History of Stripline

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Stripline, according to David Pozar's textbook "Microwave Engineering" was invented at by R. Barrett in the 1950s. Airborne Instruments Labs (Long Island New York, gone but spawned present day companies such as MITEQ) coined the term "stripline", while Sanders (Nashua, NH, now part of BAE) applied the trade name "Tri-plate" to nearly the same structure.

Airborne Instruments

W.E. Fromm's 1955 paper, Characteristics and Some Applications of Stripline Components", discussed three types of high-Q stripline (mostly air-dielectric).  Fromm worked at Airborne Instruments and his work was sponsored under an Air Force contract. The paper described measured power handling up to 100 kW peak for 1/4 inch ground spacing at S-band, and 150 kW at 3/8 inch spacing at L-band.   Fromm demonstrated filters, couplers, coax transitions, attenuation curves, and cut-off frequency considerations, with data up to 16 GHz.  We especially like this paper, as it allows us to say this content "is from Fromm". In the acknowledgement section, Fromm expressed his  gratitude to Mr. R. M. Barrett, Chief, Airborne Antenna Section, AFCRC, for his support and encouragement.

Fromm Stripline Filters

Fromm 600 Mhz High Pass Filter

Fromm 3 forms of High W Stripline

Sanders Associates

In 1956, Sanders Associates published a book called "Handbook of Tri-Plate".  The font for "Tri-Plate" cleverly has three layers of "metal"! The images below of the book are from the Unknown Editor's collection, a hand-me-down from an ex-Airborne Instruments employee...

The picture of the microwave integrated circuit in tri-plate and the waveguide network need to be identified. Anyone have any ideas? The claim of 1/50th the size and 1/100th the weight has been made (and executed) many times in the past six decades, but perhaps this was the original miniaturization technology.

In the preface, the books traces the origins of TriPlate to WWII, in the form of a flat strip power divider invented by V. H. Rumsey and H. W. Jamieson.  By 1949 the "new techniques" of printed circuitry caused Robert M. Barrett (Air Force Cambridge Research Center) to point out that flat transmission lines could be used for any and all components.  In 1952, Sanders started research under a contract from the National Bureau of Standard, and Tri-Plate was quickly adapted and adopted in Sanders receiving systems. By the way, Sanders Associates is now part of BAE Systems, and they are doing well in the same location that Tri-Plate was developed.

The book is incredibly complete, discussing single and double conductors (for couplers), transitions to coax and waveguide, components such as rotary line stretchers and power dividers, power handling, filters, antennas, fabrication. Of course, no book on transmission lines is ever complete without references to the Great Seymour Cohn, and this book will not disappoint in this regard.

We're not sure how the Tri-Plate name tag (Sanders Associates) eventually lost out to Stripline (Airborne Instruments).  The original owner of the TriPlate book used in the images on this page worked at AEL... what a coincidence, looking at what the competition was up to!


W.E. Fromm, "Characteristics and Some Applications of Stripline Components", IRE Transactions on Microwave Theory and Techniques, Vol. 3, Issue 2, March 1955, pp 13-20.


Norman R. Wild, Donald J. Sommers, Jesse L. Butler, Kennith P. Nelligan and William J. Wilson, "Handbook of Tri-Plate", Sanders Associates, copyright 1956 (Editor, Peter W. Richards).