Good Practice Guide on Making Rectangular Waveguide Connections at Frequencies above 100 GHz

Good P ac ice Guide on Making Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz Tho s en P obs , Ka s en Kuhlmann, Nick Ridle , James Wa s July, 2019 This documen and all pa s con ained he ein a e p o ec ed by copy igh and a e subjec o he C ea i e Commons use license CC BY-ND 4.0 (h ps://c ea i ecommons.o g/licenses/by-nd/4.0/deed.en). ; Sugges ion o he quo a ion o he e e ences: P obs , Tho s en ; Kuhlmann, Ka s en ; Ridle , Nick ; Wa s, James. Good P ac ice Guide on Making Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz, 2019. Physikalisch-Technische Bundesans al . DOI: h ps://doi.o g/10.7795/530.20190805 Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz Acknowledgemen The au ho s acknowledge suppo by he Eu opean Me ology P o- g amme o Inno a ion and Resea ch (EMPIR) P ojec 17SIP08 “New Wa eguide In e aces o Te ahe z Technologies”. The EMPIR p og am is co- inanced by he pa icipa ing coun ies and om he Eu opean Union’s Ho izon 2020 esea ch and inno a ion p og am. Con en s 1 In oduc ion 1 1.1 O e iew o ec angula wa eguide s anda d documen s . . . 1 1.2 Wa eguide designa ion and compa ibili y . . . . . . . . . . . 3 1.3 Rec angula wa eguide basics . . . . . . . . . . . . . . . . . . 3 2 The IEEE 1785 se ies o s anda ds 5 2.1 IEEE S d 1785.1-2012 . . . . . . . . . . . . . . . . . . . . . . 6 2.2 IEEE S d 1785.2-2016 . . . . . . . . . . . . . . . . . . . . . . 6 2.3 IEEE S d 1785.3-2016 . . . . . . . . . . . . . . . . . . . . . . 7 3 Pe o ming p ecise measu emen s 9 3.1 P epa a ions ........................... 9 3.2 Measu emen se -up . . . . . . . . . . . . . . . . . . . . . . . 11 3.3 Somep ac ical ips........................ 13 3.3.1 Use o a p ecision wa eguide sec ion as a es in e ace 14 3.3.2 Di e en wa eguide ape u es . . . . . . . . . . . . . . 14 3.3.3 Wa eguide o coaxial adap e s . . . . . . . . . . . . . 14 3.4 Example Measu emen s . . . . . . . . . . . . . . . . . . . . . 15 3.4.1 Measu emen s o 75 o 110 GHz: WR10 / WM-2540 / R 900 / WG 27 . . . . . . . . . . 16 3.4.2 Measu emen s o 220 o 330 GHz: WR3 / WM-864 / R 2.6k / WG 32 . . . . . . . . . . . 21 4 So wa e 23 4.1 So wa e o Unce ain y Calcula ion o Wa eguide Connec ions 23 Re e ences 24 h ps://doi.o g/10.7795/530.20190805 i Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz Pu pose A equencies o app oxima ely 100 GHz and abo e, ec angula me allic wa eguide is o en he p e e ed ansmission medium o making eliable, p ecision, measu emen s. A p e equisi e o hese ypes o measu emen s is he use o he co ec ypes o wa eguide in e ace, and, he need o ollow he co ec ope a ing p ocedu es. This documen is aimed a people in e - es ed in making ep oducible measu emen s wi h ela i ely low measu emen unce ain y, in ec angula wa eguide, a hese equencies. I can be con- side ed as a suppo ing documen o exis ing s anda ds ha a e a ailable o wa eguide and wa eguide in e aces used a hese equencies (e.g. as published by IEEE, IEC, MIL, EIA, e c). This documen concen a es on ec angula wa eguides. Howe e , many aspec s ha a e p esen ed migh also be applicable o ci cula wa eguides. h ps://doi.o g/10.7795/530.20190805 ii Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz 1 In oduc ion 1.1 O e iew o ec angula wa eguide s anda d documen s Today he IEC and IEEE a e he wo main in e na ional s anda disa ion bodies o ec angula wa eguides o use a equencies abo e 100 GHz. O he s anda disa ion bodies, such as Uni ed S a es Mili a y (MIL), he Elec onic Indus ies Alliance (EIA) o he Uni ed Kingdom Minis y o De ence (MoD), a e also e e enced by some manu ac u e s, al hough some o hese documen s a e no longe main ained. Table 1 lis s he la es edi ions o hese documen s. S anda d Dimension In e ace Pub- lica- ion yea max / GHz MIL-DTL-85/3D X X 2012 325 S d1785.1-2012 [1] X X 2012 3300 IEC 60153-2:2016 [2] X X 2016 3300 EIA RS-261-B:1979 X X 1979 325 MIL-DTL-3922/67E w/Amendmen 1[3] X2014 110 IEEE S d1785.2-2016 [4] X2016 3300 IEC 60154-2:2016 [5] X2016 3300 Table 1. Selec ion o exis ing s anda ds o ec angula wa eguides. Usually, one s anda d p o ides in o ma ion conce ning he equency bands and he associa ed wa eguide ape u e sizes, and ano he s anda d desc ibes he wa eguide in e aces (also e e ed o as langes). In he 5 h column o Table 1, max indica es he highes equency he s anda d suppo s. In 2012 and 2016 IEEE and IEC published new s anda ds o co e equency bands up o he e ahe z equency egion [1], [2], [4], [5]. Figu e 1 shows an example o a wa eguide lange used a millime e(mm)- wa e equencies and abo e. Usually, he wa eguide opening (ape u e) is cen ed, while he alignmen and connec ion mechanisms (i.e. dowels, holes, and h eaded holes) a e placed a ound he ape u e. A mo e comple e o e iew abou exis ing wa eguide sizes and langes can be ound in [6]–[9]. h ps://doi.o g/10.7795/530.20190805 1 o 25 Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz an i- cocking ing align- men pin h eaded hole WG ap- pe u e p ecision alignmen holes boss align- men hole ab Fig. 1. Example lange o ec angula wa eguide. Wa eguide Designa ion IEEE MoD IEC EIA / GHz WM- WG R WR 2540 27 900 10 75-110 2032 28 1.2k 8 90-140 1651 29 1.4k 7 110-170 1295 30 1.8k 5 140-220 1092 31 2.2k 4 170-260 864 32 2.6k 3 220-330 710 - 3.2k - 260-400 570 - 4k - 330-500 470 - 5k - 400-600 380 - 6.2k - 500-750 310 - 7.4k - 600-900 250 - 9k - 750-1100 200 - 12k - 900-1400 164 - 14k - 1100-1700 130 - 18k - 1400-2200 106 - 22k - 1700-2600 86 - 26k - 2200-3300 Table 2. O e iew o ec angula wa eguide designa ions o selec ed equencies[6]. h ps://doi.o g/10.7795/530.20190805 2 o 25 Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz 1.2 Wa eguide designa ion and compa ibili y Table 2 gi es an o e iew o some common wa eguide designa ions. The ecommended equency anges speci ied in he di e en s anda ds migh a y sligh ly, hus ounded alues a e used he e. Mos s anda dised langes om IEEE and IEC a e mechanically compa ible wi h olde designs (e.g. om MIL, EIA, MoD, e c.) o he same ype o lange and compa ible wi h each o he , hough he elec ical pe o mance migh be signi ican ly deg aded [10]. One excep ion is IEEE 1785.2c, which is a plug and jack design. Only he plug ype design is compa ible wi h he o he langes. In p ac ice, many manu ac u e s o wa eguide componen s o use a equen- cies abo e 100 GHz ha e chosen o mi iga e his pe o mance deg ada ion by de ia ing om he s anda d designs. This is ypically achie ed by inc easing he diame e o he alignmen pins o educing he diame e o he alignmen holes. Whils hese non-s anda d langes can s ill be ma ed wi h each o he and wi h s anda dised lange designs, some combina ions o manu ac u e s’ langes will no ma e a all due o he impac o ole ances on he c i ical dimensions. I i is no known which s anda ds a pai o langes ollows, one mus make he connec ion e y ca e ully. Mos wa eguide in e aces ollow a simila connec ion s a egy. The e is basically one lange design o se e al equency bands, and he alignmen is ealised ia holes and dowels wi h a ce ain p ecision. Howe e , he e a e some excep ions, e.g. lange ype G (IEC 60154-2:2016 [5]). In IEEE 1785.2-2016, he e a e ac ually h ee di e en langes designs, and he align- men mechanisms a e somewha di e en when compa ed o each o he , o o lange designs gi en in o he s anda ds. This will be desc ibed in de ail in Sec ion 2.2. A mo e comple e o e iew o lange compa ibili y can also be ound in [6], [9]. 