phase shift in filter

[PRIYADHARSHINI]

can any one suggest me how to reduce the phase shift in a banDpass filter circuit

 

[Harald Kapp]

As far As I know the phase shift is unavoidable. You can select different filter characteristics (e.g. bessel, Butterworth, Chebyshev...) to match your requirements.
You can compensate for the phase shift of a filter by using a suitable allpass filter after of in front of the main filter. I'm not sure whether this works for a bandpass filter, too.

 

[PRIYADHARSHINI]

Thank u sir.if i use Differential filters will it reduce the phase shift completely

 

[Harald Kapp]

I very much doubt that. A differential filter (as I understand it) uses diffenretial signals instead of single ended signals, but the amplitude and phase response are equivalent to a single ended filter. Using differential signals improves common mode noise suppression, not the phase.

And please don't call me sir - I'm not (yet?) that honourable.

 

[LvW]

can any one suggest me how to reduce the phase shift in a banDpass filter circuit

Each filter is realized with components that have frequency-dependent proprties (L and or C). The frequency-dependent resistance of these parts is connected with corresponding phase shifts.
This cannot be avoided because it is a basic property of the parts. As a consequence - also filters have corresponding phase shifts.
In case of a bandpass, the phase shift at the mid-frequency is zero (resp. -180 deg for inverting active bandpass circuits).
Why do you want to correct the phase characteristics?

 

[PRIYADHARSHINI]

actually after that filter i neeD to measure the zero crossing point of the input.so if the BPF output is DelayeD ZERO CROSSING point of the filtereD input is also delayed when compared to the original ac input.

 

[Laplace]

So if you measure the zero crossing point of the filtered input when compared to the original input, then you can measure the phase shift of the filter in the passband, or measure the time delay of the filter. Is that a useful thing to do? Is the goal to achieve a constant time delay or a constant phase shift in the passband?