power directional power power reverse power directional passive devices field radio technology couple defined electromagnetic power transmission line port enabling signal circuit essential feature directional couple power flowing direction power entering output port coupled isolated port coupled port directional frequently constructed coupled transmission lines set close energy passing coupled technique favoured microwave frequencies transmission line designs commonly implement circuit elements component devices possible lower frequencies microwave frequencies particularly higher bands designs correspond conducting transmission line designs types unique directional power applications include providing signal sample measurement monitoring feedback combining feeds antennae antenna beam forming providing cable distributed systems cable separating transmitted received signals telephone lines symbols symbols directional shown figure symbol factor marked directional ports port input port power applied port coupled port portion power applied port appears port transmitted port power port portion went port directional frequently symmetrical exists port isolated port portion power applied port coupled port device normally mode port usually terminated matched load typically termination internal device port accessible user effectively results port device utility second symbol directional figure symbols form formula article meaning port input port symbol power shown figure power directional class device directional tends port devices loosely coupled small fraction input power appears coupled port power devices tight commonly power provide half input power output ports usually considered port device parameters common properties desired directional wide operational high good match ports ports terminated matched loads general characteristics discussed factor factor defined formula input power port output power coupled port figure factor represents primary property directional factor negative quantity exceed passive device practice exceed result power output coupled port power transmitted port effect roles reversed negative quantity minus sign frequently dropped implied running text authors far define positive quantity constant varies frequency different designs reduce perfectly flat theoretically built directional specified terms accuracy frequency band center loss main line loss port port loss formula loss power going coupled port called loss given loss formula loss ideal directional consist entirely loss real directional loss consists combination loss loss conductor loss loss depending frequency range loss significant losses constitute majority total loss theoretical loss shown figure table isolation isolation directional defined difference signal levels input port isolated port ports terminated matched loads isolation formula isolation defined output ports case output ports input considered output port ports input isolated terminated matched loads consequently formula isolation input isolated ports different isolation output ports example isolation ports isolation ports different value isolation estimated plus return loss isolation high possible actual isolated port completely isolated power present directional best isolation directly related isolation defined formula output power coupled port power output isolated port high possible high design frequency sensitive function frequency depends cancellation wave components directional best directly calculated addition isolation negative measurements formula note positive definition formula results formula parameters matrix ideal infinite isolation perfectly matched symmetrical directional given formula formula transmission formula general formula formula complex frequency dependent numbers matrix main diagonal consequence perfect matching power input port reflected port matrix consequence perfect isolation input isolated port passive directional addition formula power entering input port leave ports loss related formula formula factor related formula formula non zero main diagonal entries related return loss non zero entries related isolation similar expressions authors define port numbers ports results scattering matrix longer balance terminology defines power difference output ports hybrid ideal hybrid circuit difference practical device balance frequency dependent departs ideal difference phase balance phase difference output ports hybrid depending type like balance phase difference sensitive input frequency typically vary degrees transmission line types directional coupled transmission lines common form directional pair coupled transmission lines realised number technologies including technologies implementation shown figure quarter directional power coupled line flows opposite direction power main line port arrangement shown figure numbering remains reason called backward main line section ports coupled line section ports directional linear device figure arbitrary port input example seen figure result directly connected port transmitted port adjacent port coupled port diagonal port isolated port directional main line designed high power operation large coupled port use small connector connector internal load power rating limit operation coupled line accuracy factor depends dimensional coupled lines printed technologies comes resolution printing process determines minimum track width produced puts limit close lines placed problem tight required use different design tightly coupled lines produced air permits manufacture printed technology design lines printed opposite sides lines width greater edge coupled line design good work popular format designs exist reason medium different transmission strip leads transmission modes usual mode found circuits propagation odd modes different leading signal better solution coupled line shorter shown figure disadvantage factor rises noticeably frequency variation design encountered coupled line higher main line shown figure design fed power monitoring higher line results higher voltage given main line power making work easier frequency range specified manufacturers coupled line main line response wider instance specified main line operate distributed element circuits coupled response periodic frequency example coupled line responses odd single coupled section good octave achieve greater multiple sections design proceeds way design distributed element filters sections treated sections filter adjusting factor section coupled port classic filter responses flat filter equal filter specified filter response maximum variation output coupled port usually quoted plus minus value nominal factor shown coupled line directional formula purely real formula purely imaginary frequencies leads matrix result coupled port phase output port applications use phase difference letting formula ideal case operation formula branch line branch line consists parallel transmission lines physically coupled branch lines branch lines spaced apart represent sections multi section filter design way multiple sections coupled line section controlled branch lines main coupled line formula system sections higher ratio branch lines high lines narrow tracks usually limits design sections formats manufacturing limitations similar limitation applies factors low requires narrow tracks coupled lines better choice loose required branch line good tight hybrids branch line usually wide coupled lines style good implementing high power air solid bar formats rigid structure easy support construction similar filter paralleled lines achieve strong range power earliest transmission line power simple junctions suffer poor isolation output ports large power reflected port finds way port shown theoretically possible simultaneously match ports passive port poor isolation possible ports fundamental