Hi Marcus,
here is the flow graph and the output signals with movement across the antennae
and without.
http://tinypic.com/r/a5et5k/8 (GRC flow)
http://tinypic.com/r/nbeq0k/8 (without movement)
http://tinypic.com/r/2s7dnye/8 (with movement)
Thank you.
Dimitris.
OK, so I looked at the flow-graph you posted. There's a lot of
confusion in there, it has a lot of "confusion per unit area" of
flow-graph, so there's
a list:
o You're mixing sample-rates without doing any interpolation or
decimation. For example, slamming your 100ksps signal source into a
USRP hardware
source that will try to suck samples out at 20Msps.
o You're trying to mix this 100ksps source with a USRP source running
at 25ksps (which isn't a valid rate for any USRP that I'm aware of).
o You're using a throttle block in a chain that includes hardware --
I'm *guessing* that you thought maybe it would do sample-rate conversion
or something, but it isn't clear what your intention is here.
o You're trying to generate a 1MHz signal source with a sample-rate
of only 100ksps. This violates Nyquist rather badly.
I think you need to understand what your bandwidth requirements are, and
let that guide your sample-rate decisions. If this is a CW radar, you
don't need a lot of bandwidth, and thus, sample-rate.
You don't mention what USRP hardware you have, but in general, the
sample-rate must be a proper integer fraction of the master-clock rate,
and generally, the resulting decimation can be no higher than 512.
Some USRPs (B100, E1xx, B2xx) have variable master-clocks, so you
can achieve a variety of different rates.
Further, my suspicion from all the above is that your current grasp of
DSP techniques isn't all that solid--I could be wrong, but it *seems* that
way from the flow-graph. My suggestion would be to step back, trying
to really understand what you want to do, and maybe curl up with
a book on DSP *first*. While "stumbling around" when you're just
building RX flow-graphs with real hardware doesn't do any harm, doing the
same with TX flow-graphs can get unwanted visits from the Federal
Authorities in some countries....
--
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
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