(1) Most of the tutorials discuss the effect of the loop bandwidth and the damping factor on the PLL behaviour. Is there any reference about the same with respect to the SNR? (2) Any reference deriving the tracking error variance, pull-in range, etc.? Thanks for your help. _____________________________ Posted through www.DSPRelated.com
PLL and SNR
Started by ●August 15, 2013
Reply by ●August 15, 20132013-08-15
On 8/15/2013 5:57 PM, commsignal wrote:> (1) Most of the tutorials discuss the effect of the loop bandwidth and the > damping factor on the PLL behaviour.Because PLL of the 2nd order is nice linear problem.> Is there any reference about the same > with respect to the SNR?If SNR is above 10 dB, PLL behaves like linear filter. Just integrate noise over the bandwidth. If SNR is below 10 dB, PLL gets nonlinear and intractable, and you left to simulations and approximations.> (2) Any reference deriving the tracking ivariance, pull-in range, > etc.?It is easy to get ballpark estimate; however it depends on particulars. Vladimir Vassilevsky DSP and Mixed Signal Designs www.abvolt.com
Reply by ●August 16, 20132013-08-16
On Thu, 15 Aug 2013 17:57:06 -0500, commsignal wrote:> (1) Most of the tutorials discuss the effect of the loop bandwidth and > the damping factor on the PLL behaviour. Is there any reference about > the same with respect to the SNR? > (2) Any reference deriving the tracking error variance, pull-in range, > etc.?There are several books on PLL theory out there. It is a book-length topic, so getting a book is useful. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Reply by ●August 16, 20132013-08-16
On Friday, August 16, 2013 1:15:16 PM UTC-4, Tim Wescott wrote:> On Thu, 15 Aug 2013 17:57:06 -0500, commsignal wrote: > (1) Most of the tutorials discuss the effect of the loop bandwidth and > the damping factor on the PLL behaviour. Is there any reference about > the same with respect to the SNR? > (2) Any reference deriving the tracking error variance, pull-in range, > etc.? There are several books on PLL theory out there. It is a book-length topic, so getting a book is useful. -- Tim Wescott Wescott Design Services http://www.wescottdesign.comPhaslock Techniques 2nd Edition Gardner is a good place to start Mark
Reply by ●August 16, 20132013-08-16
On Fri, 16 Aug 2013 10:23:01 -0700, makolber wrote:> On Friday, August 16, 2013 1:15:16 PM UTC-4, Tim Wescott wrote: >> On Thu, 15 Aug 2013 17:57:06 -0500, commsignal wrote: > (1) Most of the >> tutorials discuss the effect of the loop bandwidth and > the damping >> factor on the PLL behaviour. Is there any reference about > the same >> with respect to the SNR? > (2) Any reference deriving the tracking >> error variance, pull-in range, > etc.? There are several books on PLL >> theory out there. It is a book-length topic, so getting a book is >> useful. -- Tim Wescott Wescott Design Services >> http://www.wescottdesign.com > > Phaslock Techniques 2nd Edition Gardner is a good place to start > > MarkDoes that one cover PLL in the digital world, or just PLL circuits? Not that there's a huge difference -- but when you implement an algorithm running on digital hardware there are things that become much more feasible much sooner than when you implement a circuit. (And visa-versa -- sampling can get in the way sometimes). -- Tim Wescott Wescott Design Services http://www.wescottdesign.com
Reply by ●August 16, 20132013-08-16
On Fri, 16 Aug 2013 12:15:16 -0500, Tim Wescott <tim@seemywebsite.really> wrote:>On Thu, 15 Aug 2013 17:57:06 -0500, commsignal wrote: > >> (1) Most of the tutorials discuss the effect of the loop bandwidth and >> the damping factor on the PLL behaviour. Is there any reference about >> the same with respect to the SNR?There is loop SNR and there is input SNR. The detector behavior is also likely to change with SNR, and if the detector gain changes with SNR then it'll affect the loop accordingly. As mentioned, consult some good reference books, and I'll second that Gardner's is a very oft-used reference. Having a copy handy is worthwhile if you do a lot of PLL stuff. There are other texts, but that seems to be the most commonly referenced. Another reference that I find handy that is comm-specific is Lindsey and Simon, Telecommunications System Engineering. It is a pretty dry text, and isn't only about PLLs. http://www.amazon.com/Telecommunication-Systems-Engineering-Dover-Electrical/dp/048666838X/ref=sr_1_3?s=books&ie=UTF8&qid=1376676085&sr=1-3&keywords=Lindsey+and+Simon>> (2) Any reference deriving the tracking error variance, pull-in range, >> etc.?Pull range is partly a function of the detector. e.g., it doesn't matter what the loop is doing if the detector can't discern frequency beyond a certain window. But, yes, pull range is a useful metric that is usually treated in good PLL texts, including Gardner's.>There are several books on PLL theory out there. It is a book-length >topic, so getting a book is useful.Yes. If you don't find what you're looking for after studying the texts then do come back and ask. Getting PLLs right efficiently is a pretty involved topic and involves a bit of art sometimes.> >-- > >Tim Wescott >Wescott Design Services >http://www.wescottdesign.com >Eric Jacobsen Anchor Hill Communications http://www.anchorhill.com
Reply by ●August 16, 20132013-08-16
On 8/16/13 10:59 AM, Tim Wescott wrote:> On Fri, 16 Aug 2013 10:23:01 -0700, makolber wrote: > >> On Friday, August 16, 2013 1:15:16 PM UTC-4, Tim Wescott wrote: >>> On Thu, 15 Aug 2013 17:57:06 -0500, commsignal wrote:> (1) Most of the >>> tutorials discuss the effect of the loop bandwidth and> the damping >>> factor on the PLL behaviour. Is there any reference about> the same >>> with respect to the SNR?> (2) Any reference deriving the tracking >>> error variance, pull-in range,> etc.? There are several books on PLL >>> theory out there. It is a book-length topic, so getting a book is >>> useful. -- Tim Wescott Wescott Design Services >>> http://www.wescottdesign.com >> >> Phaselock Techniques 2nd Edition Gardner is a good place to start >> >> Mark > > Does that one cover PLL in the digital world, or just PLL circuits? > > Not that there's a huge difference --seems to me that a z^-1 (or e^(-sT)) in the feedback loop might be a significant qualitative difference. but i haven't ever done a PLL (unless you count the servo mechanism in an ASRC, that's sorta PLL-like).> but when you implement an algorithm > running on digital hardware there are things that become much more > feasible much sooner than when you implement a circuit. (And visa-versa > -- sampling can get in the way sometimes).it seems to me that you can well model an analog PLL with a digital PLL if the sample rate is high. -- r b-j rbj@audioimagination.com "Imagination is more important than knowledge."
