
D electromagnetic modelling to answer this question. Some validation is carried out in to verify that modelling will give correct results. Modelling will be carried out using ideal shielding material for cap (perfect electric conductor) not a material that is used in real life (conductive cloth that is far from ideal shielding material–SAR
) will be used for evaluation. Maximum Specific Absorption Rate (SAR
) will be modelled separately for brain, back brain and body muscles.SAR
(specific absorption rate) is an indication of the amount of radiation that is absorbed into a head whilst using exposed by electromagnetic fields, the higher theSAR
rating the more radiation that is absorbed into the head. ASAR
value is a measure of the maximum energy absorbed by a unit of mass of exposed tissue of a person in electromagnetic field, over a given time or more simply the power absorbed per unit mass.SAR
values are usually expressed in units of watts per kilogram (W/kg) in either1
g or10
g of tissue.EM
field) is a physical field produced by electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction. It is one of the four fundamental forces of nature (the others are gravitation, weak interaction and strong interaction).1
. Above human model (situation when electromagnetic field (EMF
) source is located above person– roof antennas, antennas in plane fuselage, antennas on upper floors, etc.);2
. Below human model; (situation when electromagnetic field (EMF
) source is located below person– antennas in plane floor, antennas on lower floors, etc.);3
. In front of human model;4
. Behind human model;5
. On left of human model;6
. On right of human model;433
MHz,900
MHz,2
.4
GHz.433
MHz is aUHF
band in which licence free communication devices are allowed to operate. Many wireless devices are operating in this range.900
MHz isUHF
radio spectrum internationally allocated to amateur radio on a secondary basis. This is one of most popular frequencies for cellular phones.2
.4
GHz Wi-Fi networks, Bluetooth, ZigBee, car alarms, microwave ovens.1
. human body with and without cap is represented. Modelling environment with electromagnetic field is shown in Fig.2
. In this case, plane wave (red plane) is located in front of human body and it is horizontally polarised. Human body tissues– brain, back brain, body muscles are modelled with real tissue electromagnetic parameters as defined in “COMPILATION
OF
THE
DIELECTRIC
PROPERTIES
OF
BODY
TISSUES
AT
RF
AND
MICROWAVE
FREQUENCIES
” by Camelia Gabriel in the U.S. Air Force ReportAFOSR-TR-
96
.There are lot of clothes in market to protect sensitive humans from electromagnetic fields (). Do they work? As I am not electromagnetic field sensitive and I am not good enough situated to buy and test these clothes, I cannot answer this question for sure with% certainty.As theoretical scientist and electromagnetic compatibility engineer () involved in testing of shielding materials, measurements of electromagnetic devices,modelling of complex electromagnetic situations, I’ve knowledge to measure and model. In this case, to evaluate cap it is necessary to have couple of them for measurements. None ofclothes manufacturers and sellers wanted to contribute to this article by lending some caps for measurements and tests. And it is understandable– not all the facts written in item characterization is true.I’m not here to expose or criticize players in electromagnetic field () protection. I’m curious by myself– can cap made of special conductive textiles protect humans. I’m usingelectromagnetic modelling to answer this question. Some validation is carried out in to verify that modelling will give correct results. Modelling will be carried out using ideal shielding material for cap (perfect electric conductor) not a material that is used in real life (conductive cloth that is far from ideal shielding material– link ) as it takes considerable less computing power. If cap made out of ideal shielding material can help to protect from electromagnetic fields, then further research can be carried out with real life materials– textiles.Cap covers the head and it obviously is used to protect the most important organ in human body– brain. Specific Absorption Rate () will be used for evaluation. Maximum Specific Absorption Rate () will be modelled separately for brain, back brain and body muscles.(specific absorption rate) is an indication of the amount of radiation that is absorbed into a head whilst using exposed by electromagnetic fields, the higher therating the more radiation that is absorbed into the head. Avalue is a measure of the maximum energy absorbed by a unit of mass of exposed tissue of a person in electromagnetic field, over a given time or more simply the power absorbed per unit mass.values are usually expressed in units of watts per kilogram (W/kg) in eitherg org of tissue.Also electromagnetic field strength will be modelled in brain to see what are the electromagnetic field values in brain with and without cap.An(alsofield) is a physical field produced by electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction. It is one of the four fundamental forces of nature (the others are gravitation, weak interaction and strong interaction).Source of the electromagnetic field will be located:. Above human model (situation when electromagnetic field () source is located above person– roof antennas, antennas in plane fuselage, antennas on upper floors, etc.);. Below human model; (situation when electromagnetic field () source is located below person– antennas in plane floor, antennas on lower floors, etc.);. In front of human model;. Behind human model;. On left of human model;. On right of human model;Evaluation will be carried out at three frequenciesMHz,MHz,GHz.MHz is aband in which licence free communication devices are allowed to operate. Many wireless devices are operating in this range.MHz isradio spectrum internationally allocated to amateur radio on a secondary basis. This is one of most popular frequencies for cellular phones.GHz Wi-Fi networks, Bluetooth, ZigBee, car alarms, microwave ovens.In Fig.. human body with and without cap is represented. Modelling environment with electromagnetic field is shown in Fig.. In this case, plane wave (red plane) is located in front of human body and it is horizontally polarised. Human body tissues– brain, back brain, body muscles are modelled with real tissue electromagnetic parameters as defined in “” by Camelia Gabriel in the U.S. Air Force Report
Fig. 1. Human body with and without cap
Fig. 2. Human body in modelling domain with plane wave (red) in front
900
MHz electromagnetic field modelling with human body with cap is given in Fig.3
. Electromagnetic field source is in front of human. Zoomed head with cap is shown in Fig.4
. As can be seen electric field strength on cap surface is very high. Brain is zoomed in Fig.5
. for the same situation.
