Design of Electric Field Sensors for Measurement of Electromagnetic Pulse

Transcription

1 Snsors & Transducrs, Vol. 162, Issu 1, January 214, pp Snsors & Transducrs 214 by IFSA Publishing, S. L. Dsign of Elctric Fild Snsors for Masurmnt of Elctromagntic Puls Hui ZHANG, Yinghui ZHOU, Lihua SHI, Rupo MA, Zhngyu HUANG National Ky Lab on Elctromagntic Environmntal Effcts and Elctro-Optical Enginring, PLA Univrsity of Scinc and Tchnology, Nanjing, 217, hina * Tl.: , fax: * @qq.com Rcivd: 28 Octobr 213 /Accptd: 9 January 214 /Publishd: 31 January 214 Abstract: In this papr, a D-dot lctric fild snsor and a fibr-optic transmission lctric fild snsor ar dvlopd for masurmnt of lctromagntic puls. Th D-dot snsor is a diffrntial modl snsor without sourc and has a simpl structur. Th fibr-optic transmission snsor is in th typ of small dipol antnna, which uss its outsid shilding layr as a pair of antnnas. Dsign of th snsor circuit and th tst systm ar introducd in this papr. A calibration systm for ths pulsd fild snsors is stablishd and th tst rsults vrifid th ability of th dvlopd snsors for masurmnt of th standard lctromagntic puls fild (th half pak width is 25 ns and th rising tim is 2.5 ns). opyright 214 IFSA Publishing, S. L. Kywords: Elctromagntic puls, Elctric fild snsor, Fibr-optic transmission, D-dot, Antnna. 1. Introduction Elctromagntic puls (EMP) is a kind of transint lctromagntic phnomnon with fast lading dg, wid frquncy band and larg amplitud. It can b producd by nuclar xplosion, lightning, lctro-static discharg and powr switching procss [1]. For th xampl of nuclar xplosion producd EMP, som intrnational standards hav spcifid its basic wavform for tst vrification. In th rvisd IE61-2-9(1998) [2] and MIL-STD-461E [3], th amplitud, ris-tim and half pak width of EMP is 5 kv/m, 2.5 ns and 25 ns, rspctivly. This kind of nvironmnt will svrly damag or disturb modrn lctronic and lctric facilitis if thy ar not prfctly protctd. It is of vital importanc for th traffic systms, th scurity systms, th powr systm and th communication systm to b hardnd and tstd against EMP. Th masurmnt of such kind of pulsd lctromagntic filds rcivs grat attntion [4, 5]. Unlik othr traditional small antnnas, EMP lctric fild snsor is mainly usd for tim-domain wavform masurmnt and its rspons should b a constant ovr th whol frquncy band from D to hundrds of mga-hrtz. Additionally, EMP snsors usually work in th nvironmnt with strong intrfrnc, th data transmission systm should hav good immunity to th nvironmntal noiss. Som EMP snsors hav bn dvlopd in rcnt yars and thy can b dividd into two catgoris, th diffrntial mod snsor and th slf-intgral mod snsor. For th diffrntial mod snsor, th output is proportional to th tim drivativ of th masurd lctric or magntic fild. To prvnt th intrfrnc in data transmission form th snsor to th rcording instrumnts, smi-ridgd coaxial cabl or th fibroptic transmission link ar adoptd [6, 7]. Howvr, th markt availabl snsors ar vry xpnsiv and Articl numbr P_

