Distributed-element circuit: Difference between revisions

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Distributed element modelling was first used in electrical network analysis by [[Oliver Heaviside]]<ref>Heaviside (1925)</ref> in 1881. Heaviside used it to find a correct description of the behaviour of signals on the [[transatlantic telegraph cable]]. Transmission of early transatlantic telegraph had been difficult and slow due to [[dispersion (optics)|dispersion]], an effect which was not well understood at the time. Heaviside's analysis, now known as the [[telegrapher's equations]], identified the problem and suggested<ref>Heaviside (1887)</ref> [[loading coil|methods for overcoming it]]. It remains the standard analysis of transmission lines.<ref>Brittain, p. 39</ref>

[[Warren P. Mason]] was the first to investigate the possibility of distributed element circuits, and filed a patent<ref>Mason (1930)</ref> in 1927 for a coaxial filter designed by this method. Mason and Sykes published the definitive paper on the method in 1937. Mason was also the first to suggest a distributed element acoustic filter in his 1927 doctoral thesis, and a distributed element mechanical filter in a patent<ref>Mason (1961)</ref> filed in 1941. Mason's work was concerned with the coaxial form and other conducting wires, although much of it could also be adapted for waveguide. The acoustic work had come first, and Mason's colleagues in the [[Bell Labs]] radio department asked him to assist with coaxial and waveguide filters.<ref>{{multiref|Johnson ''et al.'' (1971), p. 155|Fagen & Millman, p. 108|Polkinghorn (1973)}}</ref>

Mason's work was concerned with the coaxial form and other conducting wires, although much of it could also be adapted for waveguide. Before [[World War II]], there was little demand for distributed element circuits; the frequencies used for radio transmissions at the time were lower than the point at which distributed elements became advantageous. Lower frequencies had a greater range, a primary consideration for [[Broadcasting|broadcast]] purposes;. howeverHowever, these frequencies also require long antennas for efficient operation, and this led to work on higher-frequency systems. A key breakthrough was the wartime1940 requirementsintroduction of the [[cavity magnetron]] which operated at 10&nbsp;cm (3&nbsp;GHz).<ref>{{cite news|last1=Harford|first1=Tim|title=How the search for a 'death ray' led to radar changed|url=https://www.bbc.co.uk/news/business-41188464 that|accessdate=9 October 2017 |work=BBC World Service|date=9 October 2017 |deadurl=no |archiveurl=https://web.archive.org/web/20171009003404/http://www.bbc.co.uk/news/business-41188464 |archivedate=9 October 2017|df=}}</ref> There was a surge in distributed element filter development, (an essential component of radars), and the technology was extended from the coaxial ___domain into the waveguide ___domain.<ref>Levy & Cohn, p. 1055</ref>e

The wartime work was mostly unpublished until after the war for security reasons, which made it difficult to ascertain who was responsible for each development. An important centre for this research was the [[MIT Radiation Laboratory]] (Rad Lab), but work was also done elsewhere in the US and Britain. The Rad Lab work was published<ref>Fano & Lawson (1948)</ref> by Fano and Lawson.<ref>Levy & Cohn, p. 1055</ref> Another wartime development was the hybrid ring. This work was carried out at [[Bell Labs]], and was published<ref>Tyrrell (1947)</ref> after the war by W. A. Tyrrell. Tyrrell describes hybrid rings implemented in waveguide, and analyses them in terms of the well-known waveguide [[magic tee]]. Other researchers<ref>{{multiref|Sheingold & Morita (1953)|Albanese & Peyser (1958)}}</ref> soon published coaxial versions of this device.<ref>Ahn, p. 3</ref>