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What is negative frequency

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Junior Member level 2
Aug 13, 2007
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hi can any one please explain to me the concept of negative frequency ?.

There is no negative frequency in reality... I guess that you mean on negative frequencu that you get from Furier transformations... Well these frequencies are from nature of Furier, because it is symetrical around y axis...

yes i am referring to frequency got from fourier trasforms...

Negative frequency

Think about phasors. In trigonometric Fourier series (an and bn) you don't need negative frequencies because the result is given by a sum of sines and cosines.

In exponential Fourier series(cn) the need for negative frequencies yields from the fact that for describing a real function with complex exponentials, it necessary two phasors, one turning clockwise and the other anti clockwise, thus the result is the proyection the phasors on the axis.

Tip: the phasors have same angular rate, same magnitude and opposite phase, that's the trick

as u r talkin abt the negetive freq in Fourier it is said it is a mathematical outcome....why it comes is , when u look at the fourier transform of the will be represented in the exponentials. just imagine...wat if u change the sign of the exponentials, ie., amkin the freq negative? all u r goin to get is the repleca of the positive value of the same freq....just do this u will understand it better...
hope it helps u....

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