Analysis of pulsed electromagnetic fields radiated by powerful sources

292 Ad ances in Elec ical and Elec onic Enginee ing ANALYSIS OF PULSED ELECTROMAGNETIC FIELDS RADIATED BY POWERFUL SOURCES K. Maceika Vilnius Gediminas Technical Uni e si y, An anas Gus ai is a ia ion ins i u e, Rodunios kelias 30, LT-02187 Vilnius, Li huania Tel.: +3705 2744816, E-mail: kazimie as.maceika@ai. g u.l Summa y Calcula ion me hod p oposed o powe ul sou ces adia ion e alua ion. Taken a en ion ha in calcula ions i is necessa y o use a e age adia ed powe . Fo example in case o ada s i depends on wo ac s: ada adia es sho adio impulses wi h long pauses be ween hem and o a ed an enna wi h na ow pa e n o di ec i i y in ho izon al plane adia es in o chosen poin a sho pa o an enna’s o a ion pe iod. Calcula ion is made o Thomson ada acco ding p oposed equa ions. I is shown ha an enna in 5 m heigh adia es powe lux densi y in o le el o man head mo e imes smalle han pe mi ed le el acco ding Li huanian no ma i e - 20,0 W/cm2. 1. INTRODUCTION Public heal h se ice equi es calcula ions o elec omagne ic ield in ensi y a ound powe ul adia ion sou ces be o e hei moun ing. Such e alua ion akes place in spi e o he manu ac u e s heo e ical analyse and expe imen al measu emen s o e e y conc e e equipmen adia ion. The me hod o e alua ion is e y simple and has been used many imes. I is necessa y o use an a e age alue o adia ed powe in calcula ions o an enna elec omagne ic ield exposu e. The pulse du a ion is hund ed imes sho e han pulse epe i ion, hus an a e age alue o powe densi y is hund eds imes lowe han a peak alue o he adia ion. Addi ionally he o a ing ada an enna adia es he EM ield a he measu emen poin pe iodically wi hin a e y sho ime, which s ongly depends on he wid h o he main lobe o pa e n and scan sec o o he an enna. Li huania has acc edi ed no ma i e o pe mi ed le els o elec omagne ic adia ion, so esul s o calcula ions can be compa ed wi h hese le els and p ac ical conclusions can be made o ada es ablishing. Example o e alua ion o Thomson ada an enna adia ion in ensi y is shown in his pape . The calcula ed adia ion is many imes smalle han he pe mi ed le el and is no dange ous o popula ion. The eal si ua ion will become clea a e moun ing o he ada a place and expe imen al es s o EM ield in ensi y. 2. CALCULATION OF RADIATED POWER DENSITY The densi y o adia ed powe o he powe ul sou ce is e i ied a equencies g ea e han 300 MHz. This densi y calcula ion me hod is known [1, 2, 5] and o en has been used. Figu e 1 explains he si ua ion. Fig. 1. Finding o an enna adia ed powe lux densi y a poin B Wa es sp ead om he ada an enna and each poin B a le el o a man’s head in wo ways: di ec and e lec ed om Ea h su ace. The ene gy may each e y high alues o powe densi y in peak, a ela i ely low le els o powe densi y a e aged in ime. This is because he pulse du a ion τ o he ada adia ion is many imes sho e han pulse epe i ion T p , hus an a e age alue o powe densi y is many imes lowe han he peak alue also. Due o he o a ion o he ada an enna, he poin B is exposed o pulse modula ed mic owa e adia ion pe iodically wi hin a e y sho ime ag eeably o he wid h o a main lobe o he an enna in ho izon al plane. I is easy o guess ha an a e age alue o powe P a , a e aged o e pulse epe i ion and o e a pe iod o an enna o a ion, is low: , 360 0 0 ατ p peaka T PP = ( 1 ) in such a si ua ion he p oposed pa ame e o cha ac e ize he ada adia ion will be a e age powe lux densi y Sa a poin B: ).1()( 4 202 2 pG R P S a a += ηθ π ( 2 ) In (2) G – an enna gain in di ec ion o maximum adia ion, Analysis o pulsed elec omagne ic ields adia ed by powe ul sou ces 293 ( Θ º) – an enna’s pa e n o di ec i i y in e ical ele a ion plane (dependence o elec ic ield in ensi y om angle Θ º ), η - e iciency ac o o an enna and wa eguide, less han one, p – coe icien o elec omagne