Magnetic Femtotesla Inductor Coil Sensor for ELF Noise Signals- ( 0.1Hz to3.0 Hz)

Transcription

1 IOSR Journl of Electricl nd Electronics Engineering (IOSR-JEEE) e-issn: ,-ISSN: , Volume 7, Issue 3 (Se. - Oct. 013), PP Mgnetic Femtotesl Inductor Coil Sensor for ELF Noise Signls- ( 0.1Hz to3.0 Hz) Rjendr Arnthi 1, Ved Vys Dwivedi 1 (Reserch Scholr, Fculty of Technology nd Engineering, C U shh University) (Pro Vice Chncellor, C. U. Shh University, Wdhwncity Gujrt, INDIA ) Abstrct: The reserch roject for detecting mgnetic fields in the femtotesl rnge t extremely low frequency noise is develoed, including ntenn, trnsformer nd mlifier. Ech comonent is described with relevnt trdeoffs which llow lrge vriety of receivers to be esily designed for ny mgnetic field sensing in the very low-frequency noise rnge. This er introduces new ELF noise signl Inductor sensor design nd find stbility for re mlifier & mgnetic inductive. A system using n imednce ntenn is develoed further s n exmle tht hs been used extensively in mesurement liction in the frequency below 30Hz using MATLAB softwre tools. Keywords: Extremely Low Frequency, mlifiers, loo ntenns, mgnetic field mesurement, mgnetometers I. INTRODUCTION Mgnetic field receivers re used to sense low-frequency [(LF); <30 khz] electromgnetic wves becuse of their suerior noise erformnce t low frequencies nd their reltive tolernce of nerby metllic structures comred to electric field sensors. Suerconducting Quntum Interference Devices (SQUIDs) re commonly vilble mlifiers in this frequency rnge. These generlly use high-inut imednce mlifier nd then use feedbck to reduce the inut imednce s seen by the sensor [1], [], [3]. Although good noise erformnce is obtined, they must be oerted below the criticl temerture of the suerconductors, ner 0.K. In generl, it is difficult to design SQUID-bsed mlifier to hve inut imednce s low s is required while remining stble [4].In system designed for room temerture lso uses feedbck toology; however, the noise erformnce suffers [5]. Another system develoed by Stuchlyet [6] senses mgnetic fields between 600 Hz nd 10 MHz with trnsformer between the sensor nd the mlifier. But we re using this toology nd nlysis we re design mgnetic sensor for senses 0.1 to 3 Hz noise signl. However, they use not only high-inut imednce mlifier with feedbck but lso shunt resistor increses the noise significntly nd is used in lictions where the noise is not rimry concern. In their cse, noise mesurements re not even reorted. In groundbsed mgnetos heric reserch, we re interested in receiving signls with lrge loo ntenns nd design re mlifier circuit from 0.1 Hz to 30 khz. Nturl signls in this frequency rnge include sferics nd tweks generted by lightning, whistlers creted when sferics enetrte the ionoshere nd trvel long mgnetic field line to the other hemishere, nd chorus nd hiss due to lsm instbilities in the mgnetoshere. Mn-mde signls include those from the very LF (VLF) nvigtion nd communictions trnsmitters. Using these signls, we study the rocesses tht occur during geomgnetic storms, urore, nd wht is now often clled sce wether. These signls hve more or less constnt ower sectrl density from 4 Hz to 30 Hz; thus, we need the receiver to hve flt frequency resonse over this rnge rther thn one, for exmle, roortionl to frequency. If we use receiver with low inut imednce, the increse in induced electromotive force in the ntenn with frequency is countercted by the increse in inductive rectnce of the ntenn, mking the current into the receiver flt with frequency. The roblem is to design low-imednce mlifier with good noise figure when connected to n inductive source. We hve found tht common bse inut stge gives good results, much