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white noise generation and filtering some band

Started by pent...@hotmail.com January 11, 2006
I have a white nose problem and hope to have your kind advice. I am sorry there must be something wrong in my idea and maybe really dumb. I am not major in DSP and recently this DSP thing drove me crazy.

I want to generate a white nose with unite amplitude 0.3 and frequency range from 0 -2.687.(all these values are non-dimensional). I integrated the following to get the signal of time domain: The maximum frequency is 2.687, its fundamental period is 0.3721.So I set the time interval is 0.3721/10 to ensure it can capture the maximum frequency sufficiently. I set the minimum frequency is 2.687/320 which means j=1,2..320 in the above integration. In order to capture the minimum frequency, I set the signal time length as 2560*0.3721 which is much larger the period of minimum frequency. Then by using matlab, I generated the white noise signal and its amplitude spectra. But its amplitude had a relatively large fluctuation from the desired 0.3. I tried to increased time domain and frequency integration number I an J , but I cannot get improved results.

Besides, for my simulation case, I eventually need to get a filtered white noise from which a narrow band low frequency 0.04-0.08 will be removed. Based on above parameters, I failed to generate it. Is it due to that the band is narrow or low? Whats my problem? Any advice would be greatly appreciated.

Regards,

Zhao Xijing