I've taken a look at Gardner's text earlier and he does mention 3rd order PLLs. Also, I found the text with the chapter by Harris. Good reference.
Thanks. On Tue, May 31, 2011 at 6:16 AM, Tom Rondeau <trondeau1...@gmail.com> wrote: > On Sat, May 28, 2011 at 2:29 AM, Colby Boyer <colby.bo...@gmail.com>wrote: > >> Hi All, >> >> Recently, I've gone down the road of timing synchronization and ended >> up learning basics for PLLs and such. So far in GNURadio, it seems >> that the loop filters used in the existing GNURadio synch blocks are >> only first order. From what I understand, increasing the filter order >> of the PLL can help it to lock in the presence of noise, for both >> timing and frequency. Any else care to comment on the performance >> gains for higher orders? >> >> I propose to come up with a block that can cascade a series of >> integrators and gains to form a loop filter. The total order and gains >> of the filter can perhaps be defined in the block constructor. The >> idea is make the block generic enough so that you can drop it in with >> an outside NCO and phase error detector. >> >> Thoughts, questions or concerns? >> >> Colby > > > > Colby, > You're general thought about having an implementation for these loops could > work well, since we repeat them frequently in various blocks. > > I will point out, though, that the PLLs are (I'm pretty sure) second order > loops since they have the two accumulator stages in them. These of course > look different than the types of circuits you normally see for PLLs, like in > Gardner's book. But if you can get it, fred harris has a paper called "Let's > assume the system is synchronized" that gives a great overview of the > various synchronization problems. It also contains many block diagrams for > these different systems, including a block diagram for a digital PLL. You > can pretty much trace the code in these PLL blocks to his diagrams. > > Tom > > >> > >
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