Hi Daniele, > Also, I don't see why you cannot combine other blocks to realize > your own PLL implementation. Where did you read that you "can’t use > companion to add and drop the current available blocks to construct a > phase locked loop"? Wai Yee has a point here -- you can't have a circle in your (sample stream) flow graph -- GNU Radio doesn't allow that for reasons of causality.
You can have a "loose" loop with feedback done with message ports, but that's not the same as a control loop (since there's no defined delay between the sample for which a error was estimated and the sample where the error correction is applied when using the asynchronous messages). Thus, you can't drag'n'drop together a "proper" control loop from discrete things like adders and integrators that you could design and analyze theoretically. In effect, GNU Radio's control loops are monolithic blocks -- that's somewhat sad from a modularity perspective, but then again, there's the control loop base class that allows you to implement arbitrary control loops rather easily, so Wai Yee, I recommend looking at the documentation [1], the referenced paper and the source code[2] of the existing costas loop. Best regards, Marcus Müller PS: > I am using *USRP N210* for the hardware and I have installed *Gnuradio > Companion* in *Ubuntu 12.04 LTS* (running in VMplayer). as a side note, I don't recommend running your digital signal processing for a high-rate capable device inside a VM, unless you know what you're doing -- the additional overhead in network packet handling might prove to be a problem. At lower rates, it should work fine. Also, why are you using a three years old Ubuntu? There's a new LTS release, almost a year old now, 14.04; I recommend using a modern platform. [1] http://gnuradio.org/doc/doxygen/classgr_1_1digital_1_1costas__loop__cc.html [2] https://github.com/gnuradio/gnuradio/blob/master/gr-digital/lib/costas_loop_cc_impl.cc On 03/17/2015 09:12 AM, Daniele Nicolodi wrote: > On 17/03/15 02:05, yee_yy1992 wrote: >> Hi, Currently I am doing my Final Year Project to develop a phase >> measurement using Phase Locked Loop theory. I am using *USRP N210* for >> the hardware and I have installed *Gnuradio Companion* in *Ubuntu 12.04 >> LTS* (running in VMplayer). I have studied online that I can’t use >> companion to add and drop the current available blocks to construct a >> phase locked loop. > Hello, > > what to you mean by that last sentence? GNURadio comes with PLL blocks > in a few different fashions that can be used from the companion just > fine. Also, I don't see why you cannot combine other blocks to realize > your own PLL implementation. Where did you read that you "can’t use > companion to add and drop the current available blocks to construct a > phase locked loop"? > > Cheers, > Daniele > > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio