High Directivity Microstrip Coupler Using Variable Width Structure

Transcription

1 IOS Jounal of Eletonis and Communiation Engineeing IOS-JECE e-issn: ,p- ISSN: Volume 9, Issue 4, Ve. V Jul - Aug. 04, PP 4-8.iosjounals.og Hig Dietivity Miostip Couple Using Vaiable Widt Stutue S.Maesai, T.Jayanty ea Sola, Satyabama Univesity, India Pinipal, Panimala Institute of Tenology, India Abstat: A metod to impove te dietivity of te miostip ouple is pented. Te idt of te ouple is modified fo pa veloity ompensation i esults in ig dietivity. Using tis poedue, a 5 db ouple is designed and simulated at 0.9 GHz using SONNET ftae. A ig dietivity of 46 db is obtained. Te validity of te design onept is veified and ompaed it onventional ouple by simulations. Keyods: oupled lines, dietional ouple, miostip, and mioave. I. Intodution Miostip ouples ae idely ud in mioave appliations su as antenna feeds, balaned mixes, modulatos, pa siftes and on. But, tey suffe fom poo dietivity, due to te inequality beteen te odd and even mode pa veloities. Vaious ompensation teniques ave been epoted to impove te dietivity. Te iggly line ouple [] impoves te dietivity and suffes due to lak of design equation. Te apaitive ompensation as ud to impove te dietivity []; oeve te apaito as to be plaed in te nao spaing beteen te oupled lines. Te indutive ompensation impoves te ilation and needs te iteation design poess [3,4]. Te oupled spu line [5], and efleted poe anelle appoa [6] ok itin a nao band. Te Epsilon negative tansmission line [7] as ud but it needs moe numbe of unit ells to impove te auay, i leads to fabiation diffiulty. Delay lines [8] ee ud, but te ouple oupies moe spae tan te onventional one. Te e-entant mode stutue [9], peiodi metalli ylindes [0], and metamateial [] ee al epoted to impove te ilation, ee te ouple onstution is omplex. Peiodi floating ondutos [] ee ud to impove te dietivity fo a ide bandidt fo a maximum dietivity of 30 db. In tis pape, te dietivity of te ouple is impoved, using te pa veloity ompensation metod. It is obtained by modifying te idt of te ouple. Te pa veloity of te even and odd modes an be vaied by vaying te distibuted indutane and apaitane of miostip lines of te ouple. Te distibuted paametes an be vaied by modifying te idt of te miostip ouple stutue. In te popod ouple, indutane and apaitane of te miostip lines ae vaied by vaying te idt of te miostip lines. In one miostip line, te idt of te miostip line is edued by intoduing slots at one end of te miostip line and inead at te ote end. In anote miostip line, te idt of te miostip line is kept onstant. Even toug te stutue beomes asymmeti, te aateisti impedane of ea miostip line is maintained to be 50oms by popely leting te idt of te miostip line. Using tis metod a 5dB miostip ouple is designed, and ilation of te ouple is impoved up to 64.4dB. Advantages of te popod metod ae tat te stutue is plana, tee is no speial fabiation tenique needed, onstution is simple and it does not equie any iteation design poess. II. Design Of Miostip Couple Te dimension atios of te miostip ouple ae alulated using te design poedue given in [3]. e assume tat pot impedane Zo, oupling db and, te opeational fequeny ae knon paametes at beginning of te design. Te even and odd impedanes, Z oe and Z oo, of te miostip ouple an be found as Zoe Zo Zoo Zo.iosjounals.og 4 Page

2 Hig Dietivity Miostip Couple Using Vaiable Widt Stutue.iosjounals.og 5 Page 4.4 exp exp 8 3 and ae te sape atios fo te equivalent single a oesponding to even mode and odd mode geomety espetively and ae found as Z oe 4 Z oo 5 Te oeted tem is given as Ten te spaing atio s an be found as s os os os os os 7 and te pysial lengt of te ouple is alulated using eff f l ee ε eff an be alulated using 9 as given in [4] t F eff ] 0.04[ F fo F fo ee, =3*0 8 m and f is opeational fequeny in Hz and ε eff is te effetive pemittivity onstant of te oupled stutue and t is te tikness of te onduto. III. Simulated esults Using te above design poedue a onventional 5dB miostip ouple is designed using F4 substate E = 4.4, =.6 mm it design values ae idt of te miostip line = 0.3 m, spaing beteen te lines s = 0.07m and te lengt of te ouple l = 4.6 m at 0.9 GHz. Te miostip ouple stutue is simulated using te SONNET ftae and is n in Fig. In te Fig, pot, indiates te input and toug pot. Pot 3, 4 indiates te oupled pot and ilated pot. Te simulated esults ae n in Fig.

