90 and 180 Phase Shifter Using an Arbitrary Phase-Difference Coupled-line Structure

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1 This articl has bn accptd and publishd on J-STAGE in advanc of copyditing. Contnt is final as prsntd. IEICE Elctronics Exprss, Vol.* No.*,*-* 90 and 80 Phas Shiftr Using an Arbitrary Phas-Diffrnc Coupld-lin Structur Yzi Dong, Luhong Mao a), Qiwi Song, Shng Xi School of Elctrical and Information Enginring, Tianjin Univrsity, Tianjin 30007, China Institut of Automation, Chins Acadmy of Scincs, Bijing, 0090, China a) Abstract: In this papr, an arbitrary phas-diffrnc structur using short-circuit stubs and coupld-lin with wak coupling is prsntd. Compard with convntional coupld-lin phas shiftrs, th proposd coupld-lin configuration covrs a wid phas rang ovr a broad band. Th simulation xhibits a phas rang from 5 to 80. To vrifid th configuration, 90 and 80 phas shiftrs ar fabricatd and masurd. According to th masurmnt rsults, both 90 and 80 phas shiftrs achiv bandwidths ovr 60% with in-band prformanc of rturn loss gratr than 0 db, insrtion loss lss than db, and phas dviation lss than ±5. Kywords: Arbitrary phas-diffrnc, coupld-lin, phas shiftr Classification: Microwav and millimtr wav dvics, circuits, and systms Rfrncs IEICE 07 DOI: 0.587/lx Rcivd Sptmbr, 07 Accptd Octobr 6, 07 Publicizd Octobr 3, 07 [] Q. Liu, and Y. A. Liu.: A compact ultra-widband quadratur hybrid basd on coupld-lin phas shiftr and powr dividr, Microw. Opt. Tchnol. Ltt., 57 [] (05) 3. [] B. M. Schiffman.: A nw class of broad-band microwav 90-dgr phas shiftrs, IRE Trans. Microw. Thory Tch., (958) 3. [3] J. L. R. Quirart and J. P. Starski.: Novl Schiffman phas shiftrs, IEEE Trans. Microw. Thory Tch., [] (993) 9. [] Q. Liu, Y. t al.: Widband singl-layr 90 phas shiftr using stppd impdanc opn stub and coupld-lin with wak coupling, IEEE Microw. Wirlss Compon. Ltt., [3] (0) 76. [5] P.Huang and H. Lu.: Broadband Low Phas Error Phas Shiftr Using High-Pass Ntwork With a Coupld Lin Sction, IEEE Microw. Wirlss Compon. Ltt., 5 []

2 (05) 775. [6] S. Y. Eom.: Broadband 80 bit phas shiftr using a λ/ coupld lin and paralll λ/8 stubs, IEEE Trans. Microw. Thory Tch., [5] (00) 8. [7] X. Tang and K. Mouthaan.: Dsign of a UWB phas shiftr using shunt λ/ stubs, IEEE MTT-S Int. Microw. Symp. Dig., (009) 0. [8] S. Y. hng, W. S. Chan, and K. F. Man.: Broadband phas shiftr using loadd transmission lin, IEEE Microw. Wirlss Compon. Ltt., 0 [9] (00) 98. [9] A. M. Abbosh.: Ultra-widband phas shiftrs, IEEE Trans. Microw. Thory Tch., 55 [9] (007) 935. [0] A. M. Abbosh.: Broadband fixd phas shiftrs, IEEE M icro w. W irlss Compon. Ltt., [] (00). [] L. Guo, H. hu, and A. Abbosh,: Widband Phas Shiftr With Wid Phas Rang Using Paralll Coupld Lins and L-Shapd Ntworks, IEEE Microw. Wirlss Compon. Ltt., 6 [8] (06) 59. Introduction Phas shiftr is widly usd in modrn microwav systms. It is a critical componnt in bamforming applications, such as phas-array antnna systms and intllignt antnna systms. Morovr, phas shiftr can connct with powr dividr to work as a thr-port hybrid with spcific phas diffrnc in microwav applications []. Svral kinds of structurs hav bn proposd to achiv broadband phas shiftrs with diffrnt dgrs. Th convntional Schiffman phas shiftr [] and som modifid configurations [3-5] can achiv a narly constant phas shift ovr a wid band, but it is difficult to obtain a phas shift mor than 90 du to th rquirmnt of xtrmly tight coupling which rsults in unralizabl narrow coupling gaps. A modifid configuration basd on Schiffman phas shiftr with paralll opn and short λ/8 stubs was prsntd in [6] which is suitabl for larg phas shifts such as 90 and 80. Transmission lin loadd with short-circuit stubs can raliz a phas shift rang from 0 to 70 ovr a larg bandwidth [7]. Manwhil, transmission lin loadd with opn-circuit stub can achiv a phas shift rang from 60 to 0, and a bandwidth of 8% is obtaind for 90 phas shiftr using T shap opn stub [8]. Broadsid coupling structurs can achiv a phas rang from 5 to 8 with on sction [9] or from 30 to 90 with two sctions [0] across th ultra-widband (UWB). Howvr, this structur rquirs thr layrs of printd circuit board (PCB) which may caus incompatibility with othr componnts during circuit intgration. Aiming at widband wid phas shift rang dsign, a structur using paralll coupld lins and L-shapd ntworks was prsntd in [], which achivd a phas shift rang from 5º to 80º across 00% fractional bandwidth. In this papr, a broadband arbitrary phas-diffrnc structur using short-circuit stubs and coupld-lin with wak coupling is prsntd. In Sction II, th proposd structur is analyzd by using vn- and odd-mod analysis. Th simulations xhibit that th proposd coupld-lin configuration can achiv a

