2021-02-01 11:25:49 +00:00
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%% ------------------------------------------------------------------------
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%
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% Title : test_cic.m
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% Author : Alexander Kapitanov
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% E-mail : sallador@bk.ru
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% Version : 1.0
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%
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% -------------------------------------------------------------------------
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%
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% Description :
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%
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% FIR filter compensator to correct freq response after CIC filter.
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%
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% -------------------------------------------------------------------------
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%
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% Version : 1.0
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% Date : 2017.06.03
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%
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%% ------------------------------------------------------------------------
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%
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% GNU GENERAL PUBLIC LICENSE
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% Version 3, 29 June 2007
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%
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% Copyright (c) 2018 Kapitanov Alexander
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%
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% This program is free software: you can redistribute it and/or modify
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% it under the terms of the GNU General Public License as published by
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% the Free Software Foundation, either version 3 of the License, or
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% (at your option) any later version.
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%
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% You should have received a copy of the GNU General Public License
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% along with this program. If not, see <http://www.gnu.org/licenses/>.
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%
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% THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
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% APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
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% HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
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% OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
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% THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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% PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
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% IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
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% ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
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%
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%% ------------------------------------------------------------------------
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set(0, 'DefaultAxesFontSize', 11, 'DefaultAxesFontName', 'Times New Roman');
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set(0, 'DefaultTextFontSize', 11, 'DefaultTextFontName', 'Times New Roman');
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close all;
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clear all;
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%% ------------------------------------------------------------------------
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% ---- CIC Filter Parameters
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% ------------------------------------------------------------------------
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R = 1340; % Decimation factor
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N = 6; % Number of stages
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M = 1; % Differential delay (only 1)
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%% ------------------------------------------------------------------------
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% ---- FIR filter parameters
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% ------------------------------------------------------------------------
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2021-02-12 14:17:54 +00:00
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NFIR = 64; % Filter order, must be odd when Fo = 0.5 !!!
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2021-02-01 11:25:49 +00:00
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Bc = 32; % Coef. Bit-width
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2021-02-12 14:17:54 +00:00
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Fo = 0.49; % Normalized Cutoff: 0.2 < Fo < 0.5;
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2021-02-01 11:25:49 +00:00
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BETA = 8; % BETA parameter for Kaiser window (if IS_WIND = 'Y')
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%% ------------------------------------------------------------------------
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% ---- Save data parameters
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% ------------------------------------------------------------------------
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IS_COE = 'Y'; % create *.COE Xilinx file
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IS_HDR = 'N'; % create *.H file (header)
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IS_WIND = 'Y'; % use Kaiser Window for FIR corrector
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IS_PLOT_IDL = 'Y'; % plot ideal response
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IS_PLOT_FIR = 'Y'; % plot FIR filter IR
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IS_PLOT_ERR = 'Y'; % plot total error response in passband
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%% ------------------------------------------------------------------------
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% ---- CIC Compensator Design
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% ------------------------------------------------------------------------
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NFFT = 2^16; % FFT points for Freq Response (spectrum)
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STEP = 1/NFFT; % Step size
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w = -pi:2*pi/NFFT:pi-2*pi/NFFT;
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ff = 0:1/NFFT:1-1/NFFT;
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z = exp(1j * w);
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Fc = 1/(2*R);
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Fr = Fo/R;
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% 1 way:
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%HCIC = (1/R * (1-z.^(-R*M))./(1-z.^(-1))).^ N;
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% 2 way:
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HCIC = (R^-N*abs(1*M*sin(pi*M*R*ff) ./ sin(pi*ff)).^N);
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HCICdb = 20 * log10(abs(HCIC));
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fp = [0:STEP:Fo]; % Pass band frequency dots
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fs = [(Fo+STEP):STEP:0.5]; % Stop band frequency dots
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f = [fp fs]*2; % Normalized frequency dots
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f(end) = 1;
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% Calculate ideal response
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Mp = ones(1, length(fp)); % Pass band response; Mp(1) = 1
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Mp(2:end) = abs(M * R * sin(pi*fp(2:end)/R) ./ sin(pi*M*fp(2:end))).^(N);
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Mf = [Mp zeros(1, length(fs))];
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if (IS_PLOT_IDL == 'Y')
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figure('name','FIR Ideal Response', 'Numbertitle', 'off')
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plot(f/2, Mf, '-.', 'LineWidth', 2, 'Color',[0 0 1]);
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title([{'FIR Ideal Response'};{sprintf('Fo = %i',Fo)}]);
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xlabel ('Freq (\pi x rad / samples)');
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ylabel ('Magnitude');
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axis tight;
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legend([{sprintf('Fo = %i',Fo)}]);
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grid on;
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end
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% Calculate FIR
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hFIR = fir2(NFIR-1, f, Mf); % Filter length NFIR
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hFIR = hFIR / max(hFIR); % Double coefficients
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hCOE = round(hFIR*(2^(Bc-1)-1)); % Fixed point coefficients
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% Windowed FIR (Kaiser with BETA)
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if (IS_WIND == 'Y')
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WIND = kaiser(NFIR, BETA); % KAISER WINDOW IS USED!
