%processgunndata.m
% to process data collected from Gunn radar
% 30 November 2006, Jim Lux

% data is in a stereo wav file collected with a PC
% we use the Matlab spectrogram to do the display

[y,fs]=wavread('logfile2.wav'); % get data and sample rate
yc=complex(y(:,1),y(:,2));      % turn into a complex vector
wsize=1024;overlap=512;nfft=1024;
spectrogram(yc,wsize,overlap,nfft,fs)
colorbar
%
% look only at the bottom 1 kHz or so
%
yca=decimate(yc,10,'fir');
figure
wsize=512;overlap=256;nfft=512;
[yy,F,T,P]=spectrogram(yca,wsize,overlap,nfft,fs/10);
% let's rearrange F and data to make positive and negative frequencies right
XP=[P(nfft/2+1:nfft,:);P(1:nfft/2,:)];
XF=[-F(nfft/2:-1:2);F(1:nfft/2+1)];
surf(T,XF,10*log10(abs(XP)),'EdgeColor','none');
axis xy; axis tight; colormap(jet); view(0,90);
xlabel('Time (secs)');
ylabel('Frequency (Hz)');
colorbar