NETWORK ANALYSIS OF ANTENNA BASED ON SCATTERING PARAMETERS

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1 Intentionl Jounl of Industil Electonics nd Electicl Engineeing, IN: Volume-3, Issue-, Fe.-5 NETWORK ANALYI OF ANTENNA BAED ON CATTERING ARAMETER RENU INGH, KUMARI MAMTA Resech chol Associte ofesso Jhkhnd Ri Univesity, Rnchi, Indi E-mil:- Astct: Antenn design involves mny electicl nd mechnicl metes. The most imotnt electicl metes include dition ens, gin, diectivity, inut imednce, ndwidth, nd efficiency. This e develos new fom of two ot netwok nlysis of n ntenn system sed on sceing metes (-metes) of n ntenn element nd its dition en. In this fomultion, ntenn dition is consideed in tems of electomgnetic couling etween the test ntenn nd oe ntenn. Keywods: Antenn metes, ceing mete Test ntenn, oe ntenn. I. INTRODUCTION In the field of ntenn thee e some of the oul ntenn nlysis methods ely on numeicl techniques, such s the method of moments (MoM), the finite element method (FEM), nd the finitediffeence time-domin method (FDTD) [-3], to diectly solve Mxwell's equtions. The vilility of numeous commecil softwe ckges, llow electicl enginees to vey esily nd idly nlyze ntenns of vious geometies. At the sme time, these comlex simultions codes e often used imoely nd code oututs e not inteeted oely. This e esents new sceing mete sed netwok model fo the nlysis of ntenn. The model includes desciion fo the mutul couling etween y elements nd the couling though the souce netwok. This model llows comct desciion of the imednce chcteistics nd the dition chcteistics of ntenn fom the sme set of -metes. ceing metes e imotnt in micowve design ecuse they e esie to mesue nd wok with t high fequencies thn those of othe kinds of metes. These models llow comuion of dited field nd dited owe in tems of wve incident on the ntenn element o the y elements. The incident wves nd the dited owe cn e used to comute ntenn design metes such s diectivity, gin nd efficiencies. Thee is need fo technique tht integtes the tetment of ll the ntenn metes in systemtic wy duing the design ocess. Netwok desciions of ntenn systems llow the integtion of some of the ntenn electicl metes [4-7]. Then mete in mtix fom cn e wien s, ( ceingmtix ) The incident wves, eflected wves nd metes cn e elted s follows Whee, mtix elements,, nd e efeed to s the sceing metes o the - metes (figue ). The metes, hve the mening of eflection coefficients, nd, the mening of tnsmission coefficients. The tveling wve viles, t ot nd, t ot e defined in tems of V, I nd V, I nd el-vlued ositive efeence imednce Z s follows: V Z I z V Z I z V Z I z V Z I z tvelingwves The ctul mesuements of the -metes e mde y connecting to mtched lod, Z L = Z. Then, thee will e no eflected wves fom the lod, = nd the -mtix equtions will give: Netwok Anlysis Of Antenn Bsed On ceing metes

