D.Baatarkhuu, B.Myagmarsuren, others, Journal of agricultural sciences 15 (02): , 2015

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1 15 D.Baatarkhuu, B.Myagmarsurn, othrs, Journal of agricultural scincs 15 (): , 15 A NEW DESIGN METHOD FOR A DUAL BAND BRANCH LINE HYBRID COUPLER D.Baatarkhuu*, B.Myagmarsurn, R.Baigalmaa School of Enginring and Tchnology, MULS *-Corrsonding author, -mail: baatar_khuu@yahoo.com ABSTRACT This ar rsnts th dsign of a dual band branch lin hybrid coulr(blhc) with diffrnt owr division ratios at two bands. In th roosd dsign, transmission lins of th BLHC ar transformd to ππty quivalnt circuits which rrsnt diffrnt imdancs and λ/4 lctrical lngth at two frquncy bands. In ordr to vrify th roosd mthod, a dual band coulr with diffrnt owr division ratios is dsignd for.9 GHz and GHz alications. Th dsird owr division ratios ar 1:1 and 1:3 at th two orating frquncy bands. Th masurd rsults show xcllnt rformanc with an insrtion loss of lss than.33 db, a rturn loss of lss than db, and good isolation charactristics. KEY WORDS: Dual band, branch lin hybrid coulr, imdanc, on stub. INTRODUCTION Information and communication systms hav always mattrd in agricultur as wll. Evr sinc ol startd growing cros, raising livstock or caught fish, thy hav sought information from on anothr for vryon s bnfit. Using siml communication tools, such as storytlling, wisdoms of th villag ldrs hav assd on gnrations aftr gnrations, with continuous knowldg addition from th community in ach stag. By using mobil hon tchnology, thr hav bn divrs tys of innovations taking lac in th agricultur sctor, which includ commodity and stock markt ric information and analysis, mtorological data collction, advisory srvics to farmrs for agricultural xtnsion, arly warning systms for disastr rvntion and control, financial srvics, tracability of agricultural roducts, agricultural statistical data gathring, tc. It is ar rdictd that th availability of broadband Intrnt, 3G and 4G connctivity will soon b availabl in rural aras. Th rics of smart hons ar dcrasing and thy ar bcoming affordabl. Tchnology thrfor is not considrd a major constraint although its adoion and adaation to local nds ar [1]. Dvlomnt of th modrn wirlss communication systms with various frquncy standards is accomanid by th activ usag of multiband microwav dvics. As a dirctional coulr is on of th bas comonnts of Radio Frquncy (RF) arts of ths systms and can b usd in structur of amlifirs, mixrs, has shiftrs and othr dvics, thrfor in rcnt yars much attntion is givn to nw schms for th coulrs, orating at two arbitrary frquncy bands. In th cas of widly usd branch-lin coulrs, a lot of dual-band schms ar roosd in th litratur. In th majority of rorts

