^. Hollow Waveguide Directional CoulZler ; .. __. _-.... ine, pre'sentinvention relates to a, hollow waveguide directionál couDler having two hollow r--""'""'"'.--.------ .....,,.. . waveguide sections connected to each, other by a plurality of coupling openings formed in a wall extending between the hollow waveguide sections. Such directional couplers are generally known. Directional, couplers of this type, having tWQ coupling openings are described e. g.. in. Meinke-Gundlach-Taschenbuch der .-_ : _ _ _, _ . _ _ _ ___,..-,. __..,,, __, r. , .,, ..... ,. __ __ Hochfre, uenztechnik 5. ulagez ; ; v, S, ringer, 1 ; 92,, hapt x L7 : 4,. Such diirect'ional cou le, rs have : good. directivity for wavelengths X. g in a range of four, times the distance between the C r ^, Jw S Z z. s = z. r Ç r S n a. ;.-i 5-L ^ coupiihg openmgs'wnere'lg'is the ave&nh* or he"nomin R g, p,,.,. g . :. g, g.,-.. a,.. q. Y : : òperal1ng tr : que, ncytrange otXt, ne 4 irectíònal~covuplër. T,'dl''rectlvlts 1<S megon'theffãct operating trequene y : range ot me directional'Coupler."The direct vity 's base'oh'the fact ,......... "thahe fielSs'cbupled'at transit hollow waveguide section to the s., col4P,,, 9, driven : nollow, w. aeguide., section. propagate in, both, directions _in the driven hollow wåvegrjulffie, ana tnat the'fiel¢s that propaga'te in the sametdircctioii åvsR"int'the~tränstit ç ER^1 r_ tJS, t i7j r-r. ; 7 rz ill3 ~ E. t ;,"rv., r"í 8 v rs, r ;, ri vVavegun'm'erere : comstructW ely, yhereas, in the opposlte clirection, ; they have ay phase >L La r ; r.-^rdrsa rx dlffer, encezor'i ane'thu'¢ » cel, e'iaGh. CJxét rl : r-w 3s 5$t rrdri tJW r* c, 5 ~ tl3Ft 1F tit Brrt s & Dv Hollow-wävegulde d1recti az couplers havmg a pluranty of couplmg openlngs rare described e'"ih"'R.'t. evy"narysis and'yhUiesis'or'Wave'guideMulS-aperture p ers aving p Ity Directiohal"Couplers IEbh irans7 on Microwave iheory and Tech''vi ? MTT-i No. '12 nRcember 968% ndm*S [. Scrinuedel'et'al."Field'Tneory'Design ofKectangular 8--an in r i'i : s- t, : f. & t', jZt, ' y-a ; i-ii PZS ,,..,. rvE -a :.-, c.--. Waveguide Multiple-Slot Narrow-Wall Couplers. lEEEjTrans. on Microwave Theory and a f ?. t -T-r-r r r z-t, ; a t r E e r r , ; f s, u choLMT3'4o.'

