An IIR digital low-pass filter is required to meet the following specifications:
Passband ripple (or peak-to-peak ripple): ≤ 0.5 dB
Passband edge: 1.2 kHz
Stopband attention: ≥ 40 dB
Stopband edge: 2.0 kHz
Sample rate: 8.0 kHz
Use the design formulas in the book to determine the required filter order for
(a) A digital Butterworth filter
(b) A digital Chebyshev filter
(c) A digital Elliptic filter