function [BI, BQ] = demod_iqII (y)

%%%%%%%%%%%%%%%%%%%%%%%
%% Extract the I,Q components utilising Poly-phase Filter digitally quadrature.

global k Fc Fd Fs n;

N = length(y);

%BI = y(0:2:N-1);
%BQ = y(1:2:N);

for i = 1 : N/2
    BI(i) = y(2*i-1 ) * (-1)^(i-1);
    BQ(i) = y(2*i) * (-1)^(i-1);
end

Num_I = [ 0.000000,     -3.0689215e-4, -1.1993570e-2, 4.8911806e-2, 0.1767598, 4.8911806e-2,  -1.1993570e-2, -3.0689215e-4 ];
Num_Q = [ 8.3456202e-5, -4.2909505e-3, -4.1642617e-3, 0.1333630,    0.1333630, -4.1642617e-3, -4.2909505e-3, 8.3456202e-5 ];

Den = [1];

BI = filter(Num_Q, Den ,BI) *4;
BQ = filter(Num_I, Den ,BQ) *4;


%Analize Spectrum

%figure (202);
%analysis_spec (BI, BI, n(1:2:N), Fs);
%title ('Waveform of Quadrature Component I'); 

%figure (203);
%analysis_spec (BQ, BQ, n(1:2:N), Fs);
%title ('Waveform of Quadrature Component Q');

%figure (202);
%analysis_spec (BQ, BI, n(1:2:N), Fs);
%title ('Waveform of Quadrature Component Q I'); 

%下面是屏蔽原來的畫圖程序

%%for i = 1:1     % set 1:0 to cancel the plot function.
    
%%figure (202);
%%subplot (2,1,1);
%%stairs ((1:N/2), BI);
%%title ('Waveform of Quadrature Component I');

%%subplot (2,1,2);
%%stairs ((1:N/2), BQ);
%%title ('Waveform of Quadrature Component Q');

%%end