better thn, for exmle, terminting the loo with resistor of the sme imednce even if followed by n idel noise-free mlifier[7]. In this er, we describe sensitive VLF receiver design method originlly develoed by E. Pschl. The vrious design equtions nd trde of fs of the ntenn, trnsformer, nd low-noise mlifier re discussed. Section II begins by describing the design of the loo ntenn [8]. Next, we discuss the trde of fs involved in the trnsformer design in Section III. Section IV follows, describing the mlifier design. In Section V, n exmle system using 1-Ω 1-mH inductive ntenn design is resented, nd the corresonding erformnce is shown in Section VI. II. ANTENNA DESIGN Mgnetic field ntenns re lrge ir-coil loos of wire with Ntures nd re A. Air loos re used insted of ferrite core loos for better linerity nd reduced temerture deendence. When designing n ir loo ntenn, there re three rmeters vilble: the re of the ntenn, the dimeter of the wire, nd the 65 Pge

2 Mgnetic Femtotesl Inductor Coil Sensor for ELF Noise Signls-( 0.1Hz to3.0 Hz) number of turns. These rmeters determine the ntenn s wire resistnce R nd inductnce L Fig. 1, section I in Fig 1 for ntenn imednce model, which, in turn, she the system resonse nd sensitivity. Fig.1. System design of fully differentil mgnetic field receiver, including ntenn model, trnsformer model, nd noise model of mlifier. TABLE I [1, 3] CONSTANTS FORVARIOUSMAGNETICLOOPANTENNASHAPES Sr.No She of Loo Constnt 1 Constnt 1 Circulr Regulr Octgon Regulr Hexgon Squre Equilterl tringle Right Isosceles Tringle Winding ccitnce nd skin effects re negligible t these frequencies. It is therefore imortnt to derive the reltionshi mong the three rmeters nd the resulting R, L, nd sensitivity. Loo she is usully chosen bsed on its ese of construction given desired re Seen in grh mnsion bellow. GRAPHE I. VARIOUS MAGNETIC LOOP ANTENNA SHAPES A vriety of common loo shes vilble re listed in Tble I. The constntc1is relted to the geometry of the ntenn nd llows for generl exression of the length of ech turn tht is vlid for ny she Antenn Turn C A Length (1) Using this exression, the ntenn resistnce for ny she is 4NC1 A R d () 8 1.7*10 Where ρ is the resistivity of the wire (for coer, Ωm), nd is the dimeter of the wire. Adting from [6, ], the inductnce for ny loo ntenn is 7 C1 A L.0010 NC1 A ln C Nd (3) Where Cis lso geometry-relted constnt nd cn be found in Tble I for vriety of loo shes. The two vribles R nd L form the totl imednce of the ntenn (Z) tht is the source imednce seen by the first stge of the receiver Z R jl 66 Pge

3 Mgnetic Femtotesl Inductor Coil Sensor for ELF Noise Signls-( 0.1Hz to3.0 Hz) V jfn A Bcos( ) (4) wherefis the frequency,bis the mgnetic flux density, nd θ is the ngle of the mgnetic field from the xis of the loo. If thexis of the loo is horizontl, the resonse ttern of the ntennis diole in zimuth. In the following, we shll be concerned with the resonse of the loo to n roritely oriented fieldnd will omit the term cos(θ). Since VLF receiving loo is very smll comred to wvelength (λ= 1000Km t 300 Hz nd 10 Km t 30 KHz), the rdition resistnce of the loo is negligible comred to the wire resistncer. The minimum detectble signl is limited by the therml noise of R. We define the sensitivity of the ntenns s the field equivlent of the noise density, i.e., the mlitude of n incident wve which would give n outut voltge equl to the therml noise of Rin 1-Hz bndwidth. Using (5), we cn lso design VLF nd ELF Amlifier receiving loo very smll comred to wve length s very smll noise signl 0.1 to 3 Hz, we cn exress the sensitivity s Q is sensitivity 4kTR Q fn A (5) The ntenn sensitivitys decreses with frequency (i.e,the ntenn becomes more sensitive) t 