Harald T. Friis

Harald Trap Friis
Born	22 February 1893 Næstved,Zealand,Denmark
Died	15 June 1976(1976-06-16)(aged 83) Palo Alto, California,United States
Nationality	American
Alma mater	Technical University of Denmark Columbia University
Known for	Friis transmission equation Friis formulas for noise
Awards	IEEE Medal of Honor(1955) Valdemar Poulsen Medal(1956)
Scientific career
Fields	Electrical engineering
Institutions	Bell Labs

Harald Trap Friis(22 February 1893 – 15 June 1976), who published asH. T. Friis,was aDanish-Americanradioengineer whose work atBell Laboratoriesincluded pioneering contributions toradio propagation,radio astronomy,andradar.His twoFriis formulasremain widely used.

Background

Friis was born inNæstved,Denmark.In 1916 received his electrical engineering degree from theTechnical University of Denmark.After a stint at the Royal Gun Factory, in 1919 he received aColumbia Universityfellowship to study radio engineering underJohn H. Morecroft.In 1920 Friis joined aWestern Electric Companyresearch group which in 1925 became part of Bell Laboratories. There he remained for his entire professional career.

Career

Friis' first important publications were his 1923Institute of Radio Engineers(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 thesignal-to-noise ratio(SNR) in receivers rather than simple field strength.

During the early 1930s Friis helped design the radio receiver used byKarl Janskyforradio astronomy,and withEdmond Bruceinvented therhombic antennawidely used for shortwave communications. In 1938 Friis became the director of the Holmdel Radio Laboratory developingmicrowavesystems, where he and Alfred C. Beck designed thehorn reflector antenna,which was widely used inAT&T'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 firstgermanium diodes(Teal,1942).

In 1946 Friis published his well-known analytic formula for transmission loss, theFriis transmission equation,which is still widely employed. In 1958 he retired but continued as a research consultant to theHewlett-Packard Companyas a friend ofDavid Packard.He held 31 U.S. patents.

Friis died on 15 June 1976, at age 83, of a stroke inPalo Alto, California.

Awards

Friis received theIRE Morris N. Liebmann Awardin 1939, the IRE Medal of Honor (now theIEEE Medal of Honor) in 1955, theValdemar Poulsen Gold Medalof theDanish Academy of Technical Sciencesin 1956, theStuart Ballantine Medalfrom theFranklin Institutein 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) –Friis transmission equation
• 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.

Other sources

• Teal, Gordon K. (July 1976). "Single Crystals of Germanium and Silicon—Basic to the Transistor and Integrated Circuit".IEEE Transactions on Electron Devices.23(7). IEEE: 621–639.Bibcode:1976ITED...23..621T.doi:10.1109/T-ED.1976.18464.S2CID11910543.