LMS6002D support of LTE

sergey kostanbaev sergey.kostanbaev at gmail.com
Sun Oct 14 07:35:57 UTC 2012


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
>
>
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