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Add transfer function between geophones

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Thomas Dehaeze 2019-04-18 09:20:31 +02:00
parent d80ae7509b
commit 030dae7ab1
4 changed files with 37 additions and 2 deletions
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@ -96,8 +96,8 @@ The voltage amplifiers include a low pass filter with a cut-off frequency at 1kH
** Compute PSD
#+begin_src matlab :results none
[pxx1, f1] = pwelch(x1, hanning(ceil(length(t)/100)), 0, [], 1/dt);
[pxx2, f2] = pwelch(x2, hanning(ceil(length(t)/100)), 0, [], 1/dt);
[pxx1, f1] = pwelch(x1, hanning(ceil(1/dt)), 0, [], 1/dt);
[pxx2, f2] = pwelch(x2, hanning(ceil(1/dt)), 0, [], 1/dt);
#+end_src
** Take into account sensibility of Geophone
@ -147,6 +147,7 @@ The cut-off frequency is set at 1kHz.
set(gca, 'xscale', 'log');
set(gca, 'yscale', 'log');
xlabel('Frequency [Hz]'); ylabel('PSD [m/s/sqrt(Hz)]')
xlim([2, 500]);
#+end_src
#+NAME: fig:psd_velocity
@ -159,3 +160,37 @@ The cut-off frequency is set at 1kHz.
#+CAPTION: Spectral density of the velocity
#+RESULTS: fig:psd_velocity
[[file:figs/psd_velocity.png]]
** Transfer function between the two geophones
#+begin_src matlab :results none
[T12, f12] = tfestimate(x1, x2, hanning(1/dt), 0, [], 1/dt);
#+end_src
#+begin_src matlab :results none
figure;
ax1 = subplot(2, 1, 1);
plot(f12, abs(T12));
set(gca, 'xscale', 'log'); set(gca, 'yscale', 'log');
set(gca, 'XTickLabel',[]);
ylabel('Magnitude');
ax2 = subplot(2, 1, 2);
plot(f12, mod(180+180/pi*phase(T12), 360)-180);
set(gca, 'xscale', 'log');
ylim([-180, 180]);
yticks([-180, -90, 0, 90, 180]);
xlabel('Frequency [Hz]'); ylabel('Phase');
linkaxes([ax1,ax2],'x');
xlim([2, 500]);
#+end_src
#+NAME: fig:tf_geophones
#+HEADER: :tangle no :exports results :results value raw replace :noweb yes
#+begin_src matlab :var filepath="figs/tf_geophones.pdf" :var figsize="full-tall" :post pdf2svg(file=*this*, ext="png")
<<plt-matlab>>
#+end_src
#+NAME: fig:tf_geophones
#+CAPTION: Estimated transfer function between the two geophones
#+RESULTS: fig:tf_geophones
[[file:figs/tf_geophones.png]]