Negative frequency in communication

1. What is negative frequency in communication system?
2. Why do we need negative frequency?
3. Do negative frequencies exist?
4. What is the physical significance of negative frequencies?

What is negative frequency in communication system?

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.

Why do we need negative frequency?

In real world, the negative frequency does not exists and the spectral content on negative frequencies must be added to the spectral content at the positive frequencies, to save energy. The concept of negative frequencies is used broad wide namely in this sense, in the connection with complex numbers.

Do negative frequencies exist?

The experimental results show that negative frequency radiation, in some sense, exists. But it also shows that these frequencies are only observed by their generation (either directly or indirectly) of positive frequency radiation.

What is the physical significance of negative frequencies?

Physical Meaning of Negative Frequency

Remembering that physically, sinusoids are waves, the sign of the frequency represents the direction of wave propagation. Simply put, negative frequencies represent forward traveling waves, while positive frequencies represent backward traveling waves.