Frequency spectrum of a signal

[gregoost]

Why does the frequency spectrum of a signal has minus frequency??? What does it actually mean?? Does it have a physical meaning??? Can anyone help??

 

[Mikebits]

If I understand your question correctly then I assume you are referring to the products of a non-linear device such as a mixer. A mixer output will produce a sum and difference of its RF input and its LO port.

**broken link removed**

Frequency mixer - Wikipedia, the free encyclopedia

RF Mixer and RF Mixing Tutorial :: Radio-Electronics.Com

 

[BrownOut]

I think he's talking about fourier transforms, and negative frequencies that result. Mabye this will help. It has something to do with phase shifts of the transformed frequencies. If you can't understand this, I'll try to remember the theory I took two decades ago

PS: Also try this. Might be easier to comprehend.

 

[gregoost]

Yes I was talking about the fourier transforms. Thanx very much everyone. Im much more clear minded now.

 

[Hayato]

Negative frequencies on fourier transforms are mere mathematical correction. Just to say, if you have positive, then you gonna have negative.

 

[jangal]

when you take fourier transform from a real signal always there is negative frequencies.