|
| From: | Jose Rodriguez |
| Subject: | Re: [Discuss-gnuradio] Discuss-gnuradio Digest, Vol 135, Issue 21 |
| Date: | Mon, 17 Feb 2014 13:41:19 -0500 |
Send Discuss-gnuradio mailing list submissions to
address@hidden
To subscribe or unsubscribe via the World Wide Web, visit
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
or, via email, send a message with subject or body 'help' to
address@hidden
You can reach the person managing the list at
address@hidden
When replying, please edit your Subject line so it is more specific
than "Re: Contents of Discuss-gnuradio digest..."
Today's Topics:
1. Trouble with SSB demod of real signal (Louis Brown)
2. Re: Trouble with SSB demod of real signal (Tom McDermott)
3. forecast (Miklos Maroti)
4. Re: Trouble with SSB demod of real signal (Louis Brown)
5. Re: Trouble with SSB demod of real signal (Louis Brown)
6. Segfault in analog.quadrature_demod_cf (Matt Mills)
7. Re: forecast (Marcus M?ller)
8. Re: WSR14 and Hackfest (Martin Braun)
9. ADS-B UAT decoder and hardware (David)
----------------------------------------------------------------------
Message: 1
Date: Sun, 16 Feb 2014 11:10:10 -0600
From: Louis Brown <address@hidden>
To: GNURadio List Discussion <address@hidden>
Subject: [Discuss-gnuradio] Trouble with SSB demod of real signal
Message-ID: <address@hidden>
Content-Type: text/plain; CHARSET=US-ASCII
Hi,
I'm exploring the LF spectrum (< 500 kHz) using a USRP N210+LFRX+active loop antenna, and GR 3.7. I'm pulling my hair out trying to down convert the USB as I can't get the LSB rejected. My GRC flow graph is here:
https://dl.dropboxusercontent.com/u/49570443/test.grc.png
It is based on figure 5 of below; quadrature, direct down conversion with Hilbert transform.
http://www.arrl.org/files/file/Technology/tis/info/pdf/98qex003.pdf
I'm taking the real output (i.e. the DAC hooked to the LFRX channel 1) of the N210 at 25 Msps with 0 Hz DDS, then low-pass filtering at 550 kHz and decimating to 1.25 Msps. This seems to provide better rejection of the AM band than using the DDS tuning internal to the N210.
I then use the translating FIR filter to tune a 2 kHz passband, decimated to 5 ksps.
Problem comes when I try to do the LSB rejection with the Hilbert. I think I'm using it correctly; I have tried swapping the Re and Im outputs of the Hilbert with no luck. Maybe there is something conceptually I am missing since I am starting with a real signal. I have done SSB demod with complex USRP signal with no problems.
Any ideas of what I am doing wrong? This should be basic stuff but I'm not getting something.
Thanks,
Lou
------------------------------
Message: 2
Date: Sun, 16 Feb 2014 09:19:17 -0800 (PST)
From: Tom McDermott <address@hidden>
To: Louis Brown <address@hidden>, GNURadio List Discussion
<address@hidden>
Subject: Re: [Discuss-gnuradio] Trouble with SSB demod of real signal
Message-ID:
<address@hidden>
Content-Type: text/plain; charset="iso-8859-1"
Hi Lou - the diagram you sent isn't going to perform a single-signal conversion.
Taking just the real part of the received signal (and throwing away the imaginary part)
gets rid of information that distinguishes negative frequency components from
positive frequency components. After that point there is no possibility to separate out
the LSB components from the USB components.
?
You will need a bit more complicated design, I've used the following configuration for
implementing a phasing type receiver. There are other ways as well, the Weaver method,
and a filter method (using complex taps to a filter).
?
http://www.tapr.org/~n5eg/index_files/DCC_2013_Gnuradio_Presentation%20-%20Rev%205.pdf
?
Look at about slide 14.
?
-- Tom, N5EG
?
________________________________
From: Louis Brown <address@hidden>
To: GNURadio List Discussion <address@hidden>
Sent: Sunday, February 16, 2014 9:10 AM
Subject: [Discuss-gnuradio] Trouble with SSB demod of real signal
Hi,
I'm exploring the LF spectrum (< 500 kHz) using a USRP N210+LFRX+active loop antenna, and GR 3.7.? I'm pulling my hair out trying to down convert the USB as I can't get the LSB rejected.? My GRC flow graph is here:
https://dl.dropboxusercontent.com/u/49570443/test.grc.png
It is based on figure 5 of below; quadrature, direct down conversion with Hilbert transform.
http://www.arrl.org/files/file/Technology/tis/info/pdf/98qex003.pdf
I'm taking the real output (i.e. the DAC hooked to the LFRX channel 1) of the N210 at 25 Msps with 0 Hz DDS, then low-pass filtering at 550 kHz and decimating to 1.25 Msps. This seems to provide better rejection of the AM band than using the DDS tuning internal to the N210.
