Change in osmo-trx[master]: lms: User correct scale factor for transmit samples

Harald Welte gerrit-no-reply at lists.osmocom.org
Thu Nov 29 12:27:05 UTC 2018


Hello Jenkins Builder, 

I'd like you to reexamine a change. Please visit

    https://gerrit.osmocom.org/12006

to look at the new patch set (#2).

Change subject: lms: User correct scale factor for transmit samples
......................................................................

lms: User correct scale factor for transmit samples

Due to (I believe) a copy+paste mistake from the USRP1 code,
we were using only a scale range of up to 9830 when transmitting
samples, rather than the full 16 bit signed integer range up to
32767.

As a result, we were loosing almost two bits (MSBs) of resolution
as well as a lot of transmit power.

This changes the scale factor to 0.707 (1/sqrt(2)).

Please note that the much higher DAC output level means that the analog
gain should be reduced.  The theoretic range of up to 73dB should not
be used, but Lime Microsystems suggest a value of 61..67 dB.  This can
be achieved by using a "osmotrx tx-attenuation" value of 6..12 inside
the osmo-bts-trx configuration file.

Related: OS#3341
Related: OS#3342
Change-Id: I71702feaa11f53e7614a6938a984dd748405474a
---
M Transceiver52M/device/lms/LMSDevice.h
1 file changed, 8 insertions(+), 1 deletion(-)


  git pull ssh://gerrit.osmocom.org:29418/osmo-trx refs/changes/06/12006/2
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Gerrit-Project: osmo-trx
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I71702feaa11f53e7614a6938a984dd748405474a
Gerrit-Change-Number: 12006
Gerrit-PatchSet: 2
Gerrit-Owner: Harald Welte <laforge at gnumonks.org>
Gerrit-Reviewer: Jenkins Builder (1000002)
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