LMS6002D support of LTE

Andrey Sviyazov andreysviyaz at gmail.com
Mon Oct 15 11:22:24 UTC 2012


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 at 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 at 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 at 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 at 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
>>>
>>>
>>
>>
>
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