Design and Simulation Model for Compensated and Optimized T-junctions in Microstrip Line

Transcription

1 Intenational Jounal of Advanced Reseach in Compute Engineeing & Technology (IJARCET) Volume 3 Issue, Decembe 4 Design and Simulation Model fo Compensated and Optimized T-junctions in Micostip Line Alok Kuma Rastogi, Munia Bano, Shanu Shama Abstact Advances in micowave solid state devices have simulated inteest in the integation of the micowave cicuits. Micostip lines ae being consideed as viable candidates fo micowave communication and othe applications. Micostip due to its vaious design advantages is paticulaly vey attactive. This ceates the need fo accuate modeling and simulation of micostip tansmission lines. Vitually all pactical distibuted cicuits must contain discontinuities as staight uninteupted lines would be of little engineeing use. Micostip discontinuities such as cossings, T-junctions, bends and impedance steps ae elements of many complex micostip cicuits like filtes, powe divides, ing couples, and impedance tansfomes. Theefoe knowledge of exact eflection and tansmission popeties in dependence on fequency is of geat impotance. A simulation model is pesented hee fo analyzing the T-junctions in micostip lines though Sonnet Softwae at low fequencies (below GHz). The paametes of micostip lines ae detemined fom the empiical fomulae which ae based on full wave analysis. The simulation wok has been pefomed on Alumina substate. The T-junctions ae simulated and S-paametes hence calculated show the tansmission popeties of the discontinuity and thei fequency dependency. The T-junction is also compensated to get bette tansmission popeties, and optimized which gives impotant esults fo designing desied fequency micowave cicuits. Index Tems Full wave analysis, Micostip line, Micostip discontinuities, T-junctions, Steps in width, Sonnet Softwae, Substate pemittivity and S-paametes. Fig.. Vaious Plana Tansmission Line Stuctues I. INTRODUCTION In Micowave integated cicuits (MICs), the tansmission stuctue should be plana in configuation i.e. the chaacteistics of the element can be detemined by the dimensions in a single plane. As fo example, in a micostip line on a dielectic substate the width can be adjusted to contol its impedance. The commonly used diffeent types of pinted tansmission lines fo MICs ae micostip line, stip line, suspended stip line, slot line, coplana waveguide and fin line, as shown in Fig.. Micostip line is one of the most popula lines in a tansmission stuctue, mainly due to the fact that the mode of popagation in a micostip is almost TEM []. The physical stuctue of a micostip is shown in the Fig.. Manuscipt eceived Dec,4 D. Alok Kuma Rastogi, Depatment of Physics & Electonics, Institute fo Excellence in Highe Education, Bhopal, India, Munia Bano, Depatment of Physics & Electonics, Institute fo Excellence in Highe Education, Bhopal, India, Shanu Shama, Depatment of Physics & Electonics, Institute fo Excellence in Highe Education, Bhopal, India, Fig.. Physical & Constuctional view of Micostip line A. Micostip Discontinuities All pactical distibuted cicuits, whethe in waveguides, coaxial lines o any othe popagation stuctue, must inheently contain discontinuities. A staight uninteupted length of tansmission stuctue would be of little engineeing use, and in any case junctions ae essential. Although such discontinuities give ise to only vey small capacitances and inductances (often <.pf and <.nh) the eactance of these become paticulaly significant at the high micowave and millimete wave fequencies. Many cicuits such as filtes, mixes and oscillatos involve seveal discontinuities. All technologies whethe based on hybid MICs o MMICs (Monolithic Micowave Integated Cicuits) inheently involves tansmission discontinuities []. Discontinuity modeling is based upon equivalent capacitances and All Rights Reseved 4 IJARCET 46

