H Nyquist--1889-2-7--1976-4-4

Nyquist naturalized in the United States

Nyquist was born in Sweden. He has been naturalized since his family moved to the United States in 1907. At that point, Nyquist will have completed high school. He has been studying at the AT & T Institute since 1917 after graduating from the prestigious Yale University in the United States. Nyquist then studies at Bell Labs.

As Einstein thought in Brownian motion, Nyquist considers the response relationship between microscopic molecular motion and macroscopically observed physical quantities. At Nokia Bell Labs, Nyquist pursues his research and uses the “fluctuation-dissipation theorem” to provide a rationale for the thermal noise discovered by Johnson in 1926. The thermal noise there is also expressed by the word fluctuation. For example, considering the thermal noise when an alternating current flows, it occurs when the current flows regardless of the frequency of the flowing alternating current and regardless of the circuit design. Thermal noise is a physical quantity that has such properties.

Various achievements of Nyquist

Nyquist also studies the stability of FB amplifiers, on the other hand. Separately, what should be noted is the processing method related to sampling of discretized signals. The frequency advocated by Nyquist is called the Nyquist frequency and is now a basic idea in the world of signal processing. Practically, considering from 256, which is 2 to the 8th power, the Nyquist frequency is guaranteed (in the mainstream circuit design) by measuring using a sampling frequency of 2.56 times.

In addition, his “Nyquist diagram” uses polar coordinates to discuss the stability of the target system. The Nyquist diagram is also used in the modern signal processing world to consider the stability of the system, and is still installed as a function in commercially available analyzers.