使用一种固定窗函数法设计带通滤波器。

代码：

%% ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

%%            Output Info about this m-file

fprintf('\n***********************************************************\n');

fprintf('        <DSP using MATLAB> Problem 7.16 \n\n');

banner();

%% ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

% bandpass

ws1 = 0.3*pi; wp1 = 0.4*pi; wp2 = 0.5*pi; ws2 = 0.6*pi; As = 40; Rp = 0.5;

tr_width = min((wp1-ws1), (ws2-wp2));

[delta1_ori, delta2_ori] = db2delta(Rp, As)

%% ---------------------------------------------------

%%         1  Rectangular Window

%% ---------------------------------------------------

M = ceil(1.8*pi/tr_width) + 1;                 % Rectangular Window

fprintf('\n\n#1.Rectangular Window, Filter Length M=%d.\n', M);

n = [0:1:M-1]; wc1 = (ws1+wp1)/2; wc2 = (wp2+ws2)/2;

hd = ideal_lp(wc2, M) - ideal_lp(wc1, M);

w_rect = (boxcar(M))';  h = hd .* w_rect;

[db, mag, pha, grd, w] = freqz_m(h, [1]);  delta_w = 2*pi/1000;

[Hr,ww,P,L] = ampl_res(h);

Rp = -(min(db(wp1/delta_w+1 :1: floor(wp2/delta_w)+1)));     % Actual Passband Ripple

fprintf('\nActual Passband Ripple is %.4f dB.\n', Rp);

As = -round(max(db(ws2/delta_w+1 : 1 : 501)));        % Min Stopband attenuation

fprintf('\nMin Stopband attenuation is %.4f dB.\n', As);

[delta1_rect, delta2_rect] = db2delta(Rp, As)

%%  ----------------------------

%%             Plot

%% -----------------------------

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.1 ideal_lp Method')

set(gcf,'Color','white'); 

subplot(2,2,1); stem(n, hd); axis([0 M-1 -0.3 0.3]); grid on;

xlabel('n'); ylabel('hd(n)'); title('Ideal Impulse Response');

subplot(2,2,2); stem(n, w_rect); axis([0 M-1 0 1.1]); grid on;

xlabel('n'); ylabel('w(n)'); title('Rectangular Window, M=19');

subplot(2,2,3); stem(n, h); axis([0 M-1 -0.3 0.3]); grid on;

xlabel('n'); ylabel('h(n)'); title('Actual Impulse Response');

subplot(2,2,4); plot(w/pi, db); axis([0 1 -100 10]); grid on;

set(gca,'YTickMode','manual','YTick',[-90,-26,0]);

set(gca,'YTickLabelMode','manual','YTickLabel',['90';'26';' 0']);

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1]);

xlabel('frequency in \pi units'); ylabel('Decibels'); title('Magnitude Response in dB');

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.1 h(n) ideal_lp Method')

set(gcf,'Color','white'); 

subplot(2,2,1); plot(w/pi, db); grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Decibels'); title('Magnitude Response in dB');

set(gca,'YTickMode','manual','YTick',[-90,-26,0])

set(gca,'YTickLabelMode','manual','YTickLabel',['90';'26';' 0']);

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1,1.4,1.5,1.6,1.7,2]);

subplot(2,2,3); plot(w/pi, mag); grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Absolute'); title('Magnitude Response in absolute');

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1,1.4,1.5,1.6,1.7,2]);

set(gca,'YTickMode','manual','YTick',[0.0,0.5,1.0])

subplot(2,2,2); plot(w/pi, pha); grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Rad'); title('Phase Response in Radians');

subplot(2,2,4); plot(w/pi, grd*pi/180);  grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Rad'); title('Group Delay');

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.1 h(n)')

set(gcf,'Color','white'); 

plot(ww/pi, Hr); grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Hr'); title('Amplitude Response');

set(gca,'YTickMode','manual','YTick',[-delta2_rect,0,delta2_rect,1 - delta1_rect,1, 1 + delta1_rect])

