A Miniaturization Technique of a Compact Omnidirectional Antenna

Transcription

1 RADIOENGINEERING, VOL. 8, NO. 4, DECEMBER A Miniatuization Technique of a Compact Omnidiectional Antenna Saah SUFYAR, Chitophe DELAVEAUD CEA-LETI MINATEC F-3854 Genoble, Fance aah.ufya@cea.f, chitophe.delaveaud@cea.f Abtact. Thi pape dicue a miniatuization technique of a compact omnidiectional antenna. A lot loading technique i applied to a well-known low-pofile antenna tuctue whoe adiation chaacteitic ae imila to equivalent monopole one. An equivalent cicuit which model the antenna input impedance including the lot effect i alo developed in ode to illutate the antenna woking pinciple. The typical dimenion (width x height) of the obtained antenna ae λ / x λ /75 (λ i the fee pace opeating wavelength) which make it a miniatue antenna that can be integated inide mall wiele eno node uing naow band communication ytem. It pefomance ae in accodance with claical fundamental limit, the opeating bandwidth and efficiency ae ignificantly educed with the antenna ize eduction. Keywod Omnidiectional adiation, miniatuization, lot loading, fundamental limit.. Intoduction Antenna miniatuization i an old and well documented topic egulaly completed by ecent advance in the antenna liteatue [], []. Telecommunication ytem development have been a majo motivato of mall antenna eeach duing the lat decade, mot paticulaly fo mobile teminal. The tudy of new Wiele Seno Netwok i geneating a need fo new kind of aeial whoe adiating popetie ae citical fom the netwok communicating tategy. In paticula, fo compact eno device opeating at low UHF fequencie, a tong containt i placed on the antenna miniatuization and integation inide node tuctue. Thi pape deal with a miniatuization technique applied to a compact antenna tuctue. The initial antenna tuctue, which i claically conideed eithe a a top loaded folded monopole o a a hoted micotip antenna [3], contitute a compact low-pofile antenna with typical lage length of λ /6 (λ being the fee pace opeating wavelength) and a height of λ /, depending on the wihed opeating bandwidth. Numeou development have been caied out to impove and extend the antenna pefomance. Wide band [4], [5] and moe ecently Ulta Wide Band popetie [6] have been demontated. Othe impotant development uch a multiband behavio [7] o multi-function capabilitie [8] have been obtained uing thi antenna concept. Since the antenna tuctue i electically mall, few wok dealing with it ize eduction ae available in the liteatue. Howeve, a a claical downizing technique, miniatuization attempt have been pefomed uing high pemittivity mateial a antenna ubtate [9]. Anothe olution to educe the ize of uch an antenna i popoed in thi pape. Among the numeou miniatuization technique available in the liteatue, lot loading technique i a claical olution ued to ize eduction, bandwidth enlagement and multi-band opeation mode of micotip patch antenna []. Thi technique i applied to the paticula antenna tuctue whoe opeating mode ignificantly diffe fom claical patch antenna. It can be equally highlighted that the ue of lot ha aleady been tudied with thi antenna tuctue but with the objective of dual band behavio []. The tudied antenna geomety i depicted in Section. The next ection peent the lot loading effect on antenna impedance and adiation popetie uing expeimental eult and 3D electomagnetic imulation tool. In Section 4, the antenna behavio i fitly analyzed by popoing an equivalent cicuit which imulate the antenna impedance at low fequencie. Then the antenna miniatuization i dicued uing typical citeia of miniatue antenna uch a quality facto, fequency bandwidth, efficiency and antenna volume. The antenna popetie function of ize eduction ae compaed to the claical well-known fundamental limit of electically mall antenna.. Antenna Geomety The baic tudied antenna tuctue i commonly known a a top loaded folded monopole o a hoted micotip antenna [3]. The latte i vey inteeting fo application in numeou wiele device due to it compact ize, low pofile and omnidiectional adiation popetie. Hence, it contitute an attactive tuctue whoe popetie can evolve with the communication

