13 Oct
2012
13 Oct
'12
10:47 p.m.
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?
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.
--
Regards,
Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио
http://fairwaves.ru
13 Oct
13 Oct
11:11 p.m.
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? We run the A/D
converters in the LMS6002d at sample rates greater than 14 Msps all
the time, including 30.72 Msps.
--
John Orlando
Epiq Solutions
http://www.epiqsolutions.com
11:30 p.m.
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:
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.
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? 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.
--
Regards,
Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио
http://fairwaves.ru
14 Oct
14 Oct
12:24 a.m.
On Sat, Oct 13, 2012 at 4:30 PM, Alexander Chemeris
<alexander.chemeris(a)gmail.com> wrote:
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
Hi John,
On Sat, Oct 13, 2012 at 11:11 PM, John Orlando <john(a)epiqsolutions.com> wrote:
Yes, this refers to the analog baseband filter bandwidth.
On Sat, Oct 13, 2012 at 3:47 PM, Alexander
Chemeris
<alexander.chemeris(a)gmail.com> wrote:
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.
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? 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.
5:54 a.m.
John,
On Sun, Oct 14, 2012 at 12:24 AM, John Orlando <john(a)epiqsolutions.com> wrote:
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
On Sat, Oct 13, 2012 at 4:30 PM, Alexander Chemeris
<alexander.chemeris(a)gmail.com> wrote:
Ok, thanks for the clarification.
Hi John,
On Sat, Oct 13, 2012 at 11:11 PM, John Orlando <john(a)epiqsolutions.com> wrote:
Yes, this refers to the analog baseband filter bandwidth. On Sat, Oct 13, 2012 at 3:47 PM, Alexander
Chemeris
<alexander.chemeris(a)gmail.com> wrote:
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. 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? 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. 
6:18 a.m.
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:
Yes, this refers to the analog baseband filter bandwidth.
Ok, thanks for the clarification.
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
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. 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.
9:30 a.m.
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:
--
Regards,
Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио
http://fairwaves.ru
John,
On Sun, Oct 14, 2012 at 12:24 AM, John Orlando <john(a)epiqsolutions.com>
wrote:
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 On Sat, Oct 13, 2012 at 4:30 PM, Alexander
Chemeris
<alexander.chemeris(a)gmail.com> wrote:
Ok, thanks for the clarification.
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. > 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. 
9:35 a.m.
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:
--
Robin Coxe | Close-Haul Communications, Inc. | Boston, MA
+1-617-470-8825
--
Regards,
Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио
http://fairwaves.ru
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
9:47 a.m.
Hum, 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(a)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(a)gmail.com> wrote:
--
Regards,
Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио
http://fairwaves.ru
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:
--
Regards,
Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио
http://fairwaves.ru
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 
1:11 p.m.
Hi Alexander,
You can simply replace 26MHz TCXO with foot print compatible 61.44MHz
TCXO. Divide by 2 would be required to construct PLL reference below max
41MHz (61.44/2 = 30.72MHz) while having IQ interface still running at
61.44MHz which corresponds to 30.72MS/s converters sample rate. This is
something we usually do with LMS eval board when customers want to
evaluate more bandwidth demanding modulations such as 20MHz LTE.
Regards, Srdjan
On 14/10/2012 08:47, Alexander Chemeris wrote:
Hum, 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(a)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(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
>
2:19 p.m.
Hi Srdjan,
Doh, I completely forgot that we would need to divide by 2 for PLL if
we install 61.44MHz clock.
Andrey Sviyazov - I think we don't have a way to divide PLL clock on
UmTRXv2, right? If so, for LTE sample rates we're limited by 30.72MHz
on UmTRXv2.
On Sun, Oct 14, 2012 at 3:11 PM, Srdjan Milenkovic
<s.milenkovic(a)limemicro.com> wrote:
Hi Alexander,
You can simply replace 26MHz TCXO with foot print compatible 61.44MHz TCXO.
