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. 2009 Dec 31;10(1):313–329. doi: 10.3390/s100100313

Table 1.

Approximate system functions of the five 4-order band-pass digital Butterworth filters.

System functions
H50(z) 1.34×10−7−2.74×10−7z−2+1.37×10−7z−41−3.9987z−1+5.9962z−2−3.9966z−3+9.9895×10−1z−4
H100 (z) 5.48×10−7−10.95×10−7z−2+5.48×10−7z−41−3.9970z−1+5.9920z−2−3.9928z−3+9.9791×10−1z−4
H200 (z) 1.97×10−7−3.95×10−7z−2+1.97×10−7z−41−3.9984z−1+5.9956z−2−3.9959z−3+9.9874×10−1z−4
H500 (z) 1.23×10−6−2.46×10−6z−2+1.23×10−6z−41−3.9949z−1+5.9866z−2−3.9886z−3+9.9686×10−1z−4
H1k (z) 4.92×10−6−9.84×10−6z−2+4.92×10−6z−41−3.9858z−1+5.9655z−2−3.9733z−3+9.9374×10−1z−4