fft beamforming - RF Cafe Forums

 Post subject: fft beamforming

Posted: Tue Apr 12, 2005 3:09 am 

i'm a beginner in this area.
i just learned about the basic algorithm of fft beamforming from internet.and want to implement the algorithm by using matlab,but i don't know how to start(ps,i'm also a new user of matlab).

can anyone give me some sample souce code, even segments are okay.
I'm really stuck in mud. 

thanks in advance.

 Post subject: Beamformer

Posted: Mon May 09, 2005 5:51 am 

Dear

Here I give you a sample code for creating the filter coefficients of a Delay and Sum beamformer. if you have any question you can contact me on my email palange@hotmail.fr

Have a nice day.




[code]
c = 340; % m/s
nfft = 128; % nfft length
i_omega = -i*2*pi/c; % f will be variable
n_mic = 7;
mics = [ (-10*3:10:10*3)' zeros(7,1) ]/100;
source = [-0.2 0.63]; % to be measured
fs = 22050; % Sampling Frequency
f = (0:nfft-1)*fs/nfft; % Frequency bins
W = zeros(n_mic,nfft);
d = zeros(n_mic,1);
w = zeros(n_mic,1);
r = zeros(n_mic,1);
u = zeros(n_mic,1);
bp = zeros(nfft,181);
bps = zeros(1,181);
% Filter Coef

for k = 1:n_mic
r(k) = norm( source - mics(k,:));
end

index = 1;

for p=f
d = exp(i_omega*p*r)./r;
w=d.*r;
w=w/abs(w'*d);
W(:,index) = w;


theta_v=[-90:1:90];
source_n=norm(source);
for theta = theta_v
s=[source_n*sin(theta*pi/180) source_n*cos(theta*pi/180)];
for k=1:n_mic
u(k) = norm(s-mics(k,:));
end
d=exp(i_omega*p*u)./u;
bps(theta+91)=20*log10(abs(w'*d));
end
bp(index,:)=bps;
index = index + 1;
end

% here you can plot the BP as a function of DoA for any frequency.


% Implementing the Beamforming

start = 1;
skiprate = nfft/2;
window = triang(nfft)';

num_samples = size(data,2); % data size

num_blocks = ceil((num_samples-nfft)/skiprate);


frame = 1:nfft;

data_frame = zeros(n_mic,nfft); % frame of data ( from each mic)

data_fft = zeros(nfft,n_mic); % FFT of the frame

s = zeros(1,nfft); % frame data (time)

S = zeros(1,(n_blocks+1)*nfft/2);

for m = 1 : n_blocks

data_frame = data(:,frame);

data_fft = fft(data_frame');

s = sum(conj(W).*data_fft');

S(frame) = S(frame) + real(ifft(s.*window));

frame = frame + skiprate;

end[\code]