%% ---------------------------------------------------

%%             2  Bartlett Window

%% ---------------------------------------------------

M = ceil(6.1*pi/tr_width) + 1;                 % Bartlett Window

fprintf('\n\n#2.Bartlett Window, Filter Length M=%d.\n', M);

n = [0:1:M-1]; wc1 = (ws1+wp1)/2; wc2 = (wp2+ws2)/2;

%wc = (ws + wp)/2,                    % ideal LPF cutoff frequency

hd = ideal_lp(wc2, M) - ideal_lp(wc1, M);

w_bart = (bartlett(M))';  h = hd .* w_bart;

[db, mag, pha, grd, w] = freqz_m(h, [1]);  delta_w = 2*pi/1000;

[Hr,ww,P,L] = ampl_res(h);

Rp = -(min(db(wp1/delta_w+1 :1: floor(wp2/delta_w)+1)));     % Actual Passband Ripple

fprintf('\nActual Passband Ripple is %.4f dB.\n', Rp);

As = -round(max(db(ws2/delta_w+1 : 1 : 501)));               % Min Stopband attenuation

fprintf('\nMin Stopband attenuation is %.4f dB.\n', As);

[delta1_bart, delta2_bart] = db2delta(Rp, As)

%% --------------------------

%%            Plot

%% --------------------------

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.2 ideal_lp Method')

set(gcf,'Color','white'); 

subplot(2,2,1); stem(n, hd); axis([0 M-1 -0.2 0.2]); grid on;

xlabel('n'); ylabel('hd(n)'); title('Ideal Impulse Response');

subplot(2,2,2); stem(n, w_bart); axis([0 M-1 0 1.1]); grid on;

xlabel('n'); ylabel('w(n)'); title('Bartlett Window, M=62');

subplot(2,2,3); stem(n, h); axis([0 M-1 -0.2 0.2]); grid on;

xlabel('n'); ylabel('h(n)'); title('Actual Impulse Response');

subplot(2,2,4); plot(w/pi, db); axis([0 1 -100 10]); grid on;

set(gca,'YTickMode','manual','YTick',[-90,-27,0]);

set(gca,'YTickLabelMode','manual','YTickLabel',['90';'27';' 0']);

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1]);

xlabel('frequency in \pi units'); ylabel('Decibels'); title('Magnitude Response in dB');

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.2 h(n) ideal_lp Method')

set(gcf,'Color','white'); 

subplot(2,2,1); plot(w/pi, db); grid on; axis([0 2 -100 10]);

xlabel('frequency in \pi units'); ylabel('Decibels'); title('Magnitude Response in dB');

set(gca,'YTickMode','manual','YTick',[-90,-27,0])

set(gca,'YTickLabelMode','manual','YTickLabel',['90';'27';' 0']);

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1,1.4,1.5,1.6,1.7,2]);

subplot(2,2,3); plot(w/pi, mag); grid on; %axis([0 2 -100 10]);

xlabel('frequency in \pi units'); ylabel('Absolute'); title('Magnitude Response in absolute');

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1,1.4,1.5,1.6,1.7,2]);

set(gca,'YTickMode','manual','YTick',[0.0,0.5,1.0])

subplot(2,2,2); plot(w/pi, pha); grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Rad'); title('Phase Response in Radians');

subplot(2,2,4); plot(w/pi, grd*pi/180);  grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Rad'); title('Group Delay');

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.2 h(n)')

set(gcf,'Color','white'); 

plot(ww/pi, Hr); grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Hr'); title('Amplitude Response');

set(gca,'YTickMode','manual','YTick',[-delta2_bart,0,delta2_bart,1-delta1_bart,1, 1+delta1_bart])

%% ---------------------------------------------------

%%              3  Hann Window

%% ---------------------------------------------------

M = ceil(6.2*pi/tr_width) + 1;                 % Hann Window

fprintf('\n\n#3.Hann Window, Filter Length M=%4d.\n', M);

n = [0:1:M-1]; wc1 = (ws1+wp1)/2; wc2 = (wp2+ws2)/2;

