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DOCUMENTED PROOF: UNIVERSITY CASE STUDY FOR RFID SCANNING HUMAN FOREHEADS

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THE MARK
User ID: 714162
10/13/2009 10:00 PM
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DOCUMENTED PROOF: UNIVERSITY CASE STUDY FOR RFID SCANNING HUMAN FOREHEADS

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[link to 74.125.93.132]

Impacts of RF Radiation on the Human Body in a Passive RFID Environment

Darmindra D. Arumugam*(1), and Daniel W. Engels (1)(1) Department of Electrical Engineering, University of Texas at Arlington, Texas, USAE-mail: darumugam@uta.eduIntroduction

The characterization of RF propagation is a theoretical method for evaluating the workings of electromagnetic radiation in a given environment. Recently, there have been numerous explorations of the fundamental characterizations of passive radio frequency identification (RFID) systems in electromagnetic structures [1-4]. These studies have concentrated on various topics not limited to the holy grails of passive RFID systems, i.e.metallic and moist environments.

Because of the nature of passive systems, attenuation in these environments is relatively high and often causes an RFID tag to hover towards theno-read zones. This is typically propelled by the lack of power being harvested by the tag or attenuation of the tag reply signals. An area of research that has garnered interest is the use of passive RFID systems in and around human tissues. Human tissues are composed primarily of molecules, which tend to absorb RF energy. The rate of absorption is a dosimetric measure known as the specific absorption rate (SAR). The purpose of this paper is to study and quantify the SAR of the human body, more specifically the human head and shoulders for the passive UHF RFID reader environment.

UHF RFID reader systems operating under FCC regulations may create RF energy absorption that could represent a significant impact to the human body, when present in high densities and/or close proximities. In this paper, we present the theory and analytical evaluations to study the SAR in the human head at 1W, 10W, and 100W power output of a 7.4dB gain reader antenna. These evaluations are presented for distances of 10cm, and 100cm from the human head. The visualizations presented for the SAR are quantized meaning fully to depict the impacts of a passive RFID environment on the human body, more specifically the human head. We also show that an additive absorption environment with just 2 RFID readers at aproximity of approximately 10cm from the human head presents a SAR above 1.6 / ,the maximum value allowed by FCC in the US.

Specific Absorption Rates A living organism subjected to a static RF field or to a non-radiating near field willtypically extract energy from the radiating source. However, the quantitative descriptions of these mechanisms by which this extraction takes place, is very different at higher frequencies [5]. At these higher frequencies, both the electrical and magnetic fields of the incoming electromagnetic waves, after reflection at the boundary conditions, are further decreased due to energy dissipation [5]. Both and fields decrease exponentially in nature with distance from the boundaries as depicted in Equation 1, where the skin depth() is defined as the distance at which the field decreases to 1 =0.368 of its value just
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inside the boundaries [5], where is the ratio of conduction current to displacement current in the given media.=and=(1)It is widely known that the skin effect becomes much more apparent and significant for humans and larger vertebrates at higher frequencies [5, 6]. Specific absorption rates, or SAR, is the rate at which the body or tissues absorbs RF energy when exposed to anelectromagnetic field. A dosimetric measure that has been widely adopted is the time derivative of the incremental energy ( ) absorbed by, or dissipated in an incremental mass ( ) contained in a volume element ( ) of a given density () [5], which is expanded in Equation 2.====(2)

Experimental Test Setup

The setup used to evaluate the SAR in the human head is presented in Figure 1, where a rectangular patch antenna with a gain of 7.4dB is positioned directly in front of the human face, and the SAR is evaluated for antenna distances of 10cm and a 100cm from the human face. At each instance, results are observed for 1W, 10W, and 100W ofradiated power. The simulation environment used here is Feko 5.3, which is a software utilizing advanced computational electromagnetic (CEM) methods.

