Fig. birth radar. (Courtesy Varian Associates.) microwave industr

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PASSIVE COMPONENTS: BRIEF HISTORY
Fig. birth radar. (Courtesy Varian Associates.)
microwave industry tied birth radar. Figure whimsical look birth radar portrayed 1960s Bomac tubes. reality, radar developed primarily Radiation Laboratory (RadLab) during World Much impetus came from develop-
ment magnetron which first source adequate microwave power which British provided RadLab. There also work going Bell Laboratories, Naval Research Labs Harvard University. 1945, closing RadLab, there were very active microwave devices. Power sources were limited triodes, klystrons magnetrons. plasma tube only active switch only semiconductors were point contact germanium silicon diodes. There were varactors, PINs, bi-polar transistors, FETs, Gunn diodes, IMPATTS Schottky diodes. Thus, almost system functions were relegated passive components. development those passive components genesis microwave industry know today. PIONEERS technical staff RadLab remarkable collection highly skilled motivated physicists engineers. Much their work, like that Julian Schwinger, shown lecturing Figure endures this day. Seven them went Nobel Prizes five became National Science Advisors. more importance many took entrepre-
HARLAN HOWE,
Microwave Journal
Reprinted with permission MICROWAVE JOURNAL® from November 2005 issue. 2005 Horizon House Publications, Inc.
OVER EATURE
rectangular waveguide employed during WWII, many dimensions that became standard waveguide sizes were based availability commercial extruded tubing used decorative architectural purposes. While much early component development done waveguide, usage today primarily high power, millimeterwave very loss applications, since smaller, lower cost techniques have evolved over years waveguide limited bandwidth capability. Heinrich Hertz demonstrated propagation coaxial lines several years before Lord Rayleigh proposed hollow waveguides. also demonstrated concept "skin effect," which showed that high frequency waves only penetrated conductor very limited depth. Coaxial lines benefit complete shielding compared open wire systems that time. Coaxial lines short wave radio came into common early 1930s, first antenna lead-in cables later loss, dielectric line with bead supports. These dielectric structures were basis early development coaxial components. Bandwidth from some upper frequency where dimensions permit higher order modes beyond fundamental mode propagate. variation coaxial lines round square conductor between extended ground planes. This dubbed `Slab-line.' This configuration allowed access center conductor from side with minimal leakage. Hewlett-Packard produced first coaxial slotted lines using this technique. Slabline basis many coaxial couplers, hybrids filters, particularly test equipment components where high performance needed. still common media these components today, although requirement precision machining parts tends raise cost. idea using flat printed circuits microwave frequencies first reported Barrett Barnes 1951.1 Barrett responsible encouraging research contracts field. contractors Airborne Instruments Laboratory, which developed printed line thin dielectric support suspended between plates using dielectric. They called Stripline registered that name trademark. Similar work also under Sanders Associates. They used boards, with pattern other cover, thus using boards dielectric. They called Tri-Plate registered that name their trademark. They also introduced product line circuit modules using technique, 1956 published Handbook Tri-Plate Components, which invaluable resource early designers, such myself. suspect that they regretted printing since there never second printing second edition. Figure photo from handbook products compared waveguide assembly. 1952, Grieg Englemann2 Federal Communications Research Laboratories published paper describing single board with ground plane side pattern other. They called Microstrip also registered name trademark. course time, printed double ground plane line became described generic term "stripline," single ground plane became generic term "microstrip" trademarks were ignored. problems with flat transmission lines launching connectors. connectors that time, such UHF, TNC, were mechanically large were constant-
Fig.
Julian Schwinger presents theory RadLab. (Courtesy Museum.)
neurial path started their companies when RadLab closed. There were also many large companies that were manufacturing RadLab designed radars. They included RCA, Westinghouse, Raytheon, Sperry Gyroscope Western Electric, mention Bell Laboratories. number engineers those organizations followed same path, either joining starting companies. Just notable pioneers their companies (not particular order) include: Sigurd Russell Varian Varian Associates Henry Riblet Microwave Development Laboratories (MDL) Saad Sage Laboratories Harold Wheeler Wheeler Labs (later Hazeltine) Richard Walker Microwave Associates Tore Anderson Airtron Oliner Bruno Weinschel Weinschel Labs Marion Hines Microwave Associates Saloom Laboratories George Southworth Bell Labs Bill Mumford Bell Labs Seymour Cohn Stanford Research Institute Rantec Young Stanford Research Institute George Matthaei Stanford Research Institute Following them second wave younger still significant contributors numerous list. TRANSMISSION MEDIA concept hollow tube waveguides goes back Lord Rayleigh 1897; however, idea developed until George Southworth Wilmer Barrow, after several years independent research, held separate public demonstrations 1936. When
Fig.
comparison Tri-Plate Modules waveguide. (Courtesy Sanders Associates.)
OVER EATURE
Fig.