2 D.Baatarkhuu, B.Myagmarsurn, othrs, Journal of agricultural scincs 15 (): , th structurs of rlativly siml two-branch-lin coulrs ar considrd, two-sction toology (tribranch-lin construction) has bn usd with th objct of bandwidth broadning. Among all varity of th offrd oions of a dual band two-branch-lin coulr ralization on can not th nxt main aroachs. It may b th usag of right/lft handd mt matrial transmission lins [] [3], th usag of strtchd sgmnts of lin [4] or mandr lins [5] for branchs imlmnting, th usag of schm in which all orts ar xtndd through a transmission lin sction [6]. Branch lin hybrid coulrs ar vry oftn usd for RF and microwav systm. Dividrs consist of on inut ort, two outut orts and isolation ort [4]- [5]. Th Branch lin hybrid coulr which is satisfid with all orts matchd with isolation btwn th outut orts is th most tyical dividr among thm. As shown in Fig. I, th branch lin hybrid coulr consists vrtical lin with imdanc aa, horizontal lin with imdanc bb and quartr wav lngth of transmission lin. Equations for calculating imdanc and lctrical lngth of a transmission lins ar found asily in standard litraturs [7]-[9]. Rcntly, a lot of work has bn rsntd dmonstrating multiband oration with on comonnt [1]-[14]. Thrfor, this ar rsnts a dual-band branch lin hybrid coulr with diffrnt owr division ratios at two bands. Th organisation of th rmaining art of this ar is as follows: Sction II dscribs th thoris and th roosd mthodology to oimis th siz of th branchlin coulr that includs th dtaild mathmatical calculation and simulation rocss. Dual-band branch-lin hybrid coulr is oimally dsignd, fabricatd and masurd. Th masurd rsults agrd wll with th simulation. Sction III and IV discusss th rsults obtaind from this simulation study and th dtaild analysis. Lastly, Sction V rovids th conclusion. b,9 Port1 Port a,9 Port4 Port3 Figur 1. A schmatic of a branch-lin hybrid coulr. METHODOLOGY Pi-ty quivalnt circuit It is known that th majority of branch lin hybrid coulrs hav th structur with on or two lans of symmtry. Whn th branch lin coulr in Figur 1 is dtrmind owr couling ratio btwn th two oututs, imdanc of ach lin is calculatd by th following formula: P P 3 c k () 1 P P d c : could ort, d : dirct ort a b k 1+ k Figur (a). shows a transmission lin with lin imdanc and lctrical lngth. It is rrsntd by th ππ-ty quivalnt circuit comosd of shunt stubs and a sris lin as shown in Figur (b). Th imdanc or admittanc valus of quivalnt circuit lmnts ar calculatd by quations (4) and (5). () () 3

3 154 D.Baatarkhuu, B.Myagmarsurn, othrs, Journal of agricultural scincs 15 (): , 15 In this cas, lctrical lngth of th lin has to oby th following condition to gt th sam Y in sin sin (4) cos j sin (5) υπ ω1+ ω 36 λ υ : vlocity of th wav λ: wavlngth at ω rorty at two angular frquncis ωω 1, ωω rsctivly. 1 (6) (7) Shunt suscancs should to b minus valu at a highr frquncy band by using th abov quation. It can b ralizd by using a shunt stub lin. Equations for lctrical lngth and imdanc of th stub lin ar shown as bllow. Y Y in, ω 1 in, ω Y Y tan tan (8), (a) Transmission lin Y in Y,, (b) ππ-ty quivalnt circuit Figur. Equivalnt circuit of a transmission lin. Dsign of a dual-band branch lin hybrid coulr To obtain wid band rformanc with branch lin hybrid coulr, it should b 1 sction branch lin hybrid coulr as shown in Figur 1. Each comonnt valus ar summarizd in Tabl 1. Th 1 sction structur as shown in Figur 1 can b transformd to th roosd dual-band schm by using (1)-(8). All imdancs and lctrical lngths of Figur 3 can b comutd, and th valus ar listd on Tabl.

4 D.Baatarkhuu, B.Myagmarsurn, othrs, Journal of agricultural scincs 15 (): , 15 Scifications of th dual-band BLHC Paramtrs ff 1 ff Cntr frquncy [GHz].9 Division ratio 1:1 1:3 Inut/outut imdanc ( ) 5 5 Vrtical lin imdanc ( aa ) Horizontal lin imdanc ( bb ) Each valu of th dual-band BLHC Imdanc [Ω] Elctrical lngth [dg] tt tt Tabl 1 Tabl b, b Port1 a a Port a a Port4 b, b Port3 in, t Figur 3. Schmatic of a roosd dual band BLHC Simulation and fabrication In ordr to vrify th roosd mthod, a dual-band branch lin hybrid coulr has bn dsignd, fabricatd and masurd. First of all, th simulation using th information in Tabl II has bn rformd, and th rsults ar shown in Figur 4. Figur 4 (a) shows th siz of th signal to b transmittd to ach ort. Th valus rformancs - 3.1dB and -3.1dB at.9ghz, -6.dB and - 1.8dB at GHz idal ratio of division. Isolation and rturn loss valus hav mor than -51 db. Figur 4 (b) shows th has diffrnc btwn th two outut orts. W can b confirmd a has diffrnc of 9 at.9 GHz and GHz dsign frquncis.

