On Fri, 12 Oct 2012 12:08:46 +0200, Jeroen Belleman wrote:> On 2012-10-12 11:04, Robert Baer wrote: >> Vladimir Vassilevsky wrote: >>> "Tim Wescott"<tim@seemywebsite.com> wrote: >>>> How commonly do you see PLL designs referred to as "type I", "type >>>> II", "type III", etc.? Do the terms make sense to you? >>> >>> IMO this terminology is used only in Gardner's book; there is no >>> universal >>> meaning. >>> It is about P, PI, or PII control loop. Remnants of old times, when >>> they used to mix the details of implementation with the type of the >>> transfer function. >>> >>>> I'm writing a report; don't want to either baffle with bullshit nor >>>> leave >>>> out handy terms... >>> >>> Since nobody is going to read it anyway, why would that matter? >>> >>> Vladimir Vassilevsky >>> DSP and Mixed Signal Consultant >>> www.abvolt.com >>> >>> >> Do not know but my wild uneducated guess is that "P" stands for regular >> feedback as in a standard op-amp circuit, "PI" stands for first >> derivative (eg: "P dot") and "PII" stands for second derivative (eg: "P >> double dot"). >> >> >> > 'I' stands for an Integral term, not a derivative one. > > I think that PLL designs should be classified by the number of > significant poles and zeroes of their transfer functions. This 'type' > business only introduces an extra layer of obscurity.Both the number of poles (order), and the number of nekkid integrators (type) have relevance in telling you how the loop is going to behave. It's not obscurity if you know what it means. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
PLL Terminology Question
Started by ●October 11, 2012
Reply by ●October 12, 20122012-10-12
Reply by ●October 12, 20122012-10-12
On Fri, 12 Oct 2012 08:39:21 -0700, John Larkin wrote:> On Fri, 12 Oct 2012 10:39:14 -0400, Randy Yates > <yates@digitalsignallabs.com> wrote: > >>Tim Wescott <tim@seemywebsite.com> writes: >> >>> How commonly do you see PLL designs referred to as "type I", "type >>> II", "type III", etc.? Do the terms make sense to you? >>> >>> I'm writing a report; don't want to either baffle with bullshit nor >>> leave out handy terms... >> >>Hi Tim, >> >>We used to use those terms in the 80s in our antenna control systems at >>GTE Government Systems. If I remember correctly, the "number" refers to >>the number of integrators in the loop. >> >>I don't think they are used much today. > > The question then becomes whether you count the inherent VCO phase > integration as one of those integrators.For any control loop you pick a point in the loop and go around, counting integrators, until you get back to the same point. Because the VCO takes a voltage and turns it into a frequency (which is the integral of phase), and because a phase detector detects _phase_, the VCO-phase detector combination will always come up acting like an integrator. If you use a frequency detector instead of a phase detector, then you cannot treat the VCO as an integrator for the purposes of loop analysis, or you have to treat it as an integrator followed by a perfect differentiator. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
Reply by ●October 12, 20122012-10-12
>Nice thread, thanks Tim. > >I assume "Phaselock Techniques" by Flyod M. Gardener is the right >book. (Making my Xmas wish list.) Any advantage of the third edition >over the second? > >George H. >If you do DSP you definitely want the 3rd edition as he has added several chapters on discrete-time analysis and implementation. The second edition dates from 1979 and contains analysis on only continuous-time implementations. -Doug
Reply by ●October 12, 20122012-10-12
On Fri, 12 Oct 2012 09:23:06 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:>Can't remember the company name now, but it was in El Monte, CA (*), >(~1967-68) where I was demo-ing my first analog phase detector and VCM >combo detecting TACAN signals buried in noise. The company consultant >was none other than Gardner himself, who first declared that my >circuit couldn't be working... then had to reverse himself ;-)Perhaps Hoffman Electronics of El Monte, CA, now known as Navcom Defense Electronics of Corona, CA? -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Reply by ●October 12, 20122012-10-12
On Fri, 12 Oct 2012 11:58:59 -0500, Tim Wescott <tim@seemywebsite.com> wrote:>On Fri, 12 Oct 2012 15:42:38 +0000, Eric Jacobsen wrote: > >> On Fri, 12 Oct 2012 00:46:36 -0500, Tim Wescott <tim@seemywebsite.com> >> wrote: >> >>>On Thu, 11 Oct 2012 22:28:01 +0000, Eric Jacobsen wrote: >>> >>>> On Thu, 11 Oct 2012 16:53:50 -0500, Tim Wescott <tim@seemywebsite.com> >>>> wrote: >>>> >>>>>On Thu, 11 Oct 2012 15:58:33 -0500, Vladimir Vassilevsky wrote: >>>>> >>>>>> "Tim Wescott" <tim@seemywebsite.com> wrote: >>>>>>> How commonly do you see PLL designs referred to as "type I", "type >>>>>>> II", "type III", etc.? Do the terms make sense to you? >>>>>> >>>>>> IMO this terminology is used only in Gardner's book; there is no >>>>>> universal meaning. >>>>>> It is about