ic wa es e lec ion om g ound, R- dis ance AB (Fig.1) be ween phase cen e o an enna A and obse a ional poin B. E iciency o pa abolic an ennas is η <0,7. This pa ame e is in ol ed usually in expe imen ally measu ed pa e n o di ec i i y. Choosing o di e en alues o angle Θ º pe mi s o calcula e S a and o d aw powe densi y dependence on dis ance. Dis ance L can be ound by: L = ( h 1 – h 2 )/ g Θ º. ( 3 ) As inal esul , dependence S a om dis ance be ween an enna and poin B can be d awn. I can be used o inding o sani a y p o ec ion zone. In his zone elec omagne ic ield powe lux densi y S a is a g ea e han pe mi ed. Radius o calcula ed sani a y zone depends on: P peak - powe o ada ’s adia ed impulse, G - an enna gain, α º 3dB, Θ º 3dB – wid h o an enna’s pa e n o di ec i i y on le el 3 dB in ho izon al and e ical plane espec i ely, Θ º max – angle o an enna’s maximum adia ion in e ical plane, h 1 – an enna’s phase cen e high abo e g ound su ace. Di ec ion o maximum adia ion Θ º max and high o an ennas ins alla ion h 1 can be chosen only and hey es ima e sani a y p o ec ion zone adius R san Inc easing o h 1 bid up a cos o an enna’s ins alla ion and he ise Θ º max wo sen de ec ion o down lying ai c a s. 3. PERMITTED LEVEL OF ELECTROMAGNETIC RADIATION Hygiene no ma i e [3] desc ibes pe mi ed le el o elec omagne ic adia ion o s a iona y elec onic sys ems in li ing and wo k places in Li huania epublic. In equencies band o e 300 MHz o con inuous oscilla ion he powe lux densi y canno be g ea e han 10.0  W/cm 2 . In Eu opean s anda d [4] he pe mi ed le el o powe lux densi y is same. In Li huanian no ma i e [3] he sa e a e age le el o powe lux densi y in case o pulse adia ion named 20.0  W/cm 2 because adia ion hea s he human body du ing sho pulse ime and he body is u ning cold du ing a long pause be ween pulses. Russia has he simila no ma i e [2] o e alua ion adia ion o me eo ological ada s. I adia ed wa eleng h 10 cm ± 15%, he pe mi ed le el o a e age powe lux densi y is acc edi ed 20.0  W/cm 2 on 2 m abo e g ound su ace. Sepa a e desc ip ion o pe mi ed le els o elec omagne ic adia ion is p oposed o people wo king places. In equencies band 300 MHz-300 GHz he pe mi ed lux densi y depends on exposi ion ime [3]. I exposi ion du a ion is 5 min, he no ma i e is he g ea es – 1000  W/cm 2 . The minimal no ma i e 25.0  W/cm 2 is o wo ke s exposi ion du ing 8 hou s and mo e. 4. RADAR RADIATION LEVEL EVALUATION The e a e age powe lux densi y calcula ions ha e been made o Thomson ada which is used in Li huania. P ima y ada da a o calcula ion is aken om echnical documen a ion: - equency o oscilla ions in adia ed adio pulses - = 2900 MHz ( λ = 10,34 cm ), - peak powe o ansmi ed impulses P peak = 600 kW, - du a ion o pulse τ = 1 µ s. - pe iod o pulses epe i ion Tp = 1000 µ s. Cha ac e is ics o p ima y ada an enna AC 316 a e he ollowing: - ho izon al size o pa abolic an enna D = 4,12 m, - e ical size H = 3,3 m, - he g ea es gain o an enna G = 34,9 dB in maximum di ec ion 3°, - wid h o an enna di ec i i y pa e n in ho izon al plane on 3 dB le el is α º 3dB = 1.5°. Side lobes a e 25 dB less han he main lobe, - an enna pa e n o di ec i i y in e ical plane has he shape cosec 2  up o Θ º= 50°. Gain alues in dependence on Θ º a e aken in Tab.1. - o a ion equency o an enna – 0.4 Hz. Calcula ion p ocess. An enna’s adia ion in es iga ion was made o ins alla ion heigh : h 1 =5m and 22m. Powe lux densi y alues we e ound a heigh h 2 = 2 m o e he g ound su ace. P peak = 600 kW, τ = 1 µ s, Tp = 1000 µ s and α º 3dB = 1.5° we e aken in o (1) and ound a e age powe P a = 2.5 W. Only pa o pa e n di ec i i y in e ical plane wi h nega i e alues o angle Θ º om –0.5º ill -10º e e y 0.5º we e used because only adia ion down was in e es ing. So 20 alues o - Θ º and adequa e alues o gain G( Θ º) in dB we e ead om he pa e n (Tab.1). In equa ion (2) G( Θ º) will co espond G· 2 ( Θ º) · η se in imes ins ead o G in dB. The conc e e alues o Θ º we e ecalcula ed in o dis ance L acco ding (3) (see Fig.1). In equa ion (2) mul iplie (1-p 2 ) was inse ed co esponding o e lec ion o elec omagne ic wa es om g ound (Fig.1). Acco ding o ecommenda ions om li e a u e [2] (1-p 2 ) = 1.5 on equency 2900 MHz. I is necessa y o no e ha his alue in eali y is smalle han 1.5 because e lec ed wa e wi h di ec wa e adds oge he no essen ially in phase. 