A compact low insertion loss bandpass filter based on meandered self-coupled ring resonator

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1 MTE Wb f nfrns 3, 0006 (07 ) DOI:0.05/mtnf/ IPMMT 07 mpt lw insrtin lss bnpss filtr bs n mnr slf-upl ring rsntr hing-hin hng,*, Kng-Xin hng, Hung-Kung Kung, hin-u Wng, n ng-huy Jng Institut f Mhtrnis Enginring, hng Shiu Univrsity, Khsiung ity, Tiwn Dprtmnt f Eltrni Enginring, Ntinl Frms Univrsity, unlin, Tiwn bstrt. Th tritinl strutur f ul m bnpss filtr is frm by irulr r rtngulr rsntr, whih uss xssiv iruit rs t b upi. 5. GHz bnpss filtr, bs n th tripl-brnh slf-upl ring rsntr, is sign t hiv mst ssntil fturs suh s lw insrtin lss, mpt siz, n wi stpbn. Th upling f h upl brnh intrus th vn- n -m prturbtin, whih pru shrp bnpss n wi stpbn rspnss u t th gnrtin f bn-g trnsmissin zrs. Th simultin n msurmnt in this ppr r rsptivly vrifi by using IE3D ltrmgnti simultr n gilnt s HP87 ntwrk nlyzr. Exprimntl rsults shw tht th filtr hs 9.% bnwith ntr t 5. GHz,. insrtin lss, 5 stpbn rtin frm 6 t 9 GHz. Mrvr, th iruit siz in this ppr hs bn wn t 9 6 mm n n b ppli t mmunitin f mirwv pplitins. Intrutin Th mpnnt f pssiv iruit, suh s th filtr upying th lrgst prntg f mmunitin systm strutur, is mr imprtnt t prsrv high prfrmn n ru th ltrni iruit siz. Mny rsrhs f ul-m bnpss filtr hv bn prps in pprs [-9]. Th bnpss filtrs bs n th ul-m ring rsntr ws first nlyz by Wlff []. Sm pprs prps ul m ring rsntr bnpss filtrs by using stp-impn r ring rsntrs with iffrnt prturbtin shms [-4]. Th prturbtin lmnt is plus t r ut frm th rsntr, n it is ls viw s pitiv r inutiv [5]. On f th mths is th invstigtin f signing mpt, lw insrtin lss n shrp rtin by s ul m ring rsntr [6]. Furthrmr, ul-m mirstrip filtrs r highly ttrtiv fr ri frquny systms bus thir sizs r mpt n sy t fbrit [7]. y ing pn stubs symmtrilly n ring rsntr, th ul m filtr is rliz [8]. Hwvr, thr is nvl istribut prturbtin by slf-upl sgmnts f th ring rsntr, whih brings th sir implmnttin shm [9]. In this ppr, th ring rsntr is bs n th thry f slfupl, simpl bnpss filtr with lw insrtin lss n th mpt siz sign, whih shw th sy strutur n nrrw bnwith with tw trnsmissin zrs nr th pssbn. This filtr f 5. GHz bn is sign. Th msurmnt rsults shw g nsnsus with simultin. Filtr sign Th tritinl strutur f ul m bnpss filtr is shwn in Fig.. Gnrlly, th filtr strutur is frm by irulr r rtngulr rsntr, whih uss xssiv iruit rs t b upi. T mk up fr th isvntg, th ring rsntr ws bn in this stuy t hiv th gl f sving th filtr siz. Input ` 35 symmtry 90 Output Fig.. Strutur f tritinl ul m bnpss filtr.. Shmti f prps bnpss filtr Unlik ths stuis in th pst using th prturbtin pprh, th ring rsntr with upling mth is ppli t us th vn n m t b sprt, n t hiv rsnn ffts. Thus, th filtr ffrs n vntg f simplr iruit lyut n is sir t b implmnt. Th shmti typs f th prps slf-upl bnpss filtr with input n utput prts r shwn in Fig.. Th prps bnpss filtr is mps f slf-upl ring rsntr with prlll- * rrspning uthr: hhing@kmvs.km.u.tw Th uthrs, publish by EDP Sins. This is n pn ss rtil istribut unr th trms f th rtiv mmns ttributin Lins 4.0 (