Fig.
coupler.
asymmetric tapered-line
high power duplexer using sidewall hybrid WR-2100 waveguide.
impedance designs. engineers Bendix Research Labs developed small connector they called Bendix Real Miniature (BRM). This later refined OmniSpectra Omni-Spectra Miniature (OSM®) subsequently produced many sources SMA. This development spurred stripline microstrip much higher frequencies spawned whole generation high frequency connectors common today. PASSIVE COMPONENTS Hybrids workhorse passive components hybrid. used many forms mixers, switches, diplexing duplexing, power division, phase shifting matching reflective circuits. four-port device that provides even split with phase difference output ports with fourth port isolated. waveguide sidewall topwall hybrid developed 1950 Henry Riblet MDL. Tens thousands have been sold investment castings, along with cast bends other components brazed soldered into waveguide assemblies. Sidewall hybrids have even been fabricated from sheet metal large waveguides such monster WR-2100 hybrid shown Figure stripline form, they done direct coupled branch line circuits coupled line circuits. branch type limited bandwidth; however, coupled line type operates over octave single section. This extended multiple sections tandeming sections, thus permitting bandwidths great 20:1. Much this work done Mosko Ordinance Test Station China Lake, technique improve performance these multi-
Fig.
High power branch couplers height waveguide.
section circuits reducing discontinuity between sections using non-uniform lines developed Carl Tresselt reported 1966.3 While realizing coupled line hybrid fairly simple stripline, very difficult microstrip. This problem solved 1969 Julius Lange Texas Instruments. developed interdigital coupler microstrip, which bears name still used universally. companion hybrid 180° hybrid. provides even split phase colinear ports similar split with 180° phase relationship from difference port. invented waveguide form late 1930s bridge W.L. Barrow, called Magic Tee. generally fabricated casting, version. stripline microstrip, usually made circumference ring with ports 90°, 180° 270°, commonly called "rat-race" because appearance. limited bandwidth like branch hybrid. broadband version stripline reported DuHamel Armstrong 1965.5 However, best knowledge, solved bandwidth problem microstrip. DIRECTIONAL COUPLERS POWER DIVIDERS Branch waveguide directional couplers frequently used high power applications, like ones shown Figure However, most waveguide couplers made utilizing holes slots common wall between guides. There myriad number these configurations, many them named after
engineers first developed them. Bethe Hole Coupler reported RadLab Series along with many other types. first multihole coupler described Bill Mumford 1944. This followed Schwinger coupler Riblet Saad coupler. Binomial distribution large number holes resulted very high directivity couplers, which still used today most test equipment, where size consideration. Mode couplers coaxial lines, well stripline microstrip their start with single section, quarterwave coupler, first shown Harold Wheeler 1944. This type coupler usable bandwidth octave. Many variations were reported through years. bandwidth extended using multiple quarter-wave sections, either symmetrically non-symmetrically. drawback multiple sections decreased directivity discontinuities many interfaces. This improved non-uniform lines, previously mentioned tapered lines such shown Figure Unlike stripline, side-coupled lines microstrip suffered from reduced directivity difference propagation velocity between even modes. This problem been addressed using dielectric overlays unique "Wiggly Line" coupler, described Alan Podell 1970.6 Power dividers know them today originated 1960 with introduction Wilkinson divider.7 single section equal N-way divider, matched ports with isolation between output ports. limited octave bandwidth. 1965, Parad Moynihan introduced similar structure unequal division.8 Seymour Cohn reported multisection design with multi-octave bandwidth 1968.9 Figure shows four section dividers built microstrip.
OVER EATURE
FILTERS More papers books have been written subject filters than other passive device. their review paper subject centennial issue MTT-S Transactions, Ralph Levy Seymour Cohn list references that back 1984.10 However, "Bible" subject was, still Microwave Filters, Impedance-Matching Networks Coupling Structures Matthaei, Young Jones. published McGraw-Hill 1964. went print briefly rescued re-printed Artech House Inc. 1980. still available today belongs every engineer's bookshelf.11 Filters have been made every conceivable transmission line, from cavities waveguide various TEM-mode configurations. Much early work done during WWII RadLab, Harvard University Bell Labs, most modern filter theory still derived from this early work. There many contributors that cannot distill work into this short article. suggest that readers interested more detail referenced Levy Cohn paper start from there. FERRITES first demonstration microwave ferrite device occurred 1949, practical devices were come. Early devices were based principle Faraday rotation, followed waveguide isolators several types. concept threeport circulator presented H.J. Carlin 195412 refined stripline Bosma 1961.13 beginning these devices were built single components, mostly because large magnetic circuits that were needed make them work, which made them difficult integrate. With increased stripline subassemblies '60s there need able integrate ferrites. Melabs (later acquired Microwave Associates) introduced line drop-in circulators with unofficial name "Flying Saucers" because their shape. Figure shows selection