2 Snsors & Transducrs, Vol. 162, Issu 1, January 214, pp in practical masurmnt w usually nd to us multipl snsors for distributd masurmnt. Th aim of this papr is to dvlop low cost and high fficint EMP snsors. A D-dot lctric fild snsor and a fibr-optic transmission lctric fild snsor ar dvlopd, th first on is a passiv snsor for masurmnt of strong fild and works in diffrntial mod, th scond on is an activ snsor with vry compact fibr-optic transmission systm and works in slf intgral mod [8-1]. In th following parts, dsign of th snsor circuit and xprimntal vrification of th snsor s charactristics ar introducd. 2. Snsors Dsign 2.1. Th Equivalnt ircuit of Elctric Fild Snsor Th basic form of EMP lctric fild snsor is a pair of lctrically small antnna. Th rspons of such snsor dpnds on its capacitanc, rsistanc and th frquncy band of th masurd puls fild. An quivalnt circuit of th lctric fild snsor is shown in Fig. 1, whr A is th quivalnt ara of th snsor, is th quivalnt capacitanc, R is th load rsistanc, U is th quivalnt voltag of th load and D is th tim-drivativ of th masurd lctric flux dnsity. By Eq. (1), w can gt lctric fild intnsity E from D, whr is th fr spac prmittivity. i DA 传感器 Snsor Fig. 1. Equivalnt circuit of th lctric fild snsor. D E, (1) W can considr th snsor as a currnt sourc, thn th output currnt I s is givn by R Load 负载 U o U ( j) If R 1, thn o j E( j) A R, (4) jr1 U ( j) j E( j) A R, (5) o uo() t AR E() t, (6) t This is th tim domain rspons of a D-dot snsor. It should b notd that th availabl frquncy band of such snsor is blow f 1/(2 R). With R 5 and quals a fw pico-coulomb, f could b as high as a fw GHz. If R 1, thn E( j) A Uo ( j), (7) A Et () uo () t, (8) This is th tim domain rspons of an E snsor (th slf intgral snsor). It should b notd that th availabl frquncy band of such snsor is abov f 1/(2 R). With high input impdanc circuit, f could b as low as tns-hrtz Th Structur of Elctric Fild Snsor According to th principl of th D-dot and th E fild snsors, w dsignd two typs of EMP lctric fild snsors. A ground plan mountd small circular con is usd as th D-dot snsor to masur th strong EMP fild, its output is connctd to a 5 doubl-layr shildd coaxial cabl to liminat nvironmntal noiss. And a small dipol antnna is usd as th E fild snsor to masur frfild EMP or th inducd disturbanc within small nclosurs. Its dipol is in th form of hollow cylindrs to includ fibr-optic mitting circuit in th antnna. Th structur of th snsors is givn in Fig. 2. Prob I s DA, (2) Epikot cm Ground plat In tim domain, w hav duo() t uo() t Dt () A, (3) dt R 5 abl In frquncy domain, w hav Fig. 2 (a). Structur of th snsors: D-dot snsor. 132

3 Snsors & Transducrs, Vol. 162, Issu 1, January 214, pp Bcaus of th simpl circuit structur, th transmission tim of induction signal will b shortn. Optical signal transmits to th rcivr through 5 μm multimod optical. An optical rcivr thn convrts it to voltag signal ranging from -1 V to +1 V. Antnna R1 BJT Elctro-optical onvrtr Fig. 2 (b). Structur of th snsors: E fild snsor. Sinc th sphrical structur can rflct a smallr distortion to th masurd fild and not asy to appar point discharg. Th antnna structur of th E fild snsor is sphrical Data Procssing and Fibr-optic Transmission Th original output of th D-dot snsor nds to b intgratd to obtain th tru wavform of th masurd EMP. W choos a digital filtring approach to prform this task. Eq. (6) can b rwrittn in discrt tim domain as yi () yi ( 1) xi () Rl ( x() i u (), i y() i E()) i, (9) t Thn w can gt t yi () yi ( 1) xi ()(() x i u(), i y() i E()) i, (1) Rl By using function filtr (b, a, X) in MATLAB t softwar and spcifying a=[1,-1],b=[ ], w can Rl gt th tru wavform of th masurd lctric fild. Th inducd voltag of th E fild snsor is fd to an lctro-optical modulation circuit shown in Fig. 3, whr th antnna voltag can dirctly control th mittr and collctor currnt of th BUT(Bipolar Junction Transistor). This circuit is vry compact and can work as both amplifir and lctro-optical convrtr. Th analog bandwidth of th lctrooptical convrtr is 8 MHz and th output wavlngth is 131 nm lasr signal. By adjusting th variabl rsistor R1, th collctor currnt of BJT can b 4 ma so as to rach th currnt work ara. Antnna Shild can Fig. 3. Principl circuit of th lctro-optical modulation. 3. Exprimntal Vrification 3.1. Tst Stup A paralll plat boundd war lctromagntic puls simulator is usd to vrify th charactristics of th dvlopd snsor [11, 12]. Fig. 4 is th tst stup, whr th lft sid is th puls sourc which can gnrats a doubl-xponntial puls wavform. Th right sid is a trminal which uss a 176 matchd load. Elctromagntic puls fild is gnratd in th work spac which is btwn th two paralll plats. W must plac D-dot snsor on bottom plat to work in normal. But for E fild snsor, w can plac anywhr in th work spac. If Ut () is th pak of th input voltag, and Et () is th lctric fild strngth insid th simulator, w can gt Et () by Ut ()/ h, whr h is th hight of th working spac and quals to.8 m. Th highst lctric fild producd is 625 V/m whn th input is 5 V. A Tktronix 334 digital oscilloscop with bandwidth of 3 MHz and sampling rat of 2.5 Gs/s is usd to monitor for th snsor output. Fig. 4. Tsting stup of lctric fild snsor. 133