2 374 S. SUFYAR, C. DELAVEAUD, A MINIATURIZATION TECHNIQUE OF A COMPACT OMNIDIRECTIONAL ANTENNA ytem equiement. The tudied antenna geomety i depicted in Fig.. It peent the implet configuation of the Monopola Wie Patch antenna. The metallic top hat i hot cicuited by a cylindical conducto which intoduce a low fequency paallel eonance whee the new opeating mode i obtained. The top hat i etched on a.8 mm thick FR4 ubtate ( = 4.4, tanδ=.8) acting a mechanical uppot. The antenna ha typical lage dimenion of λ /6.5 (λ being the fee pace opeating wavelength). The dielectic ubtate uppoting the antenna hat i hanging up at a hot ditance (λ /45.5) fom the gound plane by fou pace. The gound plane of ignificant dimenion compaed to the opeating fequency i centeed below the antenna to efficiently act a claical electical mio (electical image theoy fo monopole). Moeove, it ize i choen to limit educed gound plane effect duing expeiment. By cutting a lot in the metallic top hat, the low fequency eonating mode i modified and i mot paticulaly hifted towad low fequencie. Indeed, by uing a paticula configuation of the lot (Fig. ), a ignificant eduction of the eonant fequency aociated to the opeating mode can be obtained. The fequency hift i tongly dependent on the lot length. Thi behavio i illutated and analyzed in the following ection. imulated tuctue, thee diffeent pototype wee fabicated fo expeimental validation of imulated eult: one without a lot, one with a lot length of (L) 5.5 mm and anothe one of 89.5 mm length. Meauement eult ae compaed to imulated one in ode to validate the antenna behavio and the aociated pefomance. 3. Input Impedance The evolution of the input impedance (eal and imaginay pat) i peented fo diffeent lot length (L). and meauement eult ae compaed in Fig.. The low fequency eonance fo diffeent lot length i vey imila in imulation and meauement. The intoduction of the lot hift the paallel eonance towad low fequencie. It can be equally aumed that the low eonance fequency i deceaing a the lot length i inceaing. w=8mm Top hat Slot Gound plane l=8mm Ai h = 4 mm Shoting pot Dielectic Subtate FR4 Feed pobe (a) Top hat above gound plane (b) Photo of the pototype Fig.. Deciption of the antenna tuctue. Fig.. Evolution of the low fequency eonance veu lot length (L in mm) in imulation and meauement. 3. Slot Loading Effect To tudy the lot effect, imulation and expeiment wee imultaneouly caied out. In a fit tep, the impedance matching to 5 Ohm wa not conideed and only the behavio of the antenna input impedance in the vicinity of low fequency eonance mode (aociated to the hoting wie) wa tudied. Among the numeou configuation of 3. Intinic Gain Diagam The adiation popetie of the antenna including the lot in the top hat ae tudied uing 3D electomagnetic imulation tool [] and by meauing the adiation patten plu the intinic gain of pototype (impedance mimatching i not taken into account). Fig. 3 compae the imulated and meaued gain diagam fo diffeent lot

3 RADIOENGINEERING, VOL. 8, NO. 4, DECEMBER configuation in two othogonal cut plane (ee Fig. 3 fo cut plane definition). The adiation popetie ae plotted at the paallel eonance fequency f aociated to each lot length. Fo the baic antenna tuctue, the cuve ae quite identical and the gain at hoizon (P cut plane, Fig. 3 (a)) i aound dbi. (P) (P) z θ y (P) ϕ x (P) the antenna when the fequency i loweed. A the fequency deceae, the electic ize of the gound plane i educed and the meauement cable could intoduce ome uncetaintie on the meaued adiation popetie. The maximum meaued intinic gain i aound -4 dbi fo L = 5.5 mm and -8 dbi fo L = 89.5 mm. The claical Monopola Wie Patch antenna ha a typical diagam hape identical to the equivalent monopole antenna located ove the ame gound plane (i.e. dipola hape in ou cae of limited gound plane). The omnidiectional popetie of the antenna adiation with vetical main polaization of the field ae quite peeved in the peence of the lot in the top hat. The eult obtained by meauement validate the one obtained by imulation. The maximum gain i oughly of the ame ode and deceae a the fequency educe. 