1.3 Rec angula wa eguide basics In his sec ion, some equa ions a e gi en ela ing o he p opaga ion cha ac- e is ics o hese wa eguides. This kind o in o ma ion is usually p o ided by wa eguide manu ac u e s. The cu -o equency c o he ec angula wa eguide [1] is c=c √ · 1 2·a(1) whe e c : is speed o elec omagne ic wa es in acuum, de ined as 299 792 458 m/s  : is ela i e pe mi i i y h ps://doi.o g/10.7795/530.20190805 3 o 25 Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz a: is wa eguide b oad wall dimension The a enua ion cons an αcan be app oxima ed [1] wi h α= 0.023273 · ρ ρ0· 1 b√a· c2 +2·b a q c·  c2 −1 dB/cm (2) whe e ρ: is esis i i y o he wa eguide conduc o ρ0: is e e ence esis i i y = 17.241 nΩ·m a: is wa eguide b oad wall dimension in mm b: is wa eguide na ow wall dimension in mm c: is cu -o equency in GHz : is equency a which a enua ion cons an is calcula ed in GHz Equa ion (2) does no hold o hinly pla ed su aces (e.g. whe e he pla ing hickness is less han wo imes he skindep h) and also neglec s any e ec s due he su ace oughness o he wa eguide o o he de ec (e.g. c acks o gaps in he in e nal co ne s o he wa eguide). The skindep h [11] is δ= ρ π µ = 2ρ ωµ =1ρ RS (3) whe e µ: is pe mi i i y RS: is su ace esis ance G ea ca e should be aken in using his equa ion o wa eguides whe e he wa eguide c oss sec ion is no o med om a single conduc o (e.g. wa eguides o med om a machined channel and a la co e ). Impe ec conduc ion a he joins o hese pa s can gi e ise o signi ican ly g ea e a enua ion. The in o ma ion gi en in his sec ion is only accu a e o single mode ope - a ion and o he i s T ans e se E lec ic mode TE 10 . This means, ha he elec ic ield is ans e se o he di ec ion o p opaga ion, while he magne ic ield has componen s in he di ec ion o p opaga ion. Field illus a ions can be ound e.g. in [11]. The ield o ien a ion o he TE 10 mode is also he eason o he naming o he wo e e ence planes E-plane and H-plane in ec angula wa eguides (see Figu e 2). The e ms E-plane and H-plane a e also used in an enna measu emen s and o o he mic owa e de ices o indica e he o ien a ion o he pola isa- ion o o he elec omagne ic adio wa es. h ps://doi.o g/10.7795/530.20190805 4 o 25 Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz E-plane H-plane a b ; Fig. 2. Re e ence planes in ec angula wa eguides. 2 The IEEE 1785 se ies o s anda ds A a ound he beginning o his cen u y, he e was a signi ican inc ease in use o he millime e-wa e pa o he spec um o comme cial applica ions in elec onics, ma e ials science and communica ions. In esponse o his inc ease in usage, comme cial es equipmen g adually became a ailable. Companies such as OML [12] o RPG [13] s a ed de eloping accesso ies o ec o ne wo k analyse s ha enabled he ope a ing equency o be ex ended abo e 110 GHz [14]. These measu emen capabili ies we e ex ended subsequen ly o a leas 500 GHz [15]. O he companies, such as VDI [16], con inued his end, de eloping sys ems ha ope a ed o beyond 1 THz [17]. Du ing he i s decade o his cen u y, he e was a ealisa ion ha knowledge and s anda disa ion o wa eguide a hese equencies was a he limi ed [18]. Schemes we e subsequen ly p oposed o ex end wa eguide sizes o co e hese millime e and submillime