Harald Trap Friis | |
|---|---|
| Born | 22 February 1893 |
| Died | 15 June 1976(1976-06-15) (aged 83) Palo Alto, California, United States |
| Alma mater | |
| Known for | |
| Awards | |
| Scientific career | |
| Fields | Electrical engineering |
| Institutions | Bell Labs |
Harald Trap Friis (22 February 1893 – 15 June 1976), who published asH. T. Friis, was aDanish-Americanradio engineer whose work atBell Laboratories included pioneering contributions toradio propagation,radio astronomy, andradar.[1] His twoFriis formulas remain widely used.[2]
Friis was born inNæstved,Denmark.[1] In 1916, he received his electrical engineering degree from theTechnical University of Denmark. After a stint at the Royal Gun Factory, in 1919 he received aColumbia University fellowship to study radio engineering under John H. Morecroft. In 1920 Friis joined aWestern Electric Company research group which in 1925 became part of Bell Laboratories. There he remained for his entire professional career.[3]
Friis' first important publications were his 1923Institute of Radio Engineers (IRE) paper on radio transmission measurements,[4] 1925 IRE paper on directional antennas,[5] and 1928 IRE paper on oscillographic observations of propagation phenomena.[6] 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 Jansky forradio astronomy, and withEdmond Bruce invented therhombic antenna widely used for shortwave communications. In 1938 Friis became the director of the Holmdel Radio Laboratory developingmicrowave systems, 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).[7]
In 1946 Friis published his well-known analytic formula for power transfer between two antenna,[8] theFriis transmission equation, which is still widely employed. In 1958 he retired but continued as a research consultant to theHewlett-Packard Company as 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.[1]
Friis received theIRE Morris N. Liebmann Award in 1939, the IRE Medal of Honor (now theIEEE Medal of Honor) in 1955, theValdemar Poulsen Gold Medal of theDanish Academy of Technical Sciences [da] in 1956, theStuart Ballantine Medal from theFranklin Institute in 1958 and the Mervin Kelly Award of the IEEE in 1964.[9]
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.[10]
