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<div class="moz-cite-prefix">Hi Alexander,<br>
Remaining questions are addressed below.<br>
<br>
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<title>Dr Srdjan Milenkovic</title>
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<![endif]--></o:smarttagtype></o:smarttagtype>On 13/10/2012 21:47,
Alexander Chemeris wrote:<br>
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<blockquote
cite="mid:CABmJbFWA5gdzfVio32CAa_ar2uJUQa3_wz88m2kBuzr=b5w8-g@mail.gmail.com"
type="cite">Hi Srdjan,
<div><br>
</div>
<div>We're looking into re-purposing UmTRX for LTE and there a few
things which we need to understand better.<br clear="all">
<div><br>
</div>
<div>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?</div>
<div><br>
</div>
<div>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?</div>
</div>
</blockquote>
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.<br>
<br>
<blockquote
cite="mid:CABmJbFWA5gdzfVio32CAa_ar2uJUQa3_wz88m2kBuzr=b5w8-g@mail.gmail.com"
type="cite">
<div>
<div><br>
</div>
<div>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.</div>
</div>
</blockquote>
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.<br>
<br>
<blockquote
cite="mid:CABmJbFWA5gdzfVio32CAa_ar2uJUQa3_wz88m2kBuzr=b5w8-g@mail.gmail.com"
type="cite">
<div>
<div><br>
</div>
-- <br>
Regards,<br>
Alexander Chemeris.<br>
CEO, Fairwaves LLC / ООО УмРадио<br>
<a moz-do-not-send="true" href="http://fairwaves.ru"
target="_blank">http://fairwaves.ru</a><br>
</div>
</blockquote>
<br>
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