Fivecompactmillimeter-wave 900and1800 distributed couplers arerealized intheback-end-of-the-line ofa 0.13gm SiGeBiCMOStechnology. Langecouplers smaller than 160gmonaside havebeenimplemented showing -4dBthrough, -5dBcoupling, 14dBreturn loss, and15dBisolation for60-and 77-GHzversions. Ringhybrids withphase-inverters havebeen implemented showing -4dB through, -5.6dB coupling, 18dB return loss, and21dBisolation for60-and77-GHzversions. The rings aresmaller than330,umonaside. IndexTerms- Langecoupler, ringhybrid, rat-race coupler, phaseinverter, silicon distributed passive circuits, millimeter- wavesilicon, 60GHz,77GHz,Eband, V band, W band. I.INTRODUCTION Themillimeter-wave frequency spectrum hasgained alotof attention duetotheavailability ofextremely widefractional bandwidths andreduced antenna sizes. Twobandsofinterest areat60 GHz forwireless personal areanetwork and directional linkapplications and77GHzforadaptive cruise- control radar. Commercially available silicon technology presents acost-effective option torealize highly integrated systems forthese markets. Ithasbeenshownearlier that circuit design atthese frequencies wouldnecessarily involve a combination ofanalog andmicrowave design techniques and mightevenincorporate transmission lines, splitters, and couplers (1), (2). Specifically, 900and1800 hybrid couplers areuseful forquadrature ordifferential LO generation, balanced amplifier designs, various mixertopologies, and baluns. Thesecouplers should becompact andlowloss to minimize areaandmaximize performance. Thispaperpresents compact, low-loss Langeandring- hybrid couplers at60and77GHzimplemented ina0.13-gm SiGeBiCMOStechnology. Thehybrids areimplemented completely intheback-end-of-the-line (BEOL)ofthe technology tominimize oreliminate theeffects ofthelossy silicon substrate. Thin-film microstrip (TFMS)transmission line wasusedtoimplement theLangecouplers, while finite- ground coplanar waveguide (FGCPW)wasusedtoimplement thering-hybrids. Allofthecouplers weredesigned using IE3D, amethod-of-moments based EM simulator. Theback-end-of-the-line
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