2 MTE Wb f nfrns 3, 0006 (07 ) DOI:0.05/mtnf/ IPMMT 07 upl input n utput ntwrks. Th slf-upl ring inlus ntrl upl brnh n tw thr upl brnhs, nnt t bth ns f th ntrl upl brnh. n intuitiv wy t unrstn this slfupl ring rsntr is th mnring f th nvntinl irulr ring rsntr suh tht th ring siz n b nsirbly minituriz. Diffrnt frm th lump prturbtin f th nvntinl ring rsntr, th istribut upling f th prps ring rsntr prvis th m prturbtin btwn vn n ms.. Rsnn nitins In Fig., th lyut isntinuity fft f bth upl stins r nglt, with th strutur f th ring rsntr symmtri t lin, n th vn- m thry ppli t nlyz th rsnn m hrtristis. Fig. 3() n (b) shw tht th quivlnt vn-m, -m iruits, th vn-m n m rsnn nitins n b riv frm qutin ()-(6) n ignr th upling supprt fft n bth sis f th bnt stin. Tw upl stins t ns hv th sm prmtrs: th ltril lngth f, th upling ffiint f, n th hrtristi impn. Th ntrl upl stin hs th ltril lngth f, th upling ffiint f, n th hrtristi impn f. Th vn m rsnn nitin bms Whr tn tn (3) t,,, f ; f r nrm upl stin / pn n () vn m upl stin g t W t g W g W input L L utput upl stin / upl stin symmtry pln Fig.. Strutur f prps upl-ring bnpss filtr. Th qutin riv is shwn s blw. Th quivlnt vn iruit f ul-m ring rsntr is shwn in Fig. 3 (). y lulting th input impn f th vn m, th vn m rsnts whn =. On th thr hn, th input mittn f th vn m =0. Thn tn t tn tn t tn 0 () tn t tn 0 () (b) m Fig. 3. Equivlnt vn n -m iruit f ul-m ring rsntr. Similrly, Th quivlnt iruit f ul-m ring rsntr is shwn in Fig. 3 (b), n th input impn vnishs whn th m rsnts, Thn t t tn tn tn tn 0 (4) t tn tn 0 (5) Th m rsnn nitin is btin s

3 MTE Wb f nfrns 3, 0006 (07 ) DOI:0.05/mtnf/ IPMMT 07 Whr tn tn t,,, fr ; f nrm f r (6) Unr th vn- m rsnnt frquny f r n, th,, n r th ltril lngths rsnnt frquny (GHz) =0. =0. fr fr f r,sr impn rti f Fig. 4. Rsnnt frqunis with rspt t th impn rti f. rrspning t th physil lngths n rsptivly. Thus, th rsnn frquny nitin is btin s f r f r f r. Sin th mplit frm f qutin ()-(6) is iffiult t btin th nlyti slutin, w us th grphi xprssin fr nlyzing th fft f th vnm n -m rsnnt frqunis with th impn rti n upling ffiints... Impn rti fft s but =0. n =0. is pltt in Fig. 4 n it shws th pnn f m rsnnt frqunis with rspt t th impn rti f with svrl hrtristis s blw. ) Whn impn rti =, th vn- n m rsnnt frquny r nt sprt. ) Whn impn rti <, th -m rsnnt is lwr thn th vn-m n hs th inutiv prturbtin ftur. 3) Whn impn rti >, th -m rsnnt frquny is highr thn th vn-m n th typ is in pitiv prturbtin stt. 4) Th gmtri vrg rsnnt frquny, f f f is pthtil t. r, SR r r Thrfr, ths rgumnts r trmin t supprt th prting bn n bnwith f th filtr in this ppr. () upling ffiint (b) upling ffiint Fig. 5. Rsnnt frqunis with rspt t th upling ffiint... hrtristis f upling ffiint Fig. 5 () n (b) r th rltiv rsnnt frquny btwn upling ffiint n fr iffrnt impn rtis unr th 38. Thr r svrl hrtristis s blw. ) Whn th upling ffiint inrss, th rsnnt frquny will inrs t ny impn rti. 3