Divide by 2 would be required to construct PLL reference below max 41MHz
(61.44/2 = 30.72MHz) while having IQ interface still running at 61.44MHz
which corresponds to 30.72MS/s converters sample rate. This is something we
usually do with LMS eval board when customers want to evaluate more
bandwidth demanding modulations such as 20MHz LTE.
Regards, Srdjan
On 14/10/2012 08:47, Alexander Chemeris wrote:
--
Regards,
Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио
http://fairwaves.ru
Hum, 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(a)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(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
>
12:08 a.m.
Alexander,
My replies below:
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.
Does this mean you are moving away from GSM, or you just trying to make
sure your eventual UmTRX will be able to do more then GSM, like LTE ?
Sincerely,
Martin[image:
http://photos4.meetupstatic.com/photos/event/5/1/f/6/highres_165320982.jpeg]
5:52 a.m.
On Sun, Oct 14, 2012 at 12:08 AM, Martin O'Shield
<martin(a)windycitysdr.com>wrote;wrote:
Alexander,
My replies below:
On Sat, Oct 13, 2012 at 3:47 PM, Alexander Chemeris <
alexander.chemeris(a)gmail.com> wrote:
Yes, we're exploring the possibility of doing LTE with UmTRX, as we may
start working in this direction sooner then we originally planned. We will
continue to work on GSM in any case - we believe that GSM+LTE networks are
the winning combination.
--
Regards,
Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио
http://fairwaves.ru
Hi Srdjan,
We're looking into re-purposing UmTRX for LTE and there a few things
which we need to understand better.
Does this mean you are moving away from GSM, or you just trying to make
sure your eventual UmTRX will be able to do more then GSM, like LTE ?
1:50 p.m.
Hi Alexander,
Remaining questions are addressed below.
Dr Srdjan Milenkovic 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
2:25 p.m.
Srdjan, 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(a)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
15 Oct
15 Oct
10:13 a.m.
Since we decided to make version 3 (due to additions of LMS thermosensors)
then we can also add external Fref prescaler for PLL, no problems here.
I think ICPR is more important restriction.
Srdjan said that it doesn't studied too deeply, but on my opinion, really
reachable maximum Tx power no more then 25 dBm (without DPD).
So, we can't use LMS for LTE without DPD or additional filtration (2nd Tx
IF).
In other hand, we can implement it similar to UmSEL and with upconversion,
of course, but high quality SAW filter required (all flatness) to keeping
EVM as small as possible.
Best regards,
Andrey Sviyazov.
2012/10/14 Alexander Chemeris <alexander.chemeris(a)gmail.com>
Srdjan, 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(a)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
11:03 a.m.
DPD will linearize PA, LMS should not be limiting factor in that
respect. In band spurs should be investigated before we say that LMS can
or can not be used. What output power are we looking for?
On 15/10/2012 09:13, Andrey Sviyazov wrote:
Since we decided to make version 3 (due to additions
of LMS
thermosensors) then we can also add external Fref prescaler for PLL,
no problems here.
I think ICPR is more important restriction.
Srdjan said that it doesn't studied too deeply, but on my opinion,
really reachable maximum Tx power no more then 25 dBm (without DPD).
So, we can't use LMS for LTE without DPD or additional filtration (2nd
Tx IF).
In other hand, we can implement it similar to UmSEL and with
upconversion, of course, but high quality SAW filter required (all
flatness) to keeping EVM as small as possible.
Best regards,
Andrey Sviyazov.
2012/10/14 Alexander Chemeris <alexander.chemeris(a)gmail.com
<mailto:alexander.chemeris@gmail.com>>
Srdjan, 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(a)limemicro.com <mailto:s.milenkovic@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
11:52 a.m.
Hi Srdjan.
Thank you for reply.
Our potential customer asked us about TDD with 43dBm at antenna port and
with as many of MIMO's as it possible (theoreticaly) to realize now to get
higher users density per sector. Of course, for the first look it seems
like an dreams, but it is true real customer dreams.
So, now we have to understand real LMS performances for LTE anyway.
It required to be able to answering customer either something about
0.1-0.5W and no more or to start good real project with required specs.
Please suggest us something to answer.
Best regards,
Andrey Sviyazov.