2 Intenational Jounal of Advanced Reseach in Compute Engineeing & Technology (IJARCET) Volume 3 Issue, Decembe 4 inductances. The following ae seveal foms of discontinuities emeging fom cicuit equiements: a) Open cicuits b) Seies coupling gaps c) Shot cicuits though to the gound plane d) Step width changes e) T & coss junctions The T-junctions is pehaps the most impotant discontinuity in a micostip as it is found in most cicuits such as impedance netwoks, stub filtes and banch line couples. A micostip T-junction and its equivalent cicuit ae shown in the Fig.3. whee and H Z eff w exp H h 8 4 exp H () ( ) 4 ln ln 9.9 () H 4 ln ln whee (3) (3) H is given by equation () o altenatively as a function of h w fom equation () Fig. 3. Micostip T-junction and its Equivalent Cicuit The T-junction discontinuity compensation is much moe difficult than ight angled bends and steps in width discontinuity compensation techniques. The T-junctions can be compensated by adjusting the lengths of the thee micostip lines foming the junction. Vaious appoaches have been made to calculate the equivalent cicuits fo discontinuities. Oline [3] used Babinet s pinciple to descibe stipline discontinuities, Silveste and Benedek [4]-[6], and Stouten [7] calculated the capacitances of micostip discontinuities, and Gopinath and Silveste [8], Gopinath and Easte [9], and Thomson and Gopinath [] computed the inductive elements of the equivalent cicuits. All the methods descibed in these papes ae based on static appoximations, and theefoe ae valid with sufficient accuacy only fo low fequencies. II. MICROSTRIP SYNTHESIS In actual design of micostip, one wishes to detemine the width w equied to obtain specified chaacteistic impedance Z on a substate of known pemittivity ε and thickness h. This opeation is called synthesis. Vaious eseaches have epoted fomulas fo micostip calculations [], []. Owens [3] caefully investigated the anges of applicability of many of the expessions given by Wheele, compaing calculated esults with numeical computations. The closed fomulas ae highly desiable as they ae accuate and fast. CAD algoithms can be implemented with these fomulas of Edwad & Stee [4]. A. Synthesis Fomula Fo given Z and fequency: In case of naow stips i.e. when Z > (44 - ε ) Ω h h H ln 4 6 w w (4) Fo micostip line on Alumina, this expession appeas to be accuate to. % ove the impedance ange Z 5 8 when w and ae given: h 9.9 h h Z ln 4 6 ( ) w w III. SIMULATION (5) Sonnet Softwae [5] is commecial Softwae which povides solutions fo high fequency electomagnetic analysis. This Em simulation softwae is used fo design and analysis fo high fequency micostip cicuits. The analysis engine of Sonnet Suite, Em is appopiate fo a wide ange of 3D plana stuctues. Via capabilities allow the analysis of ai bidges, wie bonds, spial inductos, wafe pobes, and intenal pots as well as fo simple gounding. IV. RESULTS AND DISCUSSION The computations descibed in this pape wee pefomed on an alumina substate, elative pemittivity (ε = 9.9), loss tangent (tan δ = -4 ) and height of the substate (h =.5 mm), though Sonnet Softwae [5]. Then fom the synthesis fomula equation () and (), we get appoximate value fo the width of micostip line w =.5 mm. Micostip T-junction is dawn in Sonnet with known height h, width w, and elative pemittivity of Alumina substate (ε ). All Rights Reseved 4 IJARCET 47

3 Intenational Jounal of Advanced Reseach in Compute Engineeing & Technology (IJARCET) Volume 3 Issue, Decembe 4 Fig. 4 Symmetical micostip T-junction though SONNET Fig.7 T -junction compensated by making gooves in the main am The T-junction is chamfeed in diffeent ways in ode to compensate the excess eactance. The compensated models ae shown in the fig. 5 and 7 along with thei thee dimensional models shown in figues 6 and 8 esp. Fig. 8 3D view of the compensated T-junction Fig. 5 Compensated T-junction with Tiangula Goove and inceased width The esults ae shown in the Fig. 9 and though gaphs of the eflection and tansmission coefficients which ae analyzed up to the fequency GHz (below X-band). Fig 