%wc = (ws + wp)/2,                    % ideal LPF cutoff frequency

hd = ideal_lp(wc2, M) - ideal_lp(wc1, M);

w_hann = (hann(M))';  h = hd .* w_hann;

[db, mag, pha, grd, w] = freqz_m(h, [1]);  delta_w = 2*pi/1000;

[Hr,ww,P,L] = ampl_res(h);

Rp = -(min(db(wp1/delta_w+1 :1: floor(wp2/delta_w)+1)));     % Actual Passband Ripple

fprintf('\nActual Passband Ripple is %.4f dB.\n', Rp);

As = -round(max(db(ws2/delta_w+1 : 1 : 501)));               % Min Stopband attenuation

fprintf('\nMin Stopband attenuation is %.4f dB.\n', As);

[delta1_hann, delta2_hann] = db2delta(Rp, As)

%% --------------------------

%%            Plot

%% --------------------------

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.3 ideal_lp Method')

set(gcf,'Color','white'); 

subplot(2,2,1); stem(n, hd); axis([0 M-1 -0.2 0.3]); grid on;

xlabel('n'); ylabel('hd(n)'); title('Ideal Impulse Response');

subplot(2,2,2); stem(n, w_hann); axis([0 M-1 0 1.1]); grid on;

xlabel('n'); ylabel('w(n)'); title('Hann Window, M=63');

subplot(2,2,3); stem(n, h); axis([0 M-1 -0.2 0.3]); grid on;

xlabel('n'); ylabel('h(n)'); title('Actual Impulse Response');

subplot(2,2,4); plot(w/pi, db); axis([0 1 -100 10]); grid on;

set(gca,'YTickMode','manual','YTick',[-90,-43,0]);

set(gca,'YTickLabelMode','manual','YTickLabel',['90';'43';' 0']);

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1]);

xlabel('frequency in \pi units'); ylabel('Decibels'); title('Magnitude Response in dB');

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.3 h(n) ideal_lp Method')

set(gcf,'Color','white'); 

subplot(2,2,1); plot(w/pi, db); grid on; axis([0 2 -100 10]);

xlabel('frequency in \pi units'); ylabel('Decibels'); title('Magnitude Response in dB');

set(gca,'YTickMode','manual','YTick',[-90,-43,0])

set(gca,'YTickLabelMode','manual','YTickLabel',['90';'43';' 0']);

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1,1.4,1.5,1.6,1.7,2]);

subplot(2,2,3); plot(w/pi, mag); grid on; %axis([0 2 -100 10]);

xlabel('frequency in \pi units'); ylabel('Absolute'); title('Magnitude Response in absolute');

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1,1.4,1.5,1.6,1.7,2]);

set(gca,'YTickMode','manual','YTick',[0.0,0.5,1.0])

subplot(2,2,2); plot(w/pi, pha); grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Rad'); title('Phase Response in Radians');

subplot(2,2,4); plot(w/pi, grd*pi/180);  grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Rad'); title('Group Delay');

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.3 h(n)')

set(gcf,'Color','white'); 

plot(ww/pi, Hr); grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Hr'); title('Amplitude Response');

set(gca,'YTickMode','manual','YTick',[-delta2_hann,0,delta2_hann,1 - delta1_hann,1, 1 + delta1_hann])

%% ---------------------------------------------------

%%             4  Hamming Window

%% ---------------------------------------------------

M = ceil(6.6*pi/tr_width) + 1;                 % Hamming Window

fprintf('\n\n#4.Hamming Window, Filter Length M=%4d.\n', M);

n = [0:1:M-1]; wc1 = (ws1+wp1)/2; wc2 = (wp2+ws2)/2;