reason port devices implement port power port devices designed power arriving port split port port terminated matching load ideal case goes port term hybrid originally applied coupled line directional directional half input power meant phase matched port isolated arms equal power division called hybrid hybrid types different phase relationships hybrid hybrid article hybrid qualification means coupled line hybrid power power consists parallel transmission lines input fed lines parallel terminated twice system design realised format natural implementation lines kept apart couple brought terminated lines run relying outer screening power matching problem simple junction low ports high isolation output ports input output port designed equal characteristic microwave system achieved making line formula system system lines approximately hybrid coupled line directional described designed called hybrid matrix ideal hybrid reduces formula output ports phase difference hybrid hybrid ring hybrid ring called rat race port directional consisting ring transmission line lines intervals shown figure power input port splits travels ways round ring ports signal arrives phase adds port phase ports phase example hybrid figure shows implementation design implemented possible produce factor different making section ring alternately low high entire ring formula port design ring approximately matrix hybrid given formula hybrid ring ports choosing different port input necessarily produce results port port input hybrid ring hybrid stated port port input results hybrid fact leads useful application hybrid ring produce sum difference signals input signals shown figure ports signal appears port signal appears port multiple output typical power shown figure input power divided equally output ports multiple like reversed channel output consists power relatively inefficient reason half input power goes port dissipated termination load coherent phases arranged cancellation occurred port power port usually entirely independent sources coherent filter networks types directional branch line branch line described implemented hole directional common simplest directional hole directional consists parallel stacked hole power guide launched hole hole example backward concept hole extended providing multiple holes holes spaced apart design parallels multiple section coupled transmission lines multiple holes allows extended designing sections filter class hole size chosen desired section filter design criteria achieve substantially flat high desired band short slot short slot wall common instead long hole slot cut allow design frequently produce reversed phase reversed phase design parallel time long common short wall centre slots cut spaced apart backward design advantage substantially flat response disadvantage strongly frequency dependent compared hole little variation factor crossed guide crossed guide stacked like hole right angles instead parallel centre holes usually cross shaped cut diagonal distance formula apart good tight applications compromise properties hole varying frequency power hybrid ring hybrid ring discussed implemented magic coherent power division accomplished means simple junctions microwave frequencies possible forms plane plane junctions split power equally different field configurations junction electric fields output arms phase plane phase plane combination form hybrid known magic magic port component perform sum difference coherent microwave signals element types hybrid standard hybrid shown figure power port split equally ports hybrid hybrid centre tap usually terminated internally possible bring port case hybrid sum difference hybrid port presents different ports require additional conversion required use port system hybrid commonly telecommunications wire conversion telephone include convert wire line wires cross connected lower frequencies compact implementation means possible figure circuit shown meant weak understood lines signal coming line pair reduces voltage signal reduces current matched argument holds direction signal relative sign induced voltage current determines direction outgoing signal given formula secondary primary turns ratio equal splitting signal transmitted port coupled port formula isolated port terminated twice characteristic system power based circuit phase compared coupled lines phase relationship simple circuit power shown figure circuit implemented delta circuit applying transform delta form uses equal system precision value system available system nominal circuit benefits simplicity low cost wide major circuit dissipate power equal split result loss instead second problem leading poor isolation output ports loss problem unequal split power instance port loss port isolation improved expense loss output ports replacing output pads isolation improvement greater loss added bridge hybrid true hybrid theoretically infinite isolation bridge circuit like circuit bridge loss disadvantage circuits addition ideal balanced lines loss issue bridge represent ports usually device exception port left permanently internally provided line device consists essentially plus port termination applications monitoring coupled output directional monitor frequency power level signal main power flow system power reduction figure making use isolation isolation high directional good combining signals feed single line receiver tone receiver tests figure signal enters port enters port exit port signal port port experience loss signal port port loss internal load isolated port dissipate signal losses port port figure neglected isolation measurement port port determines power signal generator injected signal generator injection level increases cause signal generator injection phase locking symmetry directional reverse injection happen possible problems signal generator figure effectively increase isolation directional consequently injection loss isolation directional plus reverse isolation hybrids applications hybrid include power phased array radar antenna systems phase devices hybrid coherent power applications example hybrids coherent power application given section inexpensive version power home divide cable air signals multiple sets devices output ports usually consist internally number domestic internet service provided cable companies cable internet domestic user internet cable connected port power hybrid circuits directional combine power splitting figure example shown signal split feed multiple low power feed single antenna high power phases power arranged phase coupled port hybrid phase transmitted port causes powers add output cancel isolated port representative example figure shown figure note additional fixed phase shift ports shown simplicity applying phase power input ports desired result sum appear output ports half total power approach allows use numerous expensive lower power instead single high power approach solid state feed antenna let power combined space feed lens attached antenna phase difference phase properties hybrid great advantage microwave circuits example balanced microwave input stages fed hybrid device normally poor match reflects incident energy devices essentially identical reflection device equal reflected voltage phase isolated port different input port reflected power goes load isolated port power goes input port results good input match low phase matched lines antenna input hybrid shown figure occur directly receive signal position change hybrid type line length reject signal given direction create difference pattern radar good approach phase difference create beam tilt radio station delaying phase lower elements antenna array generally phase difference fixed phase delays antenna beam forming networks butler matrix create radio beam prescribed direction
Power dividers and directional couplers