PLL Terminology Question

[Tim Wescott]

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 & Software
http://www.wescottdesign.com

[Rob Gaddi]

If I ran across those terms in a report I'd remember that somewhere
years ago I'd seen them, but I'd certainly have to Google for what
they actually meant.

--
Rob Gaddi, Highland Technology -- www.highlandtechnology.com
Email address domain is currently out of order. See above to fix.

[Vladimir Vassilevsky]

"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?

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

[Syd Rumpo]

On 11/10/2012 21:44, Rob Gaddi wrote:
> On Thu, 11 Oct 2012 15:36:55 -0500
> 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...
>>
>> --

>> Tim Wescott, Communications, Control, Circuits & Software
>> http://www.wescottdesign.com
>
> If I ran across those terms in a report I'd remember that somewhere
> years ago I'd seen them, but I'd certainly have to Google for what
> they actually meant.

1+

--
Syd

[tm]

"Tim Wescott" <t...@seemywebsite.com> wrote in message
news:zMudnS3Oobl6sOrN...@web-ster.com...

I think it has to do with the type of phase detection used.

You might look in a data book for a PLL chip.

tm

[Tim Wescott]

On Thu, 11 Oct 2012 15:58:33 -0500, Vladimir Vassilevsky wrote:

> "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?
>
> 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 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.

[robert bristow-johnson]

On 10/11/12 4:58 PM, Vladimir Vassilevsky wrote:
> "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?
>
> 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?

ooooh! zinger!

how do you know, Vlad? i am certainly interested in reading it.

personally, Tim, if the difference in "type" is what is in the PID
controller in the loop, i would just stick with "P", "I", and/or "D".

like, for phase-linear FIR filters there are Type I, Type II, Type III,
and Type IV. i know they have to do with all combinations of
even-length vs. odd-length and even-symmetry vs. odd-symmetry. but i
can't remember which Type goes with which combination, and i find the
"Type" labeling useless because it is not descriptive. and i am not
sure that all authors agree to the same convention, and that's when
confusion really gets thick.

--

r b-j r...@audioimagination.com

"Imagination is more important than knowledge."

[Joerg]

Tim Wescott 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...
>

Type I is the old vanilla version, type II with the charge pump and
pulsing. Usually. But where have you read about a type III?

Maybe this helps:

http://www.sentex.ca/~mec1995/gadgets/pll/pll.html

--
Regards, Joerg

http://www.analogconsultants.com/

[Eric Jacobsen]

On Thu, 11 Oct 2012 16:53:50 -0500, Tim Wescott <t...@seemywebsite.com>
wrote:

>On Thu, 11 Oct 2012 15:58:33 -0500, Vladimir Vassilevsky wrote:
>
>> "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?
>>
>> 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

[John S]

On 10/11/2012 3:36 PM, Tim Wescott 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...
>

Take a look at the Fairchild datasheet for the MM74HC4046. It refers to
Phase Comparators I, II, and III.

[Mark]

thats something different..

Tim, I would put the term in and also clarify it....a Type one loop
with one implicit integrator (the VCO) and a second order active loop
filter ...or whatever the case may be... providing 0 Hz frequency
error and TBD degress of phase error etc..

Mark


Mark

[Tim Wescott]

On Thu, 11 Oct 2012 22:28:01 +0000, Eric Jacobsen wrote:

> On Thu, 11 Oct 2012 16:53:50 -0500, Tim Wescott <t...@seemywebsite.com>
> wrote:
>
>>On Thu, 11 Oct 2012 15:58:33 -0500, Vladimir Vassilevsky wrote:
>>
>>> "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?
>>>
>>> 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)?

[Tim Wescott]

That's what I did. If the customer wants revisions I may look up the
meaning of "order" in a PLL and put that in there.

It'll be run by some PLL experts; I was specifically brought in to look
at their problem with a fresh eye, which means that I may not get all the
terms exactly right.

[Robert Baer]

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").

[Jeroen Belleman]

'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.

Jeroen Belleman

[John Fields]

On Fri, 12 Oct 2012 00:46:36 -0500, Tim Wescott <t...@seemywebsite.com>

---
http://www.everythingrf.com/Uploads/Content/File/Phase%20Locked%20Loop%20Design%20Fundamentals.pdf

Page 3

--
JF

[Randy Yates]

Tim Wescott <t...@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.
--
Randy Yates
Digital Signal Labs
http://www.digitalsignallabs.com

[Jim Thompson]

On Fri, 12 Oct 2012 10:39:14 -0400, Randy Yates
<ya...@digitalsignallabs.com> wrote:

>Tim Wescott <t...@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.

That is correct. From Gardner's 2nd Edition, page 11: "According to
servo terminology, the _type_ of a loop is a number equal to the
number of perfect integrators within the loop."

...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.

[John Larkin]

On Fri, 12 Oct 2012 10:39:14 -0400, Randy Yates
<ya...@digitalsignallabs.com> wrote:

>Tim Wescott <t...@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

[Eric Jacobsen]

On Fri, 12 Oct 2012 00:46:36 -0500, Tim Wescott <t...@seemywebsite.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.