e-wa e equencies [19]–[21]. Howe e , none o hese p oposed wa eguide sizes had been s anda dised o comple ely accep ed by he end-use communi y. This led o he ini ia ion o an IEEE s anda disa ion ac i i y, s a ed in 2008, o p o ide s anda dised wa eguide sizes o use a hese equencies. A he same ime, i was widely ecognised ha he elec ical and mechanical pe o mance o exis ing wa eguide langes was inadequa e o use a hese equencies. The IEEE s anda disa ion ac i i y aimed o add ess his issue as well. The IEEE S anda ds Associa ion se up and launched he Wo king G oup P1785. Beginning in 2008, h ee s anda ds co e ing (i) he wa eguide sizes, (ii) wa eguide in e ace, and (iii) ypical unce ain y speci ica ions o measu emen s a hese equencies we e de eloped. This esul ed in he publica ion o he ollowing h ee s anda ds: (i) 1785.1-2012: “IEEE S anda d o Rec angula Me allic Wa eguides and Thei In e aces o F equencies o 110 GHz and Abo e—Pa 1: F equency Bands and Wa eguide Dimensions” (ii) 1785.2-2016: “IEEE S anda d o Rec angula Me allic Wa eguides and Thei In e aces o F equencies o 110 GHz and Abo e—Pa 2: h ps://doi.o g/10.7795/530.20190805 5 o 25 Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz RCVR A IN RCVR R1 IN RCVR R2 IN RCVR B IN P1 P2P3 P4 1 2 4 2 5 66 7 8 8 10 7 6 6 9 9 10 RF IN MEAS OUT MEAS OUT REF OUT REF OUT RF INLO IN LO IN 3 Fig. 5. Al e na i e schema ic measu emen se -up wi h 4-po VNA and equency ex ende s. 1: 4-po VNA 2: Adap e 2.4 mm jack →3.5 mm jack 3: 1.85 mm e mina ion 4: Adap e NMD2.4 mm plug →NMD3.5 mm jack 5: Powe Spli e 3.5 mm jack 6: Cable 2.4 mm plug →2.92 mm plug 7: Cable 2.92 mm plug →2.92 mm plug 8: Cable 3.5 mm plug →3.5 mm plug 9: F equency Ex ende 10 : Adap e WM-2540 →WM-2540 how all componen s and cables we e a anged and whe he he wa eguide connec ions we e done in ho izon al o e ical manne . I only 1-po measu emen s a e equi ed, i migh be ad an ageous o use a e ical se -up. Thus, g a i y e ec s should no in oduce any sys ema ic in luence on he wa eguide connec ions. A e ical se -up can be achie ed by using a wa eguide bend o by e ically posi ioning he ex ende head. Fo he la e , a cus omized ix u e migh be equi ed. Fo bo h ho izon al and e ical a angemen s, one should aim o ha e a mechanically s able se -up: no unnecessa y mo emen s o ib a ions. Schema ic d awings o wo di e en se -ups a e gi en in Figu e 7. Depending on he manu ac u e , he in e nal VNA se ings e.g. AGC (au- oma ic gain con ol) can in luence he o e all measu emen unce ain y. The e o e, one should check hese se ing be o ehand. This is e en mo e impo an i he VNA i mwa e is no used o he calib a ion. I he uncal- ib a ed ( aw) da a is measu ed, e.g. o use wi h cus om calib a ion ou ines, he ope a o should check he ollowing: 1. Recei e se ings (AGC, …) 2. Possible p e-calib a ions h ps://doi.o g/10.7795/530.20190805 12 o 25 Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz MEAS IN REF IN REF IN MEAS IN P1 P2 1 RFM M RRRF LOLO 10 MHz REF OUT LAN 1 LAN REF IN OUT 3 2 3 5 4 5 4 3 3 6 6 7 7 8 8 910 11 12 Fig. 6. Schema ic measu emen se -up wi h 2-po VNA, syn hesize and equency ex ende s. 1: 2-po VNA 2: Signal gene a o 3: Cable 2.4 mm plug →2,92 mm plug 4: Cable 2,92 mm plug →2,92 mm plug 5: Adap e 2.4 mm jack →3.5 mm jack 6: F equency Ex ende 7: Adap e R900 →R900 8: Cable 3.5 mm plug →3.5 mm plug 9: Powe Spli e 3.5 mm jack 10 : Adap e 3.5 mm plug →3.5 mm plug 11 : BNC Cable 12 : E he ne Cable 3. Co ec eco ding o swi ch e ms 3.3 Some p ac ical ips Much o he in o ma ion gi en in [23] (chap e 8: Bes measu emen p ac ice and