4 MTE Wb f nfrns 3, 0006 (07 ) DOI:0.05/mtnf/ IPMMT 07 ) Whn <, th rsnnt frquny will inrs fllwing th inrmntl impn rti in th ny upling ffiint. 3) Whn >, th th rsnnt frquny will rs fllwing th inrmntl impn rti in th ny upling ffiint. 4) Whn =, it shws th highst rsnnt frquny..3 Trnsmissin zrs nlysis Th min vntg f th ring rsntr filtr is gnrting tw trnsmissin zrs nr th pssbn. us thr r tw trnsmissin pths btwn th input n utput prts, thrfr whn th urrnt f th tw pths is ffst h thr t th utput, th trnsmissin zrs n bth sis f th pssbn r gnrt. In this wy, -prmtr mtrix mth (mittn Mtrix Mth) is us t filitt th nlysis f trnsmissin zr gnrtin. Ignring th isntinuus fft f th iruit brnh bning, s shwn in Fig. 6, th ntir rsntr n b isssmbl int prlll upling lin with ltril lngth /, impn n prlll upling lin with ltril lngth, impn. Hr IO/, / n s th IO lngth f th ltril input btwn th input n th utput prt r fin, n ( ) t (7) ( ) t (8) 3 ( ) s (9) 4 ( ) s (0) ' ' ' ' ' ' ' ' ' tn t () ' tn t () t (3) upl stin upl stin 3 t s (4) (5) input utput Fig. 6. Slf-upling ring rsntr tw-wy trnsmissin pth quivlnt iruit. In Fig. 7, th qutins (7) t () r th frmuls fr th prlll upling mirstrip prmtr f th fur prts n th tw prts. Furthr, th frmuls (7) t () r nvrt int th fllwing frmuls (3) t (8) using th rltinship btwn th upling ffiint n th impn. prt prt () prt3 prt4 Fig. 7. prlll upling trnsmissin lin igrm () fur prt (b) tw prt. (b) prt' prt' 4 ' s t ' s sin (6) (7) (8) y using th frmuls (3) t (8), w n slv th psitin f trnsmissin zr in Fig. 6. Th trnsitiv frmul is shwn in qutin (9), n whn is zr, th trnsmissin zr is gnrt. ST G P u H Q u S T Q H Qu G Pu n within th frmul (9), (9) 4

5 MTE Wb f nfrns 3, 0006 (07 ) DOI:0.05/mtnf/ IPMMT 07 P u Q S u sin sin s, s, SG SG Q, T, H H btwn input prt n utput bing 60, 70, 80, 90, 00. It n b sn frm th Fig. 9 tht whn th ngl btwn th input n utput prt is 70 ~ 80, th pssbn n bth sis f th trnsmissin zr pints shws th mst symmtry. G T G H, H G H, Q Q H, Q T S Q Q, P P Q Q, S S T P P T S P, P P ST G Q, H P P T P, P P Fig. 8. rti f th nrmliztin frquny f rltinship igrm. P S t, s, Q T t, s. Th mplit frm f (9) mks it iffiult t btin th nlyti slutins in lultin. Thn w turn t th grphi xprssin f fr nlyzing th ffts f th impn rti n input-utput sprtin lngth [9]. IO.3. Efft f th impn rti Fig. 8 is th upling ffiint with n bing qul t 0., 40, 40 n rti bing 0.5,.0,.8 in th nrmliztin f th frquny f th rltinship igrm whn th ngl btwn th input n utput is 80 gr. s shwn in th Fig. 8, it n b fun tht thr is n trnsmissin zr n bth sis f th funmntl frquny pssbn whn th inutiv upling <. Whn > is pitivly upl, tw trnsmissin zrs r gnrt n bth sis f th pssbn n trnsmissin zr urs nr th sn pssbn. Whn =, th trnsmissin zr will ur nr th bs bn, strying th pssbn hrtristis..3. Efft f ngl btwn input n utput prts Fig.9 is th nrmliz frquny f rltinship igrm shwing whn th upling ffiint n r qul t 0., th rti is.8, with th ngl Fig. 9. shws th rltinship igrm iffrn btwn th input n utput prts t th nrmliz frquny. 3 Exprimntil rsults Fllwing th thrtil nlysis in stin, in this ppr, th upling ffiints n r ll us t 0., th ltril lngth 4, 38, th hrtristi impn is 09Ω, is 6.5Ω, n th impn rti =.77. Mrvr, th rltiv imnsins f th rsntr is quivlnt t W =. mm, W = 0.3 mm, W t =0. mm, L =8.5 mm, L =4.5 mm, g = 0.6 mm, g = 0.6 mm, n g t =0. mm. This filtr is fbrit n th substrt with rltiv iltri nstnt f 3.38, with lss tngnt bing n thiknss bing 0.76 mm. Th tul phtgrph f 5.GHz slf-upl bnpss filtr is shwn in Fig. 0. Th siz f slf-upl bnpss filtr is 9 x 6 mm. On th thr hn, th iruit siz is rltivly 54% f th siz t th tritinl unifrm ring s. 5

