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Alexander Chemeris alexander.chemeris at gmail.comHum, good idea for the very first try. We should try this out this week. But I still want a normal TCXO/OCXO replacement for UmTRX to make it easier to rework more UmTRX boards. On Sun, Oct 14, 2012 at 7:35 AM, sergey kostanbaev <sergey.kostanbaev at gmail.com> wrote: > Just use our ClockTamer to see how it works :) > > > On Sun, Oct 14, 2012 at 11:30 AM, Alexander Chemeris > <alexander.chemeris at gmail.com> wrote: >> >> Hi Robin, >> >> Do you mean to use ADF4002 to double the frequency? >> >> Right now I want a simple solution - just replace the TCXO on UmTRX >> from 26MHz to 61.44MHz and see how it works. Doubling the frequency >> would require PCB rework and is possible for the next generation of >> UmTRX only. >> >> On Sun, Oct 14, 2012 at 4:18 AM, Robin Coxe <coxe at close-haul.com> wrote: >> > Something like the attached Taiten VCTCXO @ 30.72 MHz + ADF4002 Phase >> > Detector/PLL synthesizer might work. I have no idea how much the >> > oscillator >> > costs. (The Pletronics oscillator on the UmTRX and the GAPfiller GSM900 >> > isn't available at this frequency.) >> > >> > >> > http://www.analog.com/en/rfif-components/pll-synthesizersvcos/adf4002/products/product.html >> > >> > -Robin >> > >> > On Sat, Oct 13, 2012 at 11:54 PM, Alexander Chemeris >> > <alexander.chemeris at gmail.com> wrote: >> >> >> >> John, >> >> >> >> On Sun, Oct 14, 2012 at 12:24 AM, John Orlando <john at epiqsolutions.com> >> >> wrote: >> >> > On 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. >> >> >> >> Ok, thanks for the clarification. >> >> >> >> >>> 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. >> >> >> >> Great! >> >> In case you know a good 61.44 MHz oscillator with a reasonable price - >> >> I would appreciate a pointer. >> >> >> >> -- >> >> Regards, >> >> Alexander Chemeris. >> >> CEO, Fairwaves LLC / ООО УмРадио >> >> http://fairwaves.ru >> >> >> > >> > >> > >> > -- >> > Robin Coxe | Close-Haul Communications, Inc. | Boston, MA >> > +1-617-470-8825 >> >> >> >> -- >> Regards, >> Alexander Chemeris. >> CEO, Fairwaves LLC / ООО УмРадио >> http://fairwaves.ru >> > -- Regards, Alexander Chemeris. CEO, Fairwaves LLC / ООО УмРадио http://fairwaves.ru