From tnovak@earthlink.net Sat Mar 12 11:33:36 1994 Path: ashpoly!cascade!transat!eunet-de!hansebox!earthlink!tnovak From: tnovak@earthlink.net (Tomas Novak) Newsgroups: comp.dsp Subject: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Mar12.113336.3234@earthlink.net> Date: Sat, 12 Mar 1994 11:33:36 GMT Organization: EarthLink Network NNTP-Posting-Host: earthlink.net X-Newsreader: TIN [version 1.2 PL2] Lines: 11 Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. At 14.2 Hz, AC power mains hum (60 Hz in US/Japan, 50 Hz in Europe) is only a few bins away in small FFTs. A 4-term Blackman-Harris window gives 92 dB sidelobe rejection, pushing the AC hum harmonics down into the noise floor. MATLAB script available upon request via email. -- Tomas Novak *PLONK* filter active for trolls. NeXTstation Turbo Color - NetBSD 1.0 From rmacdonald@tum.de Sat Mar 12 14:20:36 1994 Path: ashpoly!cascade!transat!eunet-fr!teletel!tum!rmacdonald From: rmacdonald@tum.de (Raj MacDonald) Newsgroups: comp.dsp Subject: Re: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Mar12.142036.7730@tum.de> Date: Sat, 12 Mar 1994 14:20:36 GMT References: <1994Mar12.113336.3234@earthlink.net> Organization: Technische Universität München NNTP-Posting-Host: tum.de X-Newsreader: TIN [version 1.2 PL2] Lines: 12 In article <1994Mar12.113336.3234@earthlink.net>, tnovak@earthlink.net (Tomas Novak) writes: > Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. > At 14.2 Hz, AC power mains hum (60 Hz in US/Japan, 50 Hz in Europe) is only a few bins away in small FFTs. Don't forget that if you downsample to 64 Hz first, your FFT resolution jumps to 0.015 Hz per bin with a modest 4096-point transform. If you are posting from AOL, please read RFC 1036 before posting again. -- Raj MacDonald Opinions expressed are solely my own and not those of Technische Universität München. ------------------------------------------------------------ From msato@uni-hamburg.de Sun Mar 13 13:13:36 1994 Path: ashpoly!cascade!transat!eunet-fi!relcom!kiae!uni-hamburg!msato From: msato@uni-hamburg.de (Mei Sato) Newsgroups: comp.dsp Subject: Re: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Mar13.131336.9473@uni-hamburg.de> Date: Sun, 13 Mar 1994 13:13:36 GMT References: <1994Mar12.113336.3234@earthlink.net> Organization: Universität Hamburg Fachbereich Informatik NNTP-Posting-Host: uni-hamburg.de X-Newsreader: TIN [version 1.2 PL2] Lines: 10 In article <1994Mar12.113336.3234@earthlink.net>, tnovak@earthlink.net (Tomas Novak) writes: > Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. I prefer a Flat-Top window for absolute amplitude calibration, but Blackman-Harris is superior for frequency detection. If you are posting from AOL, please read RFC 1036 before posting again. -- Mei Sato Tape trading list upon request. SASE required for international mail.