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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