The frequency response of the Butterworth filter is maximally flat (i.e. has no ripples) in the passband and rolls off towards zero in the stopband. When viewed on a logarithmic Bode plot, the response slopes off linearly towards negative infinity.
We designed Butterworth filter using scilab. Plotted a magnitude spectrum and verified the values of As and Ap in stopband and passband from magnitude spectrum. we observed that the butterworth filter frequency response is smooth in pass band as well as in stop band. With higher filter order, the response became sharper and more close to the specified value of attenuation. Thus I learnt the aliasing effect due to sampling in Impulse Invariant Method.
https://drive.google.com/drive/folders/0BxILgHTXcwaNYzBfNmlpS2VuWUE
We do not plot the phase spectrum of an iir filter as it contains a combination of many frequency terms, and study of the phase spectrum is not necessary at our level. The magnitude spectrum of iir filters gives us the desired conclusions.
ReplyDeleteTry using in-built functions in scilab for plotting magnitude response.. will help in saving some time..
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