% Program 7_4
% Computation of the order of a linear-phase
% FIR lowpass filter using Kaiser's formula
%
dp = input('Type in the passband ripple = ');
ds = input('Type in the stopband ripple = ');
Fp = input('Type in the passband edge in Hz = ');
Fs = input('Type in the stopband edge in Hz = ');
FT = input('Type in the sampling frequency in Hz = ');
num = -20*log10(sqrt(dp*ds))-13;
den = 14.6*(Fs - Fp)/FT;
N = ceil(num/den);
fprintf('Filter order is %d \n',N);