Resampling a binary data
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TEXBAT is a recorded dataset about spoofing scenarios for evaluating GPS signal authentication techniques.
On this project, there are recorded GPS signals stored as complex 16- bit samples at a rate of 25 Msps.
How can I change its sample rate from 25Msps to sample rates below than 3.2Msps?
3 个评论
Star Strider
2022-8-27
I have not looked at the file and I am not certain that this approach would apply to this problem sinc e I do not understand it, however when I do resampling in a signal processing context I prefer the Signal Processing Toolbox resample function.
Bugrahan Ustundag
2022-8-27
编辑：Bugrahan Ustundag
2022-8-27
I don't think I quite understand some of these outputs
data = repelem([1+2i, -3-4i], 1, 4).'
resample(data, 1, 2)
ifft(fft(data), 4)
interp1(1:length(data), data, 1:2:length(data)).'
data = repelem([1+2i], 1, 8).'
resample(data, 1, 2)
ifft(fft(data), 4)
interp1(1:length(data), data, 1:2:length(data)).'
I guess the fft result suggests that the power is being redistributed over the output, so the ifft output should probably be divided by the decimination factor
采纳的回答
The input vector has to be a real double array. So resample the real and imaginary parts separately.
Doing the experiment —
Fs = 1000;
t = linspace(0, 9999, 10000).'/Fs; % Assume Column Vectors
sz = exp(2*pi*1i*t*100);
% Resz = real(sz);
% Imsz = imag(sz);
[zrr,tr] = resample(real(sz),t,500);
[zir,tr] = resample(imag(sz),t,500);
szr = zrr + 1i*zir;
figure
plot(t, real(sz), '.-', t, imag(sz),'.-', 'DisplayName','Original (Fs = 1000)')
hold on
plot(tr, real(szr), 's-', tr, imag(szr), 's-', 'DisplayName','Resampled (Fs = 500)')
hold off
grid
legend('Location','best')
xlim([0 1]*5E-2)
It appears to work as expected.
.
2 个评论
Bugrahan Ustundag
2022-9-4
Star Strider
2022-9-4
I am not certain what you are referring to.
If you are sampling an analog signal, it is appropriate to do analog filtering of the signal prior to digitising it using a Bessel lowpass filter with the cutoff frequency slightly less than the sampling frequency of the A/D converter. Bessel filters are characteristically IIR filters, and are preferred here because they do not exhibit any phase distortion in the passband.
I generally prefer IIR filters unless I need them to have several different passbands or stopbands in the filter. In that situation, FIR filters are generally easier to design and implement, and I usually use them only as discrete filters with a signal that has already been digitised
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Image Analyst
2022-8-27
If you can read it into a time, t, array and gps (y) array, you might try interp1
gpsNew = interp1(t, gpsOld, tNew);
The old signal will have about 8 times as many samples as your new signal. Of course if you want to average the values in a certain window so you'll take the average of all the extra values instead of just picking a sample, you'll have to do some other things, like preprocessing the signal with movmean to get a signal averaged over the window.
2 个评论
Bugrahan Ustundag
2022-8-27
Image Analyst
2022-9-4
OK, no problem. Looks like Star solved it for you (since you accepted his answer).
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