Send USRP-users mailing list submissions to
[email protected]
To subscribe or unsubscribe via the World Wide Web, visit
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
or, via email, send a message with subject or body 'help' to
[email protected]
You can reach the person managing the list at
[email protected]
When replying, please edit your Subject line so it is more specific
than "Re: Contents of USRP-users digest..."
Today's Topics:
1. Re: Severe DC offset ([email protected])
2. Problem with USRP1 DBSRX2 (Paola Madonna)
----------------------------------------------------------------------
Message: 1
Date: Tue, 29 Mar 2011 15:24:20 -0400
From: [email protected]
To: "Matt Ettus" <[email protected]>
Cc: [email protected], [email protected]
Subject: Re: [USRP-users] Severe DC offset
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; DelSp="Yes";
format="flowed"
Current system:
1 - No driver. I use my own custom firmware at this point. We route
samples to the XUPV5 directly. As such minor firmware is needed to
control configuration of the frontend.
2 - No software
3 - Both RX and TX have the problem, but the TX signal seems to
overwhelm the "offset". This issue is removed by adjusting lo_offset.
4 - Two way, but we haven't hooked up the mac yet to test the
switching between rx and tx. We'll hook up the MAC in the next couple
of days and let you know how we fare.
5 - TX and RX are running at the same time, though we have not tested
this functionality completely.
6 - Right now we use 2442/2442Mhz (Ch. 7). We have also tested
2440/2440Mhz (Ch. 1).
7 - TX has no analog gain (even though you provide a function for it).
We apply a digital "gain" of 128x to match our baseband fixed point
with your fixed point.
8 - The sideband distortion looks to be 5-15 dB off the peak
centerband tx power. I have not measured the RX power beyond
producing the graph I sent earlier. Since we changed lo_offset things
look much better.
9 - We are using a custom FPGA build. It resembles your gnuradio
code, but I have stripped out things that we don't need that were
making timing closure difficult. Namely, no Ethernet, not timer, no
buffer pool, fewer interrupts. Eventually, I'd like to remove the SD
card as well; our firmware is simple and it can fit in BRAM. We do
use your dsp code, but I've hacked the tx and rx controllers and
linked them to the SERDES lines directly.
Old System (i.e. the one that we first notices these DC issues):
1 - old style driver built off of gnuradio head
2 - your txrx code, also built off of gnuradio head. We're interested
in hardware, so we've largely ignored gnuradio.
3- We see it on receiver side. We didn't test transmit throughly, but
no obvious problems stood out - probably because the power of the
lo_offset was overwhelmed by our signal.
4-RX only
5-No
6-We tested several frequencies and observed the same phenomena, but
mostly we were at 2442Mhz.
7-Varied up to 80 (not a valid setting on the 2400 board), we noticed
packets predominately around 23 dB. At least there was enough power
here to trip our synchronizer.
8- 10dB over signal (The graph I sent previously is derived from the
traces we were pulling out on this testing run)
9- We ran both your default image (we built it ourselves, though) and
our own custom image (like yours but with taps inserted for serdes).
As I said, we are now using USRP2 to successfully RX/TX 80211.g with
commodity equipment in real-time, suggesting that the error we see in
the gnuradio code is just one of configuration. As far as we know
the only thing that we have changed is the lo_offset parameter, which
we adjusted to match the 80211.g envelope.
-Elliott
Quoting "Matt Ettus" <[email protected]>:
> On 03/29/2011 09:42 AM, Matt Ettus wrote:
>>
>> Elliott,
>>
>> I would like to help you with this, but in order to do that, I need some
>> more information. Please tell me:
>>
>> 1 - UHD or old style drivers?
>> 2 - GNU Radio or some other software package?
>> 3 - Is the DC offset you see on the receive side?
>> 4 - Is this a two-way system or receive only?
>> 5 - Is your transmitter running at the same time as the receiver?
>> 6 - What frequency is the TX? The RX?
>> 7 - What are your gain settings?
>> 8 - What is the amplitude of the DC offset you see?
>>
>> Matt
>
>
> Also, are you using a stock FPGA image or your own design?
