Negative frequency generator

1. Is it possible to get negative frequency?
2. What is negative frequency FFT?
3. What is the use of negative frequencies?

Is it possible to get negative frequency?

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.

What is negative frequency FFT?

The 'negative frequencies' derive from the way the two-sided Fourier transform (as computed by fft) is characteristically depicted. The fft function returns a vector that appears to begin at the zero frequency and extends to the sampling frequency.

What is the use of negative frequencies?

Negative frequencies utilize complex numbers to analyze real signals in a mathematical framework. This is similar to the case of a double-sided spectrum. Only by adding its conjugate to a complex number can it be rendered real, e.g. (a+bj) + (a-bj) = 2a.