I then use the translating FIR filter to tune a 2 kHz passband, decimated to 5 ksps.
Problem comes when I try to do the LSB rejection with the Hilbert.? I think I'm using it correctly; I have tried swapping the Re and Im outputs of the Hilbert with no luck.? Maybe there is something conceptually I am missing since I am starting with a real signal.? I have done SSB demod with complex USRP signal with no problems.
Any ideas of what I am doing wrong?? This should be basic stuff but I'm not getting something.
Thanks,
Lou
_______________________________________________
Discuss-gnuradio mailing list
address@hidden
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.gnu.org/archive/html/discuss-gnuradio/attachments/20140216/955484b3/attachment.html>
------------------------------
Message: 3
Date: Sun, 16 Feb 2014 19:12:48 +0100
From: Miklos Maroti <address@hidden>
To: "address@hidden" <address@hidden>
Subject: [Discuss-gnuradio] forecast
Message-ID:
<CAEUdg=address@hidden>
Content-Type: text/plain; charset=UTF-8
Hi Guys,
If a block keeps some internal state, can the forecast method return
different values for the same number of noutput_items depending on its
internal state? Will the forecast method be called before the flow
graph is started?
Miklos
------------------------------
Message: 4
Date: Sun, 16 Feb 2014 13:13:21 -0600
From: Louis Brown <address@hidden>
To: Tom McDermott <address@hidden>
Cc: GNURadio List Discussion <address@hidden>
Subject: Re: [Discuss-gnuradio] Trouble with SSB demod of real signal
Message-ID: <address@hidden>
Content-Type: text/plain; CHARSET=US-ASCII
Tom,
Thanks for that link. The LFRX board has two separate inputs. I'm only using the one hooked to the I ADC, so the Q ADC is just noise, thus I discard the imaginary output of the UHD source. The UHD source center frequency is set to 0 Hz, so I'm direct sampling with no downconversion in the FPGA. I'm moving what's done in the FPGA into GNU Radio to get better rejection, thus I'm really not discarding the imaginary part since there isn't one until after the translating FIR.
I could drive both the I and Q ADC by splitting my received signal, but then I have to deal with the imbalance between LFRX channels.
Thanks,
Lou, KD4HSO
On Feb 16, 2014, at 11:19 AM, Tom McDermott <address@hidden> wrote:
> Hi Lou - the diagram you sent isn't going to perform a single-signal conversion.
> Taking just the real part of the received signal (and throwing away the imaginary part)
> gets rid of information that distinguishes negative frequency components from
> positive frequency components. After that point there is no possibility to separate out
> the LSB components from the USB components.
>
> You will need a bit more complicated design, I've used the following configuration for
> implementing a phasing type receiver. There are other ways as well, the Weaver method,
> and a filter method (using complex taps to a filter).
>
> http://www.tapr.org/~n5eg/index_files/DCC_2013_Gnuradio_Presentation%20-%20Rev%205.pdf
>
> Look at about slide 14.
>
> -- Tom, N5EG
>
>
> From: Louis Brown <address@hidden>
> To: GNURadio List Discussion <address@hidden>
> Sent: Sunday, February 16, 2014 9:10 AM
> Subject: [Discuss-gnuradio] Trouble with SSB demod of real signal
>
>
> Hi,
>
> I'm exploring the LF spectrum (< 500 kHz) using a USRP N210+LFRX+active loop antenna, and GR 3.7. I'm pulling my hair out trying to down convert the USB as I can't get the LSB rejected. My GRC flow graph is here:
>
> https://dl.dropboxusercontent.com/u/49570443/test.grc.png
>
> It is based on figure 5 of below; quadrature, direct down conversion with Hilbert transform.
>
> http://www.arrl.org/files/file/Technology/tis/info/pdf/98qex003.pdf
>
>
> I'm taking the real output (i.e. the DAC hooked to the LFRX channel 1) of the N210 at 25 Msps with 0 Hz DDS, then low-pass filtering at 550 kHz and decimating to 1.25 Msps. This seems to provide better rejection of the AM band than using the DDS tuning internal to the N210.
> I then use the translating FIR filter to tune a 2 kHz passband, decimated to 5 ksps.
>
> Problem comes when I try to do the LSB rejection with the Hilbert. I think I'm using it correctly; I have tried swapping the Re and Im outputs of the Hilbert with no luck. Maybe there is something conceptually I am missing since I am starting with a real signal. I have done SSB demod with complex USRP signal with no problems.
>
> Any ideas of what I am doing wrong? This should be basic stuff but I'm not getting something.
