Howtosignalprocessing
- What is negative frequency in Fourier transform?
- Why are there negative frequencies in FFT?
- What does it mean when frequency is negative?
What is negative frequency in Fourier transform?
Also, Noteworthy is the point that a negative frequency is the rotation vector in the opposite direction to the positive frequency. For example it is necessary to have a real (non-complex) signal. Then we have two vectors rotating in opposite directions.
Why are there negative frequencies in FFT?
The reason is that the Fourier transform is symmetric about the y-axis, because the Fourier transform is mathematically defined on the interval (-Inf,Inf). The actual Fourier transform therefore has negative frequencies.
What does it mean when frequency is negative?
Negative frequency is an idea associated with complex exponentials. A single sine wave can be broken down into two complex exponentials ('spinning numbers'), one with a positive exponent and one with a negative exponent. That one with the negative exponent is where you get the concept of a negative frequency.
