function dsp_filter(N,F,A,file_name)

% DSP_FILTER creates a length N+1 linear phase (real, symmetric
% coefficients) FIR filter. F is a vector of frequency band
% edges in pairs, in ascending  order between 0 and 1. A is a
% real vector the same size as F which specifies the desired
% amplitude of the frequency response of the resultant filter.
%
% Arguments of DSP_FILTER are passed to the Remez exchange
% algorithm and the resulting coefficients are output to a
% file.
%
% (Jesse & Sambit 10-1-00)

% run the Remez exchange algorithm
B = remez(N,F,A);

[H,w] = freqz(B,1,256);

% plot the coefficients

figure(1)
stem(0:N,B)

% mag and phase plots

figure(2)
subplot(2,1,1)
plot(w/pi,20*log10(abs(H)))
title('Magnitude response')
xlabel('\omega/\pi')
ylabel('Magnitude in dB')
subplot(2,1,2)
plot(w/pi,abs(H))
xlabel('\omega/\pi')
ylabel('Linear Magnitude')

%plot(w/pi,unwrap(angle(H)))
%title('Phase response')
%xlabel('\omega/\pi')
%ylabel('Phase')


% open a file to output results
file_name = strcat(file_name,'.h');
fid = fopen(file_name,'w');

for i = 1:N+1
   
   % output coef with 12 decimal places
   % and add spacing to make file readable
   
   fprintf(fid,'%13.12f',B(i));
   
   if i ~= N+1
	   fprintf(fid,',');
   end
   
end

% done writing to file
fclose(fid);