DTIC ADA420638: Radio Frequency Dosimetry at the Air Force Research Laboratory

2.6 MB·English

by  Defense Technical Information Center

AFRL-HE-BR-TR-2003-01 62

United States Air Force
Research Laboratory
a eee es

RADIO FREQUENCY DOSIMETRY AT
THE AIR FORCE RESEARCH
LABORATORY

William Hurt
Leland Johnson
Charles Kuhnel

HUMAN EFFECTIVENESS DIRECTORATE
DIRECTED ENERGY BIOEFFEGTS DIVISION
RADIOFREQUENCY RADIATION BRANCH

8262 HAWKS ROAD
BROOKS CITY-BASE TX 78235-5147

January 2004

20040505 296
ROTICES:

‘This report és published In the interest of solantite ard technica! fifrcation
exchange and daes nat canstitute approval ar dseuprave! oft Wens or findings.

‘This report is published 25 recived and has not heen edited by the publlestion
staff of tha Ait Force Research Laboratory.

Using Gavernment drawings, specifications, ar other date Jncusled in this
stooument for any purpase other than Govermmentrelated procucemant does not it
any way obligate the US Government. The fact that the Government formulated or
ssupplled the drewings, pactfications, or other data, does not Hlewnsa the halder oF
any other person ar snrzoration, of convey any rights or permission to manufectire,
tse or sell aay patented invention thst may relate tm them,

‘The Office of Public Affairs has reviewed thle paper, and itis releasable to the
National Technical Information service, where it will be available: the genaral
publi including Foreign nationale.

“This report has been reviewed and is approved for publication.

SIGNED
WALLIAM D. HuaT
Santor Physiciet
SIGNED!

GARRETT D. POLHAMUS, DR-IV (GH-15), DAF
Clef, Direcked Energy Bioeftects Division
REPORT DOCUMENTATION PAGE oi iti

; Sy eee "2 REPORT TYPE SORE CORRES Fa Te
Bazar 2005 ual Oho}. pyr ww 3122S
Hite m0 SUSTTE “1 Sa ota NUMER H

Ratio Froqrenty Dosey a1 Air Force Resowsh Taborsary

e2200F

EAITORE, PROTECT OER
‘lan D. Hor, Leena R, Johan, Chores T. Kael Te

7. PERFORHING GRGANTPATION NAME(S] AND ADORTSSTEST PERFDRING ORGANI REPORT]
‘Hara Efletivenets Diver tte i

insted Raeray Binet Divison

Ratio Frequency Raditioa Barc

5242 Hanks Road

Brooks Ciy-Dase IX 7423506147

= EPONEORING WORITORING AGENT HERESY AN GORESSTES) "AS FSRTORTTORS REROTST
yr Eilerdvenens Directrse TLE

est ergy intl Division

Radia Peqasney Redstion ranc TE SFORSGEMONTOR REPORT
252 Holy tea RUMEERE)

rooks City Bane, TR A28S147 APRL-HE-ER.TR.2003-0168

| Spel forpebe ease, embeson aioe

“Roosledge of ens E-and{L-flds, ince aurea demsies, and SARs i of tic interest inthe asetement of biological eferts nxt
‘meal aplcaons of elecemagoetic Melis. Dealt ian lperant prt of any scenic eff to atest ets of BS om
Wolpical organisa. Experiaraa dasineay is case i dctoreoig the iro! flea and he woke ody or eafzed SAR vals
fexperumatewilaphurtors or rate. Cneullypefurme experiments re oma mwa Ieee! petlions hae Wa
{ov our, easideae proses has brez achieved ix esperincotl and nimzcca dasiact. Todas «broad range of tool for dose
ali for the wide agus range available, Bacau ofthe hrngenity of de tsve nd he nomena oft ideal Fels,
Closed form slice shions ae purse nel computer cid = aeeded 1 bin the mally coupled felis. Jn Deore]
Snimery, POTD icoreely be mot aceopabls choice i digi anafonieatnodegufenan and anita arabe salve. Therma |
‘ational or reser efi ie disp of toretcaldocineny is enfiowion of We depeatene of pueiced SAR in elation
(5 de Vara in peat cehue for erst Yasue pes when using diforeat sumovce arama] mods

