iron filter iron filter type filter microwave frequencies signal variation filter longitudinal slots cut resulting internal structure appearance iron iron filters particularly suitable wide wide free transmission modes required high power handling capability applications include suppressing output design wide band industrial microwave manufacturing processes prevent escape microwave radiation microwave chamber filters analogous design appearing higher frequency smaller scale small size allows incorporated integrated circuits design techniques iron filters include image methods network synthesis methods numerical analysis methods network synthesis advanced method image techniques simple repeated pattern design desired numerical methods design description iron filter invented basis filter filter consists series ridges width filter inside surfaces rising descending ridges aligned meet middle gap iron filter addition slots cut ridges length leaves matrix square islands teeth surfaces iron filters essence low pass filters like devices transmit frequency iron filters wide low loss wide wide needed particularly good suppression modes required iron filters built wide wider possible relaxed specification operation performance issues addressed iron filter filters dependent transmission modes incident signal filters bad suppressing modes contained signal instance filter iron filter based modes strongly dependent mode number case iron filter modes nearly equally certain frequency limit frequency distance metal teeth greater half free space signal reason iron design good performance respect distance teeth longitudinal transverse directions nearly directions makes iron nearly waves directions mode wave mode waves travelling different diagonal directions modes affected nearly equally incident signals containing modes certain frequency generate modes longitudinal slots slots acting point start happen frequency height slot greater half free space signal frequency required filter effect consequence steps outside filter needed suppress modes incorporated end matching sections design criteria usually result filter match connected input output structures matching useful stepped added advantage helping suppress unwanted slot modes applications common application iron filters remove high power radar applying antenna legislation jurisdictions requires strict limits band cause interference stations application usually requires wide characteristic iron filters instance remove fifth necessary low pass filter greater times wide band nature iron filters finds applications satellite communications satellite earth station multiple connected multi band antenna delivers wide band signal different band essential signal contain band components particularly seriously interfere stop entirely communication band wider reason advantages commonly iron design iron filters industrial microwave processes industrial applications microwave energy include drying food products industrial films heating foam production melting rendering high volume production process continuous necessitating openings microwave chamber product fed exit steps need taken prevent unsafe levels microwave radiation escaping large accommodate product usual line product feed microwave material purpose absorbed heating effect severe damage material iron filters useful alternative product passed filter teeth ideal filter reflect unwanted radiation absorbing suffer example filter choke application processes techniques simultaneously iron placed nearest microwave chamber reduce energy level cause lining lining removes small design number teeth size gap design parameters control design filter example filter teeth width number rows teeth length primarily affects rows teeth better row equivalent element circuit filter section filter rows teeth theoretical rejection seven rows earliest iron filters designed image method filter design original data filter applied iron small adjustment alternative approach data image design junction equivalent circuit represent method later extended main image design method filters match good usually requires matching sections provided input output usually form multi section stepped add considerably overall length filter small improvement matching starting ending filter half space instead tooth space circuit equivalent half sections terminating filter end starting ending half tooth instead half space equivalent half sections direct synthesis avoids problems image method better account terminal designer additional degrees freedom allowing improved matching size gaps teeth tapered method design teeth different sizes according position filter compared image design sections identical approach original specification kept simultaneously improving matching stepped significantly reduced size synthesis methods allow better control precise filter response common response function filter designers filter trades transition band response best choice iron filters low pass filters pass frequencies way zero effect better choice filter filter based include special case discovered response low frequency controlled designer detrimental filter advantage response results filter better match connecting compared filter image filters design approach particularly suitable numerical method filter number finite elements elements large number simple steps ridges number methods available individual elements mode matching technique expands field element series mode matches field interface elements method expands field functions methods mixed according convenient particular type element analysis method final output needed scattering parameters matrix element overall filter response found combined scattering matrix individual element method synthetic trial design exist order analysed unlike synthesis methods starting point prescribed transfer function design modes theory excited iron filter vertical symmetry centre line practice caused poorly mating teeth modes suppressed fitting thin wires width filter space teeth vertical centre line better solution engineering components high precision results robust design multiple unit filters wide achieved iron filter units unit designed different overlapping ranges filter highest frequency smallest greatest number teeth units connected sections order progressively higher frequency operation operating different frequencies ones connected units smallest teeth shorter connected units larger teeth gives example unit iron filter designed stop second tenth combined rejection network synthesis design techniques need multiple units reduced eliminated tapering teeth allowed unit design reduced single unit wide approach length complete filter high power high power occur corners filter teeth strong electric fields present sharp corners limits power handling capability filter effect rounding edges teeth completely circular teeth best power handling circular teeth handle times power capability square teeth instance describes filter rounded teeth wide power handling capability similar filter circular teeth hand handle power connect filters parallel combining provide greater power handling filter structures analogous iron filter operate higher frequency smaller electronics like iron structures good suppression unwanted transmission modes filter operating band built parallel plate technology rejection filter constructed plates highly polished aluminium spaced apart teeth consisted gold aluminium cylinders die design convenient provide gap centre teeth microwave version instead air gap provided teeth plates filters standard industry manufacturing techniques consequently suitable incorporating chip integrated circuits technology general
Waffle-iron filter