On 12/02/2014 10:06 AM, khalid.el-darymli wrote:
Hi Marcus,
Is there a temperature sensor on-board the N200 unit? If not, does it
support installing any such sensor?
Thanks.
No, and no.
But there are a tonne of USB-based temperature sensors out there.
Google is your friend, etc.
Best regards,
Khalid
On Fri, Nov 28, 2014 at 5:44 PM, Marcus D. Leech <mle...@ripnet.com
<mailto:mle...@ripnet.com>> wrote:
On 11/28/2014 03:41 PM, khalid.el-darymli wrote:
Back to my original question, what should I do to correct for this?
Thanks in advance.
Best,
Khalid
Khalid:
Thanks very much for the very-extensive data. My main concern, as
one of the Ettus support team, was that there was something wrong with
the hardware, but the magnitude of both the apparent phase and
magnitude drift is entirely consistent with analog-hardware
temperature
effects, unrelated to clock stability, etc.
Coax cables, for example, will change their loss characteristics
and *effective length* with temperature, so with precise hardware
like USRPs, it's
easy to see these effects.
FMCW radar isn't my area of expertise, so hopefully others can
comment on RX-processing strategies to deal with this, as it
*must* also be a problem
with non-SDR FMCW radar implementations.
On Fri, Nov 28, 2014 at 12:08 PM, <mle...@ripnet.com
<mailto:mle...@ripnet.com>> wrote:
What is the magnitude of the frequency drift?
What is the magnitude of the gain drift?
What are you measuring backscatter *from*?
On 2014-11-28 10:14, khalid.el-darymli via USRP-users wrote:
Hi,
Given a set of synced /(i.e., using external GPS REF/PPS)/,
time-commanded and calibrated /(i.e., through compensating
for the phase/mag offset between digital Tx chirp prior to
transmission and ADC'ed Rx signals) /N200 devices with
LFTX/LFRX daughterboards, that work with coherent LFMCW
chirps, I am still seeing a tiny drift (both in the
magnitude and frequency) of the calibrated back-scatter Rx
chirp received at time t1 when compared to an Rx chirp
received at an earlier time t0.
The more the N200 device runs (e.g., 5 hours), the greater
the drift is. Obviously, this drift is pertinent to both the
DAC and ADCs and the GPS referenced clocks of the N200 devices.
My questions are:
1- Why I still see such drift although my devices are synced
with an external GPS? and how do I correct for it?
2- Can the *PLL Carrier Tracking *block in GRC be used to
track and correct for such a drift? If so, how do I set the
max/min freq inputs for this block?
3- Can *AGC2* or *AGC3 *block be useful in this regard? If
so, are there any examples to explain how the input
parameters of these blocks can be set up?
Thanks.
Best regards,
Khalid
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--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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