%wc = (ws + wp)/2,                    % ideal LPF cutoff frequency

hd = ideal_lp(wc2, M) - ideal_lp(wc1, M);

w_hamm = (hamming(M))';  h = hd .* w_hamm;

[db, mag, pha, grd, w] = freqz_m(h, [1]);  delta_w = 2*pi/1000;

[Hr,ww,P,L] = ampl_res(h);

Rp = -(min(db(wp1/delta_w+1 :1: floor(wp2/delta_w)+1)));     % Actual Passband Ripple

fprintf('\nActual Passband Ripple is %.4f dB.\n', Rp);

As = -round(max(db(ws2/delta_w+1 : 1 : 501)));               % Min Stopband attenuation

fprintf('\nMin Stopband attenuation is %.4f dB.\n', As);

[delta1_hamm, delta2_hamm] = db2delta(Rp, As)

%% --------------------------

%%            Plot

%% --------------------------

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.4 ideal_lp Method')

set(gcf,'Color','white'); 

subplot(2,2,1); stem(n, hd); axis([0 M-1 -0.2 0.3]); grid on;

xlabel('n'); ylabel('hd(n)'); title('Ideal Impulse Response');

subplot(2,2,2); stem(n, w_hamm); axis([0 M-1 0 1.1]); grid on;

xlabel('n'); ylabel('w(n)'); title('Hamming Window, M=67');

subplot(2,2,3); stem(n, h); axis([0 M-1 -0.2 0.3]); grid on;

xlabel('n'); ylabel('h(n)'); title('Actual Impulse Response');

subplot(2,2,4); plot(w/pi, db); axis([0 1 -100 10]); grid on;

set(gca,'YTickMode','manual','YTick',[-90,-51,0]);

set(gca,'YTickLabelMode','manual','YTickLabel',['90';'51';' 0']);

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1]);

xlabel('frequency in \pi units'); ylabel('Decibels'); title('Magnitude Response in dB');

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.4 h(n) ideal_lp Method')

set(gcf,'Color','white'); 

subplot(2,2,1); plot(w/pi, db); grid on; axis([0 2 -100 10]);

xlabel('frequency in \pi units'); ylabel('Decibels'); title('Magnitude Response in dB');

set(gca,'YTickMode','manual','YTick',[-90,-51,0])

set(gca,'YTickLabelMode','manual','YTickLabel',['90';'51';' 0']);

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1,1.4,1.5,1.6,1.7,2]);

subplot(2,2,3); plot(w/pi, mag); grid on; %axis([0 2 -100 10]);

xlabel('frequency in \pi units'); ylabel('Absolute'); title('Magnitude Response in absolute');

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1,1.4,1.5,1.6,1.7,2]);

set(gca,'YTickMode','manual','YTick',[0.0,0.5,1.0])

subplot(2,2,2); plot(w/pi, pha); grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Rad'); title('Phase Response in Radians');

subplot(2,2,4); plot(w/pi, grd*pi/180);  grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Rad'); title('Group Delay');

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.4 h(n)')

set(gcf,'Color','white'); 

plot(ww/pi, Hr); grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Hr'); title('Amplitude Response');

set(gca,'YTickMode','manual','YTick',[-delta2_hamm,0,delta2_hamm,1 - delta1_hamm,1, 1 + delta1_hamm])

%% ---------------------------------------------------

%%             5  Blackman Window

%% ---------------------------------------------------

M = ceil(11*pi/tr_width) + 1;                 % Blackman Window

fprintf('\n\n#5.Blackman Window, Filter Length M=%d.\n', M);

n = [0:1:M-1]; wc1 = (ws1+wp1)/2; wc2 = (wp2+ws2)/2;

%wc = (ws + wp)/2,                    % ideal LPF cutoff frequency

hd = ideal_lp(wc2, M) - ideal_lp(wc1, M);

w_bla = (blackman(M))';  h = hd .* w_bla;

[db, mag, pha, grd, w] = freqz_m(h, [1]);  delta_w = 2*pi/1000;