2 Intentionl Jounl of Industil Electonics nd Electicl Engineeing, IN: = + = = + = Z L Z Z L Z eflection coefficient tnsmission coefficient In two ot netwok, nd e descied in db s follows = log () = log (τ) Volume-3, Issue-, Fe.-5 dition en hving ek elized gin of G R. The oe ntenn is locted t constnt distnce in the diection θ nd zimuth ngles with esect to given efeence lne nd oigin. The test ntenn ot nd the oe ntenn ot fom two ot netwok whose teminl chcteistics cn e descied y mtix. The incident wves, eflected wves nd -mete cn e elted s follows (,)=(,)(,) (3) Whee tnsmission coefficient equls incident voltge divided y tnsmied voltge = V Tnsmied / V Incident And Reflection coefficient equls incident voltge divided y eflected voltge τ = V Reflected / V Incident is genelly etween nd -, exce some ctive cicuits such s oscillto with lge thn db. ceing mtix [] stisfies [] + [] = [I] () Whee [ ] + = ([*]) T = ([ ] T ) *. Hee suesci * eesents conjugtion, [ ] T denotes mtix tnsose nd [I] is unity mtix. Eqution () is efeed to the lossless unitity. Fo two-ot lossless netwok, the unity condition () cn e exessed s thee indeendent equtions * * () Which, in tems of tvelling wve viles, is equivlent to II. MODEL: -ARAMETER NETWORK MODEL Conside n ity test ntenn with n inut ot nd distnt oe ntenn with outut ot (figue 3). The oe ntenn is used to detect the fields dited y the test ntenn. We ssume tht the oe ntenn is line ssive device with Fig. 3: ignl flow digm fo n ity test ntenn nd oe ntenn with two othogonl oliztion ots (,, ), ), ) t t t, ), ), ), ), ) (4) is the sceing mtix, is column vecto whose element is the incident wve t ech ot, nd is column vecto in which the element is the eflected wve t ech ot [8]. The dition en is defined y the owe eceived y the oe ntenn moved ound constnt distnce fom the ntenn unde test oeting in the tnsmit mode.,, t, e the couling coefficient etween the test ntenn nd the oe ntenn. Now if the fowd coulings (the fist column of the -mtix) nd the coesonding evese coulings (the fist ow of the -mtix) e identicl, o (,)= t (,) (5) The viles nd in eqution (4) eesent the outut wves tht come out of the oe ntenn ots nd the wves tht e eflected fom the eceives ck to the oe ntenn ot. Assuming tht nd e exessed in oot men sque fom, the owes deliveed y the test ntenn to the oe ntenn ots will e del, ), ), ) (6) The deliveed owes s function of ngul osition of the oe ntenn e ootionl to the ntenn owe ens of the test ntenn. The deliveed owe is detemined y lying Mson's ule [8] on the -metes. Using the outut wves, the wves eflected fom the eceives to the oe ots e detemined y Netwok Anlysis Of Antenn Bsed On ceing metes

3 Intentionl Jounl of Industil Electonics nd Electicl Engineeing, IN: (,)= (,) (7) When the eceive lod imednces e set to the efeence imednce Z = Z o, the eflection coefficients of the eceives ecome zeo, =. Then, the oe incident wves ecome (,)= (,)= (8) Thus, the owes deliveed t the oe ots simlify to del (,, ) (,, ) (9) The outut wves fom the oes couled fom the test ntenn, Volume-3, Issue-, Fe.-5 Whee the symols hve the following menings: v = owe ville fom souce [W], in = inut owe cceed y the ntenn [W], d = owe dited y the ntenn [W], U = dition intensity [W/s], U n = til dition intensity [W/s], e = dition efficiency, q = imednce mismtch, G R = elized gin, G = gin, D = diectivity, G Rn = til elized gin, G n = til gin, D n = til diectivity, = oliztion efficiency. 3. Diectivity Diectivity quntifies how the dited owe is concentted in given diection comed to the totl dited owe. The diectivity, D (,), is defined s 4 times the tio of the dition intensity in given diection to the totl owe dited,, ), ), ), ) t s s () Theefoe the owe deliveed to the oe ntenn ots e detemined to e del, ) (, ) t, ) (, ) s s () del, ) (, ), ) t () III. RELATIONHI BETWEEN ANTENNA NETWORK MODEL AND ANTENNA ARAMETER Equtions () o () eesent the sic ntenn netwok model fo n ntenn. They include the ntenn dition en, oliztion, inut imednce, nd efficiency in comct fom. Conside the gin nd diectivity flow cht, shown in figue 4, modified fom the cht in IEEE tndd [9]. Fig. 4: Gin nd diectivity flow cht. Modified fom the cht in IEEE td. [9]. 4, ) (, ) (3), ) d D The nomlized dition en is detemined in tems of the -metes will e, ) 3. Gin mx,, (4) Gin is used to quntify how efficiently n ntenn tnsfoms the ville owe t its inut teminl to the owe dited in given diection. This mens, gin is equl to diectivity educed y losses on the ntenn, o dition efficiency (4) G(, ), ) G ( s ) R (5) deceses s inceses. When these - metes vlue e detemined with esect to efeence imednce Z o, tht is comlex conjugte of the ntenn inut imednce, the esulting will e equl to zeo, i.e when the ntenn is mtched. Then, the gin ecomes uely function of the tnsmission coefficient. This esult is consistent with the definition of gin. It is useful to define -metes tht e indeendent of distnce nd oe elized gin G R. Let us define nomlized -metes s ' (, ) 4 G R (,, ) (6) Netwok Anlysis Of Antenn Bsed On ceing metes 3