3 wid phas shift rang from 5 to 80 ovr a bandwidth gratr than 60%. For vrification, 90 and 80 phas shiftr ar fabricatd and masurd in Sction III. Circuit Dsign and Analysis Th topology of proposd arbitrary phas shiftr is shown in Fig. (a). Th phas shift path (Path ) consists of a coupld-lin and thr paralll short-circuit stubs. On of th short-circuit stub with charactristic impdancs and lctrical lngth θ is connctd to th middl of coupld-lin with vn- and odd-mod charactristic impdancs and o. Th othr two stubs with charactristic impdanc and lctrical lngth θ ar connctd to th nds of coupld-lin. Th rfrnc path (Path ) uss two short-circuit stubs loadd onto a transmission lin instad of a simpl rfrnc lin. This topology provids additional dgrs of frdom for dsign to raliz diffrnt phas shift. Fig. Th proposd arbitrary phas shiftrs (a) topology, (b) vn- and odd-mod quivalnt circuit. Th S-paramtrs of both phas shift path and rfrnc path can b found with th vn- and odd-mod analysis tchniqu. Th quivalnt vn- and odd-mod sub-circuit of th dsignd phas shiftr is shown in Fig. (b). Th rflction cofficints Γ and S-paramtrs of both paths can b xprssd as i 0 Γ i, i + 0 oi 0 Γ oi, for i or 3 () oi + 0 Γi + Γoi Γi Γoi Sii Sij for i, j +, () S S Γ i Γoi Γ ji jj i Γoi or i 3, j whr i and oi (i or 3) ar th vn- and odd-mod input impdanc of port and 3, and 0 is th port impdanc which is qual to 50 Ω. According to Fig. (b), th vn- and odd-mod input impdanc of ach path can b calculatd as ( + ) j + + (3) 3

4 3 j tan tan () o o j + o (5) o 3 j 3 tan + 35 tan (6) 3 tan tan 5 ( S ) Phas ( ) ΔΦ Phas S (7) 3 whr ΔΦ is th proposd phas diffrnc of two path. By introducing short-c ircuit stubs and 5, xtra variabls ar addd to th quations of vn- and odd-mod impdanc of ach path. A phas shift mor than 90 can b achivd with wk coupling. A simulation xampl of phas diffrncs varid from 5 to 80 with a stp siz of 5 is shown in Fig.. In this xampl, th paramtrs of coupld-lin ar st as constant whr 60 Ω, o 30 Ω, and θ 90 at cntr frquncy f 0. Th rang of charactristic impdancs of th rst of microstrip lins is btwn 30 and 00 Ω whr th width of microstrip lin is ralizabl on PCB. Th lctrical lngths θ, θ, and θ 5 ar varid from 60 to 00. Th lngth diffrnc btwn θ 3 + θ and θ approachs to ΔΦ. As a constraint condition, th in-band insrtion loss is lowr than 0.5 db and rturn loss is gratr than db for ach paths. Th simulatd rsult shows that th proposd configuration can achiv about 70% bandwidth for phas dviation of ±5 in a wid phas shift rang. Th proposd coupld-lin structur shows good potntial to raliz broadband arbitrary phas shiftr with wak coupling.

5 Fig. Simulation xampl of th proposd configuration. Fig. 3 Simulation xampl of a 90 bandpass phas shiftr. Bsids th larg phas shift rang, th introducing of short-circuit stubs also provid a band-pass fatur to both phas shift path and rfrnc path. Th phas shiftr can achiv th dsird phas diffrnc and offr a function of bandpass filtr at th sam tim. A simulation xampl of a 90 bandpass phas shiftr is dmonstratd in Fig. 3. In this simulation xampl, th phas shiftr achivs a 60% bandwidth for phas dviation lss than ±5 and rturn loss gratr than db. At th sam tim, th phas shift path (S) and rfrnc path (S3) hav similar transmission charactristics. Both paths dmonstrat bandpass fatur and th passband of ach path is almost th sam. Howvr, th bandwidth will dcras, if th similar bandpass fatur is targtd in dsign. Th phas shiftr 5

