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fixeria gerrit-no-reply at lists.osmocom.orgfixeria has uploaded this change for review. ( https://gerrit.osmocom.org/c/osmo-trx/+/22456 ) Change subject: Transceiver: use proper factor for amplitude scaling ...................................................................... Transceiver: use proper factor for amplitude scaling In Transceiver::addRadioVector() we scale the I/Q samples by scaling the output voltage of the DAC. A relative factor/divisor/ration in the voltage domain cannot be used 1:1 in the power domain. There exist two similar formulas: a) X_dB = 10 * log10(X_lin / X_ref) b) Y_db = 20 * log10(Y_lin / Y_ref) both of them are correct, and according to [1]: a) If you convert a quantity X that relates to power or energy, => the factor is 10. b) If you convert a quantity Y that relates to amplitude, => the factor is 20. Therefore we should be using 20 instead of 10. This change makes osmo-trx apply per-lchan attenuation values correctly. Otherwise it would double the values indicated in TRXD messages. [1] https://dspillustrations.com/pages/posts/misc/decibel-conversion-factor-10-or-factor-20.html Change-Id: I98bc00bd25df4913d45e55eb008d715aca76fc7c Related: SYS#4918 --- M Transceiver52M/Transceiver.cpp 1 file changed, 1 insertion(+), 1 deletion(-) git pull ssh://gerrit.osmocom.org:29418/osmo-trx refs/changes/56/22456/1 diff --git a/Transceiver52M/Transceiver.cpp b/Transceiver52M/Transceiver.cpp index 3188c70..6de266c 100644 --- a/Transceiver52M/Transceiver.cpp +++ b/Transceiver52M/Transceiver.cpp @@ -396,7 +396,7 @@ else burst = modulateBurst(bits, 8 + (wTime.TN() % 4 == 0), cfg->tx_sps); - scaleVector(*burst, txFullScale * pow(10, (double) -RSSI / 10)); + scaleVector(*burst, txFullScale * pow(10, (double) -RSSI / 20)); radio_burst = new radioVector(wTime, burst); -- To view, visit https://gerrit.osmocom.org/c/osmo-trx/+/22456 To unsubscribe, or for help writing mail filters, visit https://gerrit.osmocom.org/settings Gerrit-Project: osmo-trx Gerrit-Branch: master Gerrit-Change-Id: I98bc00bd25df4913d45e55eb008d715aca76fc7c Gerrit-Change-Number: 22456 Gerrit-PatchSet: 1 Gerrit-Owner: fixeria <vyanitskiy at sysmocom.de> Gerrit-MessageType: newchange -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.osmocom.org/pipermail/gerrit-log/attachments/20210127/4544233d/attachment.htm>