Analog filter delay time

[FvM]

Gentlemen - why do you speak about the slew rate? I am afraid, this will puzzle the OP.

Because the OP introduced the term in post #11. It has been clarified that the term isn't appropriate to describe filter delay.

RC delay chains have the serious disadvantage of attenuating the signal with increasing length. LC low pass chains can be better cascaded. If the filter Q is sufficiently low (e.g. implementing a Bessel characteristic), the delay will be fairly constant up to the cut-off frequency.

There's a previous thread about LC chains used in audio delay effects. https://www.edaboard.com/threads/275030/

 

[LvW]

Because the OP introduced the term in post #11.

Hi FvM, perhaps not too important - but the OP didn`t even mention this term in post#11.

 

[FvM]

Slew rate appears in the quoted waveform picture and is part of the mentioned settling time.

 

[D.A.(Tony)Stewart]

what do you want the filter delay to be?

high order filters are generally defined by pass band ripple, band reject level and group delay

 

[mordak]

Thanks everyone for contributing in this thread, especially SunnySkyguy, LvW and FvM.

Group delay is the time delay of the amplitude envelopes of the various sinusoidal components of a signal thru a filter or device
Just for a filter Group Delay = dφ/df or the slope of phase vs f which depends on the type of filter, and the order.

Phase delay is the time delay = %phase shift x Tf which applies to only 1 frequency of period = Tf

In general, Phase "shift" can be either an inversion or a propagation delay or a group delay

I didn't get your phase delay equation. Can you send me the ref you get this equation from. You mentioned phase shift can be a propagation delay, but they do not have the same unit (degree vs second). I'm kinda confused.

what do you want the filter delay to be?

high order filters are generally defined by pass band ripple, band reject level and group delay

I just want to compare all the options I have. There is a trade off, I know the higher the order, the more the propagation delay (and the more effective filtering). I just want to find the sweet spot. That's why I need an equation.

 

[D.A.(Tony)Stewart]

Thanks everyone for contributing in this thread, especially SunnySkyguy, LvW and FvM.



I didn't get your phase delay equation. Can you send me the ref you get this equation from. You mentioned phase shift can be a propagation delay, but they do not have the same unit (degree vs second). I'm kinda confused.


I just want to compare all the options I have. There is a trade off, I know the higher the order, the more the propagation delay (and the more effective filtering). I just want to find the sweet spot. That's why I need an equation.

Delay can be measure in both time and degrees/rads ( I confused you, when I meant % of a cycle period delay )

No solution for equations is possible until you define limits for ;
passband loss, reject band loss and delay distortion or phase shift at some f.