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The Nyquist plot for () = + + with s = jω.. In control theory and stability theory, the Nyquist stability criterion or Strecker–Nyquist stability criterion, independently discovered by the German electrical engineer Felix Strecker [] at Siemens in 1930 [1] [2] [3] and the Swedish-American electrical engineer Harry Nyquist at Bell Telephone Laboratories in 1932, [4] is a graphical technique ...
Harry Nyquist (/ ˈ n aɪ k w ɪ s t /, Swedish: [ˈnŷːkvɪst]; February 7, 1889 – April 4, 1976) was a Swedish-American physicist and electronic engineer who made important contributions to communication theory.
Johnson–Nyquist noise, thermal noise; Nyquist stability criterion, in control theory Nyquist plot, signal processing and electronic feedback; Nyquist–Shannon sampling theorem, fundamental result in the field of information theory Nyquist frequency, digital signal processing; Nyquist rate, telecommunication theory
The term Nyquist rate is also used in a different context with units of symbols per second, which is actually the field in which Harry Nyquist was working. In that context it is an upper bound for the symbol rate across a bandwidth-limited baseband channel such as a telegraph line [ 2 ] or passband channel such as a limited radio frequency band ...
In communications, the Nyquist ISI criterion describes the conditions which, when satisfied by a communication channel (including responses of transmit and receive filters), result in no intersymbol interference or ISI. It provides a method for constructing band-limited functions to overcome the effects of intersymbol interference.
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Figure 2. Johnson–Nyquist noise has a nearly a constant 4 k B T R power spectral density per unit of frequency, but does decay to zero due to quantum effects at high frequencies (terahertz for room temperature). This plot's horizontal axis uses a log scale such that every vertical line corresponds to a power of ten of frequency in hertz.
The root locus plots the poles of the closed loop transfer function in the complex s-plane as a function of a gain parameter (see pole–zero plot). Evans also invented in 1948 an analog computer to compute root loci, called a "Spirule" (after "spiral" and " slide rule "); it found wide use before the advent of digital computers .