p ac ical ad ice) can also be applied o wa eguide measu emen s abo e 100 GHz. This sec ion ocuses on good measu emen p ac ice o ypical wa eguide applica ions. h ps://doi.o g/10.7795/530.20190805 13 o 25 Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz (a) Typical ho izon al se -up. (b) Typical e ical se -up. Fig. 7. Ex ende head posi ions: (a) ho izon al, and (b) e ical. 3.3.1 Use o a p ecision wa eguide sec ion as a es in e ace O e ime and wi h use, he wa eguide in e aces o VNA equency ex ende s can become damaged o wo n, and his impac s di ec ly on measu emen epea abili y. I is good p ac ice o i sho p ecision wa eguide s aigh sec ions o he equency ex ende es po s since hese can easily be emo ed o inspec ion and calib a ion wi hou in alida ing manu ac u e s’ wa an ies. This p ocedu e is well known om coaxial measu emen s. The addi ional coaxial adap e is o en called a ”connec o sa e ” o ”in e ace sa e ”. 3.3.2 Di e en wa eguide ape u es I he same lange is used, i is possible o connec wa eguides wi h di e en ape u e sizes. This may e en be in ended in some applica ions, like e.g. o he VDI powe me e PM5 [16]. The PM5 is equipped wi h a WR-10 wa eguide, bu i is possible o measu e powe le els a equencies much highe han 110 GHz (e en up o 3 THz). Abo e a ce ain equency howe e , mo e han one wa eguide mode can p opaga e in he la ge ape u e, and i becomes di icul o p edic how much ene gy o he ac ual signal is dis ibu ed o which mode. This may e en change o each new lange connec ion (di e en exci a ion condi ions), and he epea abili y o such measu emen s should be checked e y ca e ully. In gene al, i is ecommended o use WG ape u es o he same size o o in oduce a WG ape . This should minimise coupling in o unwan ed modes, bu does no comple ely elimina e i . 3.3.3 Wa eguide o coaxial adap e s Fo ’no mal’ coaxial o wa eguide de ices i should no ma e , a which o ien a ion hey a e connec ed o he es po s. This is di e en o coaxial o wa eguide adap e s. The TEM ( ans e se elec omagne ic) mode o he coaxial line is symme ical o he inne conduc o , he TE ( ans e se elec ic) mode o he wa eguide is no . I he ansmission coe icien o a h ps://doi.o g/10.7795/530.20190805 14 o 25 Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz wa eguide o coaxial adap e is measu ed, he phase will change by 180 °, i he wa eguide connec ion o he es po is o a ed by 180 °. The e lec ion coe icien emains unchanged. This e ec poses usually no p oblem, because in da a shee s o such adap e s o en only he magni ude o he inse ions loss is gi en. I , howe e , a calib a ion ce i ica e (o simila documen ) includes all complex S-Pa ame e s o a coaxial o wa eguide adap e , he wa eguide lange o ien a ion du ing measu emen mus also be s a ed in such a documen . 3.4 Example Measu emen s In his sec ion, some WG measu emen s a e p esen ed and discussed. The ocus lies on he epea abili y o lange connec ions and he d i in luences o he measu emen equipmen . The langes ha a e used a e: • UG-387, i.e. he ype o lange ha mos measu emen de ices a e equipped wi h. • IEEE 1785.2a, p ecision lange o equencies up o THz. The o iginal UG-387 lange design does no ha e any inne p ecision alignmen holes. Bu , o achie e be e epea abili y, some manu ac u e s added added inne alignmen holes be o e IEEE o IEC published he new s anda ds. The dimension and ole ance o hese holes and associa ed dowels a e o en no he same, be ween di e en manu ac u e s, hus an ope a o mus be e y ca e ul abou connec ing langes ha look simila , a i s glance, o a oid damage due o hese dimensional di