3 Hig Dietivity Miostip Couple Using Vaiable Widt Stutue Fig.. Stutue of simulated onventional miostip ouple All dimensions ae in m Fig.. Simulated esult of a onventional miostip ouple Te simulation esults tat oupling value obtained is 4.dB it etun loss of 3.dB and intion loss of 0.37dB. Te miostip ouple as an ilation of 5.3dB at 0.9GHz. Tus te onventional ouple as a dietivity of db only. Te dietivity of te ouple an be impoved using pa veloity ompensation metod. In one miostip line, te idt of te miostip line is edued by intoduing slots at one end of te miostip line and inead at te ote end. In anote miostip line, te idt of te miostip line is kept onstant. Using tis metod a miostip ouple is designed it design values ae same as tat of onventional miostip ouple in addition to tat, in miostip line te dimensions of dept and idt of te slot is = 0.8m and =0.4m and additional inea in idt is q = 0.9m fo a lengt of p=0.7m. Tee ae tee slots ae ud in te design it same slot dimensions. Te peiod beteen te slots is m. All te dimensions ae n in m in Fig. Te simulation is done using SONNET ftae. Te paametes,, p & q ae optimized fo ige dietivity in simulation. Te simulated stutue of te popod ouple is n in Fig 3. Te simulated esults of te popod ouple ae n in Fig 4. Fig. 3. Stutue of popod miostip ouple.iosjounals.og 6 Page

4 Hig Dietivity Miostip Couple Using Vaiable Widt Stutue Fig 4. Simulated esults of popod ouple Fo te popod ouple, a maximum ilation of 64.4 db is obtained fo 0.93GHz in simulation. Te simulated oupling is 8.6 db at 0.9GHz. A maximum dietivity of 46 db is obtained at 0.93GHz. Fo a onventional ouple te ilation is 5dB only. Tus te popod ouple impoves te ilation up to 64.4 db. Te simulated value of intion loss and etun loss ae 0.4dB & 36.dB i ae bette tan te onventional ouple. Te ompain beteen te simulated esults of te popod ouple and onventional ouple ae n in Figs 5 &6. Te limitation of te ouple is its nao bandidt. Te dimensions of te slot uld be leted popely fo te equied oupling otei te oupling ill be edued. Fig 5. Compain of S & S of onventional and popod ouple Fig 6. Compain of S 3 & S 4 of onventional and popod ouple IV. Conlusion A miostip ouple it ig dietivity as been pented. Te ouple idt is modified to ange te patten of te stutue fo pa veloity ompensation. Using tis poedue, 5 db miostip ouple is designed and simulated at 0.9 GHz using SONNET ftae. A ig dietivity of 46 db is obtained. Te ouple stutue is plana and onstution is simple. It an be ud fo FID appliations. efeenes []. A. Podell, A ig dietivity miostip ouple tenique, in IEEE MTT-S Int. Mio. Symp. Dig., pp.33-36, May, 970. []. M. Dydyk, Miostip dietional ouples it ideal pefomane via single-element ompensation, IEEE Tans. Mio. Teoy Te., vol.47, no. 6, pp , Jun [3].. Pomloungsi, M. Congeaamnan, and I. D. obetn, Indutively ompensated paallel oupled miostip lines and tei appliations, IEEE Tans. Mio. Teoy &Te., vol.54, no.9, pp , Sep.006. [4]. S. Lee and Y. Lee, An induto-loaded miostip dietional ouple fo dietivity enanement, IEEE Mio. Wieless Compon. Lett., vol. 9, no. 6, pp , Jun iosjounals.og 7 Page

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