2012/10/15 Srdjan Milenkovic <s.milenkovic(a)limemicro.com>
DPD will linearize PA, LMS should not be limiting
factor in that
respect. In band spurs should be investigated before we say that LMS can or
can not be used. What output power are we looking for?
On 15/10/2012 09:13, Andrey Sviyazov wrote:
Since we decided to make version 3 (due to additions of LMS
thermosensors) then we can also add external Fref prescaler for PLL, no
problems here.
I think ICPR is more important restriction.
Srdjan said that it doesn't studied too deeply, but on my opinion, really
reachable maximum Tx power no more then 25 dBm (without DPD).
So, we can't use LMS for LTE without DPD or additional filtration (2nd Tx
IF).
In other hand, we can implement it similar to UmSEL and with upconversion,
of course, but high quality SAW filter required (all flatness) to keeping
EVM as small as possible.
Best regards,
Andrey Sviyazov.
2012/10/14 Alexander Chemeris <alexander.chemeris(a)gmail.com>
Srdjan, 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(a)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
1:22 p.m.
Hi Srdjan.
As I understand, I must to re-ask and much simpler and more correctly:
Do we need to search another components for LTE BTS with MIMO/20MHz/10-20W
or there are chances to use LMS6002?
You told about 20-23dBm output power, so please let us know what PA do you
use in this case.
Best regards,
Andrey Sviyazov.
P.S.
Sorry for my undeveloped english :)
2012/10/15 Andrey Sviyazov <andreysviyaz(a)gmail.com>
Hi Srdjan.
Thank you for reply.
Our potential customer asked us about TDD with 43dBm at antenna port and
with as many of MIMO's as it possible (theoreticaly) to realize now to get
higher users density per sector. Of course, for the first look it seems
like an dreams, but it is true real customer dreams.
So, now we have to understand real LMS performances for LTE anyway.
It required to be able to answering customer either something about
0.1-0.5W and no more or to start good real project with required specs.
Please suggest us something to answer.
Best regards,
Andrey Sviyazov.
2012/10/15 Srdjan Milenkovic <s.milenkovic(a)limemicro.com>
DPD will linearize PA, LMS should not be
limiting factor in that
respect. In band spurs should be investigated before we say that LMS can or
can not be used. What output power are we looking for?
On 15/10/2012 09:13, Andrey Sviyazov wrote:
Since we decided to make version 3 (due to additions of LMS
thermosensors) then we can also add external Fref prescaler for PLL, no
problems here.
I think ICPR is more important restriction.
Srdjan said that it doesn't studied too deeply, but on my opinion, really
reachable maximum Tx power no more then 25 dBm (without DPD).
So, we can't use LMS for LTE without DPD or additional filtration (2nd Tx
IF).
In other hand, we can implement it similar to UmSEL and with
upconversion, of course, but high quality SAW filter required (all
flatness) to keeping EVM as small as possible.
Best regards,
Andrey Sviyazov.
2012/10/14 Alexander Chemeris <alexander.chemeris(a)gmail.com>
Srdjan, 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(a)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
12:35 p.m.
On Mon, Oct 15, 2012 at 12:13 PM, Andrey Sviyazov
<andreysviyaz(a)gmail.com> wrote:
Since we decided to make version 3 (due to additions
of LMS thermosensors)
then we can also add external Fref prescaler for PLL, no problems here.
Regarding TCXO frequency.
I think we're not going to release UmTRXv3 immediately, as UmTRXv2
works well for GSM. If I remember correctly, we planned to connect
temperature sensors to unused debug pins on UmTRXv2 or to extension
connector together with UmSEL daughter-board. Meantime, I want to be
able to test LTE with UmTRXv2 and thus my question was which maximum
TCXO frequency we could use. It seems like the answer is 30.72MHz,
because we don't have prescaler for PLL.
--
Regards,
Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио
http://fairwaves.ru
4216
days inactive
4218
days old
19 comments
7 participants
participants (7)
-
Alexander Chemeris -
Andrey Sviyazov -
John Orlando -
Martin O'Shield -
Robin Coxe -
sergey kostanbaev -
Srdjan Milenkovic