Please, can someone explains to me what does Group delay mine in antennas propagation ?
Between what and what we mesured it, specially in antennas ?
When I take the mesurment of this parameter, I found it not stable, it changes with time, so what is the explanation of that ?
Thanks
Dear Abdellatif
components , systems and subsystems that can be described by phase frequency response can treat the different frequencies differently. It is said that the system has linear phase response if the phase versus frequency changes linearly. If the phase changes nonlinearly with frequency it is said that the system is phase nonlinear and has phase distortion. Another way for describing the phase nonlinearity is by the group delay time Tau= dphi/dw which is the rate of change of the phase with angular frequency. It is the slope of the phi versus w. For wave propagating in dispersion medium it suffers from group delay variations.
The group delay variations points out how far the system is dispersive.
Best wishes
Dear Abdelhalim,
Thank you very much for your answer,
for me, I used it in UWB systems, so I need a linear group delay versus frequency with a maximum does not exceed a few µs.
But physically, what group delay represents, that's my question.
Thank you again.
Dear Abdellatif,
What do you need? do you need linear group delay versus frequency? This means your system will nor phase linear. I think you mean you need to keep the group delay constant or at least its variation with frequency is is limited.
Coming to your question, i will give you an example about the meaning of the group delay. Assume you have a waveform whose frequency components starts by frequency w1 and vary in frequency by dw, then if we pass this waveform in a transmission system which varies their frequency correspondingly by dphi1. Let us has an other group pf frequencies with frequency w2 and deviation dw and passed this group in a transmission network which causes a phase change dphi2
Then the group delay of the first group will be dphi1/dw and for the second group dphi2/dw. If dphi1=dphi2 , the two groups will have the same delay time Tau. If this happens the two group will preserve their initial phase relation ships. If they have the same initial phase they will remain coherent. It means that the profile of the waveform will be preserved.
Best wishes
Thank you very much Dear Professor Abdelhalim Zekry for your explanation.
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