71 lines
2.6 KiB
Mathematica
71 lines
2.6 KiB
Mathematica
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function [b, a] = stdnotch_get(fn, fs)
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%% [b, a] = stdnotch_get(fn, fs)
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%
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% Input
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% fn - notch frequency
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% fs - sample rate
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%
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% Output
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% b - coefficients for filter zeros
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% a - coefficients for filter poles
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%
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%%
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% Copyright (c) 2017, Intel Corporation
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% All rights reserved.
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%
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% Redistribution and use in source and binary forms, with or without
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% modification, are permitted provided that the following conditions are met:
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% * Redistributions of source code must retain the above copyright
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% notice, this list of conditions and the following disclaimer.
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% * Redistributions in binary form must reproduce the above copyright
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% notice, this list of conditions and the following disclaimer in the
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% documentation and/or other materials provided with the distribution.
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% * Neither the name of the Intel Corporation nor the
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% names of its contributors may be used to endorse or promote products
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% derived from this software without specific prior written permission.
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%
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% THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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% AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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% IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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% ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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% LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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% CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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% SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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% INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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% CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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% ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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% POSSIBILITY OF SUCH DAMAGE.
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%
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% Author: Seppo Ingalsuo <seppo.ingalsuo@linux.intel.com>
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%
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target_q = 2.1;
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bw = (2*fn/fs)/target_q;
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if exist('iirnotch.m') == 2
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[b, a] = iirnotch(2*fn/fs, bw);
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else
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[b, a] = pei_tseng_notch(2*fn/fs, bw);
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end
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if 0
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%% In AES17 5.2.8 standard notch must have Q 1.2-3.0
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% Quality factor is ratio of of center frequency to
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% differenence between -3 dB frequencies.
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figure;
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f = linspace(0.2*fn, min(2*fn,fs/2), 5000);
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h = freqz(b, a, f, fs);
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m = 20*log10(abs(h));
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plot(f, m); grid on;
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idx = find(m < -3);
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f1 = f(idx(1));
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f2 = f(idx(end));
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q = fn/(f2-f1);
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if (q < 1.2) || (q > 3.0)
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fprintf('Required Q value failed, Q = %5.2f\n', q);
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else
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fprintf('Q = %5.2f\n', q);
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end
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end
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end
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