e ences. To cha ac e ise a lange in e ms o epea abili y, one can do an analysis o epea ed connec ions o s able de ices unde es (DUT), e.g. a ma ched load o a sho [23]. Bu i is also possible o es ima e he epea abili y based on he ole ance o he alignmen mechanisms o he lange. The maximum misalignmen o he UG-387 lange is app oxima ely 150 µm in bo h he H- and E-plane, and he maximum angula misalignmen is 1.2 °. Fo he IEEE 1785.2a lange, he maximum misalignmen is 25 µm in he H- plane, 20 µm in he E-plane, and he maximum angula misalignmen is 0.4 °. Wi h his in o ma ion and mode n simula ion ools, he wo s case e u n loss can be calcula ed [4], [27]. Table 4 shows hese wo s case e u n loss UG-387 IEEE.2a WR 10 / WM-2540 ≈-30 dB -60 dB WR 03 / WM-864 ≈-12 dB -39 dB WM-570 ≈-8 dB -32 dB Table 4. Theo e ical lange pe o mance o selec ed WG dimensions o UG-387 (no modi ied, wi hou inne p ecision holes) and IEEE S d. 1785.2:2016. h ps://doi.o g/10.7795/530.20190805 15 o 25 Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz alues o s anda dised lange connec ions. This able shows ha he UG-387 lange is no eally sui able o use a equencies abo e app oxima ely 110 GHz. The epea abili y should usually be be e han he wo s case e u n loss. In he ollowing, i is shown, ha his is no always he case. 3.4.1 Measu emen s o 75 o 110 GHz: WR10 / WM-2540 / R 900 / WG 27 The equency band 75-110 GHz is he lowes band suppo ed by he IEEE s anda d, bu he UG-387 lange is usually p ecise enough o ge a easonable good epea abili y and ep oducible measu emen esul s o hese equencies and is he e o e s ill widely used. In Figu e 8 he epea abili y is shown o a ma ched DUT o a ho izon al and a e ical measu emen se -up ( o educe g a i y o se s) and wi h and wi hou addi ional inne alignmen dowels used. 75 80 85 90 95 100 105 110 0 2 4 ·10−4 F equency / GHz Repea abili y wi h dowel ( e ical) no dowel ( e ical) wi h dowel (ho ion al) no dowel (ho ion al) Fig. 8. Repea abili y e alua ion wi h ou measu emen s o e ical and ho izon al posi ion wi h and wi hou alignmen dowels. The epea abili y was calcula ed as desc ibe in [23]. I is ob ained om epea ed measu emen s o a s able DUT and calcula ing he maximum di e ences, aking bo h he eal and imagina y componen s in o accoun . This is a e y conse a i e app oach and ou lie sensi i e, bu i acknowledges he ac ha he epea abili y can s ongly a y om one lange pai o ano he . As can be seen, he di e en cases yield e y simila epea abili y esul s and a e always be e han 0.0316, (≈-30 dB, see Table 4). Fo a connec ion wi h he UG-387 lange ou sc ews mus be igh ened. Because in some se -ups one o mo e sc ews migh be di icul o each (o due o ime easons) some ope a o s do no use all ou sc ews. This is likely o ha e a signi ican in luence no only on he epea abili y, bu also on he measu ed alue, as is shown in Figu e 9. One should always use all ou sc ews and also a sui able o que o igh en he sc ews. The la e can be a di icul ask, because he o que is no s anda dised, and manu ac u e s speci y di e en alues [24], [28]. The h ps://doi.o g/10.7795/530.20190805 16 o 25 Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz 75 80 85 90 95 100 105 110 0.98 0.99 1 F equency / GHz |S11| loose sc ews; ixed sc ews Fig. 9. Calib a ed e u n loss measu emen s o a lush sho -ci cui . o que needed o p oduce a p ecise and ep oducible wa eguide connec ion is a leas dependen on: • base ma e ial o he langes (e.g. coppe , be yllium coppe , b ass, aluminium, e c.), • hickness o he lange (i.e. he lange could be o med using a block) • quali y o he