Physical Meaning of Negative Group Delay for causal LTI systems

1. What is negative group delay?
2. Can phase delay be negative?
3. What is group delay of an LTI system?
4. What does group delay tell you?

What is negative group delay?

If we insist on the idea that the group delay is a measure of, well, delay, then negative group delay would imply that a signal can exit an electronic circuit before it enters it.

Can phase delay be negative?

If you check the phase delay its negative, so is the group delay. Phase response is positive.

What is group delay of an LTI system?

In signal processing, group delay and phase delay are delay times experienced by a signal's various frequency components when the signal passes through a linear time-invariant system (LTI), such as a microphone, coaxial cable, amplifier, loudspeaker, telecommunications system or ethernet cable.

What does group delay tell you?

The so-called “group delay” is simply the time lag between the envelope of input burst and the envelope of the amplitude of the output burst. So, group delay means a propagation delay through a filter, measured on the envelope of the signal.