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Squelch improvement

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Continuously calculate noise floor and lower threshold level if less noise
was received. High noise or ongoing transmission during start of program will
not cause a threshold that is too far above the actual noise floor.
This commit is contained in:
Andreas Eversberg
2017-12-05 10:55:13 +01:00
parent 9f901384de
commit f2eb6b3e70
1 changed files with 16 additions and 9 deletions
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25
src/libsquelch/squelch.c
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@@ -44,9 +44,9 @@
*/ */
/* NOTE: SQUELCH must be calibrated !AFTER! DC bias, to get the actual noise floor */ /* NOTE: SQUELCH must be calibrated !AFTER! DC bias, to get the actual noise floor */
#define SQUELCH_INIT_TIME 1.1 /* wait some time before performing squelch */ #define SQUELCH_INIT_TIME 0.1 /* wait some time before performing squelch */
#define SQUELCH_AUTO_TIME 1.0 /* duration of squelch quelch calibration */ #define SQUELCH_AUTO_TIME 0.5 /* duration of squelch quelch calibration */
#define SQUELCH_AUTO_OFFSET 6.0 /* auto calibration: offset above noise floor */ #define SQUELCH_AUTO_OFFSET 10.0 /* auto calibration: offset above noise floor */
void squelch_init(squelch_t *squelch, int chan, double threshold_db, double mute_time, double loss_time) void squelch_init(squelch_t *squelch, int chan, double threshold_db, double mute_time, double loss_time)
{ {
@@ -89,12 +89,19 @@ enum squelch_result squelch(squelch_t *squelch, double rf_level_db, double durat
squelch->auto_count += duration; squelch->auto_count += duration;
squelch->auto_level_sum += rf_level_db; squelch->auto_level_sum += rf_level_db;
squelch->auto_level_count++; squelch->auto_level_count++;
if (squelch->auto_count < SQUELCH_AUTO_TIME) if (squelch->auto_count >= SQUELCH_AUTO_TIME) {
return SQUELCH_MUTE; double noise_db, threshold_db;
squelch->threshold_db = squelch->auto_level_sum / (double) squelch->auto_level_count; noise_db = squelch->auto_level_sum / (double) squelch->auto_level_count;
PDEBUG_CHAN(DDSP, DEBUG_INFO, "RF signal measurement: %.1f dB noise floor, using threshold of %.1f dB\n", squelch->threshold_db, squelch->threshold_db + SQUELCH_AUTO_OFFSET); threshold_db = noise_db + SQUELCH_AUTO_OFFSET;
squelch->threshold_db += SQUELCH_AUTO_OFFSET; /* must be 0.1 dB smaller, so we prevent repeated debugging message with similar value */
squelch->auto_state = 0; if (threshold_db < squelch->threshold_db - 0.1) {
squelch->threshold_db = threshold_db;
PDEBUG_CHAN(DDSP, DEBUG_INFO, "RF signal measurement: %.1f dB noise floor, using squelch threshold of %.1f dB\n", noise_db, threshold_db);
}
squelch->auto_count = 0.0;
squelch->auto_level_count = 0;
squelch->auto_level_sum = 0.0;
}
} }
/* enough RF level, so we unmute when mute_count reched 0 */ /* enough RF level, so we unmute when mute_count reched 0 */