17 Jun
2013
17 Jun
'13
11:23 a.m.
Hello,
Im an engineer from Spain and Im interested in a GSM receiver because I
would like to study the internal signals for a research project. In
particular, Im interested in the analysis of the IF signal, but, as
Alexander told me, the LMS6002D uses zero-IF architecture, so there is no
real "IF" signal, there is only baseband signal. I guess I could also use
this signal for my purposes, but only if all 124 GSM channels can be found
at that point. Im not sure if this is possible, since there is a low-pass
filter before. Does anybody know if I can extract that information, that is,
the analogic 124 channels after the RF mixer? If it is not possible with
this board, does anybody know if I can do it with another GSM transceiver
board?
Thank you very much in advance.
Best regards,
Albert
17 Jun
17 Jun
11:41 a.m.
If you need to extract them all simultaneously then you'd need about 25 MHz
baseband bandwidth, which I think at the moment is a bit more than the
UmTRX can do on one channel, you might be able to do something clever and
look across both channels maybe. That's a whole lot of processing as well,
I'm guessing you'll be analyzing the signals offline? USRP2 or USRP N
series and do about 25 MHz sustained on one channel, you'll need some good
network hardware on your PC to prevent overruns.
John
On 17 June 2013 10:23, Albert-Miquel Sánchez <albertm(a)salleurl.edu> wrote:
Hello,****
I’m an engineer from Spain and I’m interested in a GSM receiver because I
would like to study the internal signals for a research project. In
particular, I’m interested in the analysis of the IF signal, but, as
Alexander told me, the LMS6002D uses zero-IF architecture, so there is no
real "IF" signal, there is only baseband signal. I guess I could also use
this signal for my purposes, but only if all 124 GSM channels can be found
at that point. I’m not sure if this is possible, since there is a low-pass
filter before. Does anybody know if I can extract that information, that
is, the analogic 124 channels after the RF mixer? If it is not possible
with this board, does anybody know if I can do it with another GSM
transceiver board?****
Thank you very much in advance.****
Best regards,****
Albert****
--
*Dr. John Wilson*
Product development engineer, Path
Intelligence<http://www.pathintelligence.com/>
T +44 2392 388442 @pathintel
DETECT • ANALYSE • PREDICT • INFLUENCE
Path Intelligence Limited, registered number 5176274. Registered in
England,
registered office at 1000 Lakeside North Harbour, Western Road, Portsmouth,
UK, PO6 3EN
12:08 p.m.
Thank you very much for your response. I didnt mention it, but I only want
to extract the analog signal (the 25 MHz baseband bandwidth), in order to
analyze the spectral content (I would capture this signal with another board
developed by us). Therefore, I dont need to process it with the UmTRX.
However I need the UmTRX in order to do this analysis while keeping a phone
communication.
Best regards,
Albert
De: john.wilson(a)pathintel.com [mailto:john.wilson@pathintel.com] En nombre
de John Wilson
Enviado el: lunes, 17 de junio de 2013 11:41
Para: Albert-Miquel Sánchez
CC: umtrx(a)lists.osmocom.org
Asunto: Re: UmTRX
If you need to extract them all simultaneously then you'd need about 25 MHz
baseband bandwidth, which I think at the moment is a bit more than the UmTRX
can do on one channel, you might be able to do something clever and look
across both channels maybe. That's a whole lot of processing as well, I'm
guessing you'll be analyzing the signals offline? USRP2 or USRP N series and
do about 25 MHz sustained on one channel, you'll need some good network
hardware on your PC to prevent overruns.
John
On 17 June 2013 10:23, Albert-Miquel Sánchez <albertm(a)salleurl.edu> wrote:
Hello,
Im an engineer from Spain and Im interested in a GSM receiver because I
would like to study the internal signals for a research project. In
particular, Im interested in the analysis of the IF signal, but, as
Alexander told me, the LMS6002D uses zero-IF architecture, so there is no
real "IF" signal, there is only baseband signal. I guess I could also use
this signal for my purposes, but only if all 124 GSM channels can be found
at that point. Im not sure if this is possible, since there is a low-pass
filter before. Does anybody know if I can extract that information, that is,
the analogic 124 channels after the RF mixer? If it is not possible with
this board, does anybody know if I can do it with another GSM transceiver
board?
Thank you very much in advance.
Best regards,
Albert
--
Dr. John Wilson
Product development engineer, Path Intelligence
<http://www.pathintelligence.com/>
T +44 2392 388442 @pathintel
DETECT ANALYSE PREDICT INFLUENCE
<http://www.pathintelligence.com/wp-content/uploads/2013/03/emailmarketingba
nner.png>
Path Intelligence Limited, registered number 5176274. Registered in England,
registered office at 1000 Lakeside North Harbour, Western Road, Portsmouth,
UK, PO6 3EN
1:53 p.m.