1/f. It is convenient to define frequency-indeendent quntity for comring theerformnces of different ntenns. We Qˆ define the normlized sensitivity s fq.usingrin (), we find n exression for the normlized sensitivity tht deends only on the hysiclrmeters of the ntenn Qˆ 3 d 4kTC N A (6) This exression for sensitivity cn be used to find the number of turns, ntenn re, nd wire dimeter required for trget sensitivity t secific frequency. The effect of the resulting ntenn resistnce nd imednce on the rest of the system is discussed in lter sections. Further insight cn be gined by reclculting this sensitivity s function of the mss of the ntenn. The mss of the wire used in the ntenn cn be clculted s 1 K c1d 4 N Where K is Gine where δ is the density of the wire. Solving this for nd substituting into (7) roduce normlized sensitivity c kt Qˆ 1 4 MA (8) This interesting result shows tht the only wy to imrove sensitivity with given ntenn mteril is to increse the totl mss or re of the ntenn. These receivers re usully lcedin remote res to reduce interference from ower lines (t 60 Hz nd hrmonics); thus, this fundmentl trdeoff mens tht the sensitivity must be blnced ginst rcticl limittions regrding weight nd size. The most severe limittions for these receivers re units lced t the South Pole for reserch on the mgnetoshere. Since the Erth s mgnetic field lines tht ss through these regions in the uer tmoshere cross the Erth s surfce t the oles, it is the only lce tht ground-bsed receiver cn detect the ELF noise signls 0.1 to 3.0 Hz tht follow these field lines [7,9]. III. TRANSFORMER The trnsformer electriclly isoltes the ntenn from the rest of the receiver nd stes u the imednce by fctor of the squre of the turn rtio m to imrove the imednce mtch to the remlifier. Moreover, the ELF cutoff reduces the noise from the system t frequencies below those of interest [7]. Fig. 1 shows the trnsformer model nd the equivlent noise sources from the mlifier. The combined trnsfer function of the ntenn nd trnsformer cn be found with stndrd circuit nlysis V j ml R in in (9) V k1 * k k3 d N (7) 67 Pge

4 k k k 1 3 R R Mgnetic Femtotesl Inductor Coil Sensor for ELF Noise Signls-( 0.1Hz to3.0 Hz) ( Rs jl )(1 jcsrin) Rin jl m ( R R jl )(1 jc R ), j( L L ),, s in (10), (11), (1) Using (5) nd simlifying, the roximte eqution shown, fcilittes the understnding of how the trnsfer function is ffected by both the design of the trnsformer nd the inut imednce of the mlifier: N A RinB f f jf c L m f jf f jf f jf Vin m L / t i c As er (13) the fctor ρ is the rtio of the totl inductnce on the rimry side (including the ntenn nd L ) to the trnsformer rimry inductnce lone (L ). For n idel trnsformer, L ρ =, nd ρ =1. Below the frequency f t, the shunting effect of L ρ becomes imortnt, nd the gin dros ridly. The receiver is not useful in this region, mking f t s the L F limit of the receiver resonse. The inut turnover frequency fi is the frequency where the totl resistnce in the inut circuit is equl to the inductive imednce to frequency, the current in the inut circuit bove f i is limited by the ntenn rectnce, which lso increses with frequency, giving flt overll frequency resonse. Note tht f i is much higher thn f t in good design [9]. As er (14, 15, 16) f i, the imednce of the inut circuit is dominted by the ntenn inductive rectnce πf L. Even though the induced voltge cross the ntenn terminls (5) is roortionl this is desirble for most ELF nd VLF lictions [10]. f f f t i c ( R R 1 L R s 1 C R R ) (( R R ) / m ) ( L in / L ( L s s ( R R in in L) ) / m L / m ) (14), (15), (16) The frequency fc, the trnsformer secondry shunt ccitnce C s begins to short the inut signl, nd the gin dros. The intervl of flt frequency resonse