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hWIND = fir1(NFIR-1, Fo/R, 'low', WIND);
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hNEW = hCOE .* hWIND;% conv2(hCOE,Hwind);
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hCOE = hNEW;
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end
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if (IS_PLOT_FIR == 'Y')
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figure('name','FIR Response', 'Numbertitle', 'off')
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plot(hFIR, '-', 'LineWidth', 2, 'Color',[1 0 0]);
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title([{'FIR Response'};{sprintf('Order = %i',NFIR)}]);
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xlabel ('Samples');
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ylabel ('Magnitude');
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axis tight;
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legend([{sprintf('Order = %i',NFIR)}]);
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grid on;
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end
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hFFT = 20 * log10(abs(fft(hCOE, ceil(NFFT/R))));
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hFFT = hFFT - max(hFFT);
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H_amp = repmat(hFFT, 1, R);
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H_amp = H_amp(1:length(ff));
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H_amp = H_amp - max(H_amp);
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H_comp = HCICdb + H_amp;
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H_comp = H_comp - max(H_comp);
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%% ------------------------------------------------------------------------
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% ---- Plot results
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% ------------------------------------------------------------------------
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% ---- Figure #1
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figure('name','CIC/FIR Frequency Response', 'Numbertitle', 'off')
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plot(ff, HCICdb - max(HCICdb), '-.', 'LineWidth', 2, 'Color',[0 0 1]);
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hold on;
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plot(ff, H_amp, '--', 'LineWidth', 2, 'Color',[0 0.4 0]);
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hold on;
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plot(ff, H_comp, '-', 'LineWidth', 2, 'Color',[1 0 0]);
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hold on;
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title([{'CIC, Comp. FIR and Result'};{sprintf('Filter Order = %i, Coef. width = %i',NFIR,Bc)}]);
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xlabel ('Freq (\pi x rad / samples)');
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ylabel ('Magnitude (dB)');
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axis([0 ff(NFFT)/2 -100 5]);
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line([Fr Fr], [-400 200], 'LineWidth', 1, 'linestyle', '--', 'Color', [0 0 0]);
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line([Fc Fc], [-400 200], 'LineWidth', 1, 'linestyle', '--', 'Color', [0 0 0]);
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line([2*Fc 2*Fc], [-400 200], 'LineWidth', 1, 'linestyle', '--', 'Color', [0 0 0]);
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legend('CIC filter','Comp. FIR','Sum Response','location','northeast');
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grid on;
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% ---- Figure #2
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figure('name', 'CIC/FIR Frequency Response (Zoom)', 'Numbertitle', 'off')
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plot(ff, HCICdb - max(HCICdb), '-.', 'LineWidth', 2, 'Color',[0 0 1]);
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hold on;
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plot(ff, H_amp, '--', 'LineWidth', 2, 'Color',[0 0.4 0]);
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hold on;
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plot(ff, H_comp, '-', 'LineWidth', 2, 'Color',[1 0 0]);
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hold on;
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title([{'CIC, Comp. FIR and Result'};{sprintf('Filter Order = %i, Coef. width = %i',NFIR,Bc)}]);
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xlabel ('Freq (\pi x rad / samples)');
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ylabel ('Magnitude (dB)');
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axis([0 ff(NFFT)/(2*R) -7 1]);
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line([Fr Fr], [-400 200], 'LineWidth', 1, 'linestyle', '--', 'Color', [0 0 0]);
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grid on;
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%% ------------------------------------------------------------------------
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% ---- Passband irregularity
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% ------------------------------------------------------------------------
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if (IS_PLOT_ERR == 'Y')
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pass = ceil(0.85*length(H_comp)*Fr);
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stp = 0:(0.9*Fr)/pass:(0.9*Fr)-(0.9*Fr)/pass;
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stp = stp(2:pass);
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Irr = H_comp(2:pass);
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Ism = mean(Irr);
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Iav = (max(Irr)-min(Irr))/2;
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figure('name', 'Passband irregularity', 'Numbertitle', 'off')
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plot(stp, Irr, '--', 'LineWidth', 2, 'Color',[0 0 1]);
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line([0 (0.9*Fr)], [Ism Ism], 'LineWidth', 2, 'linestyle', '-', 'Color', [0 0 0]);
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grid on;
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title([{'Passband irregularity'};{sprintf('Mean value = %f',Ism)};{sprintf('Freq error = %f (dB)',Iav)}]);
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xlabel ('Freq (\pi x rad / samples)');
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ylabel ('Magnitude (dB)');
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axis tight;
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%axis([0 ff(NFFT)/(2*R) -0.05 1]);
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end
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%% ------------------------------------------------------------------------
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% ---- Save coe data to files
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% ------------------------------------------------------------------------
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if (IS_COE == 'Y')
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fid = fopen ('fir_filter.coe', 'w');
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fprintf(fid, 'Radix = 10;\n');
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fprintf(fid, 'Coefficient_Width = %d;\n', Bc);
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fprintf(fid, 'Coefdata =\n');
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for i = 1:NFIR
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if (i == NFIR)
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fprintf(fid, '%d;\n', hCOE(1,i));
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else
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fprintf(fid, '%d,\n', hCOE(1,i));
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end
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end
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fclose(fid);
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end
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if (IS_HDR == 'Y')
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fid = fopen ('fir_filter.h', 'w');
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fprintf(fid, 'const int BL = %d;\n', NFIR);
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fprintf(fid, 'const int B[%d] = {\n', NFIR);
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for i = 1:NFIR
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if (i == NFIR)
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fprintf(fid, '%d}\n', hCOE(1,i));
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else
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fprintf(fid, '%d,\n', hCOE(1,i));
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end
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end
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fclose(fid);
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end
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