[Eric Jacobsen]

P = proportional
PI = proportional-integral
PID = proportional-integral-derivative

[Jim Thompson]

On Fri, 12 Oct 2012 08:39:21 -0700, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Fri, 12 Oct 2012 10:39:14 -0400, Randy Yates
><ya...@digitalsignallabs.com> wrote:
>
>>Tim Wescott <t...@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.

[Phil Hobbs]

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

[Jim Thompson]

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 ;-)

(*) 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 ;-)

[George Herold]

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.

[Jim Thompson]

The extra filter/integrator is usually placed above the zero dB
cross-over, just to reduce noise.

[Tim Wescott]

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!

[Tim Wescott]

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.

[Tim Wescott]

On Fri, 12 Oct 2012 08:39:21 -0700, John Larkin wrote:

> On Fri, 12 Oct 2012 10:39:14 -0400, Randy Yates
> <ya...@digitalsignallabs.com> wrote:
>
>>Tim Wescott <t...@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.

[Jeff Liebermann]

On Fri, 12 Oct 2012 09:23:06 -0700, Jim Thompson
<To-Email-Use-Th...@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 je...@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[Eric Jacobsen]

On Fri, 12 Oct 2012 11:58:59 -0500, Tim Wescott <t...@seemywebsite.com>

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).

[Tim Wescott]

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.

[Jim Thompson]

On Fri, 12 Oct 2012 11:08:15 -0700, Jeff Liebermann <je...@cruzio.com>
wrote:

>On Fri, 12 Oct 2012 09:23:06 -0700, Jim Thompson
><To-Email-Use-Th...@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!

[Jeroen]

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

[Jim Thompson]

On Sat, 13 Oct 2012 00:01:00 +0200, Jeroen <jer...@nospam.please>
wrote:

Poles are from Poland. What are zeroes? Larkin ?>:-)

[Jeroen]

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
>> <ya...@digitalsignallabs.com> wrote:
>>
>>> Tim Wescott <t...@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

[Tim Wescott]

A type 0 loop can have a bazillion poles and still be type 0.

A type 2 loop can have only two poles.

Poles and type are _different_.

[Tim Wescott]

Blargh. Indeedie.

[Jasen Betts]

On 2012-10-12, Jim Thompson <To-Email-Use-Th...@On-My-Web-Site.com> wrote:
>
> Poles are from Poland. What are zeroes?
>

Zeroes were manufactured by Mitsubishi.


--
⚂⚃ 100% natural

--- news://freenews.netfront.net/ - complaints: ne...@netfront.net ---

[Phil Hobbs]

On 10/12/2012 12:42 PM, Jim Thompson wrote:
> On Fri, 12 Oct 2012 09:29:55 -0700 (PDT), George Herold
> <ghe...@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

No, it's another lead-lag integrator, to reduce the static phase offset
due to a frequency ramp to zero. Back in the all-analogue days, that
sometimes mattered.

[Michael A. Terrell]

Jasen Betts wrote:
>
> On 2012-10-12, Jim Thompson <To-Email-Use-Th...@On-My-Web-Site.com> wrote:
> >
> > Poles are from Poland. What are zeroes?
> >
>
> Zeroes were manufactured by Mitsubishi.

And used to attack Pearl Harbor.

[Jim Thompson]

[Jim Thompson]

On Sat, 13 Oct 2012 07:23:37 -0400, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:

In _modern_ times. I've not heard that before and I'm wa-a-a-ay older
than you. Analog phase detectors locked at 90°. Although you seem
actually to be implying more loop gain??

[John Larkin]

On Fri, 12 Oct 2012 09:29:55 -0700 (PDT), George Herold
<ghe...@teachspin.com> wrote:

I am a fan of the D-flop bang-bang phase detector. It has, in theory,
an infinite phase-error gain, which makes it interesting to analyze.
That's the way to go if you want to lock an oscillator to an external
input with picosecond long-term stability.

[Eric Jacobsen]

On Fri, 12 Oct 2012 23:28:28 -0500, Tim Wescott <t...@seemywebsite.com>
wrote:

>On Sat, 13 Oct 2012 00:09:54 +0200, Jeroen wrote:
>
>> 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
>>>> <ya...@digitalsignallabs.com> wrote:
>>>>
>>>>> Tim Wescott <t...@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.
>
>Blargh. Indeedie.
>

I get that backwards all the time, too. I don't know why.

[Bob Penoyer]

On Fri, 12 Oct 2012 09:29:55 -0700 (PDT), George Herold
<ghe...@teachspin.com> wrote:

>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.

Different loop types exhibit different error characteristics.

A Type-0 loop (no integrator) has position error.
A Type-1 loop has no position error.
A Type-2 loop has no position or velocity error.
A Type-3 loop has no position, velocity, or acceleration error.

The references to error here refer to steady-state conditions.

[Phil Hobbs]

Yes, third order loops (or type III to salve Tim's wounded control-guy feelings) really use
three integrators in the loop, on purpose. If you put a linear ramp into a control system
like that, the DC error is zero. Of course it's as squirrelly as can be when it's coming into
lock, which is why you need a bunch of analogue switches and so forth to make it work right.