9 shows that when the T-junction is compensated the etun loss o the eflection coefficient [S] deceases which is much bette in both the ways of compensation athe than the symmetical T-junction. Fig. shows that the tansmission along the T-junction is also inceased by compensating it in eithe of the ways which is shown by the magnitude of [S]. The cuent distibution of the compensated T-junction is shown in the Fig. which clealy eveals that the maximum cuent flows in the oute pats of T-junction and deceases as we go towads the inteio potion. Fig. 6 Thee Dimensional View of the compensated T-junction All Rights Reseved 4 IJARCET 48

4 Intenational Jounal of Advanced Reseach in Compute Engineeing & Technology (IJARCET) Volume 3 Issue, Decembe 4 width of the line is.9 mm. If the width is changed fom this value (eithe inceased o deceased), the eflection inceases hence inceasing the etun loss. Thus the gaph hee suppots ou calculations as well as simulation. Thus afte optimizing we can fix the width of the T-junction to make ou etun loss minimum and pope tansmission of waves. Fig 9 Reflection Coefficient Vs Fequency fo Micostip T-junction and its compensated models Fig. The compensated model used fo optimization with width as the vaiable Fig Tansmission Coefficient Vs Fequency fo Micostip T-junction and its compensated models Fig. 3 Results of Optimizing the T-junction V. CONCLUSION As soon as a tansmission line is used in pactical cicuits, thee will be no longe a continuous coss-section geomety, but thee will be changes bought about by the joining togethe of lines, the changing of chaacteistic impedance o popagation diection and the connection to vaious loads. Fig. Cuent Density of the compensated T-junction along with scale depicting the value The compensated T-junction is then optimized in ode to get bette esults as shown in Fig.. The optimization tool in Sonnet is used to see the vaiation in etun loss when the width of the T-junction is vaied. The esults of optimization ae shown in the Fig. 3. As it can be seen fom the figue that the minimum etun loss is obtained when the compensated A method is descibed fo calculating the dynamical popeties of vaious micostip T-junctions. The elements of scatteing matix (i.e. eflection and tansmission coefficients) give impotant esults fo lowe fequencies. CAD models ae used to compensate the T-junctions fo bette efficiency at low fequencies. Sonnet Softwae is used to optimize the width of the compensated T-junction which gives a way to lowe the etun loss in the cicuit. The methods descibed in this pape may lead to the possibility of studying compensation methods fo powe All Rights Reseved 4 IJARCET 49

5 Intenational Jounal of Advanced Reseach in Compute Engineeing & Technology (IJARCET) Volume 3 Issue, Decembe 4 divides and simila cicuits. REFERENCES [] K. C. Gupta, Ramesh Gag, I. J. Bahl, Micostip Lines and Slot Lines, Atech House Inc. Washington, 979. [] Wheele, H.A., Tansmission Line Popeties of a Stip on a Dielectic Sheet on a plane, IEEE Tans. Vol. MTT-5, 977, pp [3] A. A. Oline, Equivalent cicuits fo discontinuities in balanced stip tansmission line, IEEE Tans. Micowave Theoy Tech. (Special Issue on Symp. On Micowave Stip Cicuits), Vol. MTT-3, pp , Nov [4] P. Silveste and P. Benedek, Equivalent capacitances of micostip open cicuits, IEEE Tans. Micowave Theoy Tech., Vol. MTT-, pp. 5-56, Aug. 97. [5] P. Benedek and P. Silveste, Equivalent capacitances of micostip gaps and steps, IEEE Tans. Micowave Theoy Tech., Vol. MTT-, pp , Aug. 97. [6] P. Silveste and P. Benedek, Micostip Discontinuity capacitances fo ight angled bends, T-junctions and cossings IEEE Tans. Micowave Theoy Tech., Vol. MTT-, pp , May 973. [7] P. Stouten, Equivalent Capacitances on T-junctions, Electon. Lett., vol. 9, pp , Nov [8] A. Gopinath and P. Silveste, Calculation of inductance of finite length stips and its vaiation with fequency, IEEE Tans. Micowave Theoy Tech., Vol. MTT-, pp , June 973. [9] A. Gopinath and B. Easte, Moment method of calculating discontinuity inductance of micostip ight angled bends, IEEE Tans. Micowave Theoy Tech.