Figure 1: Experimental Test Setup for the Human Body SAR in the Human Head Figure 2 presents the SAR in the human head cross-section of the eyes for the radiated source power of 1W, 10W and 100W at a distance of 100cm. Here we notice that the maximum absorption is below the accepted limits as required by FCC in the US. Furtherevaluations for radiated power at 100 W at a distance of 100cm also reveal limits belowthe FCC regulations.
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Figure 2: SAR for the human head at 100cm distance of 1W, 10W, and 100W radiated power

To study the impact of an environment with a high density of RFID readers or readers at close proximity, we study the direct effects at a distance of 10cm instead. These results are depicted in Figure 3 for the case of 1W, 10W and 100W.

Figure 3: SAR for the human head at 10cm distance of 1W, 10W, and 100W radiated power From Figure 3 we notice that even at distances of 10cm from the human head, theinduced SAR is below FCC regulated limit of exposure for the human body. However,we also realize that this limit is breached somewhere within the boundaries of 1W and 10W at this distance from the human face. To study in more detail the level at which this breach occurs, and to better quantify this problem for an environment pervaded withRFID systems, we examine the SAR details for all 10cm and 100cm scenarios.
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Figure 4: SAR (W/kg) versus radiated power (W) at distances of 10cm and 100cmFigure 4 is a plot of the of the SAR results from the experiments at 10cm and 100cm forall radiated power levels. It can be easily conceived from this figure that the FCC limit is breached between the 1W and 10W radiated power levels at reader antenna to humanface distances of 10cm. Using the equation for the trend-line as depicted in Figure 4, we can solve for 1.6 / to arrive at 1.89711 . Since, the FCC limit for RFID reader systems are at 1W of radiated power, it is clear that 2 reader antennas placed 10cm away from the human face would provide much higher SAR (Equation 3) than that allowed by FCC in the US. = 0.0203 . в = 2.02763 / (3)ConclusionIn this paper, we present an experimental study on the SAR of the human head in anenvironment with a typical RFID reader system. The results predict that 2 RFID reader antennas at distances of 10cm from the human head operating additively, will contributeto a SAR in the human head of up to a maximum of 2.02763 / , which is above the limit for safe exposure of RF radiation as allowed by FCC is the US (1.6 / ). References[1] Arumugam, D.D. (2007) ‘Characterization of RF Propagation in Metal Pipes for Passive RFID Systems’, Master Thesis, University of Texas at Arlington.[2] Arumugam, D.D. and Engels, D.W. (2007) ‘Characterisation of RF Propagation inMetal Pipes for Passive RFID Systems’, Int. J. Radio Frequency IdentificationTechnology and Applications, Vol. 1, No. 3, pp. 303-343.[3] Arumugam, D.D. and Engels, D.W. (Accepted 2007) ‘Characterisation of RFPropagation in Rectangular Metal Pipes for Passive RFID Systems’, Int. J. RadioFrequency Identification Technology and Applications.[4] Arumugam, D.D., Gautham, A., Narayanaswamy, G. and Engels, D.W. (Accepted2007) ‘Impacts of RF Radiation on the Human Body in a Passive WirelessHealthcare Environment’, IEEE APiPH Conference 2008.[5] Polk, C.; Postow, E., Handbook of Biological Effects of Electromagnetic Fields,CRC Press, LLC, ISBN 0-8493-0641-8, 1996.[6] Poljak, D., Human Exposure to Electromagnetic Fields, WIT Press, LLC, ISBN 1-85312-997-6, 2004.

ShadowDancer
User ID: 287857
10/16/2009 7:45 PM

Re: DOCUMENTED PROOF: UNIVERSITY CASE STUDY FOR RFID SCANNING HUMAN FOREHEADS

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Right hand or forehead-that way biometric data can also be retrieved and the thought police can access easier.

*************************************
"But I don't want to go among mad people," Alice remarked.
"Oh, you can't help that," said the Cat: "we're all mad here. I'm mad. You're mad."
"How do you know I'm mad?" said Alice.
"You must be," said the Cat, "or you wouldn't have come here."
~Alice's Adventures in Wonderland

There is little gain in attempting to change external conditions, you must first change the core of inner beliefs, naturally outer conditions will change accordingly.
BECOME it to achieve it.

Wisdom strengthened the wise more than ten mighty men which are in the city. Ecclesiastes 7:19

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Does the shadow appear to be growing darker? The light that is casting shadows is becoming much brighter; in utter darkness it is luminous.

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