15 Oct
2012
15 Oct
'12
7:22 a.m.
Hi Srdjan.
As I understand, I must to re-ask and much simpler and more correctly:
Do we need to search another components for LTE BTS with MIMO/20MHz/10-20W
or there are chances to use LMS6002?
You told about 20-23dBm output power, so please let us know what PA do you
use in this case.
Best regards,
Andrey Sviyazov.
P.S.
Sorry for my undeveloped english :)
2012/10/15 Andrey Sviyazov <andreysviyaz(a)gmail.com>
Hi Srdjan.
Thank you for reply.
Our potential customer asked us about TDD with 43dBm at antenna port and
with as many of MIMO's as it possible (theoreticaly) to realize now to get
higher users density per sector. Of course, for the first look it seems
like an dreams, but it is true real customer dreams.
So, now we have to understand real LMS performances for LTE anyway.
It required to be able to answering customer either something about
0.1-0.5W and no more or to start good real project with required specs.
Please suggest us something to answer.
Best regards,
Andrey Sviyazov.
2012/10/15 Srdjan Milenkovic <s.milenkovic(a)limemicro.com>
DPD will linearize PA, LMS should not be
limiting factor in that
respect. In band spurs should be investigated before we say that LMS can or
can not be used. What output power are we looking for?
On 15/10/2012 09:13, Andrey Sviyazov wrote:
Since we decided to make version 3 (due to additions of LMS
thermosensors) then we can also add external Fref prescaler for PLL, no
problems here.
I think ICPR is more important restriction.
Srdjan said that it doesn't studied too deeply, but on my opinion, really
reachable maximum Tx power no more then 25 dBm (without DPD).
So, we can't use LMS for LTE without DPD or additional filtration (2nd Tx
IF).
In other hand, we can implement it similar to UmSEL and with
upconversion, of course, but high quality SAW filter required (all
flatness) to keeping EVM as small as possible.
Best regards,
Andrey Sviyazov.
2012/10/14 Alexander Chemeris <alexander.chemeris(a)gmail.com>
Srdjan, thanks for the answers. This is enough
for us at the moment.
On Sun, Oct 14, 2012 at 3:50 PM, Srdjan Milenkovic
<s.milenkovic(a)limemicro.com> wrote:
Hi Alexander,
Remaining questions are addressed below.
On 13/10/2012 21:47, Alexander Chemeris wrote:
Hi Srdjan,
We're looking into re-purposing UmTRX for LTE and there a few things
which
we need to understand better.
1. Is it possible to support 15MHz and 20MHz LTE channel bandwidths? To
achieve this we at least need to sample at 23.04Msps and 30.72Msps
respectively. LMS6002D datasheet specifies the maximum I/Q samplerate
of
14Msps, which is not enough. But at the same
time, datasheet claims
that ADC
and DAC are specified up to 50Msps. How does this
fits together?
2. Do you have any experience what maximum output power we could
achieve
with LMS and proper amplifiers, while still
staying in the bounds of
the LTE
Standard? What would be the limiting factor for
the further power
increase?
The limiting factor here would be absolute specs on ACPR, out of band
spurs
... i.e. TX spectrum mask, expressed in dBm not
in dBc. For example,
you may
meet <= -45dBc ACPR but on the other hand you
can not inject noise into
adjacent channel more than xdBm. LMS device is OK for 20-25dBm
modulated
output power. We can probably push it more
however this is not tested
so
far.
3. Is there any issues using TDD mode in LMS6002D? We've been using
onnly
FDD mode so far and it would be great to know
what issues could we
expect
when switching to TDD mode.
TDD mode should be just fine. We measured around 20us TX<->RX switching
time. We will probably need to reconfigure VCO supplies on UmTRX board
to
simplify switching control while keeping
switching time at 20us. Lat
us know
when you are ready for such experiment.
--
Regards,
Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио
http://fairwaves.ru
--
Regards,
Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио
http://fairwaves.ru