% Filter design for Lab C2

fs_2 = 8000/2;     % half sampling rate

% lowpass1
f1 = [0 1750 2500 4000]/fs_2;
a1 = [1 1 0 0 ];
L1 = 33;
h1 = remez(L1-1,f1,a1);
clf;
stem((0:L1-1),h1);
xlabel('discrete time n','fontsize',14);
ylabel('lowpass 1, h[n]','fontsize',14);
print -depsc lowpass1.eps

fid = fopen('lowpass1.txt','wt');
fprintf(fid,'#define FilterLength %d \n',L1);
fprintf(fid,'float x[FilterLength]; \n');
fprintf(fid,'float h[FilterLength] = {');
for l = 1:L1-1,
  fprintf(fid,'%1.6f, ',h1(l));
end;
fprintf(fid,'%1.6f};',h1(L1));
fclose(fid);

% lowpass2
f2 = [0 500 750 4000]/fs_2;
a2 = [1 1 0 0];
L2 = 99;
h2 = remez(L2-1,f2,a2);
clf;
stem((0:L2-1),h2);
xlabel('discrete time n','fontsize',14);
ylabel('lowpass 2, h[n]','fontsize',14);
print -depsc lowpass2.eps

fid = fopen('lowpass2.txt','wt');
fprintf(fid,'#define FilterLength %d \n',L2);
fprintf(fid,'float x[FilterLength]; \n');
fprintf(fid,'float h[FilterLength] = {');
for l = 1:L2-1,
  fprintf(fid,'%1.6f, ',h2(l));
end;
fprintf(fid,'%1.6f};',h2(L2));
fclose(fid);

% highpass1
f3 = [0 1500 2250 4000]/fs_2;
a3 = [0 0 1 1];
L3 = 33;
h3 = remez(L3-1,f3,a3);
clf;
stem((0:L3-1),h3);
xlabel('discrete time n','fontsize',14);
ylabel('highpass 1, h[n]','fontsize',14);
print -depsc highpass1.eps

fid = fopen('highpass1.txt','wt');
fprintf(fid,'#define FilterLength %d \n',L3);
fprintf(fid,'float x[FilterLength]; \n');
fprintf(fid,'float h[FilterLength] = {');
for l = 1:L3-1,
  fprintf(fid,'%1.6f, ',h3(l));
end;
fprintf(fid,'%1.6f};',h3(L3));
fclose(fid);

% magnitude response
H1 = 20*log10(abs(fft(h1,1024)));
H2 = 20*log10(abs(fft(h2,1024)));
H3 = 20*log10(abs(fft(h3,1024)));
f = (0:511)/512*fs_2;
clf;
plot(f,H1(1:512)); hold on;
plot(f,H2(1:512),'r--');
plot(f,H3(1:512),'k:');
legend('lowpass1','lowpass2','highpass1',4);
xlabel('frequency / [Hz]');
ylabel('magnitude response / [dB]');
axis([0 4000 -80 5]);
print -depsc FilterDesignMagResp.eps