On 09/24/2015 06:37 PM, Simon Olvhammar wrote:
Yes, in my current Python Gnuradio application I have implemented
Dicke-switching by syncing it with external signals that indicate S/R
as well as transition state of RF. I have not seen any issues with
overlapping fft:s. The switch frequency is 1 Hz and the transition
state signal has an interval of perhaps 100us where no storing of ffts
is done.
I'm still very new to signal processing and I'm having trouble to
understand the relation between alpha and how much is averaged, I just
see a scale factor in the transfer function? 0.01 seconds seems quite
alot and to reduce this to 0.001 seconds I could perhaps choose
alpha=0.1 and N=10 if I'm understanding you right? Are we talking same
delay times if I were to implement this is my current non FPGA
gnuradio app?
I have attached a flowgraph and it would be greatly appreciated if you
could check if it looks right for the purpose of just storing averaged
FFT:s.
Just looked at your flow-graph. Looks OK to me, but at 100Msps, I
imagine that your computer is working very, very hard.
Also, Gnu Radio doesn't have predictable latency, so trying to
synchronize to your external Dicke-switching hardware will be a significant
challenge.
Another approach, that Ken Tapping and I have used successfully, is what
we call a differential radiometer:
http://www.sbrac.org/files/DTP_RX.pdf
This happens to use RTLSDR dongles, but the same approach of identical
SDR RX chains providing full-time "sky" in one channel and
"reference" in another eliminates the switching hardware, and the
need to synchronize yourself with it....
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