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Fix the doppler correction mechanism 

The doppler correction mechanism has successfully passed the first tests
using the GPredict software for the radio control. The corrections seems
to be quite smooth. The next step is to apply it at an audible signal.
This commit is contained in:
Manolis Surligas 2016-03-31 21:58:29 +03:00
parent b218ed282c
commit 82c9ff2850
2 changed files with 65 additions and 48 deletions
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77
grc/satnogs_doppler_correction_cc.xml
View File

@ -1,38 +1,49 @@
<?xml version="1.0"?>
<block>
<name>doppler_correction_cc</name>
<key>satnogs_doppler_correction_cc</key>
<category>satnogs</category>
<import>import satnogs</import>
<make>satnogs.doppler_correction_cc($target_freq)</make>
<!-- Make one 'param' node for every Parameter you want settable from the GUI.
Sub-nodes:
* name
* key (makes the value accessible as $keyname, e.g. in the make node)
* type -->
<param>
<name>...</name>
<key>...</key>
<type>...</type>
</param>
<name>Doppler Correction</name>
<key>satnogs_doppler_correction_cc</key>
<category>satnogs</category>
<import>import satnogs</import>
<make>satnogs.doppler_correction_cc($target_freq, $sampling_rate, $corrections_per_sec)</make>
<!-- Make one 'sink' node per input. Sub-nodes:
* name (an identifier for the GUI)
* type
* vlen
* optional (set to 1 for optional inputs) -->
<sink>
<name>in</name>
<type><!-- e.g. int, float, complex, byte, short, xxx_vector, ...--></type>
</sink>
<param>
<name>Target Frequency</name>
<key>target_freq</key>
<type>real</type>
</param>
<param>
<name>Sample Rate</name>
<key>sampling_rate</key>
<value>samp_rate</value>
<type>real</type>
</param>
<param>
<name>Corrections per Second</name>
<key>corrections_per_sec</key>
<value>1000</value>
<type>int</type>
</param>
<!-- Make one 'source' node per output. Sub-nodes:
* name (an identifier for the GUI)
* type
* vlen
* optional (set to 1 for optional inputs) -->
<source>
<name>out</name>
<type><!-- e.g. int, float, complex, byte, short, xxx_vector, ...--></type>
</source>
<sink>
<name>freq</name>
<type>message</type>
</sink>
<sink>
<name>reset</name>
<type>message</type>
<optional>1</optional>
</sink>
<sink>
<name>in</name>
<type>complex</type>
</sink>
<source>
<name>out</name>
<type>complex</type>
</source>
</block>

36
lib/doppler_correction_cc_impl.cc
View File

@ -24,6 +24,7 @@
#include <gnuradio/io_signature.h>
#include "doppler_correction_cc_impl.h"
#include <satnogs/log.h>
#include <volk/volk.h>
namespace gr
@ -75,7 +76,7 @@ namespace gr
* and the input message handler are NOT reentrant.
*/
set_max_noutput_items (d_samp_rate / 2.0);
set_alignment(8);
set_alignment (8);
set_msg_handler (
pmt::mp ("freq"),
@ -104,11 +105,15 @@ namespace gr
d_freq_diff = d_target_freq - new_freq;
if (!d_have_est) {
d_freq_est_num++;
if (d_freq_est_num > d_est_thrhld - 1) {
d_have_est = true;
}
d_doppler_freqs.push_back (
freq_drift (nitems_written (0), d_freq_diff));
if (d_freq_est_num > d_est_thrhld - 1) {
d_doppler_fit_engine.fit (d_doppler_freqs);
d_doppler_fit_engine.predict_freqs (d_predicted_freqs,
d_corrections_per_sec,
d_update_period);
d_have_est = true;
}
}
else {
d_doppler_freqs.pop_front ();
@ -121,6 +126,7 @@ namespace gr
d_doppler_fit_engine.predict_freqs (d_predicted_freqs,
d_corrections_per_sec,
d_update_period);
d_corrections = 0;
}
}
@ -180,20 +186,20 @@ namespace gr
d_update_period);
d_corrections = 0;
}
}
cnt = std::min(d_update_period - d_corrected_samples,
(size_t) (noutput_items - produced));
/* Perform the doppler shift correction */
volk_32fc_x2_multiply_32fc (out + produced, in + produced,
d_nco_buff + d_corrected_samples, cnt);
cnt = std::min (d_update_period - d_corrected_samples,
(size_t) (noutput_items - produced));
/* Perform the doppler shift correction */
volk_32fc_x2_multiply_32fc (out + produced, in + produced,
d_nco_buff + d_corrected_samples, cnt);
/* Make the proper advances */
produced += (int) cnt;
d_corrected_samples += cnt;
/* Make the proper advances */
produced += (int) cnt;
d_corrected_samples += cnt;
if(d_corrected_samples == d_update_period) {
d_corrected_samples = 0;
}
if (d_corrected_samples == d_update_period) {
d_corrected_samples = 0;
}
}
}