Albert,
In this case yes, it's possible. You could get RXOUT values on
the four test points at the north-west corner of the chip (TST5 - TST8).
Note, that they are differential and separate I/Q.
To acquire 25MHZ you could set LPF to 28MHz, as Sylvain pointed or
completely disable it. I strongly recommend you to use an external bandpass
filter in the latter case.
On Mon, Jun 17, 2013 at 2:08 PM, Albert-Miquel Sánchez <albertm(a)salleurl.edu
wrote:
> Thank you very much for your response. I didn’t mention it, but I only
> want to extract the analog signal (the 25 MHz baseband bandwidth), in order
> to analyze the spectral content (I would capture this signal with another
> board developed by us). Therefore, I don’t need to process it with the
> UmTRX. However I need the UmTRX in order to do this analysis while keeping
> a phone communication.****
>
> ** **
>
> Best regards,****
>
> ** **
>
> Albert****
>
> ** **
>
> *De:* john.wilson(a)pathintel.com [mailto:john.wilson@pathintel.com] *En
> nombre de *John Wilson
> *Enviado el:* lunes, 17 de junio de 2013 11:41
> *Para:* Albert-Miquel Sánchez
> *CC:* umtrx(a)lists.osmocom.org
> *Asunto:* Re: UmTRX****
>
> ** **
>
> If you need to extract them all simultaneously then you'd need about 25
> MHz baseband bandwidth, which I think at the moment is a bit more than the
> UmTRX can do on one channel, you might be able to do something clever and
> look across both channels maybe. That's a whole lot of processing as well,
> I'm guessing you'll be analyzing the signals offline? USRP2 or USRP N
> series and do about 25 MHz sustained on one channel, you'll need some good
> network hardware on your PC to prevent overruns.****
>
> John****
>
> ** **
>
> On 17 June 2013 10:23, Albert-Miquel Sánchez <albertm(a)salleurl.edu wrote:
> ****
>
> Hello,****
>
> I’m an engineer from Spain and I’m interested in a GSM receiver because I
> would like to study the internal signals for a research project. In
> particular, I’m interested in the analysis of the IF signal, but, as
> Alexander told me, the LMS6002D uses zero-IF architecture, so there is no
> real "IF" signal, there is only baseband signal. I guess I could also use
> this signal for my purposes, but only if all 124 GSM channels can be found
> at that point. I’m not sure if this is possible, since there is a low-pass
> filter before. Does anybody know if I can extract that information, that
> is, the analogic 124 channels after the RF mixer? If it is not possible
> with this board, does anybody know if I can do it with another GSM
> transceiver board?****
>
> Thank you very much in advance.****
>
> Best regards,****
>
> Albert****
>
>
>
>
> --
> *Dr. John Wilson*
> Product development engineer, Path
Intelligence<http://www.pathintelligence.com/>
> T +44 2392 388442 @pathintel
> DETECT • ANALYSE • PREDICT • INFLUENCE
>
>
> Path Intelligence Limited, registered number 5176274. Registered in
> England,
> registered office at 1000 Lakeside North Harbour, Western Road,
> Portsmouth, UK, PO6 3EN ****
>
--
Regards,
Alexander Chemeris.
CEO, Fairwaves LLC / ООО УмРадио
http://fairwaves.ru
11:45 a.m.
Hi,
I’m an engineer from Spain and I’m interested in a GSM
receiver because I
would like to study the internal signals for a research project. In
particular, I’m interested in the analysis of the IF signal, but, as
Alexander told me, the LMS6002D uses zero-IF architecture, so there is no
real "IF" signal, there is only baseband signal.
Well, they also have a optional GSM front end board that has an IF.
However it has a very narrow IF filter since the goal was to about
in-band interference from neighbour channels ...
I guess I could also use
this signal for my purposes, but only if all 124 GSM channels can be found
at that point. I’m not sure if this is possible, since there is a low-pass
filter before. Does anybody know if I can extract that information, that is,
the analogic 124 channels after the RF mixer?
The filters can be set to 28 MHz wide and the LMS has analog I/Q debug
outputs, so yes you could get the analog out.
But it's I/Q not a single signals so you'll need two fast ADC to get
it digitized.
OTOH why wouldn't you just use the ADC in the LMS ? They're clocked at
26 Mhz (or could even be fed higher frequency) and so you should be
able to get the whole 25 MHz of P-GSM band.
Cheers,
Sylvain
3977
days inactive
3977
days old
4 comments
4 participants
participants (4)
-
Albert-Miquel Sánchez -
Alexander Chemeris -
John Wilson -
Sylvain Munaut