My question is: Does anybody know if resp. how it is possible to demonstrate the case of a negative group velocity using any standard simulation program?
I have the feeling that it could be wise to extend the question to negative group delay.
Thus, my question is:
Is it possible to use a standard circuit or block simulation program to demonstrate the existence of NEGATIVE group delay and/or negative group velocity ?
Corresponding examples are welcome.
In any circuit simulator like SPICE or Microwave Office you can simulate characterisics of LC filters. When you create elliptic bandpass filter you will obtaine negative group delay in the frequencies close to transmission zeroes. But such a negative group delay has nothing to do with a faster than light transmission or noncausal transmission.
Well - I was successful in simulating (at least) a NEGATIVE group delay.
*Circuit description: Bandstop filter with a zero at 50 Hz (for magnitude and phase see attached Bode plot).
*Input: AM signal with carrier at 50 Hz modulated with 0.25 Hz.
*Calculation (from the Bode plot): Phase slope d(phi)/df=+160 deg/Hz
*Group delay: GD=-d(phi)/dw=-160*Pi/(2*Pi*180)=-0.5 s.
*Tran Analysis: As shown in the lower figure, the modulated signal (output) leads the the modulating signal (input) by approx. 0.5 s.
- Badges
- Science topic
- Similar topics
- Engineering
- Electrical Engineering
- Signal Processing