4 Intentionl Jounl of Industil Electonics nd Electicl Engineeing, IN: The nomlized -mete eesents the couling fom the test ntenn to the oe ntenn e unit din. Using the nomlized -mete the gin y (5) simlifies to Volume-3, Issue-, Fe.-5 4 G(, ) ( s ) (, ) (7) Which is vlid when the oe ntenn is sufficiently f wy fom the test ntenn ( ) such tht vey lile intection occu etween them. 3.3 Rdition Efficiency The dition efficiency of n ntenn is detemined y the tio etween the gin nd diectivity, Tle : A summy of electicl efomnce of the sti diole inted ntenn on n infinite dielectic sustte ove n infinite gound lne detemined y oosed model. e = G(,) / D (,) e G R 4 ( ), ) d e (, ) d IV. MEAUREMENT REULT Let us ly this model to the geomety of single sti diole element inted on n infinite sustte. The sti diole hs length of L = 38 mm, width W = mm nd dielectic constnt =.33. The sustte is susended ove n infinite gound lne t height of h = mm. We will designte the dition en nd the inut imednce of the single sti diole inted on this sustte s the isolted element en nd the isolted element imednce. It must e noted tht the tem isolted does not eesent the sti diole in fee sce. The dielectic sustte nd the gound lne e included in the nlysis. A single sti diole element inted on sustte ws simulted using IE3D fom Zelnd [] to detemine the -mete nd the dition en. All of the sceing metes esented in this exmle e efeenced to Z = 5Ω. The zeo cossing of the imginy t of the -mete ne 3 GHz, nd nely zeo vlue fo the el t of the -mete t the sme fequency indictes tht the ntenn is esonnt ne 3 GHz, with the inut imednce of oximtely 5Ω. Tle : A summy of electicl efomnce of the sti diole inted ntenn on n infinite dielectic sustte ove n infinite gound lne simulted using IE3D. The simulted esults (Tle ) hve good geement with ll stndd metes detemined y oosed model (Tle ), exce fo the mgin of exeimentl eo e it fo odside diectivity, odside gin, odside elized gin, dition efficiency, imednce mismtch fcto o inut imednce t 3GHz. Aove ll, ticully thee is n excellent mtch fo -mete t 3 GHz which hs een t the centl theme nd focus of the e. CONCLUION The ojective, in this e ws to esent the deivtion of single ntenn desciion using two-ot, -mete netwok model nd do its vlidtion using IE3D. The -metes in the netwok wee extended to include the stil deendency to model the couling fom the test ntenn to the oe ntenn locted t (,). The deliveed owe to the oe ntenn ots when the test ntenn is excited with souce ws deived. Fom the deliveed owes, the ntenn metes wee deived in tems of ntenn netwok - metes. The simultion esults otined e found to e in good geement with ll the stndd mete vlues detemined y the oosed model within the limit of exeimentl eo. Netwok Anlysis Of Antenn Bsed On ceing metes 4

5 Intentionl Jounl of Industil Electonics nd Electicl Engineeing, IN: REFERENCE [] Gyen, Rintu K nd Ds, ushut, A high-gin od-nd wveguide longitudinl slot y ntenn, ogess In Electomgnetics Resech C, 3; 44: []Li, J Y, Li, L W nd Gn, Y B, Method of Moments Anlysis of wveguide slot ntenns using he EFIE, J. of Electomgnetics. Wves nd l., 5; 9 n3: [3] Ellio, R, An imoved design ocedue fo smll ys of shunt slots, IEEE Tns. Antenns ogtion, 983; 3 n: [4] Hington R F, Antenn exciion fo mximum gin, IEEE Tns. Antenns ogt., 965; A-3 n6: Volume-3, Issue-, Fe.-5 [5] Khn, W K nd Wsylkiwskyj W, Couling, dition nd scing y ntenns in Genelized Netwoks, J. Fox, Ed., vol. XVI. New Yok: olytechnic ess, New Yok, 966; [6] Gtely, A C J tock, D J R nd Cheo, B R, A netwok desciion fo ntenn olems, oc. IEEE, 968; 56 n7: [7] Wieseck, W nd Heidich, E Wide-Bnd multiot ntenn chcteiztion y olimetic RC mesuements, IEEE Tns. Antenns ogt., 998; 46 n3: [8] Kuokw, K, owe wves nd the sceing mtix, IEEE Tns. Micowve Theoy Tech., 965; 3: 94-. [9] IEEE tndd Definition of Tems fo Antenns, IEEE td , IEEE, 993. [] IE3D Use's Mnul, Relese 7, Zelnd oftwe, Inc., Femont, Clifoni, 999. Netwok Anlysis Of Antenn Bsed On ceing metes 5

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