Bioefet,Kadiofequecy Radon Speciic Absorption Rate

ae Se [ee
Sa TERE area — tec [RRNA |
| Fines

=a
TABLE. OF CONT

1.0 STRODUCTION.
2.0 EXPERIMENTAT. DOSIMETRY,
2.1 Exposure Fuclities.
2.2 Measuring SAR...

2.3 Tenperanure Measurement Techniques

2.4 Bleetre Ficld Mcasuremsut Techniques.
2.3 Power Difforence Method,

3.0 SAR MODELING. ......
311 Finite Difference Time-Domain Code.
32 Models.
3.3 Electrical Properties.

410 INTERNATIONAL EMF DOSIMETRY HANDBOOK,

5.0 SUMMARY,
6.0 REFERENCES,

FIGURES

Figure 1. AppSied Hleoromagneties 35194 GTlz System.
Figure 2. Peak Power Emission System (PPES).
Figure 3. Chamber 1 iu Bldg. 1161 with Miz dipote and comer reflector antenna

Figure 4. Chamber # in Bldg, 1183
Figure 5. Map of HEDR Compound,

Figure 6, Temperature measurement and acquisition system (TMAS).
Figure ?, Linux-baied Beowulf parallel pressing ayaiem.....
Buue 8. Miser o? A) Rat B) Got € £9) Morey, and E) Pha Mont.

Figured. Vis

le Man Model

igure 10, Dislectc value (©) and conductivity (ain mS!) ofthe ausle sre
shown as 2 function of frequency”. Three major dispersion «, B, wad
sre typical forall tissues and eels in suspension, although magnitudes
and dispersion frequencies vary. Additionally smaller relaxation effects
outibuttotahigh Buen tle of «end dapsone ini

by the dashed curve...
Figure 11, MP S10 Network Analyzer

TABLES

Table 1. RF Measurement Resources
Table2. Available Exposure Systems,
Table 3. Available Chambers...

Table 4, HEDR TMAS Specifications,
1.0 INTRODUCTION

‘nthe last three deoatts, ths use of devicas thot emit ratio Fequoney (RE? fields
thas inereased dramatically. The proliferation of RF devices has heer. accompanied by
inuresied voncer about ensuring the safely ofthe asc, Throughout the world many
‘organizations, both governenenr and non-government, hive established RF safety
standards or guidelines for exposure. Because f differen, sufaty philosophies, the former
[USSR and sone of the Laster European countries have more stringent safety standards
than most Western countries, The maxizaum permissible exponure in some Kasteca
European and Western countries differby aver two orders of mugnitade, Those
differenses have raised concerns about dhe lack of uniformity and have Ted to public
concer and disttust about clootomagnetic fields (FMF) exposures in controled und
\acormmlled environments’, One coucem about these diffirences is interpretation of dala
fom animal stades. Cun the effects observed in animals exposed to EMFs be used ta et
‘muman exposure standards? Which effects are important for human safery and which ate
‘nol? In applying safery standards the istue of how to measure EMF sbssmption in the
‘body is not casily solved. Typically, whal is specificd in the safety stantanl is field
suength or poser density thet should not be exceeded, These limits axe designed to
prevent excessively high spevific absorption mate: (SAR) in the bumian bods. Thus, better
‘methods are aeoded to properly messure EM absomption and, extrapolate or relate
effects observed in animals to those expected to be found in people. The reaulting data
could fead to mundi fication of existing safety stmdards or establishment of new safety
standards,

Accurate dosimetry rep-esents an essential coment ofthe research in determining
the biological effects of HME. Hlectromagnetie energy is absorbed non-unifimmly in
biological tissues". A large number of factors euch us a body" shapo and position, as
well as its oriemation inthe field influonee these non-uniform distributions” ‘. In short,
(heres no single answer to the question, “How much electromagnetic field snsrgy will
be dbnorhel?”. Tr ordor fo ensure the safe use of EMY emitting deviees, a number of
techniques for measuring FMF cxpostue have been develapod, however, they all have
limitations, Sines the energy absorbed is direely related us the intemal EME (hat is, che
‘EMF inside the object, not the EMT ineiden| upon the abject), dosimetry ie alka
‘nterpreted as the determination of internal EM lied, Fir, wo ncad dosimetry to
dctermine which internal fields in sanemals cause 2 given biological effect. ‘Then we need
ssimeiry 1 detcemine which incident fields would produce similar iatemal fields in
people, aml chetefore a similar biological effect. Dosimoty is needed whether the offers
‘10 produced by Tow-level intemal Sclds or by more inuenae felds that cause body
femperaiure to rise. Since ietemal and incident EMF ean be quite iliferent depending oo
‘he sire und shape of the objec, is electrical propertcg, is avientatian with respect to the
incident EMT, and the fequoncy of the incident fields the development af thenetical
dosimetry modeling technique snd powerful computer hardware has resulted in
osimevy modeling as a principe cal in determining EMF exposure.