is thus from f i to f c. The trnsformer lekge inductnce L does not significntly ffect erformnce becuse it ers in series with the much lrger m L, s seen on the secondry side of the trnsformer. The min sources of noise in the system re the therml noise of the ntenn (E ), voltge noise of the mlifier (E n ), nd the current noise of the mlifier (I n ). The noise sources from the mlifier E n nd I n re ssumed to be sttisticlly uncorrelted. This is usully true t udio frequencies; if they re correlted, the error is, t most, 30 % [11, 1]. The system sensitivity S sys is directly ffected by the trnsformer turn rtio nd the rtio of current nd voltge noise of the mlifier. E En / m In m Z Ssys (17) N A Since the effect of the mlifier noise voltge is reduced by the trnsformer turn rtio while tht of the noise current is incresed, the choice of turn rtio hs direct effect on the sensitivity. Tyiclly, we choose m so tht R=R in /m. Tht is, we choose the turn rtio so tht the inut imednce of the mlifier s seen t the trnsformer rimry is bout the sme s the ntenn resistnce for good blnce between low-nd highfrequency noise concerns. With common bse inut stge, this lso gives E E n/m, thus mking the ELF noise figure bout 3 db. With this choice, the sensitivity imrove with higher frequency for decde or two bove fi until the current noise I n flowing through m Z becomes imortnt nd the sensitivity levels off. Note tht common bse inut stge of inut resistnce R in gives much better noise erformnce thn n ctul resistor of size R in, even if followed by noiseless mlifier becuse is tht the current noise of the common bse circuit is much lower thn the Johnson therml current noise of the rel resistor [1]. (13) 68 Pge

5 Mgnetic Femtotesl Inductor Coil Sensor for ELF Noise Signls-( 0.1Hz to3.0 Hz) However, rel trnsformer dds some noise nd so chnges the resonse. When the rel trnsformer model is used, the totl inut-referred voltge noise is find the sensitivity, convert the inut-referred noise to the equivlent field using the ntenn rmeters Ein Ssys (18) N A Comring this to (6), we see tht the sensitivity of the system is similr in form to tht of the ntenn by itself. At given frequency, the receiver roches idel erformnce s Eni decreses towrd E. E in E E E s (1 ( f f cn ) f tn f f in E n ) f m (fl ) I n m R (1 ) R R R f tn ( L L ) 1 f cn C s m L (19),(0),(1) The trnsformer hs severl imortnt effects on the overll noise. The most imortnt effect is the series resistnces in the trnsformer. The therml noise of these resistnces dds directly to the noise nd so must be ket s smll s ossible. At low frequencies, f/f C n 0, nd the voltge noise is multilied by the fctor. Therefore, for good LF noise erformnce, must be ket smll (i.e. L mde lrge). Moreover, t frequencies below f tn, the noise erformnce deteriortes ridly; thus, f tn must be ket smll. At high frequencies, more of the mlifier voltge noise ers cross the trnsformer ccitnce C s nd increses the noise. Therefore, for good high-frequency noise erformnce, f cn should be ket lrge. It is imortnt to note tht the trnsformer design deends on the imednces nd noise chrcteristics of both the ntenn nd mlifier. This requires tht the system be designed s unit (ntenn, trnsformer, nd mlifier) to roduce the desired frequency resonse nd sensitivity. IV. AMPLIFIER The mlifier hs mny unique requirements tht require custom design. The first requirement comes from the definition of f i from (11). Assuming n idel trnsformer for simlicity (resistnces 0, L, ndl 0), f i becomes RRin / m fi () L Which shows tht R in is reduced, the useful bndwidth of the receiver increses. The other min requirement of this receiver involves the noise. Not only do the noise comonents need to