Thdimensipns. ofthes. e coupling openings ah wall sections between them are ,'. ;,...., ;.,,,, . : : -, f. :,. .. S... obviously-p'roportional to=the RF wavelengths with wh'ich-they are to'be used: Applications ^. s (', ;,,--rn t . t t. : : s'k4. 2, ; !e-i. ^. ° la i ...., ' F n', '. !..'. ri . °7, ; r. : . 51 yt. >. in. the n ; ullimetei'wayclcngth nf-thecquplins bpenings and the in.. the,. millirneter-wavelen th ran e : re. uire_ diriiensioris. f the cou lin ; openings_'. and the -wall, portions which,.,, with conventional'manufacturing techniques such as edging and machining. In particular when strong couplings are required, a.'hi. gh ; humber. of coupling jppenings, is, necessary, because. the cros ,. a, hlgh, nu,, ; m, be, r, o£ coupling ; openings, ils, nLe, ce, ssary,, pecaus, el !, the, cr, o$s, ; sect, ionj aWreatof a Nsinghe, coupling opening is limited by the requirement that a wall portion separating it frpm an "''.'must. be sfron'enou H. tov ithstand the. l. ads to.. which : it is P-pu ..-G£ a, r$fsib 1 y. d, v. I. " _, _l. Id 54r u, E I Iv. ,. _.. _, .'4.-. un1 _....... _ Lxpo, sect, dunngrrianufacture. :, ; :. bt, -<, r :..".,.. .. aa^, a. :-, : Ff,. Rtg,. ta. k_,... ry.., It is readily apparent ; that'the ; effort for manufacturing such, a. directional cpuprer. increases with thnumb. erpf,. cpupling''ppening& that"mustbe manufactured. The *eff6rt"f6r'he 6j* I 4d with-the ldhktti'76f-ih iiianuracmre ot the direcfiohal coupler does not only increase linearly witn'the nunlber of ... aa. xpr. e : 5 'J ldtH 'a 1. i-,.. uav ; t . : r. L'. , i. . 4'at. u'.'. r. et°_ , , s. . 4. -. . 1 i required coupling openings'or, what is more'or less equivalent, with the length of the , 479A. 8. t » y J. yn. G, 3' ;. (f j. N , . 1. ll", ; a. . n... sy, Ah d. _4. P i' f, ty p . J9. YniS) 7'.. 5. : lJlf. yRl 6 T. Z m. :... y r-... coupling section but exponentially. The reason for this is the non-vanishing probability . lta : te.. ., °ezca, t. >cxrxF, _ Y ; f_tr.., libl"'C. e2'', s » _. 9. i, ..-. >,. ., Y. r. Cq''<Ss''. yw (r. y. °.. : r f :. vr. fq.- that during manufacture'a wall portion becomes damaged and the complete directional §pi5iled."Ttio_highe, the nurfibet-of'6xi'sti'ng-Wall'p6rtions,', the less'is, the probability that all of them will survive the rnanufacture undaniaged. probability that all of them will survive the manufacture undamaged. Accordingly, there is a need for a directional coupler, in particular for radio frequencies in ire G_ __. _ _ _-__. __ _ _ _ _. __ _. _r. _ _. the nuuimetre wavelength range, that can be manufactured with conventional methods and F. °. sJ. $7. . s ° 4. F. l7, de w1Wh a good'yield''

Th' : dbjeGt : tS :, a ; phiee : dIbyr ^. sw. ac ievedb e a-ollov : v ae, uicle-. dlret'oriaFvcou : er, mh n, : t e. featiireso -------- By increasing the distance between adjacent coupling 6pening"s t6an uneven multiple of g/4 with respect'to conventional directional co'uplers, the same phase relation between g _ _ _.... _ _ _. _ fields coupling from the transit waveguide section into the driven waveguide section and, uius,'the same'directivii ; is achie'vu'ás wì'á bonvzen'ti, õ'nål"B14-direction !'cer tlius ; y the sarie'directmty ys acliieved_as mth a c'onventional ? J4 directional coupler : . _, :. a,,.-,. : e ; ; t..,-a^iyt : °r.. :, -, t,. ;. 3 :,. W"r, . r :.--. /Ff4T3} F !'\. r- to aamágen [ì £'t Z1t t r^tt t Z59. S ; As.