Reply by ●August 17, 20132013-08-17
On Friday, August 16, 2013 2:20:40 PM UTC+12, Vladimir Vassilevsky wrote:> On 8/15/2013 5:57 PM, commsignal wrote: > > > (1) Most of the tutorials discuss the effect of the loop bandwidth and the > > > damping factor on the PLL behaviour. > > > > Because PLL of the 2nd order is nice linear problem. > > > > > Is there any reference about the same > > > with respect to the SNR? > > > > If SNR is above 10 dB, PLL behaves like linear filter. Just integrate > > noise over the bandwidth. > > If SNR is below 10 dB, PLL gets nonlinear and intractable, and you left > > to simulations and approximations. > > > > > (2) Any reference deriving the tracking ivariance, pull-in range, > > > etc.? > > > > It is easy to get ballpark estimate; however it depends on particulars. > > > > > > Vladimir Vassilevsky > > DSP and Mixed Signal Designs > > www.abvolt.comNonsense, I have used a PLL down to 0dB (with great difficulty though). Most people don't understand how to stabilise the loop. I normally use a lag-lead compensator, most of the textbooks give simple solutions.
Reply by ●August 17, 20132013-08-17
On 8/17/2013 12:38 AM, gyansorova@gmail.com wrote:> On Friday, August 16, 2013 2:20:40 PM UTC+12, Vladimir Vassilevsky > wrote: >> On 8/15/2013 5:57 PM, commsignal wrote: >> >>> (1) Most of the tutorials discuss the effect of the loop >>> bandwidth and the >> >>> damping factor on the PLL behaviour. >> >> >> >> Because PLL of the 2nd order is nice linear problem. >> >> >> >>> Is there any reference about the same >> >>> with respect to the SNR? >> >> >> >> If SNR is above 10 dB, PLL behaves like linear filter. Just >> integrate >> >> noise over the bandwidth. >> >> If SNR is below 10 dB, PLL gets nonlinear and intractable, and you >> left >> >> to simulations and approximations. >> >> >> >>> (2) Any reference deriving the tracking ivariance, pull-in >>> range, >> >>> etc.? >> >> >> >> It is easy to get ballpark estimate; however it depends on >> particulars. >>> > Nonsense, I have used a PLL down to 0dB (with great difficulty > though).That is no good idea. PLL in nonlinear zone is clearly inefficient method for tracking; and even less efficient for acquisition.> Most people don't understand how to stabilise the loop. > I normally use a lag-lead compensator, most of the textbooks give > simple solutions.Most people have no clue what they doing. VLV
Reply by ●August 17, 20132013-08-17
On Sat, 17 Aug 2013 00:57:39 -0500, Vladimir Vassilevsky <nospam@nowhere.com> wrote:>On 8/17/2013 12:38 AM, gyansorova@gmail.com wrote: >> On Friday, August 16, 2013 2:20:40 PM UTC+12, Vladimir Vassilevsky >> wrote: >>> On 8/15/2013 5:57 PM, commsignal wrote: >>> >>>> (1) Most of the tutorials discuss the effect of the loop >>>> bandwidth and the >>> >>>> damping factor on the PLL behaviour. >>> >>> >>> >>> Because PLL of the 2nd order is nice linear problem. >>> >>> >>> >>>> Is there any reference about the same >>> >>>> with respect to the SNR? >>> >>> >>> >>> If SNR is above 10 dB, PLL behaves like linear filter. Just >>> integrate >>> >>> noise over the bandwidth. >>> >>> If SNR is below 10 dB, PLL gets nonlinear and intractable, and you >>> left >>> >>> to simulations and approximations. >>> >>> >>> >>>> (2) Any reference deriving the tracking ivariance, pull-in >>>> range, >>> >>>> etc.? >>> >>> >>> >>> It is easy to get ballpark estimate; however it depends on >>> particulars. >>> > >> >> Nonsense, I have used a PLL down to 0dB (with great difficulty >> though). > >That is no good idea. >PLL in nonlinear zone is clearly inefficient method for tracking; and >even less efficient for acquisition.I've never had that much trouble down to the ~0dB range, either. You just need to know what you're doing.>> Most people don't understand how to stabilise the loop. >> I normally use a lag-lead compensator, most of the textbooks give >> simple solutions. > >Most people have no clue what they doing.But some here do.> >VLVEric Jacobsen Anchor Hill Communications http://www.anchorhill.com