P, PI, or PII control loop. Remnants of old times, when >>>>>> they used to mix the details of implementation with the type of the >>>>>> transfer function. >>>>> >>>>>It certainly has universal meaning in control systems terms: it's the >>>>>number of integrating stages that are cascaded in the loop, either >>>>>from the compensator or the plant. >>>> >>>> I only encountered this recently when using a very old JPL paper that >>>> was pertinent to a problem we were dealing with. I had to look up >>>> the meaning, and they were using it like you do, to indicate the >>>> number of integrators in the loop. >>>> >>>> Most comm people that are familiar with PLLs would likely be more >>>> comfortable with describing a loop by its order, i.e., first order, >>>> second order, etc., which isn't exactly the same thing but seems to be >>>> the more widely understood terminology in my experience. >>> >>>Dayum. Just to make sure I'm on the right page, is a 1st-order loop one >>>with a single integrator in the loop filter, or one with no integrator >>>in the loop filter (and the VCO supplying the integrator)? >>> >>>-- >>>My liberal friends think I'm a conservative kook. My conservative >>>friends think I'm a liberal kook. Why am I not happy that they have >>>found common ground? >>> >>>Tim Wescott, Communications, Control, Circuits & Software >>>http://www.wescottdesign.com >> >> I'll concur with what Doug and John posted, and I'll also concur with >> Doug that I tend to refer to Gardner's book as the "Gospel of Gardner" >> when it comes to PLLs. >> >> So a first order loop has no integrator in the filter, i.e., merely a >> proportional loop, and a PI loop is then a second-order loop. In comm >> 2nd-order loops are the most common. If I understand the "Type" >> definitions correctly many (if not most) 2nd-order loops are implemented >> as Type-2 systems, with the loop integrator and the NCO as the two >> integrators. > >Yes. You PLL guys are using "order" for "type". In control systems >terms, the order of a system is the order of the system polynomial: so a >PLL that has a PI + lowpass loop filter would be a 3rd-order control loop >(because the lowpass adds a pole to the system), but it would remain a >type 2 system (because the lowpass filter does not have infinite gain at >DC). Presumably, in PLL terms it would be correct to call it "2nd-order" >-- but that makes me want to gag!I don't think there's a disconnect. A 2nd-order loop has degree two in the denominator polynomial, and are typically implemented with two integrators (including the NCO). It is also possible to implement a 2nd-order loop with three integrators, but this is seldom done (unless it's an FLL). Eric Jacobsen Anchor Hill Communications www.anchorhill.com
Reply by ●October 12, 20122012-10-12
On Fri, 12 Oct 2012 09:29:55 -0700, George Herold wrote:> On Oct 11, 4:36 pm, Tim Wescott <t...@seemywebsite.com> wrote: >> How commonly do you see PLL designs referred to as "type I", "type II", >> "type III", etc.? Do the terms make sense to you? >> >> I'm writing a report; don't want to either baffle with bullshit nor >> leave out handy terms... >> >> -- >> My liberal friends think I'm a conservative kook. My conservative >> friends think I'm a liberal kook. Why am I not happy that they have >> found common ground? >> >> Tim Wescott, Communications, Control, Circuits & >> Softwarehttp://www.wescottdesign.com > > Nice thread, thanks Tim. > > I assume "Phaselock Techniques" by Flyod M. Gardener is the right book. > (Making my Xmas wish list.) Any advantage of the third edition over the > second? > > So in a type III system the error signal is integrated twice? Does > anyone have an example where double integration is used? It doesn't have > to be a PLL application any type of control loop would be fine.I've done it with gyroscopically stabilized platforms -- leave out the second integrator and when you (or the world) pushes on it it moves over and stays there until the push is gone. Put the second integrator in and it pushes back until it's in place. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
Reply by ●October 12, 20122012-10-12
On Fri, 12 Oct 2012 11:08:15 -0700, Jeff Liebermann <jeffl@cruzio.com> wrote:>On Fri, 12 Oct 2012 09:23:06 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>Can't remember the company name now, but it was in El Monte, CA (*), >>(~1967-68) where I was demo-ing my first analog phase detector and VCM >>combo detecting TACAN signals buried in noise. The company consultant >>was none other than Gardner himself, who first declared that my >>circuit couldn't be working... then had to reverse himself ;-) > >Perhaps Hoffman Electronics of El Monte, CA, now known as Navcom >Defense Electronics of Corona, CA?Yep, That was it! Thanks! ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●October 12, 20122012-10-12
