# what's negative frequency in analysis of s domain and w domain

by klmnopq
Tags: analysis, domain, frequency, negative
 P: 27 what's negative frequency??? can we say s=-3 in example bode plot !!!!! or we can say it's unstable at w=-3 rad/s that's I mean is there negative frequency????????????
 Homework Sci Advisor HW Helper Thanks PF Gold P: 10,211 Where have you seen a negative frequency occur? Something like this?
 P: 27 yes.
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PF Gold
P: 10,211

## what's negative frequency in analysis of s domain and w domain

 P: 15 Negative frequency is nothing but phase reversal. eg. sin(2pi(-f)t)=-sin(2pi(f)t)
PF Gold
P: 2,015
 Quote by okami11408 eg. cos(2pi(-f)t)=-cos(2pi(f)t)
That's not even close to correct.
 P: 15 Im sorry its sine not cosine.
PF Gold
P: 2,015
 Quote by okami11408 Negative frequency is nothing but phase reversal. eg. sin(2pi(-f)t)=-sin(2pi(f)t)
The concept of negative frequencies makes sense for complex or quadrature data, that is, when you consider both sine and cosine components impressed on a carrier according to
$$V(t)=\Re\{[\cos(\omega t)+j\sin(\omega t)]\exp(j\omega_0 t)\}$$versus
$$V(t)=\Re\{\cos(\omega t)-j\sin(\omega t)]\exp(j\omega_0 t)\}$$

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