4. Antenna Miniatuization (a) 4. Miniatuization Facto Fom the canonical compact antenna tuctue, the influence of the lot i thooughly analyzed uing 3D electomagnetim imulation tool []. Fig. 4 how how the low fequency paallel eonance i modified by the lot length. (b) Co-polaization Co -polaization (c) Meaue Co-polaization Co-polaization Fig. 3. Gain diagam in imulation and meauement fo diffeent lot configuation: (a) No lot, (b) L = 5.5 mm, (c) L = 89.5 mm. Some moe obviou diffeence ae obevable between meauement and imulation eult when lot i cut in the top hat. Thee dicepancie can be attibuted to the difficultie to meaue with accuacy the adiation popetie of Fig. 4. Change of the low fequency antenna eonance veu lot length (L in mm) imulated eult. The evolution of the eonance fequency f veu the lot length i diplayed in Fig. 5. Fo compaion, the fundamental half wavelength mode of the lot, pinted on the dielectic ubtate, i equally plotted in Fig. 5. Being ituated at highe fequencie, thi eonating mode doe not intefee with the low fequency eonance of the antenna. It confim the non alteation of the lot on the adiation popetie of the antenna. Conequently, the fequency hift intoduced by the lot loading can be intepeted a an inceae of the equivalent capacitance of the antenna hat. Thi phenomenon i illutated in the following ubection. In matching

4 376 S. SUFYAR, C. DELAVEAUD, A MINIATURIZATION TECHNIQUE OF A COMPACT OMNIDIRECTIONAL ANTENNA the input impedance to 5 ohm in the vicinity of the hifted eonance, the antenna tuctue including the lot i hence miniatuized. The initial antenna tuctue ha typical lage dimenion of λ /6.5 and a height of λ /45.5. Fo L = 9 mm, the lage dimenion i λ / and the height i λ /75. A fequency downhift of up to 4% of the low eonance fequency i noticed thank to the peence of the lot. Low Reonance Fequency (GHz) Half wavelength lot Meaue Slot length L (mm) Fig. 5. Low eonance fequency (f) veu the lot length. 4. Slot Effect Modeling To confim the phyical intepetation of the tudied miniatuization technique, ome development of an equivalent cicuit of the hoted micotip antenna have been caied out. Thi equivalent cicuit, aleady developed in [3], imulate the antenna impedance below the fundamental mode of the patch antenna. Thi electical model i valid fo antenna having low pemittivity ubtate above infinite gound plane. A imple model of lot ha been intoduced in the equivalent cicuit to tudy the lot loading effect. Fig. 6. Low fequency cicuit model of antenna impedance with lot effect. The antenna impedance below the fundamental mode of the antenna i detemined by diffeent contitutive element of the antenna, a illutated in Fig. 6. Fo claical pobe fed patch antenna, the impedance i given by the capacitance of the antenna C patch (contituted by the uppe plate above the gound plane) in eie with the feed pobe inductance L feed. The capacitance value due to thi kind of ectangula micotip capacito i defined a [4]: C W L h. patch = +. Ce + Ce whee Ce and Ce ae epectively the edge capacitance along width W and length L of the eonato (i.e. top hat); h i the ubtate thickne and being the elative pemittivity of the ubtate. Ce = v ϕ W L Z W h h (,, ) () () L Ce W v Z L h h = (3) ϕ (,, ) v ϕ (v ϕ ) epeent the phae velocity of the quai TEM mode popagating along the micotip line of width W (L) Z( W, h, ) vϕ = c (4) Z( W, h,) Z( L, h, ) vϕ = c (5) Z( L, h,) Z(x,h, ) i the chaacteitic impedance of the micotip line of width x [5]: π x x Z ( x, h, ) = +,393 +,667 ln +. 44, (6) h h e h + = + ( +. ) if h e < w. (7) w Fo a quae fom patch, the inductance of the coaxial pobe i expeed a follow [6] : μ h c L = feed ln( ) π π γ f. (8) whee i the adiu of the pobe, c the light velocity, γ i Eule contant (.78), h i the pobe length. Then, the gound wie, that connect the patch to the gound plane, act a a hot cicuit to the antenna capacitance. Thi element i et in paallel to the antenna capacitance and intoduce the low fequency eonance [3]. The gound wie inductance i deived uing the coaxial pobe inductance fomula (8), i the gound wie adiu. Beide, a mutual inductance M i intoduced to take into account the coupling between the inductance. The expeion i et in [3] a follow: μ h c M = ln( ). (9) π πγ d f d i the ditance between the wie axi. Loe ae intoduced by the adiation eitance R feed and R wie of wie. The adiation eitance ae defined by the expeion given in [8]:

