function  dsgnbutworth_varorder(order)
%dsgnbutworth_varorder.m
%used to design a Butterworth filter,which has a variable 
%even order(>=16)and a 1.5KHz-5KHz passband with a sampling
%rate 16KHz.
if ischar(order)
    disp('The input argument is always taken as a string when converting');
    disp('m function to console Application!');
    order=str2num(order);
end

if order<16|(mod(order,2)~=0)
    disp('The order should be an even integer,not less than 16!');
return;
end
Fs=16;
[b,a]=butter(order/2,[1.5/(Fs/2)  5/(Fs/2)],'bandpass')
freqz(b,a,512,16000)