Fig. 3. 900MHz electromagnetic field and human body
Fig. 4. 900MHz electromagnetic field and human body, head zoomed
Fig. 5. 900MHz electromagnetic field and human body, brain zoomed
In Fig.
6
. electromagnetic field strength in brain is analysed and most exposed surfaces can be located.
Fig. 6. 900MHz electromagnetic field in human brain
SAR
SAR
results are summarised in Table1
. “Ideal material” cap the best brain protection offers if source of electromagnetic wave is located on the left or on the right of your head exceeding80
% ofSAR
reduction for all three analysed frequencies–430
MHz,900
MHz,2
.4
GHz. If electromagnetic field source is located above the headSAR
reduction (brain protection by cap) varies by the frequency– at433
MHz it is only26
%, at900
MHz it is76
% and at2
.4
GHz it reaches86
%. In case if electromagnetic field source is located in front of you, absorption rate will decrease by only5
% at433
MHz, decrease by15
% at900
MHz, decrease by62
% at2
.4
GHz. In case if electromagnetic field source is located in behind you, absorption rate will decrease by only46
% at433
MHz, decrease by68
% at900
MHz, decrease by80
% at2
.4
GHz.SAR
values are increased– brain receives more electromagnetic field– in case if source of electromagnetic fields is located below the human body (if you are on roof or tower and antennas are located below you, or if you are in your flat and your neighbour below you have ). At900
MHzSAR
increases by14
%, and at430
MHz it increases by23
%.SAR
results in Table1
are marked in red ifSAR
is increasing due to cap usage.Electromagnetic field results
SAR
results as field is the energy source that heats up the brain. Electromagnetic field results are summarised in Table2
.“Ideal material” cap
the best field attenuation offers if source of electromagnetic wave is located on the left or on the right of your head. At433
MHz reduction is only7
dB, at900
MHz reduction is only6
dB and at2
.4
GHz electromagnetic field reduction is1
dB. Further analysis is not carried out as electromagnetic field reduction is less than few dB. Few dB attenuation for electromagnetic field offers very low protection, if compared to shielded electromagnetic rooms that offer more than120
dB attenuation.SAR
results in Table2
are marked in red ifSAR
is increasing due to cap usage.Results in short and in simple language
80
%, if electromagnetic field source is located on left or on the right of you. If field source is located in front, back or above head, heating reduction will be at least26
%. If source of electromagnetic field is located below you, brain will be heated up by up to23
%. In Table1
and Table2
results are marked red if cap increases electromagnetic effects on brain.
Table 1 Energy absorbtion reduction/gain in human brain if “Ideal material“cap is used
Table 2. Electromagnetic field reduction/gain in human brain if “Ideal material“cap is used
Visualisation
Visualisation of human brain is presented, to take a look how electromagnetic field is propagating inside the head. Electromagnetic field source is located above the human body.
Model with and without cap. Cap is made out of perfet material.
433MHz propagating in human brain. Cap offers no protection at this frequency, if wave is located above the head.
Electromagnetic field is amlified at some areas due to resonances in cap. Maximum field value increases by 1dB.
900MHz propagating in human brain. Cap offers poor protection at this frequency, if wave is located above the head.
Electromagnetic field is attenuated by 6dB
2.4GHz propagating in human brain. Cap offers poor protection at this frequency, if wave is located above the head.
Electromagnetic field is attenuated by only 4dB
433MHz propagating in human brain. Cap offers no protection at this frequency, if wave is located above the head. Electromagnetic field is amlified at some areas due to resonances in cap. Maximum field value increases by 1dB.
900MHz propagating in human brain. Cap offers poor protection at this frequency, if wave is located above the head. Electromagnetic field is attenuated by 6dB
2.4GHz propagating in human brain. Cap offers poor protection at this frequency, if wave is located above the head. Electromagnetic field is attenuated by only 4dB
This material is intended for education purposes only
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