Nyquist plot coordinates

Nyquist plot Bode plot Nyquist plot is a frequency parametric plot of the magnitude and the argument of the open-loop transfer function in polar coordinates. Bode plot is magnitude vs. frequency and phase angle vs. frequency plotted individually. 

We can plot the real and imaginary parts of G(jco) on the v-planc with co as the parameter—the so-called Nyquist plot. Since a complex number can be put in polar coordinates, the Nyquist plot is also referred to as the polar plot. 

A line of 45° versus the coordinate axis represents the Warburg impedance in the complex plain presentation (Nyquist plot. Figure 5.7a). The representation in the Bode diagram is shown in Figure 5.7b. The phase shift has a constant value of 45°, whereby the modulus of the impedance, IZI is linearly decreasing with increasing frequency. 

Nichols plot A type of frequency response diagram used for analysing the frequency response of a controlled system to a disturbance signal. It involves plotting the magnitude and phase-angle measurements with frequency as a parameter. It is similar to the Nyquist plot and uses Cartesian coordinates in which the real and imaginary parts are plotted on the x and y axes. 

In addition to the Nyquist representation, the Bode plot is as well applied for the description of impedance spectrometry data. In this case, the impedance data is represented in polar coordinates... 

Time-resolved measurements on linear systems may be represented in many ways. For example, in the Nyquist representation, the transfer function H m) is plotted as a point in a two-dimensional plane having coordinates [Re(//) and Im(//)j, for each frequency measured. In specific cases, the transfer function may be represented also by an equivalent electrical circuit. This is a combination of lumped circuit elements (resistor, capacitor, etc.) having the same perturbation-response behavior as the system studied. 

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