h eaded holes and sc ews (di e en ic ion loss), • su ace ma e ial (o en se e al me al laye s, e.g. nickel, gold, sil e , e c.), • su ace la ness, • su ace oughness. Fo a high quali y pai o langes (i.e. wi h la su ace and low su ace oughness, e c.) a e y small o que is o en su icien o achie e a good epea abili y o wa eguide connec ions. Bu , o equal impo ance as he o que is he weigh o a DUT o ho izon al se -ups o he alignmen o a second ex ende head o ho izon al se -ups (needed o 2-po measu emen s). Bo h migh educe he e ec i e o que on he in e ace i sel e y much and gi e he w ong imp ession, e.g. ha a high o que mus always be used. In Figu e 10 he epea abili y is shown o wo o que alues (0.06 N · m and 0.58 N · m) as well as o he o que achie ed by an expe ienced ope a o . The la e is es ima ed o be app oxima ely 0.3 N · m ( e i ied wi h a calib a ed o que me e ). Figu e 10 shows ha he epea abili y achie ed by he expe ienced ope a o can be be e han ha achie ed using he speci ied o que alues. I also shows ha mo e (o less) o que does no au oma ically mean a be e connec ion. This is one eason why alues o o que o making wa eguide connec ions a e no cu en ly speci ied in he s anda ds. Fo example, du ing connec ion, an expe ienced ope a o can conside o he aspec s ha migh impac he quali y o he connec ion – e.g. he weigh o he componen being connec ed when igh ening he lange sc ews. Howe e , i is s ill usually ecommended o use o que d i e s o achie e ep oducible esul s. h ps://doi.o g/10.7795/530.20190805 17 o 25 Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz 75 80 85 90 95 100 105 110 0.5 1 1.5 2 ·10−2 F equency / GHz Repea abili y 0.06 N·m; exp. ope a o ; 0.58 N·m Fig. 10. Repea abili y measu emen s [23] o an o se -sho o di e en o ques. When pe o ming epea abili y es s, one should no blindly do he s a is ical analysis bu also in es iga e he single measu emen s o iden i y any possible ou lie s caused by poo connec ions. Figu e 11 shows he di e ence o he single e lec ion coe icien measu emen s Γn o he mean alue Γall,mean o all epea abili y measu emen s o wo expe imen s wi h he same DUT (sho -ci cui ). In Figu e 11(a), wo ou lie s (measu emen 3 and 4) can be iden i ied. These should no be aken in o accoun o he epea abili y calcula ion. I he numbe o emaining measu emen s is oo ew (a leas 4 o mo e should be used), one should epea he expe imen comple ely. In Figu e 11(b), he epea ed expe imen (pe o med wi h mo e ca e) wi hou ou lie s is shown. All epea abili y measu emen s migh also be dis o ed due o: • Noise, • D i , • Cable mo emen s. Depending on he measu emen scena io, 1-po measu emen s usually don’ equi e cable mo emen , he la e one can o en be a oided comple ely. E en i no a comple e unce ain y budge is equi ed, he p ocedu e o ge his a e gi en in [22], [23], one should s ill do some simple es s o quan i y hese e ec s. Fo example o ge an idea how la ge he ins umen d i is, one can do a se ies o measu emen s (e.g. one e e y 60 sec.) o a s able DUT (wi hou econnec ing). In Figu e 12 he d i esul o such a measu emen is shown o he linea e lec ion coe icien o a lush sho -ci cui . The alues a e ob ained by simply calcula ing he di e ence o he i s measu emen . The d i o 4 measu emen s (co esponds o 4 minu es) a he beginning and a he end o a expe imen is nea ly iden ical and app oxima ely 1 ·10−3 . The d i o 15 measu emen s (co esponds o 15 minu es) is somewha la ge and o he same o de o magni ude as he expec ed epea abili y. In Figu e 13 he cable s abili y is shown a e pe o ming he es p o- h ps://doi.o g/10.7795/530.20190805 