be s smll s ossible but lso the rtio of the voltge noise nd current noise is imortnt [1]. In ddition, becuse of the very low frequencies, dc feedbck loos re used to mintin the needed voltge levels insted of decouling ccitors. Mny revious circuit solutions for mtching to low-imednce sensor involve using high-imednce mlifier with negtive feedbck. However, in this cse, the sensor imednce is so low (56Ωt low frequencies, s seen from the secondry of the trnsformer) tht this otion is not fesible. The feedbck resistnce would crete its own current noise tht Add s to the inut. As this resistnce is incresed to reduce the noise, the gin of the mlifier must be incresed to kee the inut imednce the sme. This cretes n mlifier of such high gin tht stbility becomes serious concern [11, 1]. A simler solution is to use common bse or common-gte inut stge becuse of their low inut imednces, s shown with device Q1 in Fig.. Biolr junction trnsistors (BJTs) were chosen becuse their inut imednce is more consistent thn tht of MOSFETs in which the common-gte imednce 1/gm cn hve lrge sred between individul discrete devices. It is lso imortnt tht the secific trnsistor rts chosen hve very low noise. In ddition, the inut stges remin differentil to reduce the second hrmonic distortion. The inut imednce of the differentil first stge is twice the inut imednce of common bsed BJT kt R r (3) in e qi E Therefore, the collector current of the inut stge BJTs cn be used to djust R in s desired. The dc current lso directly ffects the voltge nd current noise of the trnsistors. From [7,. 116], the voltge noise of BJT is 69 Pge

6 Mgnetic Femtotesl Inductor Coil Sensor for ELF Noise Signls-( 0.1Hz to3.0 Hz) E ( kt) n 4kTrb qic (4) Where b is the bse resistnce The current noise includes both shot noise nd1/f noise Y qi KI I C B n qi B (5) f However, the chosen inut trnsistor rt should hve low enough 1/f noise tht shot noise domintes. Both the current nd voltge noise deend on the collector current; thus, there is trdeoff between the desired inut imednce R in nd the noise erformnce. The current noise for the second-stge BJTs (Q ) is lso given by (18). Becuse the current gin of the first stge is one, second-stge current noise is imortnt nd ers s if it ws in rllel with the first-stge current noise t the mlifier inut. To minimize this dditionl noise, the second stge is oerted t lower collector current, roughly one-third of the current of the first stge. The second-stge Q is stndrd differentil ir. The voltge follower ir Q 3 revents the loding of the highimednce oututs t the collectors of Q. The til current for Q is controlled by Q 4. Resistors R 10 nd R 11 give negtive feedbck round the second stge. The voltge gin from the trnsformer secondry to the inut of the oertionl mlifier (o-m) is R10/re, where re is the inut imednce of the common bse trnsistors Q1. Ccitors C1 nd C rovide comenstion to ensure stbility nd limit the bndwidth to 150 khz. Proximity to ower lines nd digitl equiment cn coule noise into the ntenn nd rohibit sensitive mesurements. In our exerience, even the ticking of digitl wtches cn be clerly seen in the recorded dt. For this reson, the nlog-to-digitl converter, storge, nd ower sulies re locted 00 ft from the ntenn nd remlifier with 78-Ωcble connection. The o-m (U1) drives this line with the hel of the ste-down trnsformer (T). These combine to roduce 1-V mximum signl tht cn trvel to the system recorder. The trnsformer lso rovides dc isoltion nd differentil signl to reserve signl integrity long the long cble [8],[1],[13]. V. EXAMPLEDESIGN The ntenn design must blnce the desired sensitivity with the rcticlity of construction. The resistnce nd inductnce of the ntenn from () nd (3) ffect