6 MTE Wb f nfrns 3, 0006 (07 ) DOI:0.05/mtnf/ IPMMT 07 shws th simult n msur rsults. Finlly, thr is vry g nsnsus btwn th msur n simult rsults in this ppr tht within GHz, th msurmnt rturn lss is grtr thn n msurmnt insrtin lss is lss thn. n this nitin imprvs th rspns f pssbn. Th msur 3- bnwith is but 9.% t th ntr frquny f 5. GHz. Th filtr hs thr trnsmissin zrs ls t th pssbn t 4.39 GHz, 6.4 GHz n 7.58 GHz, whih prus shrp bnpss n wi stpbn rspns. 4 nlusin Fig. 0. Phtgrph f 5. GHz bnpss filtr Simultin Msurmnt 5. GHz ul-m bnpss filtr hs bn prps in this stuy by using slf-upl ring rsntr fr smll siz, lw insrtin lss, wi stpbn n it is sy t implmnt. Th prps filtr siz is 9 x 6 mm, thr trnsmissin zrs r ls t th pssbn t 4.39 GHz, 6.4 GHz n 7.58 GHz, n th 3- bnwith is but 9.% frm 4.75 GHz t 5.73 GHz, n insrtin lss is lss thn. t ntr frquny 5. GHz. g nsnsus hs bn rh in this stuy by simultin n msurmnt shwing highly vlubl pplitin f prps bnpss filtr in wirlss mmunitins. S () -30 knwlgmnts Frquny (GHz) () Insrtin lss W wul lik t xprss ur sinr hrtflt thnks t ur suprvisr, Mr. Shng-Fuh hng, prfssr f Dprtmnt f Eltril Enginring, Ntinl hung hng Univrsity, hiyi, Tiwn, fr his invlubl vi n nstnt hlp n th ppr. Rfrns S () Simultin Msurmnt Frquny (GHz) (b) rturn lss Fig.. shws th msurmnt n simultin rsults f bnpss filtr. Th simultin n msurmnt r rsptivly vrifi by using IE3D ltrmgnti simultr n gilnt s HP87 ntwrk nlyzr [0]. Fig.. I. Wlff, N. Knppik, Mirstrip ring rsntr n isprsin msurmnts n mirstrip lins, Eltrn. Ltt., 7 (97). I. Wlff, Mirstrip bnpss filtr using gnrt ms f mirstrip ring rsntr, Eltrn. Ltt., 8 (97) 3. M. Mtsu, H. buki, M. Mkimt, Dul-m stpp-impn ring rsntr fr bnpss filtr pplitins, IEEE Trns. Mirwv Thry Th., 49 (00) 4. S. Lu, L. hu, nvl ul-m ul-bn bnpss filtr bs n singl ring rsntr, IEEE Mirw. Wirlss mpn. Ltt., 9 (009) 5. T.W. Lin, J.T. Ku, S.J. hung, Dul-M Ring Rsntr npss Filtr With symmtri Inutiv upling n Its Minituriztin, IEEE Trns. Mirwv Thry Th., 60 (0) 6. L.H. Hsih, K. hng, mpt, lw insrtin-lss, shrp-rtin, n wi-bn mirstrip bnpss filtrs, IEEE Trns. Mirwv Thry Th., 5 (003) 6

7 MTE Wb f nfrns 3, 0006 (07 ) DOI:0.05/mtnf/ IPMMT L. thukrl, D. uimir, mpt Dul-M Opn Lp Mirstrip Rsntrs n Filtrs, IEEE Mirw. Wirlss mpn. Ltt., 9 (009) 8. W. Fng, X. G, W. h, Q. Xu, npss Filtr L With Opn Stubs Using Dul-m Ring Rsntr, IEEE Mirw. Wirlss mpn. Ltt., 5 (05) 9..H. Jng, S.F. hng,.m. hn,.j. Hung, nvl slf-upl ul-m ring rsntr n its pplitin t bnpss filtrs, IEEE Trns. Mirwv Thry Th., 54 (006) 0. IE3D V0., ELND SOFTWRE, IN.,, U.S.. 7