5 RADIOENGINEERING, VOL. 8, NO. 4, DECEMBER I( h,f, ) = π/ h f R = 4 π ( ) I(h,f, ), () c 3 co²θ in θ π / co²( Ψ. h)co² θ+ ( in² θ)in²( Ψ dθ, (). h) f Ψ = π in θ. () c The decibed equivalent electical cicuit with the aociated analytical fomulation of it component contitute the efeence cicuit to intoduce the lot effect. The antenna geomety i implified fo thi analyi due to electical cicuit limitation (lage gound plane and ai a dielectic ubtate). By cutting a lot in the antenna patch, the antenna capacitance i mainly modified. Thi effect can be modeled by intoducing the lot complex impedance in paallel to the antenna capacitance (Fig. 6). To highlight the lot effect, a imple lot impedance model i intoduced in the equivalent cicuit. Hypothei on the calculation of thi model limit the geomety of the lot, a hown in the Fig. 7. Futhe modeling wok ae equied to impove the lot impedance model (poition of the lot, poximity of the gound plane, bent lot hape). Howeve, the baic appoach povide inteeting eult, mot epecially concening the evolution of eonant fequency veu lot length. Gound wie Feed pobe Hat Slot Fig. 7. Stuctue of the lot in the antenna hat fo the electical cicuit modeling. The impedance of a lot ha been calculated uing [7]. Fo a imple taight lot (Fig. 8.) in a gound plane, the Babinet pinciple defining the equivalent dipole antenna ha been ued to obtain the electical and magnetic field of the lot. The calculation of the electomagnetic field allow the calculation of the input admittance of the lot. The lot admittance i given by : Y = G + j B (3) whee G i the conductance of the lot and B i the uceptance. Fit, the adiated powe i evaluated along the y>, in the YZ plane at ( c, θ) point, which i given in [7] ( c and θ ae the cylindical coodinate): P( c,θ) = E. (4) ϕ π Fig. 8. Slot excited by an electic field. By developing thi expeion, we obtain: π. w in ²( coθ) V π λ P( c, θ) = in ² θ.in θ. dθ. (5) π π co ² θ Knowing that the adiating powe i function of G : P( c,θ) = V G. (6) V i the potential between lot ide. By combining (5) and (6), we can deduce the expeion of G. Auming that w <<, the implified fomula i: λ w G = ( ). (7) 9 λ Finally, the uceptance i detemined knowing the input impedance of a hot-cicuited micotip line equivalent to a capacitive tub with a length of Δl [7]: with: w Z E and the length i given: π B = l e λ Δ. (8) Z π l C = if << w e w Δl =.4 l l l c (9) w +.64 e +.3 l ( ). () e.58 w +.8 l The effective pemittivity i given by (7). Hence the lot impedance (admittance) can be calculated and intoduced in the antenna equivalent cicuit. Fig. 9 compae the evolution of the low antenna eonance fequency obtained with 3D electomagnetic oftwae [] and the equivalent cicuit. Simila evolution of the eonant fequency ae obeved with both tool. The highe the length i, the lowe the eonance fequency i. The imulation eult ae in a good ageement with the modeling, in pite of the cude lot model. Thee eult con- O z y x

6 378 S. SUFYAR, C. DELAVEAUD, A MINIATURIZATION TECHNIQUE OF A COMPACT OMNIDIRECTIONAL ANTENNA fim the phyical intepetation of the lot loading technique of thi kind of compact antenna. Low Reonance Fequency (GHz) Equivalent Cicuit Slot length (mm) Fig. 9. Evolution of the low eonance fequency (f) veu lot length. 