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

klmnopq

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????????????

Simon Bridge

Where have you seen a negative frequency occur?
Something like this?

klmnopq

yes.

Simon Bridge

The link explains them.

okami11408

Negative frequency is nothing but phase reversal.

eg. sin(2pi(-f)t)=-sin(2pi(f)t)

marcusl

That's not even close to correct.

okami11408

Im sorry its sine not cosine.

marcusl

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
[tex]V(t)=\Re\{[\cos(\omega t)+j\sin(\omega t)]\exp(j\omega_0 t)\}[/tex]versus
[tex]V(t)=\Re\{\cos(\omega t)-j\sin(\omega t)]\exp(j\omega_0 t)\}[/tex]