‘The results of the ouput fron: any mode, including Finite-Difference Tims-
Domain {FDTD}, are questionable if the model has not been validated with enmpirical
data, Validation isthe key issue in caming the credihiity of wlvancod theoretical
rmodsling and offers a unique bridge berwccu theoretical and experimental dosimeny.
Sinse applied methods in expctimental dosimetry require the implentaion of thermal ur
E-field probes into deep bly organs, it is noi feasible to perform such studies n hunan
subject theretors validation attempts of the cormputer models rast he acoamplished
‘sing phantoms (Simplistic gcomtry and tissue equivalent materials) an! lahorstory
animes, Got corrslation helwoer the predicted und crpirical phantom and anima: data
‘would provide incressod confidence in the result predicted hy the man model A
simple phantom enmuposed of a sphere isa uselul and coovenieut meikod 0 validate
FIST predictions of the SAR vatucs”". Ta addition, the Mie solution °, whieh provides
fn exact value for spheres, can be usod to meagre error in both empirical data wnd FDTD
cau, Many sophisticated, bigh-teolution digital auatomical medals that are being
developed call for validation that enmploys not only simplistic geometry models, bur alsa
the actual type of organisms uscd to develop these models, The brur of the rut offers un
‘deal organ for comparison, duc tothe precision of stereataie peohe placement, #8 vell
as the ability to casily conf prob placements in tissue sections following
‘experimentation

‘The facilities athe Ratoffequency Radian Branch (HEDR), Air Forse
‘Rescarch Tshoratory for accomplishing (heac empirical measurements are described
below,

2.0 EXPERIMENTAL DOSIMETRY

‘Measurements of the extemal fields (ar th evalustion of exposure conditions are
‘wsually considered a pay of experimental dasimeny. Tw place the mewsuremenss of
‘external ficlds vs. intemal fields in proper perspective, ote must realize tha the
instruments and meihods Zor measurements of internal fields sre not suitable for use om
Jhunuans except in byperthermie trewtment for cancer therapy. Therofore, ly provent
Potentially hazardous expestres to humans, the extemal fields are measured. ta on the
intensities of external fie'ds that potentially constitute a havard to man age obtained
‘through experimental evaluation of the inicosities ofthe internal fields and she evulting
SAR in animals and delennination of external Zckts which produce similar invemal Folds
(SAR) in ua,

2.1 Expasure Facilities

Duriug many radio Roquency (RF) expenres, itis important ta know the incident:
ower density, There are many rasans of detcratining this power deusity. The three most
sommion inet are a RF survey meter in conjunction with a corapalible probe, acalibated
Power sensor and an anteana with a well defined capture area, an cmpersiurs
sifferences (AT) measurements using an infrared camera aud carhon-foaded Teflon (See
‘Tables 1.3 and Fig. 1-5). For the irequency range of 30 kifz to 40 GHe, the favorite
‘method is using the RF survey equipment.

‘Tho are a fow manufucturers oF RF survey equipment. Narda Microwave
‘manufactures the primary insinament ase to measure electromagnetic fields, "The two
‘motors used are the 8617 analog meter with appropriate probe ot thc 8718 digital meter,
‘sing ether mete is relatively easy. Tho probe and meter are calbraled together and
zeroed ina zero eld environtnent, The probe ix then plage in the RE fcld to be
smcasurod, ‘The probes are isotnpic, bul Unsbesl practice ie to Bae the probe heed reward
thc RP some, Thove are three efenients in the probe head, so in onder to best align the
clamants, the probe is rotated through 360 ané measurements recarded every 45°. Those
‘rumibers are then averayed snd the stanard deviation iscaleulated. Next, udd the
standard deviation to the average and epply the correction factor forthe ptobe, Using a
spreadsheet makes the calcularions very quick and easy, For lower and higher frequency
flclds, ator techniques were developed,

Millimeter waves are uot easly measured usiog the RF survey equipment. A.
rmothod using a power sensor and a capmure device was developed. A combination of an
EP sAgilent WS486A waveguide pawer sensor end Millitech strwiur. gain pyramidal
hho connected to un Agilent 437B powsr master is usod to measure the Gelds from 75 —
110 GHz. The USAF Precision Meusurements Equipment Laboratory (PMEL) calibrates
‘both the power sensor and power meter, The effective aren (A.) of the homn is deventined
rom the actual gain of tae hom. For very small spot sives, un opon-cnded wavegwide
‘welion can be used in lieu of shor, The A, however, isnot essy wo devermine, ‘The ouly
file method af Uelermining the corrcetion factor iste do a side-by-side eamparison
‘witha kaown measurement device. The open-ended waveguide is very ftequeney and
angle sensisive. Attenustars can be placed in ine after the horn to extend tho useful
power measurement range, For very hich power donsties, other methods must be uscd.

