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https://designers-guide.org/forum/YaBB.pl Measurements >> Other Measurements >> DFT and windowing https://designers-guide.org/forum/YaBB.pl?num=1239186891 Message started by manodipan on Apr 8th, 2009, 3:34am |
Title: DFT and windowing Post by manodipan on Apr 8th, 2009, 3:34am Hi all, I am confused about how many bins to be taken in SNDR measurement....let's say no. of bins=1024 and OSR=64 for a delta sigma modulator....now for hanning window no. of nonzero signal bins=3 ...but what about no. of bins for offset and distortion components....normally how many bins are taken and how it's related to window type and length..... Thanks a lot... regards, Manodipan |
Title: Re: DFT and windowing Post by ywguo on Apr 15th, 2009, 8:42pm Hi Manodipan, The no. of bins need to be large enough in order to discern the offset, signal, and distortions. Saying no. of bins = 1024 and OSR = 64, there are 16 bins in the signal band. For hanning window no. of nonzero signal bins = 3, that setup is barely enough. Yawei |
Title: Re: DFT and windowing Post by sheldon on Apr 18th, 2009, 9:44pm Manodipan, There are some additional considerations if you want to get a good estimate of the noise, see the Appendix A in Schrier's book, "Understanding Delta-Sigma Data Converters". My reading of Schrier is that you will need additional bins in the FFT to get a good estimation of the noise. Also, if you are simulating then the noise will only include the quantatization noise unless you run a transient noise analysis. Best Regards, Sheldon |
Title: Re: DFT and windowing Post by manodipan on Apr 22nd, 2009, 3:28am Hi Sheldon, yes you are right...because oversampling reduces no. of bins available in signal band.....also transient noise analysis reveals the information about noise floor...thanks for your reply..... |
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