20100210

Fill out grant application stuff, sans Don's uni number and email and post to Jennifer.

Examine Matlab output of faint waveforms

Sample 11 - 1mV/div, one transmitter at 15m - visible on one of the four traces, though not this one (trace 2)

Using

[SB, Sf, St] = spectrogram(x, 4096, 3072, 4096, Fs);
bmin = max(max(abs(SB)))/10; % Top 20dB of signal
imagesc(St, Sf, 20*log10(max(abs(SB),bmin)/bmin));

Note - was still quite distinguishable at 40dB.

Sample 12 - 1mV/div, one transmitter at 20m - not visible on any of the four traces

Nothing visible in single channel 4096/3072/4096 spectrogram (by eye) - might have just been missed by the sample?

Sample 13 - 1mV/div, one transmitter at 20m - again, not visible in traces or spectrogram.

Sample 14 - Tag at 150.2 MHz + E4433B at -40dBm, 150.4 MHz. Signal generator clearly visible, tag not visible.

Sample 15 - Tag at 150.2 MHz + E4433B at -80dBm, 150.4 MHz. Signal generator not visible, tag not visible with 4096 and 1024.

Sample 18 - Tag at 150.2 MHz + E4433B at -30dBm, 150.210 MHz. Signal generator not visible, tag not visible, at 4096/3192, but is visible at 1024/768.

Zoom in on tag sample:

y = foo(776000:796000,2);
[SB, Sf, St] = spectrogram(y, 1024, 768, 1024, Fs);
bmin = max(max(abs(SB)))/15;
imagesc(St, Sf, 20*log10(max(abs(SB),bmin)/bmin));

Try an FFT of this.

N = length(y);
k=-(N-1)/2:(N-1)/2;
T=N/Fs;
freq=k/T;
bleh = fft(y)/N;
bleh = fftshift(bleh);
plot(freq, abs(bleh));

Conversion to dB, presumably:

bleh=fft(y)
plot(freq, abs(bleh));
Pyy = bleh .* conj(bleh);
Pyy = 10 * log10(Pyy)
plot (freq, Pyy)