(Shot Papes), Vol. MTT-, pp , Oct [] A. Thompson and A. Gopinath, Calculation of micostip discontinuity inductance, IEEE Tans. Micowave Theoy Tech., Vol. MTT-3, pp , Aug [] Wheele, H. A., Tansmission-line popeties of paallel wide stips by a confomal mapping appoximation, IEEE Tans. Micowave Theoy and Tech., Vol., May 964. [] Wheele, H. A., Tansmission-line popeties of paallel stips sepaated by a dielectic sheet, IEEE Tans. Micowave Theoy and Techn., Vo.3,, Ma. 965, pp [3] Owens, R. P., Accuate analytical detemination of quasi-static micostip line paametes, The Radio and Electonic Enginee, 46, No. 7, July 976, pp [4] T.C. Edwads, M.B. Stee, Foundations of Inte connect and Micostip Design, John Wiley & Sons Ltd. [5] High Fequency Electomagnetic Softwae SONNET-3.56 Use guide. and Fance) to pesent eseach papes in the Intenational Confeences. In the yea 9 UGC, New Delhi nominated D. Rastogi to visit Mauitius unde IVth UGC TEC consotium ageement to delive seies of lectues at Univesity of Mauitius fo the peiod of thee months. D. Rastogi established Micowave and Optical Fibe communication Study and Reseach Laboatoy in the Institute fo Excellence in Highe Education, Bhopal unde Mission Excellence Scheme of MPCST, Bhopal in the yea. Ms. Munia Bano she is cuently undetaking eseach in micowave communication at Institute fo Excellence in Highe Education, Bhopal unde the guidance of D. Alok Kuma Rastogi. She was awaded M.Phil (Physics) in 7 by Bakatullah Univesity, Bhopal. She is a Senio Reseach Fellow unde the Maulana Azad National Fellowship Pogamme of UGC. She has published many eseach papes in vaious scientific jounals. She has also paticipated in numeous national and intenational confeences. She has been awaded best eseach pape at Intenational Confeence on Intedisciplinay Reseach in Engineeing, Management, Phamacy and Sciences held at Saga Institute of Reseach & Technology Bhopal fom th -3 d Feb. 4. Ms. Shanu Shama Pesently she is woking as a lectue in Institute fo Excellence in Highe Education. She did M.Sc. Electonics in 8 and M.Sc. Mathematics in. She is pesuing eseach wok unde the guidance of D. Alok Kuma Rastogi in field of micowaves. She has paticipated in many national and intenational confeences. She has published many eseach papes in eputed jounals. D. Alok Kuma Rastogi Pesently D. Alok Kuma Rastogi is Pofesso & Head, Depatment of Physics & Electonics at Institute fo Excellence in Highe Education Bhopal. He did M.Phil (Physics) fom the Depatment of Physics & Astophysics, Univesity of Delhi in 984 and completed his Ph.D. Degee in Electonics Engineeing fom Bhopal Univesity, Bhopal in the yea 99. He eceived Young Scientist Awad fo his excellent eseach wok in the field of Micowave Communication in the yea 987. He eceived EC Post doctoal Maie Cuie Fellowship, awaded by Euopean Commission, Bussels, Belgium and Ministy of Science and Technology, DST, New Delhi to cay out eseach wok in Univesity of Badfod, England (U.K.) in the yea 995. Indo-Russian Long Tem Poject (ILTP) was awaded to him in 996 by Russian Academy of Science, Moscow and DST, New Delhi fo the peiod of thee yeas. He completed vaious Majo and Mino Reseach Pojects awaded by UGC, New Delhi. UGC New Delhi awaded him seveal eseach pojects to cay out eseach wok in the field of micowave communication. He is having pofessional affiliation with vaious national oganizations. He is Fellow of IETE and life membe of IE, IAPT, ISCA, ISTE, PSSI etc. Seven Ph.D. have been awaded unde his supevision in the field of micowave communication and five candidates ae peusing eseach wok fo thei Ph.D. degee unde his guidance. About eseach papes have been published in the eputed Intenational and National Jounals. Moe than Intenational confeences attended and visited many counties (U.S.A., U.K., Belgium, Holland, Luxembug, Gemany, Japan All Rights Reseved 4 IJARCET 4