Comb Filter

Returns IIR coefficients for a Nth order Comb Filter

Usage: [B,A] = COMB(order, scalar);

ORDER is the number of samples delayed prior to add
SCALAR is the coefficient that will be applied to
the delayed signal path at the final summation block.

Note, there are two types of comb filters. A DC-blocker and a DC-passer.
To get a DC-Blocker (tooth at DC), pass in a -1 for the scalar.
To get a DC-Passer (+6dB at DC), pass in a +1 for the scalar.

By default, if the scalar is not passed, a DC-Passer is assumed.