the frequency resonse nd sensitivity (11) nd (13). For this design, we hve chosen 1.03-Ω 1.08-mH ntenn imednce. The rtio gives fi bout 0.1 to3 Hz, s desired [13], nd the imednce level lends itself to simle loo construction. In fct, using (3) nd (6), we find tht there is fmily of For exmle, smll ntenn cn be used with receiver system to determine the best low-noise site to construct ermnent lrge ntenn. However, not only re lrge ntenns hevy nd difficult to construct in remote res but wind cn lso cuse vibrtions tht cn be mistken for dt. Lrge ntenns should use stiff frme to kee wind vibrtions smll. For lrge oen tringulr ntenns suorted by centrl tower, the ntenn wire should be ket slck so tht wind vibrtions re below the frequencies of interest. The trnsformer for this ntenn hs turn rtio (m) of 16 nd be interchnged nd used with the sme receiver, deending on the sensitivity required. Similr tbles cn be constructed for other imednces rimry inductnce(l ) of 10 mh. The high-frequency resonse is dominted by winding ccitnce Cs of 950 F. This ccitnce is high becuse bifilr winding is used in both the trnsformer rimry nd secondry windings to ssure blnced couling. Using single-strnd winding, C s cn be much smller. The following rmeters vlues were clculted s described in Section III: Moreover, for the noise erformnce of the trnsformer, the LF noise corner f tn is 14.5 Hz, nd the highfrequency corner f cn is 10. khz. The remlifier circuit design shown in Fig. lso includes the comonent vlues nd rt numbers used in the exmle design. The first stge uses 00μA for R in vlue of 59Ω. The MAT 0 trnsistors re used for their low 1/f noise so tht only shot nd therml noises dominte the receiver noise. The corresonding mesurements for this exmle design re in the next section coer wire loos of vrious sizes nd sensitivities, ll with the sme imednce. These ntenns, listed in Tble II, cn the smller ntenns re more ortble, while the lrge ntenns re more sensitive; thus, the ntenn choice is deendent uon the needed sensitivity nd vilble hysicl sce. f t 7. 6Hz, f c 6kHz, f i 0.1to3. 0Hz nd to Pge

7 Sr. No Mgnetic Femtotesl Inductor Coil Sensor for ELF Noise Signls-( 0.1Hz to3.0 Hz) TABLE II [1,] MAGNETICFIELDANTENNADESIGNSWITH 1.03-Ω 1.08-mH IMPEDANCE Bse (m) Wire AWG N R (Ω) L (mh) A (m ) sˆ ( V Hz/ m) Antenn *10-3 Squre * * *10-5 Squre *10-4 Right isosceles *10-5 Tringle * * *10-7 Fig.. Differentil remlifier circuit design showing inut nd outut trnsformers, by D. Shfer nd bsed on E. Pschl s originl design. The common bse first stge rovides low-imednce inut. The second stge rovides gin, nd the o-m circuit drives long cble (usully bout 50 ft), llow the digitl electronics to be locted fr from the sensitive ntenn for ELF sensor. VI. RECEIVER MEASUREMENTS When tking mesurements of these receivers in the lb, it is imrcticl to connect n ntenn to the trnsformer nd roduce known field tht is constnt cross the sn of the ntenn. In ddition, the very sensitive ntenns will ick u so much environmentl noise rticulrly from ower lines tht the mlifier will be constntly sturted. A better roch is to use dummy ntenn which hs the sme imednce s the ntenn but no collecting re. In Fig. 3, we show the dummy ntenn design used for testing. The ntenn imednce is rovided by R nd L, while R th nd C t re chosen by the following derivtion Pge

