Re: [Discuss-gnuradio] How many multiple/simultaneous PLLs can I have running on USRP2?

[Marcus D. Leech]

So maybe the PLL is not a good solution between it will have an unknown amount of initial phase offsets by the time it locks. Since the relative phase between different carriers is the essential information sought after, maybe the better way is to construct very narrowband filters. Now very narrowband can mean a lot of taps, hence a lot of resources consumed. Here is where I don’t know the limitation of resources. If I want to set up a filter of say 4 Hz bandwidth for a signal at 1MHz, and if you have a lot of these signals at different frequencies, what would be the best way to extract these? Maybe the way to go is to have the LO at 1MHz, so the many signals being looked at are +/- many hundreds of kHz. How many taps would it require to extract a signal at say 300 kHz with the 4Hz bandwidth? Can the USRP do 200 taps for each of the 30 carriers (I am just asking without exact calculation here)?

 

Thanks,

 

LD

The USRP doesn't care, since this all runs on the host under Gnu Radio--unless you were under the impression (wildly incorrect) that Gnu Radio
  blocks run on the USRP hardware--they don't.


Unless you want to implement in the FPGA.

In either case, the answer is "it depends".   Narrow filters consume insane numbers of taps, which are resource-hogs whether it's a FPGA
  implementation or host-side hardware implementation.

-- 
Marcus Leech
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org