4.3 Quality Facto and Bandwidth Diffeent expeion of the quality facto of electically mall antenna can be found in the liteatue. The antenna behavio i tudied uing the quality facto Q defined in [9]. It i deived fom the antenna impedance: ω ' Q = Z (ω ). () R (ω ) whee R i the eal pat of the complex impedance, Z i the deivative of the complex impedance and ω, i the adian fequency. Thi expeion wa applied to the antenna impedance having diffeent lot length. In Tab., we peent the value obtained at the low fequency antenna eonance f. The aociated maximum fequency bandwidth (FBW) defined fo a VSWR () of i equally epoted in lat column. Thi paamete i deived uing the following fomula [9]. β FBW = whee β = =. () Q A coect ageement i obtained between imulation and meauement eult. The publihed efeence wok dealing with fundamental limit of electically mall antenna popoe a well-known law which link togethe antenna dimenion, minimum Q facto and efficiency [], []. Slot f (GHz) Q FBW (%) length (mm) Sim. Mea Sim. Mea. Sim. Mea Tab.. Evaluation of Q and FBW fo diffeent value of the low fequency antenna eonance f. The minimum quality facto fo a ingle lowet TE (TM) mode of a compact lole adiating tuctue included inide a phee of adiu a i given by : Qmin = +. (3) 3 3 k a ka k i the wave vecto. The dependence of Q [9] veu antenna dimenion i illutated in Fig.. The conideed phee adiu to define the antenna dimenion i the half diagonal of the antenna hat. Thi choice can be dicued due to the equivalent monopole antenna behavio. Indeed, we make the hypothei that the gound plane i lage enough not to alte the antenna behavio when fequency i deceaed. Fo compaion, the minimum Q [] (η =%) i plotted in Fig.. A claically obeved, the antenna Q i much highe than the theoetical limit. Q value inceae a the antenna ize deceae. Simulated and meaued eult how imila behavio. Auming the bandwidth popotional to the invee of Q facto, the bandwidth i conequently naowing with the antenna miniatuization. Thi behavio i in accodance with the fundamental limit of electically mall antenna. Quality Facto Qmin (McLean) Meaue ka Fig.. Quality facto and factional fequency bandwidth veu antenna dimenion (ka). 4.4 Efficiency The efficiency i a citical paamete of electically mall antenna. The antenna adiation efficiency wa calculated with a 3D electomagnetim imulation tool [] and wa meaued uing the Wheele Cap method []. The obtained eult ae compaed in Tab.. A good ageement i obtained between imulation and meauement eult. Slot length (mm) Efficiency (%) Meauement Tab.. Efficiency calculated by imulation and meaued with the Wheele Cap method. 3.5 Factional Bandwidth (%)

7 RADIOENGINEERING, VOL. 8, NO. 4, DECEMBER Efficiency i plotted veu antenna ize in Fig.. Efficiency i clealy educed with the antenna ize in both imulation and meauement. The antenna pefomance ae hence in accodance with the fundamental limit. Efficiency (%) Meaue ka Fig.. Efficiency veu antenna dimenion (ka). 4.5 Bandwidth, Efficiency and Antenna Volume Fo vey compact antenna having a<<λ /π, the fundamental limit can be educed a follow: 3 η. (ka). (4) Q η being the antenna adiation efficiency. Thi fomula indicate that Quality facto (bandwidth), efficiency and antenna volume ae linked togethe. Moe peciely, the poduct of antenna bandwidth with efficiency i popotional to the antenna volume. To etimate the validity of thi elation, Tab. 3 popoe the calculation of η/q(ka) 3 fo diffeent lot length. The atio doe not eem to be contant. Actually, the hypothei on the antenna ize i not fully veified. Howeve, a the antenna ize i educing, the calculated value tend to be moe table. Additional imulated and meaued eult will be helpful to validate any concluion. Slot length (mm) k a η 3 Q (ka) Meauement Tab.3. Link between bandwidth, efficiency and the volume occupied by the antenna. 5. Concluion A lot loading technique ha been uccefully applied to educe the ize of a compact omnidiectional antenna. The lot effect ha been caefully analyzed uing 3D electomagnetic imulation tool and modeled uing a imple equivalent cicuit. The peented miniatuization technique lead to a low cot miniatue antenna with pefomance in accodance with claical fundamental antenna limit. Opeating bandwidth and antenna efficiency ignificantly educe with the antenna dimenion. Such antenna tuctue ha been developed to be integated inide mall wiele eno node demontato. Thi device ue naow band communication ytem (low data ate, low powe ytem) fo pevention and detection of foet fie and landlide. Acknowledgement Thi tudy wa done in the famewok of the WinSoc poject (FP6-5-IST-5). Refeence [] FUJIMOTO, K., HENDERSON, A., HIRASAWA, K., JAMES, J.R. Small Antenna. New Yok: John Wiley and Son, Reeach Studie Pe, 987. [] HANSEN, R.C. Electically