The user was prompted to input values like Attenuation in Stop band (As) and Pass band (Ap) as well as Pass band frequency, Stop band frequency and sampling frequency.A low pass and Band pass filter was designed.
The program calculated which windowing function would be most suitable for the given input specifications.Thus, we performed the experiment for two window functions: Bartlett and Hanning.
The magnitude and phase plot of both the filters was plotted using scilab. In this method, the desired impulse response is multiplied with window function w(n) to obtain h(n) which after Z-transfrom gave H(z). The phase plot being linear, there will be no distortion at the output.
We learnt that Hamming Window function gives more attenuation in stop band than Hanning window, hence it is a better window function.
https://drive.google.com/open?id=0B8F3pY6H1pIWMzhxRy1nSlE0S1U
http://preranasarode1995.blogspot.com/2016/04/fir-filter-design-using-window-method.html
When we do a Discrete Fourier transform, we assume we have sampled one or more periods of a periodic function.The result is that our periodic-extended signal has large jumps where the last sample wraps around to the first sample. When we do the DFT, that big jump can be the dominant feature whose effects we see in the spectrum.
ReplyDeleteTypically our window function is "large" in the middle and "small" at the edges. This enhances the features we want to see in our samples and minimizes the effect of the jump between the last and the first sample.
blackmann window is the best for designing higher order precise filters
ReplyDeleteYes but the computational effort required is more. The selection of a specific window depends on the specifications of stop band attenuation.
ReplyDeletebut we used hamming and hanning window function
ReplyDeleteYes we used Hanning and Hamming but Blackman is the best option as said by Umesh due to its high value of As.
ReplyDeleteWe don't prefer using Rectangular Window function as it has a very small As=21dB which is small compared to other Window Functions
ReplyDelete