6 with a bandpass fatur is usful in th front nd of rcivr. It can connct with a low-pass powr dividr to constitut a thr-port hybrid with arbitrary phas shift and bandpass function. 3 Implmnt and Exprimnt Rsults For xprimntal vrification, th 90 and 80 phas shiftrs wr prototypd. Th dsignd microstrip circuits wr built on a Rogrs 003C with a dilctric constant of 3.38 and a thicknss of.5 mm. Th spacing gap in coupld-lin of ach dsign is 0. mm. Th photographs of th implmntd 90 and 80 phas shiftrs ar shown in Fig.. Th board siz of 90 phas shiftr is 7 5mm, and th board siz of 80 phas shiftr is 80 5mm. Bcaus a thick PCB is usd, wid microstrip lin is rquird. Additional short lins ar ndd to connct th coupld-lin and short-circuit stubs and kp a distanc btwn paralll lins. This rsults in a slightly diffrnc btwn th ralizations and topology. In th ralization of 80 phas shiftr, stppd impndnc short-circuit stub is mployd to compos stub in phas shift path. Fig. Th photograph of th dsignd phas shiftrs: (a) 90, (b) 80. Th fabricatd phas shiftrs ar masurd by Kysight E507C ntwork analyzr. Th phas shift path (Path ) and rfrnc path (Path ) of phas shiftrs was tstd sparatly to obtain th two-port S-paramtr of ach path. Whn on path is tstd, both ports of th othr path ar connctd to a 50 Ω load. Fig. 5 and Fig. 6 dmonstrat th masurd rsults of 90 and 80 phas shiftr. In ths figurs, S rfrs th phas shift path, and S3 rfrs th rfranc path. Du to th nonidal I/O connctrs and th ffct of xtra conncting lins, th bandwidth of fabricatd phas shiftrs is a bit wors than simulations of thortical topology. But th masurd rsults showd that both 90 and 80 broadband phas shiftrs can b ralizd using coupld-lin with wk coupling which is in good agrmnt with simulations. 6

7 Fig. 5 Th masurd S-paramtrs and phas diffrnc of 90 phas shiftr. In th masurmnt of 90 phas shiftr, th insrtion loss of phas shift path is lss than db in th rang of GHz, and th minimum insrtion loss of ach path within this frquncy rang is about 0. db. Th phas dviation of 90 phas shiftr is lss than ±5 in th rang of GHz. Within this frquncy rang, th rturn losss of both paths ar bttr than 0 db. Th masurd bandwidth of th proposd structur is dfind by th rturn loss bttr than 0 db, insrtion loss lss than db, and phas dviation lss than ±5, thrfor, th fabricatd 90 phas shiftr achivd 65% bandwidth from.75 to 3.5 GHz, and th in-band insrtion loss diffrnc btwn two paths is lss than 0.3 db. Fig. 6 Th masurd S-paramtrs and phas diffrnc of 80 phas shiftr. 7

8 In th masurmnt of 80 phas shiftr, th phas dviation is lss than ±5 in th rang of GHz. Within this frquncy rang, both paths can achiv a rturn loss bttr than 0 db. Th insrtion loss of phas shift path is lss than db in th rang of.5-.9 GHz, and th minimum insrtion loss of ach path within this frquncy rang is about 0.3 db. Using th sam bandwidth dfinition, th fabricatd 80 phas shiftr achivd 6% bandwidth from.55 to.95 GHz, and th in-band insrtion loss diffrnc btwn two paths is lss than 0.5 db. Th masurd rsults vrifid that th proposd phas shiftr structur using short-circuit stubs and coupld-lin with wak coupling can achiv wid phas shift rang with ovr 60% bandwidth. Conclusion A broadband arbitrary phas-diffrnc structur using short-circuit stubs and coupld-lin with wak coupling was prsntd in this papr. Th vn- and odd-mod analysis was mad for th proposd topology. To vrifid th wid phas shift rang of th proposd coupld-lin structur with wak coupling, th simulation of diffrnt dgrs from 5 to 80 was givn in th cas that fasibl microstrip lin is usd. In furthr discussion, th bandpass faturs of both paths is shown with a simulation xampl which obtaind similar pass band in two paths. For xprimntal vrification, 90 and 80 phas shiftr wr fabricatd and masurd. As th proposd structur can provid arbitrary phas shift in broadband, it may b usd for any phas bit in bamforming applications or connct with a powr dividr to constitut a broadband thr-port arbitrary phas-diffrnc hybrid. Acknowldgmnts This work is supportd in part by th National Natural Scinc Foundation of China (No ) and by th National Natural Scinc Foundation of China (No. 6370) and by Guangxi Ky Laboratory of Prcision Navigation Tchnology and Application, Guilin Univrsity of Elctronic Tchnology (No. DH053). 8