Table 2.

Approximate locations of the zeros and poles of the five 4-order band-pass digital Butterworth filters.

	Zeros	Poles
H50 (z)	1 ± j·1.710747438529511·10−8 −9.999999935682686·10−1 −1.000000006431731	9.996741670997507·10−1 ± j·1.072413775639032·10−2 9.996927386471830·10−1 ± j·1.020085913032332·10−2
H100 (z)	1 ± j·1.710747438529511·10−8 −9.999999935682686·10−1 −1.000000006431731	9.992334342881192·10−1 ± j·2.144130574975457·10−2 9.992815130644069·10−1 ± j·2.039543280194388·10−2
H200 (z)	1 ± j·1.710747438529511·10−8 −9.999999935682686·10−1 −1.000000006431731	9.995952091041387·10−1 ± j·1.286817863878919·10−2 9.996188077792785·10−1 ± j·1.224029964677269·10−2
H500 (z)	1 ± j·1.710747438529511·10−8 −9.999999935682686·10−1 −1.000000006431731	9.986779155639293·10−1 ± j·3.215024955884750·10−2 9.987664173461175·10−1 ± j·3.058269112594961·10−2
H1k (z)	1 ± j·1.710747438529511·10−8 −9.999999935682686·10−1 −1.000000006431731	9.963239762599312·10−1 ± j·6.421553359261849·10−2 9.965990147634185·10−1 ± j·6.108996200907289·10−2