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Alexander Chemeris alexander.chemeris at gmail.comSrdjan, 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