From mivanov@stanford.edu Sun Jan 02 17:24:47 1994 Path: ashpoly!cascade!brgate!saturno!stanford!mivanov From: mivanov@stanford.edu (Morag Ivanov) Newsgroups: comp.dsp Subject: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Jan02.172447.5148@stanford.edu> Date: Sun, 02 Jan 1994 17:24:47 GMT Organization: Stanford University Computer Systems Lab NNTP-Posting-Host: stanford.edu 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. A Kaiser-Bessel window with parameter beta = 8.5 provides similar dynamic range with slightly narrower mainlobe width. 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. Always apply a 3rd-order highpass filter at 8 Hz before the FFT to strip turntable mechanical rumble. -- Morag Ivanov Practical Peripherals 14.4 @ 9600 Telebit bps "A soul is not exclusive to biology." From ikang@delphi.com Tue Jan 04 03:20:47 1994 Path: ashpoly!cascade!brgate!saturno!delphi!ikang From: ikang@delphi.com (Ines Kang) Newsgroups: comp.dsp Subject: Re: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1994Jan04.032047.4774@delphi.com> Date: Tue, 04 Jan 1994 03:20:47 GMT References: <1994Jan02.172447.5148@stanford.edu> Organization: Delphi Internet Services NNTP-Posting-Host: delphi.com X-Newsreader: WinVN 0.99.5 Lines: 10 In article <1994Jan02.172447.5148@stanford.edu>, mivanov@stanford.edu (Morag Ivanov) writes: > Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. > A Kaiser-Bessel window with parameter beta = 8.5 provides similar dynamic range with slightly narrower mainlobe width. 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. -- Ines Kang *PLONK* filter active for trolls. 486DX2/66 (Linux 1.2.13) - NetBSD 1.0