8 Mgnetic Femtotesl Inductor Coil Sensor for ELF Noise Signls-( 0.1Hz to3.0 Hz) Fig.3.Test setu using dummy loo insted of ntenn. This method llows for ccurte lb testing nd clibrtion [1, ] The current flowing in the mlifier (secondry of trns-former) from the source Vs Vs jfl (1 Rin / jfl ) Iin Rth(1 fc /( jf )) R jfl Z (6) 1 fc R thct (7) Z is the imednce on the rimry side of the trnsformer looking into the mlifier. The current roduced by the ntenn voltge V is V 1 fc /( jf ) Iin R jfl Z 1 (L ) /( jfr ) (8) If these two inut currents re equted, the reltion between Vs. nd V is found N A RthB 1 fc /( jf ) Vs L 1 (L ) /( jfr ) (9) If Cth is chosen s follows: L Ct R * Rth (30) nd (5) is used to relce V, the reltionshi between Vs nd n equivlent mgnetic field cn be found N A RthB VS L (31) Note tht ll of the terms with Z hve droed out; leving simle clibrtion method tht does not require ny knowledge of the imednce of the trnsformer nd mlifier. Only the imednce nd re of the ntenn re relevnt. The mesurements shown in this section were done using dummy loo, s described erlier, nd ssuming n exmle squre 1.03-Ω, 1.08-mH ntenn tht is 4.9 m long with six turns Tble II. The gin mesurements in Fig. 4 re dislyed s outut voltge versus inut mgnetic field. The system hs flt bnd between 1 nd 30 khz, but hs been routinely used for signls down to 10 Hz for geohysics reserch. The sensitivity, s shown in Fig. 5, is below 1 ft/hz ½ over most of the usble frequency rnge. Also lotted is the sensitivity obtined when the inut is terminted with 59-Ωresistor VII. RESULTS AND DISCUSSION In this section, we describe sensitive VLF/ELF receiver design method originlly develoed by E. Pschl. The vrious design equtions nd trde of f s of the ntenn, trnsformer, nd low-noise mlifier re discussed. We re designing in MATLAB softwre low frequency sensor using low filter ss low frequency below 0.3Hz nd high frequency stoe shown in fig 4.() mgnitude vs frequency. Also find this sensor mgnitude resonse in MATLAB shown in fig.4(b) nd we find stbility in ole nd zero in below 0.3Hz frequency in fig. 4(c) in MATLAB. Using this sensor we find hse resonse nd ste resonse in 0.3Hz frequency. Now design this VLF/ELF inductor sensor, mlifier nd trnsformer. We re using multisim softwre nd MATLAB, find multisim results in fig.4(e) to fig.4(k). In fig.4(e) low frequency sensor ACnlysis resonse find in 0.3Hz frequency nd increse frequency nd AC- nlysis resonse decresing. in fig.4.(f) Power gin of Low frequency sensor in multi sim result nd In imednce 50Ohm nd ZS=50+j0 ohm nd ZL=50+j0 ohm, fig.4.(g)time resonse of Low frequency sensor in multi sim result using 0.3 to below 3.0 Hz frequency. In multisim simultion totl 50ohm imednce in s-rmeter we find stbility nd mgnitude, hse resonse (db) for low frequency below 3.0Hz best result in.846hz frequency sense good outut shown in fig.4(h). Stbility in vlues of Zero in simultion result for this frequency in fig.4(i), in fig.4(j) Z-rmeter low frequency sensor in totl imednce 50ohm nd using frequency below 3.0Hz nd this VLF/ELF sensor used best frequency.846hz. Now this VLF/ELF sensor nd mlifier design LC-filter in MATLAB nd 7 Pge

9 Mgnetic Femtotesl Inductor Coil Sensor for ELF Noise Signls-( 0.1Hz to3.0 Hz) multisim softwre low frequency ss nd Pole Zero lce in smith chrt & gin circles for Low frequency for find good stbility nd imrove stbilized nd find imednce vlue nd Ccitor vlue for this sensor totl vlue of ccitor is 1.000e+003f, totl vlue of imednce 1.000e+003h, totl R/Z is 50ohm nd inut gin circle 0.8db, outut gin circle 1.388e-17db for this sensor in shown fig.4(k). Fig.4.() Mgnitude MATLAB result of Low frequency sensor 0.3Hz Fig.4.(b) mgnitude resonse in MATLAB result of Low frequency sensor 0.3Hz Fig.4.(c) Pole Zero resonse in MATLAB result of Low frequency sensor 0.3Hz Fig.4.(d) hse resonse in MATLAB result of Low frequency sensor 0.3Hz 73 Pge

10 Mgnetic Femtotesl Inductor Coil Sensor for ELF Noise Signls-( 0.1Hz to3.0 Hz) Fig.4.(e) Phse &Mgnitude resonse in MATLAB result of Low frequency sensor 0.3Hz Fig.4.(f) ste resonse in MATLAB result of Low frequency sensor 0.3Hz Fig.4.(e) Ac-Anlysis result of Low frequency sensor0.3hz to 3.0Hz Fig.4.(f) Power gin of Low frequency sensor in multi sim result Pge

