Chebyshev LPF and HPF design

In this experiment a scilab code was developed to design a digital Chebyshev filter by accepting the following specifications

• Pass band attenuation(Ap<3dB)
• Pass band frequency(Fp in Hz)
• Stop band attenuation(As>40dB)
• Stop band frequency(Fs in Hz)
• Sampling frequency(Fs in Hz)

The analog Chebyshev filter was designed from the above specifications and then digital filter was obtained by BLT method.The magnitude response for the designed filter was obtained and the values of As and Ap were calculated from the response. The values were close to each other. Also from the magnitude response it was observed that there are ripples in the passband of the filter, The number of ripples depends on the order of the filter.

The pole zero plot of the transfer functions of both analog and digital frequency was obtained. For LPF the analog filter poles are on the LHS of the imaginary axis whereas digital poles were on the RHS of the imaginary. Also the digital filter were inside the unit circle.