On 2012-10-12 19:02, Tim Wescott wrote:> On Fri, 12 Oct 2012 12:08:46 +0200, Jeroen Belleman wrote: > >> On 2012-10-12 11:04, Robert Baer wrote: >>> Vladimir Vassilevsky wrote: >>>> "Tim Wescott"<tim@seemywebsite.com> wrote: >>>>> How commonly do you see PLL designs referred to as "type I", "type >>>>> II", "type III", etc.? Do the terms make sense to you? >>>> >>>> IMO this terminology is used only in Gardner's book; there is no >>>> universal >>>> meaning. >>>> It is about P, PI, or PII control loop. Remnants of old times, when >>>> they used to mix the details of implementation with the type of the >>>> transfer function. >>>> >>>>> I'm writing a report; don't want to either baffle with bullshit nor >>>>> leave >>>>> out handy terms... >>>> >>>> Since nobody is going to read it anyway, why would that matter? >>>> >>>> Vladimir Vassilevsky >>>> DSP and Mixed Signal Consultant >>>> www.abvolt.com >>>> >>>> >>> Do not know but my wild uneducated guess is that "P" stands for regular >>> feedback as in a standard op-amp circuit, "PI" stands for first >>> derivative (eg: "P dot") and "PII" stands for second derivative (eg: "P >>> double dot"). >>> >>> >>> >> 'I' stands for an Integral term, not a derivative one. >> >> I think that PLL designs should be classified by the number of >> significant poles and zeroes of their transfer functions. This 'type' >> business only introduces an extra layer of obscurity. > > Both the number of poles (order), and the number of nekkid integrators > (type) have relevance in telling you how the loop is going to behave.Well yes, in essence that's what I said. We know what the poles and zeroes do. Introducing superfluous terminology like 'type' does not make it any clearer. I'd say: Drop the type.> > It's not obscurity if you know what it means. >Right. Jeroen Belleman
Reply by ●October 12, 20122012-10-12
On Sat, 13 Oct 2012 00:01:00 +0200, Jeroen <jeroen@nospam.please> wrote:>On 2012-10-12 19:02, Tim Wescott wrote: >> On Fri, 12 Oct 2012 12:08:46 +0200, Jeroen Belleman wrote: >> >>> On 2012-10-12 11:04, Robert Baer wrote: >>>> Vladimir Vassilevsky wrote: >>>>> "Tim Wescott"<tim@seemywebsite.com> wrote: >>>>>> How commonly do you see PLL designs referred to as "type I", "type >>>>>> II", "type III", etc.? Do the terms make sense to you? >>>>> >>>>> IMO this terminology is used only in Gardner's book; there is no >>>>> universal >>>>> meaning. >>>>> It is about P, PI, or PII control loop. Remnants of old times, when >>>>> they used to mix the details of implementation with the type of the >>>>> transfer function. >>>>> >>>>>> I'm writing a report; don't want to either baffle with bullshit nor >>>>>> leave >>>>>> out handy terms... >>>>> >>>>> Since nobody is going to read it anyway, why would that matter? >>>>> >>>>> Vladimir Vassilevsky >>>>> DSP and Mixed Signal Consultant >>>>> www.abvolt.com >>>>> >>>>> >>>> Do not know but my wild uneducated guess is that "P" stands for regular >>>> feedback as in a standard op-amp circuit, "PI" stands for first >>>> derivative (eg: "P dot") and "PII" stands for second derivative (eg: "P >>>> double dot"). >>>> >>>> >>>> >>> 'I' stands for an Integral term, not a derivative one. >>> >>> I think that PLL designs should be classified by the number of >>> significant poles and zeroes of their transfer functions. This 'type' >>> business only introduces an extra layer of obscurity. >> >> Both the number of poles (order), and the number of nekkid integrators >> (type) have relevance in telling you how the loop is going to behave. > >Well yes, in essence that's what I said. We know what the poles >and zeroes do. Introducing superfluous terminology like 'type' does >not make it any clearer. I'd say: Drop the type. > >> >> It's not obscurity if you know what it means. >> >Right. > >Jeroen BellemanPoles are from Poland. What are zeroes? Larkin ?>:-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
Reply by ●October 12, 20122012-10-12
On 2012-10-12 19:05, Tim Wescott wrote:> On Fri, 12 Oct 2012 08:39:21 -0700, John Larkin wrote: > >> On Fri, 12 Oct 2012 10:39:14 -0400, Randy Yates >> <yates@digitalsignallabs.com> wrote: >> >>> Tim Wescott <tim@seemywebsite.com> writes: >>> >>>> How commonly do you see PLL designs referred to as "type I", "type >>>> II", "type III", etc.? Do the terms make sense to you? >>>> >>>> I'm writing a report; don't want to either baffle with bullshit nor >>>> leave out handy terms... >>> >>> Hi Tim, >>> >>> We used to use those terms in the 80s in our antenna control systems at >>> GTE Government Systems. If I remember correctly, the "number" refers to >>> the number of integrators in the loop. >>> >>> I don't think they are used much today. >> >> The question then becomes whether you count the inherent VCO phase >> integration as one of those integrators. > > For any control loop you pick a point in the loop and go around, counting > integrators, until you get back to the same point. Because the VCO takes > a voltage and turns it into a frequency (which is the integral of phase),Harumph! Flub, phase is the integral of frequency. But you know that, of course. Jeroen Belleman