11 Mgnetic Femtotesl Inductor Coil Sensor for ELF Noise Signls-( 0.1Hz to3.0 Hz) Fig.4.(g)Time resonse of Low frequency sensor in multi sim result. Fig.4.(h).S-rmeter of Low frequency sensor in multi sim result. Fig.4.(i)Stbility in vlues of Zero Low frequency sensor in multi sim result Fig.4.(j) Z-rmeterLow frequency sensor in multi sim result 75 Pge

12 Mgnetic Femtotesl Inductor Coil Sensor for ELF Noise Signls-( 0.1Hz to3.0 Hz) Fig.4.(k) Filter LC model nd Pole Zero lce in smith chrt & gin circles for Low frequency sensor in multi sim result VIII. CONCLUSION A method of designing the VLF/ELF receiver hs been shown, including the ntenn, trnsformer, nd circuit design. The concets described cn be used to design nd build vriety of ntenn shes, sizes, nd imednces s desired. The trns-former nd mlifier inut imednces cn then be otimized for gin nd noise. An exmle using squre 1.03-Ω 1.08-mH ntenn hs lso been develoed. Any she nd size of ntenn tht hs this imednce cn be used with the sme trnsformer nd mlifier, llowing for vriety of sensitivity nd convenience otions without hving to mke ny design chnges. this sensor using in EEG,ECG nd EMR lso using in brin frequency sense technology for very low frequency sense nd neon sensor technology. REFERENCES Journl Pers: [1] Srh K. Hrrimn,Student Member, IEEE, Evns W. Pschl, nd Umrn S. Inn,Fellow, IEEE Mgnetic Sensor Design for FemtoteslLow-Frequency Signls IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. 48, NO. 1, JANUARY 010 [] S. M. Metev nd V. P. Veiko, Lser Assisted Microtechnology, nd ed., R. M. Osgood, Jr., Ed. Berlin, Germny: Sringer-Verlg, [3] Dwivedi V.V Review of Antenn designed for infrred detection: brief literture study roorgtion nd EMC technologies for wireless communiction (MAPE-005),Aug.8-1, , vol.i;ww.ieexlore.ieee.org. [4] J. Breckling, Ed., The Anlysis of Directionl Time Series: Alictions to Wind Seed nd Direction, ser. Lecture Notes in Sttistics. Berlin, Germny: Sringer, 1989, vol. 61. [5] S. Zhng, C. Zhu, J. K. O. Sin, nd P. K. T. Mok, A novel ultrthin elevted chnnel low-temerture oly-si TFT, IEEE Electron Device Lett., vol. 0, , Nov [6] M. Wegmuller, J. P. von der Weid, P. Oberson, nd N. Gisin, High resolution fiber distributed mesurements with coherent OFDR, in Proc. ECOC 00, 000, er , [7] R. E. Sorce, V. S. Reinhrdt, nd S. A. Vughn, High-seed digitl-to-rf converter, U.S. Ptent , Set. 16, (00) The IEEE website. [Online]. Avilble: htt:// [8] M. Shell. (00) IEEEtrn homege on CTAN. [Online]. Avilble: htt:// FLEXChi Signl Processor (MC68175/D), Motorol, PDCA1-70 dt sheet, Oto Seed SA, Mezzovico, Switzerlnd. [9] A. Krnik, Performnce of TCP congestion control with rte feedbck: TCP/ABR nd rte dtive TCP/IP, M. Eng. thesis, Indin Institute of Science, Bnglore, Indi, Jn [10] J. Pdhye, V. Firoiu, nd D. Towsley, A stochstic model of TCP Reno congestion voidnce nd control, Univ. of Msschusetts, Amherst, MA, CMPSCI Tech. Re. 99-0, [11] Wireless LAN Medium Access Control (MAC) nd Physicl Lyer (PHY) Secifiction, IEEE Std , [1] M Ozki, Y. Adchi, Y. Iwhori, nd N. Ishii, Aliction of fuzzy theory to writer recognition of Chinese chrcters, Interntionl Journl of Modelling nd Simultion, 18(), 1998, Note tht the journl title, volume number nd issue number re set in itlics. Books: [13] Ved Vys Dwivedi, Shwet Srivstw Linerly Tered Slot Antenn 1st edition, set.01, Lmbert Acdemic ublishing, Germny ISBN [14] Rjendr Arnthi,Ved Vys Dwivedi, Power Filter Imrove Power Qulity in Power System Engineering 1st edition, Oct-.01, Lmbert Acdemic ublishing, Germny ISBN Pge