Small Supediective and Supeconducting Antenna. Hoboken, New Jeey: Wiley, 6. [3] DELAVEAUD, C., LEVEQUE, P., JECKO, B. Small-ized lowpofile antenna to eplace monopole antenna. Electonic Lette, 6 Ap 998, vol. 34, no. 8, p [4] LAU, KL., LI, P., LUK, KM. A monopola patch antenna with vey wide impedance bandwidth. IEEE Tanaction on Antenna and Popagation, 5, vol. 53, no. 3, pp 4-. [5] ROW, J. S., YEH, S. H., WONG, K. L. A wide-band monopola plate-patch antenna. IEEE Tanaction on Antenna and Popagation.,, vol. 5, no. 9, pp [6] BOURTOUTIAN, R., DELAVEAUD, C., TOUTAIN, S. Low pofile UWB monopole antenna having a hap band notch function. In Euopean Confeence on Antenna and Popagation (EuCAP6). Nice (Fance), 6. [7] ZAID, L., STARAJ, R. Miniatue cicula GSM wie-patch antenna on mall gound plane. Electonic Lette, 4 Feb, vol. 38, no. 4, pp [8] JECKO, B., DECROZE, C. The Monopola Wie Patch Antenna concept. In Second Euopean Confeence on Antenna and Popagation, EuCAP 7, -6 Nov. 7, pp -5. [9] PASQUET, F., JECKO, B. New development of the wie-patch antenna fo ceamic technology and multifunction application. In I.E.E.E. Antenna and Popagation Society Intenational Sympoium, 8-3 July, vol. 4, pp [] WONG, K.L. Compact and Boadband Micotip Antenna. New Yok: J. Wiley & Son, Inc., Wiley Seie in Micowave and Optical Engineeing. [] JECKO, F., HAMMOUDI, M. Multi Fequencie Wie Patch Antenna (Antenne fil-plaque Multiféquence). Fench patent, n 794, Decembe. [] MICROWAVE STUDIO, Compute Technology,

8 38 S. SUFYAR, C. DELAVEAUD, A MINIATURIZATION TECHNIQUE OF A COMPACT OMNIDIRECTIONAL ANTENNA [3] DELAVEAUD, C. New kind of micotip antenna: the monopola wie-patch antenna (Etude d une nouvelle clae d antenne impimee a ayonnement monopolaie). PhD dietation, Univeity of Limoge, Oct [4] WOLFF, I., KNOPPIK, N. Rectangula and cicula micotip dik capacito and eonato. I.E.E.E Tan. on Micowave Theoy and Technique, Octobe 974, vol., no.. [5] WHEELER, H. A. Tanmiion-line popetie of paallel tip epaated by a dielectic heet. I.E.E.E. Tan. on Micowave Theoy and Technique, Mach 965, vol. 3, pp [6] LIER, E. Impoved fomula fo input impedance of coax-fed micotip patch antenna. I.E.E. Poc., Augut 98, pp [7] COMBES, P.F. Mico-onde, cicuit paif, popagation, antenne. DUNOD, Tome, 997. [8] CHI, C.L., ALEXOPOULOS, N.G. Radiation by a pobe though a ubtate. IEEE Tan. Antenna and Popagation, Septembe 986, vol. 34, no. 9, pp [9] YAGHJIAN, A. D., BEST, R. Impedance, bandwidth, and Q of antenna. IEEE Tan. Antenna and Popagation, Apil 5, vol. 53, no. 4, pp [] MCLEAN, J. S. A e-examination of the fundamental limit on the adiation Q of electically mall antenna. IEEE Tan. Antenna and Popagation, May 996, vol. 44, pp [] HARRINGTON, R. F. Effect of antenna ize on gain, bandwidth and efficiency. J. Re. Natl. Bu. Stand., Jan./Feb. 96, vol. 64-D, pp. -. [] MCKINZIE, W. E. A modified Wheele cap method fo meauing antenna efficiency. In IEEE Antenna Popagat. Soc. Int. Symp. Dig., Jul. 997, vol., pp About Autho Saah SUFYAR wa bon in Bodeaux, Fance in 985 and eceived an engineeing and Mate degee in Electonic fom ENSEIRB, Electonic Engineeing School in Bodeaux, Fance. She i a fit yea PhD tudent at CEA- LETI MINATEC, Fance and wok on econfiguable miniatue antenna ince 8. Chitophe DELAVEAUD obtained hi PhD in high fequency electonic fom the Univeity of Limoge, Fance, in 996. Fom 99 to 997, he wa a Teaching Aitant at the Univeity Intitute of Technology in Limoge, Fance. In 998, he moved to the Euopean R & D cente of Radiall / Laen Antenna Technology in Voeppe, Fance. He wa eponible fo developing new antenna concept, with the emphai on miniatue antenna, wideband and multi-band antenna fo cutome application in wiele communication. Since, he ha been a viiting lectue at the Univeity of Savoie, Chambéy, Fance. In, he joined the Atomic Enegy Commiion (CEA), Laboatoy of Electonic and Infomation Technology (LETI), Genoble, Fance, a Senio Reeache. Hi cuent eeach inteet include the analyi and development of adiating tuctue, with an emphai on miniatue integated antenna, multi-antenna ytem, ulta-wide band antenna and mat antenna fo wiele communication ytem.