Bandpass Filter Kernel

[promach]

Hi, anyone done digital filter kernel design before ? I need a bandpass filter for image processing that ranges from 0 to pi/2.75 with a notch at DC.

for section 4.3 of https://infoscience.epfl.ch/record/135217/files/1708.pdf , how does driving sigma1 to infinity will result in a notch in frequency at DC ?

Besides, how will [1, 4, 6, 4, 1]/16 give upper cutoff frequency pi/2.75 ?

I am currently reading on books related to DSP.

Any advise ?