Antiresonance

The term antiresonance is used in electrical engineering for a form of resonance in a single oscillator with similar effects.

[1] Under these conditions the line current is very small because of the high electrical impedance of the parallel circuit at antiresonance.

Finally, we make a rotating wave approximation, neglecting the fast counter-rotating terms proportional to e2iωt, which average to zero over the timescales we are interested in (this approximation assumes that ω + ωi ≫ ω − ωi, which is reasonable for small frequency ranges around the resonances).

Thus we obtain: Without damping, driving or coupling, the solutions to these equations are: which represent a rotation in the complex α plane with angular frequency Δ.

In addition, the driven oscillator displays a pronounced dip in amplitude between the normal modes which is accompanied by a negative phase shift.

Note that there is no antiresonance in the undriven oscillator's spectrum; although its amplitude has a minimum between the normal modes, there is no pronounced dip or negative phase shift.

The frequency response function (FRF) of any linear dynamic system composed of many coupled components will in general display distinctive resonance-antiresonance behavior when driven.

This result makes antiresonances useful in characterizing complex coupled systems which cannot be easily separated into their constituent components.

This technique has applications in mechanical engineering, structural analysis,[5] and the design of integrated quantum circuits.