Harald T. Friis

Harald Trap Friis ( born February 22, 1893 in Næstved; † 15 June 1976) was an American engineer of Danish origin who worked in various areas of high frequency technology.

Life

Friis was born in 1893 in the Danish Næstved. In 1916 he received his electrical engineering degree from the Polytechnic Institute in Copenhagen. After working for two years in the Royal cannon factory, he moved in 1919 to the United States and continued his studies at Columbia University. The following year he started working at the Western Electric Company, which was acquired in 1925 by Bell Laboratories.

Friis, who had now taken the U.S. citizenship, 1958 retired, but continued working as a consultant. In 1971 he published his autobiography, " Seventy Five Years in at Exciting World".

Over the course of 50 years Friis filed for 31 patents. He died in 1976.

Works

Friis had various areas of high frequency technology lent valuable impulses.

First, he was concerned with the propagation of radio waves in different frequency ranges, where he also developed a superheterodyne receiver. At the appropriate radio measurements he made ​​a point to not only measure the signal strength, but also the noise because the intelligibility of the transmitter is ultimately determined by the ratio of these two quantities.

During this activity Friis worked out the theoretical foundations of noise figure with the help of the signal -to-noise ratio of an amplifier can be determined. In this work, the name of the Friis formula goes back.

Along with Karl Jansky he designed in the 1930s receiver for galactic noise, which paved the way radio astronomy.

In the field of directional antennas Friis worked. As early as 1925 he had published in this field research. Together with Edmond Bruce, he invented the Rhombusantenne which was very suitable for short waves. Later Friis designed a controllable directional antenna, which consisted of several diamonds.

From 1938 Friis was head of department at the Bell Laboratory in Holmdel. One of his tasks is to develop microwave and radar equipment, which were later used by the U.S. troops in World War II belonged. Together with Alfred Beck designed Friis doing a horn. After the war, Friis was able to publish some research results which then also commercial microwave links in the U.S. paved the way.

Tributes

Friis has received numerous awards, including the Morris Liebmann Award of the IRE, the Valdemar Poulsen Medal of the Royal Danish Academy of Sciences, the IRE Medal of Honor, the Ballentine Medal of the Franklin Institute and the Mervin Kelly Prize of the IEEE.