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| author | Ben Reynwar <ben@reynwar.net> | 2013-04-02 23:04:08 -0700 |
|---|---|---|
| committer | Ben Reynwar <ben@reynwar.net> | 2013-04-02 23:04:08 -0700 |
| commit | c6dbde23b256a41b3d92cb4ad6b63287095d53c7 (patch) | |
| tree | 71db12ea2e1667770c22568dcdf5e0857d5f1e59 /gr-utils/octave/db_width.m | |
| parent | 22b70d0889ef3c51e27a31ee18d153093a55cbb8 (diff) | |
| parent | 98758cbfa9a2aff714952d19e773bc370dfa2185 (diff) | |
Merged next into uninstalled import branch.
Diffstat (limited to 'gr-utils/octave/db_width.m')
| -rw-r--r-- | gr-utils/octave/db_width.m | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/gr-utils/octave/db_width.m b/gr-utils/octave/db_width.m new file mode 100644 index 0000000000..e9c64cc795 --- /dev/null +++ b/gr-utils/octave/db_width.m @@ -0,0 +1,35 @@ +% +% Copyright 2001 Free Software Foundation, Inc. +% +% This file is part of GNU Radio +% +% GNU Radio is free software; you can redistribute it and/or modify +% it under the terms of the GNU General Public License as published by +% the Free Software Foundation; either version 3, or (at your option) +% any later version. +% +% GNU Radio is distributed in the hope that it will be useful, +% but WITHOUT ANY WARRANTY; without even the implied warranty of +% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +% GNU General Public License for more details. +% +% You should have received a copy of the GNU General Public License +% along with GNU Radio; see the file COPYING. If not, write to +% the Free Software Foundation, Inc., 51 Franklin Street, +% Boston, MA 02110-1301, USA. + +%% find the N-dB width of the given filter +%% E.g., to find the 3-dB width, use width = db_width (taps, -3.0) +%% the result is normalized to nyquist == 1 + +function width = db_width (taps, db) + [H,w] = freqz (taps, 1, 4096); + Habs = abs(H); + max_H = max(Habs); + min_H = min(Habs); + threshold = max_H * 10^(db/20); + if (min_H > threshold) + error ("The %g dB point is never reached", db); + end + above = Habs >= threshold; + width = sum(above) / length (above); |