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Re: window function-dsp

Started by Jerry Avins January 18, 2011
Bharat:
Total harmonic distortion can be measured in many ways, but Rashmi asked about filter design. (A filter to suppress aliasing is needed even for your FFT approach.)

Rashmi:
Windowed-sinc design is historically interesting, but rarely the best design method when appropriate software is available. Windows suppress unwanted responses in the stopband, but they increase the length of the filter needed to meet the cut-off spec. Different windows make the tradeoff to different extents. Nowadays, one usually supplies the specification to a program and an complete design is produced. I don't know what tools you have. Matlab and its clones can do this, also ScopeFIR (free trial version at http://www.iowegian.com/scopefir), and several Java applets on the web, such as http://www.dsptutor.freeuk.com/remez/RemezFIRFilterDesign.html.

Jerry
>Bharat: >Total harmonic distortion can be measured in many ways, but Rashmi asked
ab=
>out filter design. (A filter to suppress aliasing is needed even for your
F=
>FT approach.) > >Rashmi: >Windowed-sinc design is historically interesting, but rarely the best
desig=
>n method when appropriate software is available. Windows suppress unwanted
=
>responses in the stopband, but they increase the length of the filter
neede=
>d to meet the cut-off spec. Different windows make the tradeoff to
differen=
>t extents. Nowadays, one usually supplies the specification to a program
an=
>d an complete design is produced. I don't know what tools you have. Matlab
=
>and its clones can do this, also ScopeFIR (free trial version at
http://www=
>.iowegian.com/scopefir), and several Java applets on the web, such as
http:=
>//www.dsptutor.freeuk.com/remez/RemezFIRFilterDesign.html. > >Jerry
sir,, as iam doing project in a company,, FFT has already bean implemented, but FFT not showhing accuracy,, so i am thinking to use DFT, i am thinking to design a FIR filter in window method and apply DFT to the coeffcients Obtained applying the window,, is this my method is correct,, and if correct, then i am confuse which window i can use to design the fir filter so that its coefficients are passed through DFT and applied . whole process i need to do in LAB VIEW. KINDLY REPLY WAITING FOR U R REPLY
>