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Today's Topics:
1. USRP N210 low pass filter (Marc Bauduin)
2. Re: USRP N210 low pass filter (Sivan Toledo)
3. USRP time with GPSDO (Sivan Toledo)
4. Still problems with USRP time from GPSDO (Sivan Toledo)
5. Re: USRP N210 low pass filter (Matt Ettus)
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Message: 1
Date: Mon, 29 Apr 2013 09:21:22 +0200
From: Marc Bauduin <[email protected]>
To: [email protected]
Subject: [USRP-users] USRP N210 low pass filter
Message-ID:
<CA+ekp-YF9cQh8ADqoeyVsA8tvgr6BSL+dHPvAgEVRb2p=j0...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hy everyone,
I have 2 USRP N210 with a daughterbourd RFX2400 and I pilot them with
Matlab. When I make a narrowband communication, I don't observe a flat
channel but I also observe the spectrum of a filter. I searched in
documentation but I did'nt see the characteristic of the baseband filter of
the system. What are the characteristic of this filter? Is it a RRC filter?
Thanks for your answer,
Marc
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Message: 2
Date: Mon, 29 Apr 2013 10:34:00 +0300
From: Sivan Toledo <[email protected]>
To: Marc Bauduin <[email protected]>
Cc: "[email protected]" <[email protected]>
Subject: Re: [USRP-users] USRP N210 low pass filter
Message-ID:
<caol_rugp9izl2_4ofrupyxmpvnx1n0tn-rvnotakgco9vqn...@mail.gmail.com>
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I am not familiar with the RFX2400, but judging from USRP daughterboards
that I do know well, they have an analog anti-aliasing filter (or filters)
between the mixer and the ADC. The bandwidth of the filter is specified on
the schematics of the daughterboard, at least for the WBX. The FPGA will do
further digital filtering based on the sampling rate.
On Mon, Apr 29, 2013 at 10:21 AM, Marc Bauduin <[email protected]> wrote:
>
> Hy everyone,
>
> I have 2 USRP N210 with a daughterbourd RFX2400 and I pilot them with
> Matlab. When I make a narrowband communication, I don't observe a flat
> channel but I also observe the spectrum of a filter. I searched in
> documentation but I did'nt see the characteristic of the baseband filter of
> the system. What are the characteristic of this filter? Is it a RRC filter?
>
> Thanks for your answer,
> Marc
>
> _______________________________________________
> USRP-users mailing list
> [email protected]
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
>
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Message: 3
Date: Mon, 29 Apr 2013 11:41:59 +0300
From: Sivan Toledo <[email protected]>
To: "[email protected]" <[email protected]>
Subject: [USRP-users] USRP time with GPSDO
Message-ID:
<CAOL_ruFoupRciCq=mnw6c0_ext4-go9i9jq9k5rfzgjxmjw...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
We have 2 N200's with GPSDOs, connected to different Linux computers. We
discovered that their times (the metadata time stamps) differ by 2 or 3
seconds.
We eventually traced that to differences in the clocks of the two linux
boxes (one was not running ntpd). However, I am still puzzled by the fact
that the USRP time came from the computer's time and not from the GPSDO
time.
Is that behavior (getting the time from the computer even if a GPSDO is
intalled) normal?
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Message: 4
Date: Mon, 29 Apr 2013 15:10:53 +0300
From: Sivan Toledo <[email protected]>
To: "[email protected]" <[email protected]>
Subject: [USRP-users] Still problems with USRP time from GPSDO
Message-ID:
<CAOL_ruEazvnO-LPCoP=ru=wk_3u+fwihgbmv6vwaes05gjc...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
I think that my previous message was wrong, but I still have problems with
the GPSDO times from the USRP. Here is a printout from a UHD program that
queries the time in 4 different ways:
usrp->get_time_now(): 1367237083:0.517574
usrp->get_time_last_pps(): 1367237082:1.000000
metadata time stamp of recent RX samples: 1367237083:0.510384
utime() on Linux: 1367237084:0.517167
As you can see there is a difference of a whole second between the time on
the PC, which is derived from NTP using ntpd and should be accurate to at
least 10ms or so, and the times on the USRP.
The USRP is an N200 with a GPSDO fitted.
We've experienced errors by whole seconds in two different units. Is this a
bug in the firmware or image?
Thanks, Sivan
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Message: 5
Date: Mon, 29 Apr 2013 07:42:36 -0700
From: Matt Ettus <[email protected]>
To: Marc Bauduin <[email protected]>
Cc: "[email protected]" <[email protected]>
Subject: Re: [USRP-users] USRP N210 low pass filter
Message-ID:
<CAN=1kn-oxi-1Cw7PupOeS2HfTAX4kq91O=5wnp5gpaleo-o...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
If you choose an odd decimation ratio, you will have rolloff due to the CIC
filters. You need to choose an even decimation ratio to get a flat
passband.
Matt
On Mon, Apr 29, 2013 at 12:21 AM, Marc Bauduin <[email protected]> wrote:
>
> Hy everyone,
>
> I have 2 USRP N210 with a daughterbourd RFX2400 and I pilot them with
> Matlab. When I make a narrowband communication, I don't observe a flat
> channel but I also observe the spectrum of a filter. I searched in
> documentation but I did'nt see the characteristic of the baseband filter of
> the system. What are the characteristic of this filter? Is it a RRC filter?
>
> Thanks for your answer,
> Marc
>
> _______________________________________________
> USRP-users mailing list
> [email protected]
> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
>
>
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