[Hr,ww,P,L] = ampl_res(h);

Rp = -(min(db(wp1/delta_w+1 :1: floor(wp2/delta_w)+1)));     % Actual Passband Ripple

fprintf('\nActual Passband Ripple is %.4f dB.\n', Rp);

As = -round(max(db(ws2/delta_w+1 : 1 : 501)));               % Min Stopband attenuation

fprintf('\nMin Stopband attenuation is %.4f dB.\n', As);

[delta1_bla, delta2_bla] = db2delta(Rp, As)

%% --------------------------

%%            Plot

%% --------------------------

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.5 ideal_lp Method')

set(gcf,'Color','white'); 

subplot(2,2,1); stem(n, hd); axis([0 M-1 -0.2 0.3]); grid on;

xlabel('n'); ylabel('hd(n)'); title('Ideal Impulse Response');

subplot(2,2,2); stem(n, w_bla); axis([0 M-1 0 1.1]); grid on;

xlabel('n'); ylabel('w(n)'); title('Blackman Window, M=111');

subplot(2,2,3); stem(n, h); axis([0 M-1 -0.2 0.3]); grid on;

xlabel('n'); ylabel('h(n)'); title('Actual Impulse Response');

subplot(2,2,4); plot(w/pi, db); axis([0 1 -120 10]); grid on;

set(gca,'YTickMode','manual','YTick',[-90,-73,0]);

set(gca,'YTickLabelMode','manual','YTickLabel',['90';'73';' 0']);

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1]);

xlabel('frequency in \pi units'); ylabel('Decibels'); title('Magnitude Response in dB');

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.5 h(n) ideal_lp Method')

set(gcf,'Color','white'); 

subplot(2,2,1); plot(w/pi, db); grid on; axis([0 2 -120 10]);

xlabel('frequency in \pi units'); ylabel('Decibels'); title('Magnitude Response in dB');

set(gca,'YTickMode','manual','YTick',[-90,-73,0])

set(gca,'YTickLabelMode','manual','YTickLabel',['90';'73';' 0']);

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1,1.4,1.5,1.6,1.7,2]);

subplot(2,2,3); plot(w/pi, mag); grid on; %axis([0 2 -120 10]);

xlabel('frequency in \pi units'); ylabel('Absolute'); title('Magnitude Response in absolute');

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1,1.4,1.5,1.6,1.7,2]);

set(gca,'YTickMode','manual','YTick',[0.0,0.5,1.0])

subplot(2,2,2); plot(w/pi, pha); grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Rad'); title('Phase Response in Radians');

subplot(2,2,4); plot(w/pi, grd*pi/180);  grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Rad'); title('Group Delay');

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.5 h(n)')

set(gcf,'Color','white'); 

plot(ww/pi, Hr); grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Hr'); title('Amplitude Response');

set(gca,'YTickMode','manual','YTick',[-delta2_bla,0,delta2_bla,1-delta1_bla,1, 1+delta1_bla])

%% ---------------------------------------------------

%%             6  Kaiser Window

%% ---------------------------------------------------

M = ceil((As-7.95)/(2.285*tr_width)) + 1;                 % Kaiser Window

if As > 21 || As < 50

	beta = 0.5842*(As-21)^0.4 + 0.07886*(As-21);

else

	beta = 0.1102*(As-8.7);

end

fprintf('\n\n#6.Kaiser Window, Filter Length M=%d, beta=%.4f\n', M,beta);

n = [0:1:M-1]; wc1 = (ws1+wp1)/2; wc2 = (wp2+ws2)/2;

%wc = (ws + wp)/2,                    % ideal LPF cutoff frequency

hd = ideal_lp(wc2, M) - ideal_lp(wc1, M);

w_kai = (kaiser(M,beta))';  h = hd .* w_kai;

[db, mag, pha, grd, w] = freqz_m(h, [1]);  delta_w = 2*pi/1000;

[Hr,ww,P,L] = ampl_res(h);

