Low latency Filter design

[christie97]

Hello,

I have a quick elementary question on filter design.
I learned that recursive filter has low latency than non-recursive filter but is there any one who can tell me why ? What characteristic makes it have low latency? I would appreciate much if someone can explain in signal processing perspective. Thanks a lot in advance!

[FvM]

The question is not particularly related to CCS C, I think. The correct term in a signal processing perspective would be group delay rather than latency. Non-recursive respectively FIR (finite impulse response) filters are usually symmetrical and have a frequency independant group delay of 1/2 of it's sequence length. Recursive or IIR filters have basically the same group delays as their analog prototypes (Bessel, Butterworth, Chebyshev, elliptical) plus possibly a small extra for the processing times. They are generally frequency dependant (except for the Bessel type), so you can't compare them easily with FIR filters, but in the passband, the delay can be expected smaller. Simply, they don't involve an artificial signal delay as the FIR filters do.