Re: LMS6002D support of LTE

Just use our ClockTamer to see how it works :) On Sun, Oct 14, 2012 at 11:30 AM, Alexander Chemeris <alexander.chemeris(a)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(a)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/produ… >> >> -Robin >> >> On Sat, Oct 13, 2012 at 11:54 PM, Alexander Chemeris >> <alexander.chemeris(a)gmail.com> wrote: >>> >>> John, >>> >>> On Sun, Oct 14, 2012 at 12:24 AM, John Orlando >>> <john(a)epiqsolutions.com> >>> wrote: >>>> >>>> On Sat, Oct 13, 2012 at 4:30 PM, Alexander Chemeris >>>> <alexander.chemeris(a)gmail.com> wrote: >>>>> >>>>> Hi John, >>>>> >>>>> On Sat, Oct 13, 2012 at 11:11 PM, John Orlando >>>>> <john(a)epiqsolutions.com> >>>>> wrote: >>>>>> >>>>>> On Sat, Oct 13, 2012 at 3:47 PM, Alexander Chemeris >>>>>> <alexander.chemeris(a)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 >