Rp = -(min(db(wp1/delta_w+1 :1: floor(wp2/delta_w)+1)));     % Actual Passband Ripple

fprintf('\nActual Passband Ripple is %.4f dB.\n', Rp);

As = -round(max(db(ws2/delta_w+1 : 1 : 501)));               % Min Stopband attenuation

fprintf('\nMin Stopband attenuation is %.4f dB.\n', As);

[delta1_kai, delta2_kai] = db2delta(Rp, As)

%% --------------------------

%%            Plot

%% --------------------------

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.6 ideal_lp Method')

set(gcf,'Color','white'); 

subplot(2,2,1); stem(n, hd); axis([0 M-1 -0.2 0.2]); grid on;

xlabel('n'); ylabel('hd(n)'); title('Ideal Impulse Response');

subplot(2,2,2); stem(n, w_kai); axis([0 M-1 0 1.1]); grid on;

xlabel('n'); ylabel('w(n)'); title('Kaiser Window, M=92');

subplot(2,2,3); stem(n, h); axis([0 M-1 -0.2 0.2]); grid on;

xlabel('n'); ylabel('h(n)'); title('Actual Impulse Response');

subplot(2,2,4); plot(w/pi, db); axis([0 1 -120 10]); grid on;

set(gca,'YTickMode','manual','YTick',[-90,-72,0]);

set(gca,'YTickLabelMode','manual','YTickLabel',['90';'72';' 0']);

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1]);

xlabel('frequency in \pi units'); ylabel('Decibels'); title('Magnitude Response in dB');

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.6 h(n) ideal_lp Method')

set(gcf,'Color','white'); 

subplot(2,2,1); plot(w/pi, db); grid on; axis([0 2 -120 10]);

xlabel('frequency in \pi units'); ylabel('Decibels'); title('Magnitude Response in dB');

set(gca,'YTickMode','manual','YTick',[-90,-72,0])

set(gca,'YTickLabelMode','manual','YTickLabel',['90';'72';' 0']);

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1,1.4,1.5,1.6,1.7,2]);

subplot(2,2,3); plot(w/pi, mag); grid on; %axis([0 2 -100 10]);

xlabel('frequency in \pi units'); ylabel('Absolute'); title('Magnitude Response in absolute');

set(gca,'XTickMode','manual','XTick',[0,0.3,0.4,0.5,0.6,1,1.4,1.5,1.6,1.7,2]);

set(gca,'YTickMode','manual','YTick',[0.0,0.5,1.0])

subplot(2,2,2); plot(w/pi, pha); grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Rad'); title('Phase Response in Radians');

subplot(2,2,4); plot(w/pi, grd*pi/180);  grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Rad'); title('Group Delay');

figure('NumberTitle', 'off', 'Name', 'Problem 7.16.6 h(n)')

set(gcf,'Color','white'); 

plot(ww/pi, Hr); grid on; %axis([0 1 -100 10]);

xlabel('frequency in \pi units'); ylabel('Hr'); title('Amplitude Response');

set(gca,'YTickMode','manual','YTick',[-delta2_kai,0,delta2_kai,1-delta1_kai,1, 1+delta1_kai])

　　运行结果：

设计指标，As=40dB，Rp=0.5dB；换算成绝对指标，为δ1=0.0288，δ2=0.0103。

由书中表7.1可知，矩形窗（Rectangular）和三角窗（Bartlett）不满足设计要求，这里我们也进行贴图验证。

上图可知，rectangualr窗和bartlett窗不符合设计要求。

下面将以上几种窗函数设计结果，总结如下

序号 名  称 长度M As Rp
1 Rectangular 19 26 1.918
2 Bartlett　　 62 27 0.1059
3 Hann　　 63 43 0.1242
4 Hamming 67 51 0.0488
5 Blackman　　 111 73 0.0027
6 Kaiser 92 72 0.0049

由上表得知，满足设计要求的是用长M=63的Hann窗截断得到的滤波器。

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