-s 1 ZJZZ n » ZZ Ii ; £Zc ii e. ari tine> ; Ltf iargercross Section areahevemor st'aDie than cuhv'ehiionar ones'ahlBssisuceptibl'e ti to damage. ii orcer to_ keep the, rength 'of tlie directional couplr ow, the clstance, of the coupling _ . _. c _ ;, ,. 4, l n s a. ^. iaa, ns. rh... A.. : . openings is preferably chosen as 3 Ag/4. ew, v . . _. 5n , :, v-, » =a . e, 'v.. a'a , a, ;,, ihe wall in wRich the coupling openings are formed mayoe a broad or a narrow side-wall t'SLawre t'. 5s 5 ;, srsats'LFi3 UUt't briAt P,/jf tN of the couplmg. rectangular hollow waveguide sections. If tSe coùplmg is carried out by broad side-walls of the hollow waveguide sections, there is an advantage in that the complete directional coupler can be manufactured from two za. aa :. r : :, 6Al Cr :. h"i.' v lh =b',. 'k :, a,- t,. ,,- : Ar : r.. yetE^. F ?. Ja l3S'. 3 ; warf_''. t_ 4r, c- r v. : t°caa 5t 1 5., 5 tH i, t"« J t.),. A t $. « r A", i', U E ! tgJ i s) l ltWs St,, ! st X, J t t r,.,, @ P I AAL, mirror-symmetric half-shells, each of which receives one half of the free cross section of e'ansiand'dnveh fiollowwave'auidesec The i unctions at which the two half- shells meet correspond here to, a node line of transversal currents induced in the walls of _, __ t_ _ _, _ . _ _ _ _ _ , _, _ the. lioIlow'w'a. yeguTde"sections'by a TEiQ wave'sohaftransRio'Impedances between the , tE aly§s haRe, Ano m¢nçe. o. n the indu. c. e, d, curre, nts. D t o

A coupling of the hollow waveguide portions by their narrow side-walls has the advantage that the. channel' that must be. etched, machinedror formed in any other appropriate. manner - : ; s,,. w. _... . . _. _.. _. _. has, a ! depth which is, rather small in relation to its width and can thusfbe formed in a rather betw'en the"ti o-, o ling shorttime.-At the sametime. the heightof the wall sections between the two. coupling ,. _ imDroved. fi >>Y. Y Y irilpovecl. E, dlrec3tl9lnltOfieho Ow ; Tzww< ; ì5Yir ! r2t bX t ttir qd S-thtÇ ti-q _ s : , La. l°. 6. ', JAbnt. n. iv y°- ? nfil't, 3haab"L%', 2 ZG G6l7_P"°3ii P ; l F. fi', .. °L di'i ! J'ro"Y iax..- direction of hehollow waveguice sectioris my be made greater"tianiri"a'conventional cureGUonal coupler, preferably it can be set to A./8 and, preferably, to a-value ofA/4 that , nove,,., t3,. .", e ; °'T. P . g... y a. : : rxn ; yza.. E, t.... r. v.., -ratW ; o ;. ". s. to.. enzia, :-e.. ; : r,--.. _.. ___. e.. , ua. r.., t,..., _. : ; "un pcnimgs'auows the number ofcouplmg_openmgs reqmredor a gmen coupling a, d.. t-. -,-, r, p, ," _ lal. iTr, ; v t. P. : .- a., a^ i uphug openings allows the number'of coupling openings required for a given coupling efficiency to be reduced, whereby, again, the cost of manufacture is decreased. Since a Sddj.. =3',.. 5'rrR, ;. :,,. _-. . f ; _ strong coupling is easily achieved, the thickness of the wau between the coupling hdllbw waveguide portions may be chosen greater than in conventional directional couplers, . c- u rae, - : r. rac.. yh... ;.... y, aF..' ! fi W : \J' J ;. m :'. . °. L whereby, aajn, the manutactunns process is simplified : ... : z_. _... _.. _ In order to achieve"as high a bandwidth of coupling as possible, the coupling openings shouldhave a lensthwhich decreases from the centre to the ends of the directional coupler. e, : C : .-. aeW i P3<li'°>'. . L : i",. lFe. F^. 9-'fiv. t_Y y'd, i'6. A. 4dlS : ; 2e. e& :.'bT-5 h'4iC. E.'. 1. (SLP. G. .. °"l. n'^-"rE., M_...'', Furthefeatures and advantages of the myention will become apparent from'the subsequent 4 E r X 6'« P- «, S z tS'_>tl, ? 7 b tO J t ç a tk description of emBodiments'with reference to the appended'ffgures'ih wncti'

