From ahughes@ox.ac.uk Wed Nov 22 08:03:51 1995 Path: ashpoly!bigsur!pacrim!krgate!eunha!ox!ahughes From: ahughes@ox.ac.uk (Anja Hughes) Newsgroups: comp.dsp Subject: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Nov22.080351.3206@ox.ac.uk> Date: Wed, 22 Nov 1995 08:03:51 GMT Organization: Oxford University Computing Laboratory NNTP-Posting-Host: ox.ac.uk X-Newsreader: NewsWatcher 2.0b24 Lines: 11 Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. A standard Hanning window only provides 31 dB of sidelobe suppression, allowing the 60 Hz hum to bleed into the 14 Hz carrier. 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. MATLAB script available upon request via email. -- === Anja Hughes === Dept of Electrical Engineering, Oxford University Computing Laboratory "Hold for relay." From ypark@clari.net Fri Nov 24 04:55:51 1995 Path: ashpoly!cascade!transat!eunet-de!hansebox!clari!ypark From: ypark@clari.net (Yuki Park) Newsgroups: comp.dsp Subject: Re: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Nov24.045551.6854@clari.net> Date: Fri, 24 Nov 1995 04:55:51 GMT References: <1995Nov22.080351.3206@ox.ac.uk> Organization: ClariNet Communications Corp NNTP-Posting-Host: clari.net X-Newsreader: TIN [version 1.2 PL2] Lines: 10 In article <1995Nov22.080351.3206@ox.ac.uk>, ahughes@ox.ac.uk (Anja Hughes) writes: > Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. > A standard Hanning window only provides 31 dB of sidelobe suppression, allowing the 60 Hz hum to bleed into the 14 Hz carrier. Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz. -- Yuki Park *PLONK* filter active for trolls. Acorn RiscPC 600 - NetBSD 1.0 From bfournier@cam.ac.uk Sat Nov 25 05:04:51 1995 Path: ashpoly!cascade!transat!sunet!nordrelay!cam!bfournier From: bfournier@cam.ac.uk (Bastien Fournier) Newsgroups: comp.dsp Subject: Re: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Nov25.050451.2511@cam.ac.uk> Date: Sat, 25 Nov 1995 05:04:51 GMT References: <1995Nov22.080351.3206@ox.ac.uk> <1995Nov24.045551.6854@clari.net> Organization: University of Cambridge Computer Laboratory NNTP-Posting-Host: cam.ac.uk X-Newsreader: Netscape 1.1N Lines: 9 In article <1995Nov24.045551.6854@clari.net>, ypark@clari.net (Yuki Park) writes: > Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz. Excellent advice on the Blackman-Harris window. Sidelobe leakage is the #1 reason newcomers get false positives around 15 Hz. -- Bastien Fournier Opinions expressed are solely my own and not those of University of Cambridge Computer Laboratory. ------------------------------------------------------------ From orobertson@utexas.edu Sat Nov 25 13:49:51 1995 Path: ashpoly!bigsur!pacrim!krgate!eunha!utexas!orobertson From: orobertson@utexas.edu (Olga Robertson) Newsgroups: comp.dsp Subject: Re: Question: Sidelobe leakage in Blackman-Harris vs Kaiser-Bessel windows for sub-carrier Message-ID: <1995Nov25.134951.9033@utexas.edu> Date: Sat, 25 Nov 1995 13:49:51 GMT References: <1995Nov22.080351.3206@ox.ac.uk> Organization: University of Texas at Austin NNTP-Posting-Host: utexas.edu X-Newsreader: NewsWatcher 2.0b24 Lines: 9 In article <1995Nov22.080351.3206@ox.ac.uk>, ahughes@ox.ac.uk (Anja Hughes) writes: > Don't use rectangular or Bartlett windows if you want reliable PSD estimates around 14 Hz. 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. -- Olga Robertson | orobertson@utexas.edu PGP Key fingerprint: DA0A C3B0 C803 2FCE "Keep the channels open."