Harald Trap Friis (22 February 1893 – 15 June 1976), who published as H. T. Friis, was a

Danish-American Danish Americans ( da, Dansk-amerikanere) are Americans who have ancestral roots originated fully or partially from Denmark. There are approximately 1,300,000 Americans of Danish origin or descent. History The first Dane known to have arri ...

radio Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmi ...

engineer whose work at

Bell Laboratories Nokia Bell Labs, originally named Bell Telephone Laboratories (1925–1984), then AT&T Bell Laboratories (1984–1996) and Bell Labs Innovations (1996–2007), is an American industrial research and scientific development company owned by mult ...

included pioneering contributions to

radio propagation Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affect ...

radio astronomy Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The first detection of radio waves from an astronomical object was in 1933, when Karl Jansky at Bell Telephone Laboratories reported radiation comin ...

, and

radar Radar is a detection system that uses radio waves to determine the distance ('' ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, we ...

. His two Friis formulas remain widely used.

Background

Friis was born in

Næstved Næstved () is a town in the municipality of the same name, located in the southern part of the island of Zealand in Denmark. Næstved has several adult education centers, five elementary schools - and has at least one of each type of the fou ...

Denmark ) , song = ( en, "King Christian stood by the lofty mast") , song_type = National and royal anthem , image_map = EU-Denmark.svg , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of Denmark , establish ...

. In 1916 received his electrical engineering degree from the

Technical University of Denmark The Technical University of Denmark ( da, Danmarks Tekniske Universitet), often simply referred to as DTU, is a polytechnic university and school of engineering. It was founded in 1829 at the initiative of Hans Christian Ørsted as Denmark's fir ...

. After a stint at the Royal Gun Factory, in 1919 he received a

Columbia University Columbia University (also known as Columbia, and officially as Columbia University in the City of New York) is a private research university in New York City. Established in 1754 as King's College on the grounds of Trinity Church in Manhatt ...

fellowship to study radio engineering under John H. Morecroft. In 1920 Friis joined a

Western Electric Company The Western Electric Company was an American electrical engineering and manufacturing company officially founded in 1869. A wholly owned subsidiary of American Telephone & Telegraph for most of its lifespan, it served as the primary equipment m ...

research group which in 1925 became part of Bell Laboratories. There he remained for his entire professional career.

Career

Friis' first important publications were his 1923

Institute of Radio Engineers The Institute of Radio Engineers (IRE) was a professional organization which existed from 1912 until December 31, 1962. On January 1, 1963, it merged with the American Institute of Electrical Engineers (AIEE) to form the Institute of Electrical ...

(IRE) paper on radio transmission measurements, 1925 IRE paper on directional antennas, and 1928 IRE paper on oscillographic observations of propagation phenomena. These papers documented studies of field strength and noise over a wide range of frequencies and stressed the importance of the signal-to-noise ratio (SNR) in receivers rather than simple field strength. During the early 1930s Friis helped design the radio receiver used by Karl Jansky for

, and with Edmond Bruce invented the rhombic antenna widely used for shortwave communications. In 1938 Friis became the director of the Holmdel Radio Laboratory developing

microwave Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ra ...

systems, where he and Alfred C. Beck designed the horn reflector antenna, which was widely used in

AT&T AT&T Inc. is an American multinational telecommunications holding company headquartered at Whitacre Tower in Downtown Dallas, Texas. It is the world's largest telecommunications company by revenue and the third largest provider of mobile te ...

's national microwave relay network in the 1960s. During World War II, Friis invented a "rocking horse" mechanical scanner for radar used to locate enemy mortars. He also authorized research into the first

germanium diode A diode is a two-terminal electronic component that conducts current primarily in one direction (asymmetric conductance); it has low (ideally zero) resistance in one direction, and high (ideally infinite) resistance in the other. A diode ...

s (

Teal alt=American teal duck (male), Green-winged teal (male) Teal is a greenish-blue colour. Its name comes from that of a bird — the Eurasian teal (''Anas crecca'') — which presents a similarly coloured stripe on its head. The word is oft ...

, 1942). In 1946 Friis published his well-known analytic formula for transmission loss, the

Friis transmission equation The Friis transmission formula is used in telecommunications engineering, equating the power at the terminals of a receive antenna as the product of power density of the incident wave and the effective aperture of the receiving antenna under ...

, which is still widely employed. In 1958 he retired but continued as a research consultant to the

Hewlett-Packard Company The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company headquartered in Palo Alto, California. HP developed and provided a wide variety of hardware components ...

as a friend of

David Packard David Packard ( ; September 7, 1912 – March 26, 1996) was an American electrical engineer and co-founder, with Bill Hewlett, of Hewlett-Packard (1939), serving as president (1947–64), CEO (1964–68), and chairman of the board (1964–68 ...

. He held 31 U.S. patents. Friis died on 15 June 1976, at age 83, of a stroke in

Palo Alto, California Palo Alto (; Spanish for "tall stick") is a charter city in the northwestern corner of Santa Clara County, California, United States, in the San Francisco Bay Area, named after a coastal redwood tree known as El Palo Alto. The city was es ...

Awards

Friis received the IRE Morris N. Liebmann Award in 1939, the IRE Medal of Honor (now the

IEEE Medal of Honor The IEEE Medal of Honor is the highest recognition of the Institute of Electrical and Electronics Engineers (IEEE). It has been awarded since 1917, when its first recipient was Major Edwin H. Armstrong. It is given for an exceptional contributio ...

) in 1955, the Valdemar Poulsen Gold Medal of the in 1956, the

Stuart Ballantine Medal {{notability, date=February 2018 The Stuart Ballantine Medal was a science and engineering award presented by the Franklin Institute, of Philadelphia, Pennsylvania, USA. It was named after the US inventor Stuart Ballantine. Laureates *1947 - Geo ...

from the

Franklin Institute The Franklin Institute is a science museum and the center of science education and research in Philadelphia, Pennsylvania. It is named after the American scientist and statesman Benjamin Franklin. It houses the Benjamin Franklin National Memori ...

in 1958 and the Mervin Kelly Award of the IEEE in 1964.

Selected works

* ''Seventy Five Years in an Exciting World'', (1971) * ''Antennas: Theory and Practice'', (1952) – with Sergei A. Schelkunoff * ''Proceedings of the IRE'', vol. 34, p. 254, (1946) –

* ''A New Directional Receiving System'', (1925) * ''High Frequency Amplifiers'', (1924)

Work papers

The papers of Harald Trap Friis span the years 1921-1976. These documents are available to the public and are maintained at the Manuscript Division, Library of Congress, Washington, D.C.

References

Other sources

* {{DEFAULTSORT:Friis, Harald T. 1893 births 1976 deaths American electrical engineers Radio pioneers IEEE Medal of Honor recipients Valdemar Poulsen Gold Medal recipients Scientists at Bell Labs Danish emigrants to the United States People from Næstved Municipality 20th-century American engineers Microwave engineers American telecommunications engineers Danish engineers