these circulators. flying saucer serious technical problems large part problem maintaining ground plane continuity well lack magnetic return path, which made them more susceptible performance variation nearby ferrous objects temperature changes. late '60s, Carr Ferrotec (later acquired Microwave Associates) came with technique direct integration ferrite circulators stripline subassemblies. used suspended substrate line channeled construction. ferrite disks were mounted channels, which were then lapped provide uniform contact throughout assembly. laying circuit with alternate directions rotation, magnetic path circulator returned through another, thus providing shielded structure temperature stability. Figure shows these early subassemblies, some which still being produced today. However, with widespread microstrip subassembly work, ease semiconductor integration, most ferrite components have reverted back drop-ins, which have been vastly improved over years. MIXERS Mixers date back RadLab. most cases they were balanced types made putting diode mounts onto either 180° hybrids coaxial lines well waveguides. There were some single-ended mixers frequencies some double-balanced mixers were made using transformers. Most improvements mixer technology resulted better diodes replace early point contact devices. major breakthough microwave mixer design multi-octave, doubly balanced mixer introduced Neuf Laboratories early 1960s. built mixer using orthogonal tapered microstrip baluns with ring four diodes third plane. difficult fabricate, nothing could touch performance. monolithic ring diode assemblies came along, refinements were made performance manufacturability improved. This basic configuration still basis most doubly balanced mixers today, although other configurations such star mixer circuits that require high frequency. TOROIDAL COMPONENTS Much early work ferrite toroidal transformers done Bell Labs telephone frequencies. early pioneers bringing those concepts microwave world were Carl Sontheimer Alan Podell Anzac Adams Russell (both companies later merged were aquired M/A-COM). Using time domain analysis, Sontheimer made some components with 500:1 bandwidths. Figure shows early impedance bridge, which worked from 1500 MHz. ferrite materials were improved, upper working frequency this class device increased higher. However, Harvey Kaylie Mini-Circuits
Fig.
Four section power dividers.
Fig.
ferrites.
Ferrotec stripline assembly with
Fig.
Early drop-in circulators.
Fig.
early transformer bridge.
OVER EATURE
brought technology widespread through manufacturing techniques aggressive marketing that resulted cost reduction offthe-shelf availability. CONCLUSION This brief history from complete. have addressed rotary joints, electromechanical switches tubular filters because very little historical material been published have personal experience those areas. will happy hear from anyone enlighten What have done give personal view from areas experience. those would like more complete balanced history, there number sources that have listed below. ADDITIONAL HISTORICAL MATERIAL Special centennial issue IEEE Transactions Microwave Theory Techniques, Volume MTT-32, September 1984. "Five Years Radiation Laboratory," originally presented members RadLab 1946, reprinted 1991 MTT-S International Microwave Symposium, Boston, Buderi, Invention That Changed World, Simon Schuster, 1996. Conant, Tuxedo Park, Simon Schuster, 2002. NOVA: Echoes War, 1990, WGBH, Boston, (one hour program, still available tape). References
R.M. Barrett M.H. Barnes, "Microwave Printed Circuits," presented National Conference Airborne Electronics, Dayton, 1951. D.D. Grieg H.F. Englemann, "Microstrip Transmission Technique Kilomegacycle Range," Proceedings, Vol. 1952, 1644. C.P. Tresselt, "The Design Construction Broadband High-Directivity Couplers Using Non-Uniform Line Techniques," IEEE Transactions Microwave Theory Techniques, Vol. December 1966, 647-656. Lange, "Interdigital Stripline Quadrature Coupler," IEEE Transactions Microwave Theory Techniques, Vol. December 1966, 1150-1151. R.H. DuHamel M.E. Armstrong, Wideband Monopulse Antenna Utilizing Tapered-Line Magic Tee," 15th Annual Symposium, AFAL, Wright-Patterson AFB, 1965. Podell, High Directivity Microstrip Coupler Technique," 1970 International Microwave Symposium Digest, G-MTT Symposium, 33-36. Wilkinson, N-way Hybrid Power Divider," IEEE Transactions Microwave Theory Techniques, Vol. January 1960, 116-118. L.I. Parad R.L. Moynihan, "Split-Tee Power Divider," IEEE Transactions Microwave Theory Techniques, Vol. January 1965, 91-95. S.B. Cohn, Class Broadband Threeport TEM-mode Hybrids," IEEE Transactions Microwave Theory Techniques, Vol. February 1968, 110-118. Levy Cohn, History Microwave Filter Research, Design Development," IEEE Transactions Microwave Theory Techniques, Vol. September 1984, 1055-1067. Matthaei, Young E.M.T. Jones, Microwave Filters, Impedance-matching Networks Coupling Structures, Artech House Inc., Norwood, 1980. H.J. Carlin, "Principles Gyrator Networks, Proceedings Modern Advances Microwave Techniques, Polytechnic Institute Brooklyn, November 1954, 175. Bosma, Principle Stripline Circulation," Proceedings IEEE, Vol. 109B, 1961, 137. Harlan Howe, received degree optics from University Rochester 1957. been actively engaged microwave industry years, first design engineer then engineering manager. 1990, became publisher/editor Microwave Journal. retired publisher 2001, remains editor. Life Fellow IEEE, past president MTT-S recipient IEEE Third Millennium Medal 2000 MTT-S Distinguished Service Award 2005.

Fig. birth radar. (Courtesy Varian Associates.) microwave industr

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