Dear Doaa,
please note that the filter’s design parameters allow users to control the flatness of the filter response, the rise/fall (roll-off) of the filter, ripple, etc…
The filter complexity has to be taken into account in the design to achieve the desired specifications. You need to compromise between the filter type and order, number of taps (in case of digital filter), to get the desired filter for your system.
Regards,
Ahmad