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. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
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 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.comI'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. Eric Jacobsen Anchor Hill Communications www.anchorhill.com
Reply by ●October 12, 20122012-10-12
On Fri, 12 Oct 2012 01:04:53 -0800, Robert Baer <robertbaer@localnet.com> 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"). >P = proportional PI = proportional-integral PID = proportional-integral-derivative Eric Jacobsen Anchor Hill Communications www.anchorhill.com
Reply by ●October 12, 20122012-10-12
On Fri, 12 Oct 2012 08:39:21 -0700, John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> 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.It is. Read Gardner. ...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 10/12/2012 01:46 AM, Tim Wescott 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)? >Yup, that's how I learned it at the knee of a master of the art, back in about 1982. First order = no loop filter, or at least no loop filter poles below omega = Kvco*Kphi. Second order loop = lead/lag integrator Third order loop = two lead/lag integrators plus some analogue switches to prevent it from oscillating during acquisition. A second order loop with extra poles out past the unity gain cross to help with the ripple rejection is still considered a second order loop. Gardner talks about third order loops being used to get rid of static phase error due to linear frequency chirp, e.g. in satellite receivers. Since high-order loops are squirrelly, and a small constant phase error is easy to get rid of in software, even for an analogue loop, I sort of doubt anybody does that nowadays. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●October 12, 20122012-10-12
On Fri, 12 Oct 2012 12:02:59 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 10/12/2012 01:46 AM, Tim Wescott 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)? >> > >Yup, that's how I learned it at the knee of a master of the art, back in >about 1982. First order = no loop filter, or at least no loop filter >poles below omega = Kvco*Kphi. > >Second order loop = lead/lag integrator > >Third order loop = two lead/lag integrators plus some analogue switches >to prevent it from oscillating during acquisition. > >A second order loop with extra poles out past the unity gain cross to >help with the ripple rejection is still considered a second order loop. > >Gardner talks about third order loops being used to get rid of static >phase error due to linear frequency chirp, e.g. in satellite receivers. > Since high-order loops are squirrelly, and a small constant phase >error is easy to get rid of in software, even for an analogue loop, I >sort of doubt anybody does that nowadays. > >Cheers > >Phil HobbsCan'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 ;-) (*) Quite a hilarious trip, after we survived. I was there with a Motorola salesman. An employee of the company offered to drive us back to the airport. On the way, his car battery bracket failed and dumped the battery out onto the freeway. CHIPs comes along and tickets him for impeding traffic :-) We hail a cab. Cabby is a chatty Cathy and, while turned toward us in the back seat, rear-ends a car in the airport exit lane. We hail another cab and finally make it to the airport. Chatty Cathy cabby has the gall to contact us at Motorola and ask us to support his claim that rear-ending wasn't his fault ;-) ...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 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.comNice 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. George H.
Reply by ●October 12, 20122012-10-12
On Fri, 12 Oct 2012 09:29:55 -0700 (PDT), George Herold <gherold@teachspin.com> 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. > >George H.The extra filter/integrator is usually placed above the zero dB cross-over, just to reduce noise. ...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 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! -- 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 07:10:45 -0500, DougB 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. >> >> >>>I had to sweat through it in my undergraduate days, then help >>>undergrads > >>>sweat through it as a TA getting my Master's degree. >>> >>>>> 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? >>> >>>Pbpbpbpbpbtht. It will become a cult classic among my customer's >>>customers, eagerly read and handed down from elder, competent and >>>stately > >>>engineers to youngsters who are wet behind the ears and trying to make >>>their systems match the performance of the existing ones in the field. >>> >>>-- >>>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 >> >>Eric Jacobsen >>Anchor Hill Communications >>www.anchorhill.com >> >> > Gardner distinguishes between 'type' and 'order' where 'type' refers to > the number of integrators in the loop and order is simply the order of > the denominator polynomial in the transfer function. Take a look at > section 2.2.2 of his book (3rd edition). These days, particularly with > discrete time loops, the order of the denominator polynomial may have > little relevence, since other circuitry/code/register delay's etc. > inside the loop will add to the loop order but not change the type. > > I think Gardner's book is the gospel on this subject so I wouldn't have > any problem using those terms as standards.Gardner is following proper control systems terminology, then. -- 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
