LMS6002D support of LTE
alexander.chemeris at gmail.com
Sun Oct 14 12:25:50 UTC 2012
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
> 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.
> Alexander Chemeris.
> CEO, Fairwaves LLC / ООО УмРадио
CEO, Fairwaves LLC / ООО УмРадио
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