>
> Thanks,
> Lou
>
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
>
>
------------------------------
Message: 5
Date: Sun, 16 Feb 2014 13:37:05 -0600
From: Louis Brown <address@hidden>
To: Tom McDermott <address@hidden>
Cc: GNURadio List Discussion <address@hidden>
Subject: Re: [Discuss-gnuradio] Trouble with SSB demod of real signal
Message-ID: <address@hidden>
Content-Type: text/plain; CHARSET=US-ASCII
Tom,
OK I got it fixed after looking at your link. See diagram below:
https://dl.dropboxusercontent.com/u/49570443/test.grc_fixed.png
I was using the Delay block to give me a 65 sample delay to account for the delay in the Hilbert. This will not work as I assume there is more delay in the Hilbert than just the 65 taps. The real output of the Hilbert is a properly delayed version of the input, so I replaced the delay with that. It now works well What's shown in the diagram is LSB though, not USB.
Thanks,
Lou KD4HSO
On Feb 16, 2014, at 11:19 AM, Tom McDermott <address@hidden> wrote:
> Hi Lou - the diagram you sent isn't going to perform a single-signal conversion.
> Taking just the real part of the received signal (and throwing away the imaginary part)
> gets rid of information that distinguishes negative frequency components from
> positive frequency components. After that point there is no possibility to separate out
> the LSB components from the USB components.
>
> You will need a bit more complicated design, I've used the following configuration for
> implementing a phasing type receiver. There are other ways as well, the Weaver method,
> and a filter method (using complex taps to a filter).
>
> http://www.tapr.org/~n5eg/index_files/DCC_2013_Gnuradio_Presentation%20-%20Rev%205.pdf
>
> Look at about slide 14.
>
> -- Tom, N5EG
>
>
>
>
>
------------------------------
Message: 6
Date: Sun, 16 Feb 2014 13:52:19 -0700
From: Matt Mills <address@hidden>
To: "address@hidden" <address@hidden>
Subject: [Discuss-gnuradio] Segfault in analog.quadrature_demod_cf
Message-ID:
<CAHH1NCcuLNgDeAt5Xexkeiq62x4jQT6WsYqP=address@hidden>
Content-Type: text/plain; charset="iso-8859-1"
Application that reproduces segfault:
http://pastebin.com/Fw0y7qM9
debug backtrace: http://pastebin.com/FjnHu6Cs
patch that fixes it for me, although I'm sure theres a better place to fix
it: http://pastebin.com/4gSW57Wt
Thanks,
Matt.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.gnu.org/archive/html/discuss-gnuradio/attachments/20140216/1591c4dc/attachment.html>
------------------------------
Message: 7
Date: Sun, 16 Feb 2014 23:23:49 +0100
From: Marcus M?ller <address@hidden>
To: address@hidden
Subject: Re: [Discuss-gnuradio] forecast
Message-ID: <address@hidden>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Hi Miklos,
yes, a forecast might be different for different situations.
Greetings,
Marcus
On 02/16/2014 07:12 PM, Miklos Maroti wrote:
> Hi Guys,
>
> If a block keeps some internal state, can the forecast method return
> different values for the same number of noutput_items depending on its
> internal state? Will the forecast method be called before the flow
> graph is started?
>
> Miklos
>
> _______________________________________________
> Discuss-gnuradio mailing list
> address@hidden
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
------------------------------
Message: 8
Date: Sun, 16 Feb 2014 23:25:14 +0100
From: Martin Braun <address@hidden>
To: address@hidden
Subject: Re: [Discuss-gnuradio] WSR14 and Hackfest
Message-ID: <address@hidden>
Content-Type: text/plain; charset=ISO-8859-1
Sebastian, thanks for organizing this!
On Tuesday, March 11th, there will also be the (by now traditional)
meeting of GR enthusiasts in Vogelbr?u [1]. I'll book a table for 19:00.
MB
[1] Address: Kapellenstra?e 50, http://www.vogelbraeu.de/
On 02/16/2014 03:58 PM, Sebastian Koslowski wrote:
> After the workshop we'll hold a 3-day hackfest here at the CEL- 2
> 1/2 days to be exact, that is March 13-15. Over the last years hackfests
> have become a regular event for GR developers to get together and work
> on new features, bug fixes, and discuss where to go next. As far as I
> know this will be the first hackfest in Europe and so we would like to
> invite everyone interested to stay a few days longer in Karlsruhe and do
> some GR coding.
------------------------------
Message: 9
Date: Sun, 16 Feb 2014 18:41:00 -0600
From: David <address@hidden>
To: <address@hidden>
Subject: [Discuss-gnuradio] ADS-B UAT decoder and hardware
Message-ID: <address@hidden>
Content-Type: text/plain; charset=UTF-8; format=flowed
Hi list,
I recently posted the source code and hardware design files for a ADS-B
UAT/FIS-B receiver and decoder to Google code. There's also a python
script that contains the algorithms to decode the FIS-B weather radar
data. Perhaps they might be useful to someone working on ADS-B with
GnuRadio.
https://code.google.com/p/lone-star-ads-b/
David
------------------------------
_______________________________________________
Discuss-gnuradio mailing list
address@hidden
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
End of Discuss-gnuradio Digest, Vol 135, Issue 21
*************************************************
| [Prev in Thread] | Current Thread | [Next in Thread] |