Fig. la schematic representations ofa"direotion according to a first embodiment of the invention, in which the coupling openings are formed at a narrow side of two coupling hollow waveguide sections ; and - Pif-2 is an exploded cross sectional view of the two half-shells of a directional coupler according to a second embodiment of the invention, wherein the coupling openings are formed in à broad side-wall of the hollow waveguide sections. "Ffg. 1 showsperspectiveview ot two itangmafhouow waveguides,'herereferred to as gf6vs-1'-Iw'wav"e'ui'-ef-ed-to transit waveguide 1 and driven waveguide 2. There is no physical difference between the I 'two hdlldw"waveguides implied'by the"different terminology, one is the exact specular image of the other with respect to a plane extending between the two and defined by dash- u .--_ _1C dof lines y, z.' --U-S/r., q «,.. f, 5l<r Sbtvt, £R ;). Between two paralteX sections 3, 4 of the twò wavegu1des 1, 2, there extends a wall 5 which forms a narrow side-wall of the two sections 3, 4. In the example shown, the wall 5 r. aj. a,-n. gf. tv'. _ 2 f., ed ilk, rE.-E :,. - 6. A 4rd) f'T-A , S. L :.' Lbri°t'tl'R, %/l. r ['An.. ., ae a-cai. :. _.., v e t j j is'interrupted at three places by coupling openings o, 7. The centres of two adjacent ". _. :. t _. _ _. _ _. _.. _ _.. _ _. _ _... _. r :. FF ;... c rea. ma, x. Ets, paaw t. . tx :, : vca _ coupimn opemng 6 is aDDroximatelv Ap/4, that of the two peripheral coupling openings/is coupim, ope, mng&8 lS anoroxlmatelv X, J/4 that of the two peSpheral coupling opemngs/1S ;, oupiy opening- is annroximatelv 7al4, that o the two perpheralcouplmg openW gs i m Ag/8. This imphes a width of the wall portions 5a of wall 5 delimited by the coupling '. LfF,. h. flN. "1 e'_. _. opemngs 6, 7 of 9/l6kg. - r,.. r. L « F w< » ORS J > J i, b} 6 t. i q/Zt ! The width of the opening 6, 7 may be greater than Eg/4 Y, ~ g 5'"D. r ç -Pi g. 2 shows an ; exploded. iewof a directronarcpupler according to a second cmDoqimeni, mwnicnme wall 5, wim coupling openings ; 6' formed in iUs a broad side-wallofthetwo coupling hollow waveguide-sections 3', 4'. The distance of the coupling openings 6', 7'in the wall 5'from each other and the width in propagation direction of the same is described with respect to, Fig. 1. The-walls of-the directional coupler are formed by two identical metallic or superficially metallized half-shells 8, 9,'from which the upper one 9 is shown with one half of it c : ut away so,,. as to show the interior of the lower half-shell 8. , r Xtke, assembled. d1recXlon, coupl, er, Ae two haYf-shel s t tuch eac other at shàded t t e two.--s'elrs- wavelength A. g only'the'TE'io'wave can propagate, mere'ls'nocurrent'nwing perpend wavregth , g-orily theTlo wavecan propagate ; zriereis nocurreiit livingpei-penclicuIar zu iaes are-ctirnens : fonea sucn tnat, at in'e' . _.,, :, ,, g Y, ___ g ___ p, . r.. ..... _ _ .. y is without relevance for the dampmgpt the directional. c f. tV t ; f í ; Sf ; t] t t f>-r r n r ? 2 =s tF j 6'to d F A ls, wl, thout relev, ance foro thte da"mp1ng of the a1rectlonal, coupler.