4 Snsors & Transducrs, Vol. 162, Issu 1, January 214, pp Rspons of th D-dot Snsor Whn a puls (1 %-9 % ris tim: 2.5 ns, 5 %- 5 % puls width: 25 ns) is applid, th masurd puls wavform by D-dot snsor is shown in Fig. 5, whr th wavform is th diffrntial rsult of th masurd lctric fild. By using th digital filtr mntiond in 2.3, w compar th intgration wavform with th standard fild wavform (normalizd wavform), th rsult is shown in Fig. 6 and Fig D-dot U/V Fig. 5. Puls rspons of D-dot snsor. D-dot Fig. 6. Whol wavform of D-dot snsor. From Fig. 6, w know that th wavform of D-dot snsor is basically th sam as th standard fild wavform. Fig. 7 illustrats that th rising tim is approximatly 2.5 ns. This snsor has th advantag of fast rspons and stabl output bcaus it uss passiv circuit. It can b usd as a standard snsor to monitor th incidnt EMP filds in various tsts Fig. 7. Lading dg of D-dot snsor Rspons of th E fild Snsor Th sam puls lctric fild is applid to th E fild snsor with fibr-optic transmission. Fig. 8 and Fig. 9 show th normalizd snsor wavform and th standard fild wavform. Th normalizd output of th E fild snsor is slightly diffrnt from th ral input fild. This diffrnc is probably du to th ovrshoot of th rspons at its lading dg, Fig. 9 also this ffct, whr th rising tim is 2 ns and a littl lss than th input. Although a fast rising tim is dsird for EMP snsors, th unwantd fast lading dg still nd to b adjustd in latr circuit dsign. Th E fild snsor has th advantag of adjustabl amplitud rspons and fibr-optic data link. It nd not to us a ground rfrnc plan and is suitabl to masur EMP filds insid a small nclosur Fig. 8. Whol wavform of E fild snsor. 4. onclusion E fild This papr prsntd dsign and tsting of two kinds of lctric fild snsors for EMP masurmnt. 134

5 Snsors & Transducrs, Vol. 162, Issu 1, January 214, pp Fig. 9. Lading dg of E fild snsor. E fild Th D-dot snsor can b usd as a standard snsor for monitoring of EMP nvironmnt and th E fild snsor can b usd as a snsitiv snsor to masur th inducd filds insid shildd nclosurs to study its EMP rspons. Exprimntal rsarch has vrifid th rspons charactristics of ths snsors. Furthr improvmnt is till undr considration to solv th ovrshoot problm of th E fild snsor. Acknowldgmnts This rsarch was supportd by Program for Nw ntury Excllnt Talnts in Univrsity (NET) and National Scinc Foundation of hina undr Grant No Rfrncs [1]. B. H. Zhou, B. hn, L. H. Shi, EMP and EMP Protction, National Dfns Industry Prss, Bijing, 23. [2]. IE , Dscription of HEMP Environmntradiatd Disturbanc, Intrnational Elctrotchnical ommission, [3]. MIL-STD-461E, Rquirmnts for th ontrol of Elctro-magntic Intrfrnc haractristics of Subsystms and Equipmnt, Dpartmnt of Dfns, USA, [4]. R. Hoad, N. J. artr, Rnds in EM suscptibility of IT quipmnt, IEEE Transactions on Elctromagntic ompatibility, Vol. 46, Issu 2, 24, pp [5].. E. Baum, From th lctromagntic puls to highpowr lctromagntics, Procdings of th IEEE, Vol. 8, Issu 6, 1992, pp [6]. Y. X. Li, L. H. Shi, B. H. Zhou, Masurmnt of puls lctromagntic fild using wid band fibr optic analogu transmission systm, High Voltag Enginring, Vol. 32, Issu 2, 26, pp [7].. Q. Zhu, Dvlopmnt of a mini-prob for tsting pulsd E-fild, High Voltag Enginring, Vol. 35, Issu 8, 29, pp [8]. I. A. Mtwally, oaxial D-dot prob: dsign and tsting, in Procdings of th Elctrical Insulation and Dilctric Phnomna onfrnc, Egypt, Octobr 1995, pp [9]. T. Wbr, L. Hasborg, Masurmnt tchniqus for conductd HPEM signals, IEEE Transactions on Elctromagntic ompatibility, Vol. 46, Issu 3, 24, pp [1]. W. A. Stygar, R. B. Spilman, D-dot and B-dot monitors for Z-Vacuum-sction powr-flow masurmnt, in Procdings of th 11 th IEEE Intrnational Pulsd Powr onfrnc, Baltimor, Maryland, USA, 1997, pp [11]. Q. W. Wang, L. H. Shi, Y. X. Li, Dvlopmnt of nanoscond liquid switch usd in high voltag fast puls sourc, High Voltag Apparatus, Vol. 2, Issu 4, 211, pp [12]. J. hn, L. H. Shi,. Gao, Tim domain calibration of pulsd lctric fild snsors with fibr optic transmission systm, Safty & EM, No. 6, 26, pp opyright, Intrnational Frquncy Snsor Association (IFSA) Publishing, S. L. All rights rsrvd. ( 135