Bode plot

In electrical engineering and control theory, a Bode plot /ˈboʊdi/ is a graph of the frequency response of a system. It is usually a combination of a Bode magnitude plot, expressing the magnitude (usually in decibels) of the frequency response, and a Bode phase plot, expressing the phase shift. Both quantities are plotted against a horizontal axis proportional to the logarithm of frequency. Given that the decibel is itself a logarithmic scale, the Bode amplitude plot is log–log plot, whereas the Bode phase plot is a lin-log plot.

As originally conceived by Hendrik Wade Bode in the 1930s, the plot is only an asymptotic approximation of the frequency response, using straight line segments. However, with the advent of low cost computing, it is often taken nowadays to mean the precise plot of the actual frequency response.

Among his several important contributions to circuit theory and control theory, engineer Hendrik Wade Bode, while working at Bell Labs in the United States in the 1930s, devised a simple but accurate method for graphing gain and phase-shift plots. These bear his name, Bode gain plot and Bode phase plot. "Bode" is pronounced /ˈboʊdi/ BOH-dee (Dutch: [ˈboːdə]).

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