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John Orlando john at epiqsolutions.comOn Sat, Oct 13, 2012 at 4:30 PM, Alexander Chemeris <alexander.chemeris at gmail.com> wrote: > Hi John, > > On Sat, Oct 13, 2012 at 11:11 PM, John Orlando <john at epiqsolutions.com> wrote: >> On Sat, Oct 13, 2012 at 3:47 PM, Alexander Chemeris >> <alexander.chemeris at gmail.com> 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? >> >> Alexander, >> Can you provide a reference to where the datasheet calls out a max I/Q >> sample rate of 14 Msps? The analog low pass filters support a max >> bandwidth of 14 MHz (which leads to 28 MHz RF bandwidth assuming >> zero-IF operation)...is this what you're referencing? > > The datasheet is not very clear on this topic. I'm referring to the > following line at the Table 1: > Baseband Bandwidth 14MHz > > Originally I read this line as "digital I/Q bus has limitation of > 14Msps" and this is what confuses me. > Yes, this refers to the analog baseband filter bandwidth. >> We run the A/D >> converters in the LMS6002d at sample rates greater than 14 Msps all >> the time, including 30.72 Msps. > > Just to be sure - do you mean you feed RX_CLK and TX_CLK of LMS6002D > with 61.44MHz clock? It's divided by 2 internally, so if you feed them > with 30.72MHz clock you actually get only 15.36Msps out of LMS6002D. Correct, when running the A/D at 30.72 Msps, the RX_CLK signal needs to run at 61.44 MHz. -- John Orlando CEO/System Architect Epiq Solutions http://www.epiqsolutions.com