‘Numerous materials were investigated as tools to over come the resection of
povier density or spot size. ‘These materials were Jooked at with au infared camera to
easure comperature tise Verse power density. RT cloth or carben-impregnated cloth was
first tied. This material responds to RF exposure with a very uallort temperature Tse,
‘out with no significant thermal mas, it wus very susecptible to environmental conditions,
Carbou loaded Teflon was tied next This material hus very unigorm ebaracterstos and
thus epousdh mass ta be minimally cifceted by ervironmental conditions, Ixtenaive
(emperaturerige measurements using an inffared camera were performed in an
environmentally controlled chamber. Power dersiy was measured using the waveguide
sensor described carlier. A series of poims were generated anil wn eqcation developed to
ovrelate the rnperalure rine wih power density, The carbou-laaded Teflon is also very
tusefal in mapping elds that have mueerenee paiens, Tho mmkimum and minienun
points arc casiy determined. From the interference patterns, the average delivered prwer
canbe caleulaied. Othor uscs for carbon-loaded Teflon are stil being investigated. More
sneurate and defined calibration procodutcs are being developed. With time, this
‘technique should prove very’ use

“these are only a fow types of measurements thal can be mado, Dipole antennas
spd FI-Feld Toapes are some other cmon methods that have heen used", Other
techniques may altow us i tke mame mocurste measurements,

‘Ail power measurement equipment cd blackbody source calibration fs perfarme
by or centificd by PMEL located at Btooks City-Base under the 311 Mission Support
Group Lagistios @ st MSGLG),
‘able 1. RF Measurement Resources

RESOUEE TAKE, MeoEL EaiGr ROC
Be PowecWoui | ele Packer] ——11P237 | Datei By Ao os
lL Probe Tied 2 ori 65!
Poser Naer Weal ba DecmibsaRy "Deemed By
. Pes aed Probe Viel
RE Fawr Sch’Tlewiea Pasta | HEA] —T8Giicto 10 Power ncaa
ea 3
iPower Sema: | Thser Packard | Essen, “| GS GR wal ower Linc
~ Gus _ aie
Whee Pabe Nei 7 FHM sire 23S
Ge 50 Gia)
= LasaR Ce
. 250GHe)
Ti Power eke Se ees DORA 16 Ge aes Mow
Soy li 2248
(G00 LHe 1
_ _ GH)
Tallies 1 SGR TORU | TEAC Tames
r : $2 GH
wesepille oan FAIOTE Sata Fen
Atantor
TR Came Fir “TamaCan | aPC TTT re
500
Rm i Tiana AEST | IEC we OHS Car Fe
- vg ~
TG aig Set Chea ER
Te Conc “Air Redinte-1 | teivrnined By] Detained By
‘Thermgenhic | piace Bodecal | duck Body Cal
Dpencinded | Fabel NA Tsl0GHe —|' ‘Deteraiaed By
Swaveguide home a Compara
[Bist Soar |" “Miron ia ie fC rsd
[aatecy Somes [" “sion 45x8__[ “Too w as. 0e¢ | tome
Table 2. Available Exposure Systems

Wee] on” | RGR] Bg _Rovm ] — Atmuneitce —] — Comment
2 quay | gover | renee ‘conmber
_ sy |v
a SN TTT
saa | 2k |-"ew] ner rr SwahnoatResere | — Sali Sas
‘tate 7
te RT ote oz ‘satay
= 2004
Tee er
Tea 7 Tobe Fare
na MCL. Porable
ner 1186 ‘ppied Taal Frey
Fhcrornetice Chiat
Wer “xanlsd Dual Fg
! Enscroraguelin ‘Cabinet
Tie cel .
Het War -
TIS BRCIS Remora in
fea a Hf
11s cas a=
1185)? | enor Flere —Weheted for
L A DEMO
Tet abe Panto PER
TBE Tobe Past of FES
Tes Cae Part of FES
exion “aga aE FaraPPPES_
94000 sat." | “ae [Lies [a | Nev
‘ryure2, Peak Poser iitioa Sata (PFS),