5 156 D.Baatarkhuu, B.Myagmarsurn, othrs, Journal of agricultural scincs 15 (): , 15 (a) Insrtion, rturn, and isolation loss (b) Phas diffrnc btwn two outut orts Figur 4. Circuit simulation rsults of th roosd dual band branch lin hybrid coulr. Figur 5. Photograh of th fabricatd a dual band BLHC Figur 5 shows a hotograh of th fabricatd dualband branch lin hybrid coulr. Th adod substrat was RT 588 with a dilctric constant of. and a thicknss of 31mils. (a) Insrtion, rturn, and isolation loss (b) Phas diffrnc btwn two outut orts Figur 6. Masurd rsults of th fabricatd circuit.

6 D.Baatarkhuu, B.Myagmarsurn, othrs, Journal of agricultural scincs 15 (): , RESULTS Fig.6 rsnt th masurd charactristics.th masurmnt rsult show that insrtion loss had an rror of lss than.33 db in ach db, db at low frquncis, rturn loss and isolation charactristics ar mor than db and -1.4 db. On th othr hand, th high frquncy show that insrtion loss had an rror of about.49 db in ach db, db, rturn loss and isolation charactristics ar mor than -.55 db and -.98 db. Figur 6 (b) shows th has diffrnc btwn th two outut orts. Th rang rror was 9±.74 at low frquncy of.9 GHz and 9±. at high frquncy of GHz. DISCUSSION Hirota's mthod to rduc th siz of a branch-lin hybrid coulr is widly adod in th dsign of dual-band dividrs [15]. In this study, a siz rduction of branch-lin coulr tchniqu using ight two-st stubs has bn rortd in. In comarison to convntional hybrid coulrs, th rducd siz coulr offrs lowr insrtion loss and highr comactnss (a significant rduction of 5% in th circuit ara). Additional dgrs of dsign choic can b obtaind by including shunt on stubs and all ths ar th rasons for th major rduction in siz. Th rducd siz coulrs ar otntial lmnts for th growing wirlss communications markt. Vry oular aroach in obtaining th dual-band oration of th branch-lin coulr is basd on th us of stub lins. Th structurs in which on-circuit or short-circuit stubs ar connctd to all inut orts ar roosd in [7]. Furthr similar dual-band structurs with som scializd functions wr considrd in [8] [1]. CONCLUSION A dual-band branch lin hybrid coulr with qual slit owr at two frquncis has bn roosd. A nw mthod to calculat th rquird lin imdancs and lctrical lngth for both frquncis was adod in modling a π-ty quivalnt circuit for two orating frquncy bands. Th formulas which satisfy th dsign conditions wr xtractd for all imdancs (suscancs) and lin lngths. In ordr to vrify th roosd mthod, th dual-band branch lin hybrid coulr was dsignd and masurmnts wr takn, for a O.9GHz cllular systm and a GHz 3rd gnration communication systm. Th masurd owr division ratios at two outut orts wr qual slit owr at both bands. It is anticiatd that th roosd dsign mthod can b alicabl for dualband oration dvic with only on comonnt. REFERENCES 1. Grard Sylvstr, Information and communication tchnologis for sustainabl agricultur 3rd d., Ra ublication 13/14, Food and agricultur organization of th Unitd Nations, rgional offic for Asia and th Pacific, Bangkok 13. Ivan PRUDYUS, Valriy OBORHYTSKYY, "Dsign of Dual-Band Two-Branch-Lin Coulrs with Arbitrary Couling Cofficints in Bands " Radio mginring, vol. 3, no. 4, , Dcmbr YU, C.-H., PANG, Y.-H. Dual-band unqualowr quadratur branch-lin coulr with could lins. IEEE Microwav and Wirlss Comonnts Lttrs, 13, vol. 3, no. 1, David M. Pozar, Microwav Enginring 3rd d., MA John Wily & Sons, Inc., Robrt E. Collin, Foundations for Microwav Enginring, nd d, Nw York: IEEE rss, Symour B. COHN, "A Class of Broadband Thr-Port TEM-Mod Hybrids," IEEE Trans. Microwav Thory & Tch., vol. MTT-16, no., , Fbruary S. Lim, U.-H. Park, Y.-C. Jong, K.-S. Choi, D.Ahn "8-5MHz ultra-widband CPW balun," Elctronics Lttrs., vol. 4, no. 18,., , August 6.

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