294 Ad ances in Elec ical and Elec onic Enginee ing Tab. 1. Da a o ada an enna’s pa e n o di ec i i y in e ical plane and a e age adia ed powe lux densi y dependence on dis ance -  ° G 2 (  °)  , dB G 2 (  °)  L,m S a ,  W/cm 2 0.5 27.6 575 113 0.0095 1 25.3 339 119 0.0088 1.5 22.9 195 126 0.0059 2 20.0 100 133 0.0041 2.5 17.9 61.7 142 0.0052 3 15.8 38 151 0.0056 3.5 13.9 24.5 162 0.0058 4 12.1 16.2 175 0.0051 4.5 10.5 11.2 190 0.0051 5 10.0 10.0 208 0.0054 5.5 8.9 7.76 229 0.0058 6 7.9 6.17 255 0.0052 6.5 7.2 5.25 286 0.006 7 7.1 5.13 327 0.0069 7.5 6.4 4.37 382 0.0079 8 5.5 3.55 457 0.0089 8.5 3.9 2.45 573 0.0092 9 5.0 3.16 763 0.0101 9.5 6.3 4.27 1145 0.0078 10 6.2 4.17 2291 0.0033 The esul s o calcula ion acco ding (2) o a e age powe lux densi y depending on dis ance in Tab. 1 ha e maximum he 0.0101  W/cm 2 a dis ance 763 m. This alue is many imes smalle han he pe mi ed le el 20.0  W/cm 2 . So i is possible o educe heigh o an enna and o win in i s p ice. Dependence o a e age powe lux densi y on dis ance in case o heigh 5 m is shown on Fig. 2. Cu e has a maximum o wo ac o s. Powe lux densi y dec eases o ene gy dissipa ion in eceding om ada an enna acco ding law 1/ R 2 . On ano he hand adia ion inc eases wi h dis ance because in an enna’s pa e n o di ec i i y in e ical plane a le el o adia ion is g ea e . Fu he he lux densi y a e y as dec eases a e maximum. Maximal go powe lux densi y 0.45  W/cm 2 a dis ance 115 m is smalle hen he pe mi ed le el acco ding no ma i e - 20,0  W/cm 2 . In his case sani a y p o ec ion zone absen and elec omagne ic adia ion o ada ’s an enna is no dange ous o popula ion. 0 200 400 600 800 1000 1200 1400 0.0 0.1 0.2 0.3 0.4 0.5 A e age powe lux densi y S a e , µ W/cm 2 Dis ance L, m Fig. 2. G aphical p esen a ion o he a e age powe lux densi y om dis ance a an enna heigh 5 m 5. CONCLUSIONS 1. P oposed e alua ion me hod o ada s an enna’s mic owa e adia ion uses in calcula ions a e age alue o adia ed powe densi y, which is compa ed wi h pe mi ed le el acco ding no ma i e. 2. Li huania and Eu ope Union ha e he same no ma i e in equencies band 300 MHz - 300 GHz o pe mi ed le els o elec omagne ic ield powe lux densi y - 10,0  W/cm 2 i adia ion is con inuous and in case o impulse adia ion - 20,0  W/cm 2 . 3. I phase cen e o ada an enna is on heigh 5 m, he adia ed powe lux densi y is 40 imes smalle han pe mi ed le el and is no dange ous o popula ion. I an enna is equipped highe , he maximum o adia ion in ensi y is u he bu wi h many imes smalle ampli ude. REFERENCES [1] Me hodical guidelines o diagnosis and no malisa ion o elec omagne ic si ua ion in me eo ological ada s places. USSR Minis y o Heal h Ca e, 1985. [2] Maceika K. No ma i e o pe missible elec omagne ic ields le el. P oc. o XI In . Con e ence on Elec omagne ic Dis u bances, Bialys ok BTU, pp.641-642. [3] Hygiene’s no ma i e HN 80:2000: Elec omagne ic ield in wo k places and esiden ial a ea. Pe mi ed alues and measu emen equi emen s in 10 kHz-300 GHz equencies. Minis y o Heal h Ca e o Republic Li huania, Vilnius, 2000. [4] S anda d EN 50364: 2001: Limi a ion o human exposu e o elec omagne ic ields om de ices ope a ing in he equency ange 0 Hz o 10 GHz, used in Elec onic A icle Su eillance (EAS), Radio F equency Iden i ica ion (RFID) and simila applica ions. [5] Skolnik M.I.: In oduc ion o Rada Sys ems. McG aw-Hill, 2001.