>
> Matt
>
------------------------------
Message: 2
Date: Wed, 30 Mar 2011 18:28:38 +0200
From: "Paola Madonna" <[email protected]>
To: <[email protected]>
Subject: [USRP-users] Problem with USRP1 DBSRX2
Message-ID: <[email protected]>
Content-Type: text/plain; charset="us-ascii"
Hello,
we have a USRP1 and a DBSRX2 dautherboard and our aim is to acquire gps
signal. We installed uhd under ubuntu 10.10 and we run the file
uhd_usrp_probe that displays :
| Device: usrp1 device
| _____________________________________________________
| /
| | Mboard: usrp1 mboard - 4d6c375f
| | serial: 4d6c375f
| | _____________________________________________________
| | /
| | | RX DSP: usrp1 ddc0 + hb
| | | Codec Rate: 64.000000 Msps
| | _____________________________________________________
| | /
| | | RX DSP: usrp1 ddc1 + hb
| | | Codec Rate: 64.000000 Msps
| | _____________________________________________________
| | /
| | | TX DSP: usrp1 duc0
| | | Codec Rate: 128.000000 Msps
| | _____________________________________________________
| | /
| | | TX DSP: usrp1 duc1
| | | Codec Rate: 128.000000 Msps
| | _____________________________________________________
| | /
| | | RX Dboard: usrp1 dboard (rx unit) - A
| | | _____________________________________________________
| | | /
| | | | RX Subdev: DBSRX2 (0x0012)
| | | | Antennas: J3
| | | | Freq range: 800.000 to 2400.000 Mhz
| | | | Gain range GC1: 0.0 to 73.0 step 0.1 dB
| | | | Gain range BBG: 0.0 to 15.0 step 1.0 dB
| | | | Connection Type: c
| | | | Uses LO offset: No
| | | _____________________________________________________
| | | /
| | | | RX Codec: usrp1 adc - ad9862 - slot A
| | | | Gain range PGA: 0.0 to 20.0 step 1.0 dB
| | _____________________________________________________
| | /
| | | RX Dboard: usrp1 dboard (rx unit) - B
| | | _____________________________________________________
| | | /
| | | | RX Subdev: Unknown - Unknown (0xffff)
| | | | Antennas:
| | | | Freq range: 0.000 to 0.000 Mhz
| | | | Gain Elements: None
| | | | Connection Type: C
| | | | Uses LO offset: No
| | | _____________________________________________________
| | | /
| | | | RX Codec: usrp1 adc - ad9862 - slot B
| | | | Gain range PGA: 0.0 to 20.0 step 1.0 dB
| | _____________________________________________________
| | /
| | | TX Dboard: usrp1 dboard (tx unit) - A
| | | _____________________________________________________
| | | /
| | | | TX Subdev: Unknown - Unknown (0xffff)
| | | | Antennas:
| | | | Freq range: 0.000 to 0.000 Mhz
| | | | Gain Elements: None
| | | | Connection Type: C
| | | | Uses LO offset: No
| | | _____________________________________________________
| | | /
| | | | TX Codec: usrp1 dac - ad9862 - slot A
| | | | Gain range PGA: -20.0 to 0.0 step 0.1 dB
| | _____________________________________________________
| | /
| | | TX Dboard: usrp1 dboard (tx unit) - B
| | | _____________________________________________________
| | | /
| | | | TX Subdev: Unknown - Unknown (0xffff)
| | | | Antennas:
| | | | Freq range: 0.000 to 0.000 Mhz
| | | | Gain Elements: None
| | | | Connection Type: C
| | | | Uses LO offset: No
| | | _____________________________________________________
| | | /
| | | | TX Codec: usrp1 dac - ad9862 - slot B
| | | | Gain range PGA: -20.0 to 0.0 step 0.1 dB
We launched the file rx_samples_to_file --type="short" --nsamps="160000"
--rate="8000000" --freq="1575420000" --bw="2000000". So we acquired 20ms of
signal and we computed the fft using Matlab but it doesn't display the GPS
spectrum. The Matlab script is the following:
fid=fopen('filename.dat');
data=fread(fid,'int16');
fclose(fid);
I=data(1:2:end);
save I
Q=data(2:2:end);
save Q
data=I + i .* Q;
F=fft(data);
figure(1);
plot(fftshift(real(F)))
Please help us as soon as possible. Could be a driver problem or a hardware
problem?
Thanks,
Paola Madonna
T.R.S. Spa
80079 Bacoli(Naples)
Italy
+390815272837
-------------- next part --------------
An HTML attachment was scrubbed...
URL:
<http://lists.ettus.com/pipermail/usrp-users_lists.ettus.com/attachments/20110330/a545efe0/attachment.html>
------------------------------
_______________________________________________
USRP-users mailing list
[email protected]
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
End of USRP-users Digest, Vol 7, Issue 51
*****************************************