18 o 25 Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz 75 80 85 90 95 100 105 110 0 0.5 1 1.5 2·10−3 F equency / GHz ||Γn|−|Γall,mean|| 1; 2; 3; 4 (a) Di e ence be ween e lec ion coe icien magni udes and hei mean alue, wi h ou lie s. 75 80 85 90 95 100 105 110 0 0.5 1 1.5 2·10−3 F equency / GHz ||Γn|−|Γall,mean|| 1; 2; 3; 4 (b) Di e ences be ween e lec ion coe icien magni udes and hei mean alue, wi hou ou lie s. Fig. 11. Re lec ion measu emen s o a s able DUT no malised o he mean o n=4 measu emen s: (a) po 1 and (b) po 2. 75 80 85 90 95 100 105 110 0.5 1 1.5 2 ·10−3 F equency / GHz S abili y d i n=4; d i n=15; d i end n=4 Fig. 12. S abili y e alua ion (d i ) wi h n=15 measu emen s, one measu emen each minu e. cedu e gi en in [23]. This consis s o epea ed mo emen s and e lec ion measu emen s o a cable (he e se e al cables including equency ex ende ) e mina ed wi h a ma ched load and a sho -ci cui and calcula ing he maximum di e ences, aking bo h magni ude and phase in o accoun . h ps://doi.o g/10.7795/530.20190805 19 o 25 Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz 75 80 85 90 95 100 105 110 1 1.5 2 2.5 ·10−2 F equency / GHz T ansmission s abili y / dB 10 cm mo emen ; 25 cm mo emen (a) T ansmission s abili y in dB (cg-12) 75 80 85 90 95 100 105 110 0.1 0.15 0.2 F equency / GHz T ansmission s abili y / ° 10 cm mo emen ; 25 cm mo emen (b) T ansmission s abili y in deg (cg-12) 75 80 85 90 95 100 105 110 −90 −85 −80 −75 F equency / GHz Re lec ion s abili y / dB 10 cm mo emen ; 25 cm mo emen (c) Re lec ion s abili y in dB (cg-12) Fig. 13. Cable s abili y [23] o 10 cm and 25 cm cable mo emen s. In his case, he esul s a e in he o de o magni ude one would expec a hese equencies and don’ change much o cable mo emen s o 10 cm o 20 cm. This indica es, ha all cables connec ed o he ex ende s a e qui e s able. I he esul s a e no as good as expec ed, one should es all cables sepa a ely. Usually his in ol es coaxial measu emen s up o only 20 GHz o less and ollowing he same p ocedu e. h ps://doi.o g/10.7795/530.20190805 20 o 25 Rec angula Wa eguide Connec ions a F equencies abo e 100 GHz 3.4.2 Measu emen s o 220 o 330 GHz: WR3 / WM-864 / R 2.6k / WG 32 The wa eguide band 220 GHz o 330 GHz is suppo ed by he langes desc ibed in IEEE S d. 1785.2-2016 and he UG-387 lange. Al hough he UG-387 lange can be used a hese equencies, i is no ecommended, unless a modi ied e sion inco po a ing imp o ed alignmen ea u es is used. The IEEE S d. 1785.2-2016 lange designs p o ide be e elec ical pe o mance a hese equencies. 220 230 240 250 260 270 280 290 300 310 320 0 5 10 ·10−3 F equency / GHz S abili y d i n=4; d i n=15 d i end n=4 Fig. 14. S abili y e alua ion (d i ) wi h n lush sho -ci cui measu emen s. In Figu e 14 he s abili y based on epea ed measu emen s on a ixed imescale (one e e y 60 sec.) o a s able DUT (wi hou econnec ing) is e alua ed. Compa ed o he measu emen s up o 110 GHz, see Figu e 12, he sys em d i is la ge . In 4 minu es i is app oxima ely 2·10−3 and o 15 minu es i eaches 10·10−3 a he highes equency. The main eason o his is he lowe s abili y o he equency ex ende s, hus any epea abili y measu emen s a e s ongly supe imposed by he ins umen d i . 220 230 240 250 260 270 280 290 300 310 320 0 5 10 ·10−3 F equency / GHz Repea abili y UG-387 mod. IEEE 1785.2a Fig. 15. Repea abili y measu emen s [23] o a s able DUT o di e en langes. In Figu e 15 epea abili y measu emen s a e shown o di e en lange con igu a ions: s anda d lange o he equency ex ende (modi ied UG- h ps://doi.o g/10.7795/530.20190805 21 o 25