Getting that right is such a pain, and so vulnerable to unforeseen circumstances, that it's
far, far easier to estimate the ramp rate in software and put some small DC offset on the PD
output to compensate.

Cheers

Phil Hobbs

[Phil Hobbs]

The metastability problem is for real, though. Many moons ago (actually in the same DBS
system I mentioned in the H parameters thread) I used a 75S74 as a frequency mixer in an
offset loop to generate the pilot tones for the satellite uplink. Even with very clean
input signals, when I looked at the d-flop output on a spectrum analyzer, the peak looked
like one of those old-fashioned drinking fountains that ran all the time--it wobbled and
bounced all over, especially at low modulation frequency.

I'm really surprised that you can get good stability out of something that ugly. Or has the
metastability issue somehow gone away since 1982?

Cheers

Phil Hobbs

[John Larkin]

I don't even remember 1982!

I used an EclipsLite flop as the bang-bang phase detector in the NIF
timing system, differential ECL data and clock at 155.52 MHz, VCXO.
Loop bandwidth was something like 10 KHz in search mode, 1 KHz
operating, so if there was the occasional metastability, I didn't
notice it. We got a couple of ps RMS jitter out of our whole box, so
the PLL must have been better.

Holding 1 ps out of 6 ns, longterm, is asking a lot of the analog
stability of any phase detector, and of the opamps and stuff
downstream.


TTL logic, with symmetric master-slave flops, tends to dither a lot.
Its metastability mode tends to be oscillatory, which essentially
clips the positive-feedback loop gain and generally confuses the poor
thing. ECL and CMOS gates are more likely to just resolve a little
slower.

74LS74s could oscillate for tens of cycles if you teased them just
right. Candidate for worst logic family ever, after RTL.

Gotta finish fixing the roof. The rainy season is almost here.

[Jim Thompson]

On Sat, 13 Oct 2012 17:52:57 -0400, Phil Hobbs
<pcdhobbsSpa...@electrooptical.net> wrote:

A D-flop, by itself, is only good with a VCO that's constrained to
less than 2:1 tuning range. Otherwise you can get harmonic locking...
not necessarily bad, I've used it to advantage... see my patents.

[Phil Hobbs]

My application was a pilot tone generator that needed to make 70 +-
10/11 MHz pilot tones. (Don't ask me why, that's what the system
engineers came up with.) Instead of using two synthesizers, I made 70
MHz from the 10 MHz system clock, then used a 74LS92 plus a couple of
gates (or some such thing) to divide the 10 MHz by 11, and then used the
two halves of a 74S74 to generate the pilot tones. Because the mixing
was so ugly, I wound up using a couple of crystal oscillators locked 1:1
to the d-flop outputs. It eventually worked fine, but the extreme
ugliness of the output spectrum from those d-flops has stayed with me!

Even if I'd used a nice diode-bridge mixer for the job, I'd probably
still have needed the crystal oscillators, because the jitter spec was
ridiculous.

Cheers

Phil Hobbs

[George Herold]

> Tim Wescott, Communications, Control, Circuits & Softwarehttp://www.wescottdesign.com- Hide quoted text -
>
> - Show quoted text -

Interesting, what's the detector in a gyro? (I assume it was not an
optical gyro.)

George H.

[George Herold]

> Tim Wescott, Communications, Control, Circuits & Softwarehttp://www.wescottdesign.com- Hide quoted text -
>
> - Show quoted text -

OK Well I thought I was getting the type 'thing', but I'm confused
again.

First what's type zero?
I was thinking about a (type I?) loop with just gain control that I've
used to lock a diode laser to the side of an absorption line. You've
got to put a (single pole) lowpass between the error signal and the
gain, or it's pretty much an oscillator.

George H.

[George Herold]

On Oct 13, 12:04 pm, John Larkin

Well no picoseconds, but I've used the switched gain AD630 for phase
sensitive lockins

George H.
>
> --
>
> John Larkin                  Highland Technology Incwww.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- Hide quoted text -

[Tim Wescott]

Type 0 is a loop that has no naked integrators (a low-pass isn't
considered a naked integrator in this context, as it has finite DC gain).

[George Herold]

> >> Softwarehttp://www.wescottdesign.com-Hide quoted text -

>
> >> - Show quoted text -
>
> > OK Well I thought I was getting the type 'thing', but I'm confused
> > again.
>
> > First what's type zero?
> > I was thinking about a (type I?) loop with just gain control that I've
> > used to lock a diode laser to the side of an absorption line.  You've
> > got to put a (single pole) lowpass between the error signal and the
> > gain, or it's pretty much an oscillator.
>
> > George H.
>
> Type 0 is a loop that has no naked integrators (a low-pass isn't
> considered a naked integrator in this context, as it has finite DC gain).
>
> --
> 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- Hide quoted text -
>
> - Show quoted text -

Hmmm OK, For the diode laser locking thing, the piezo (plant) has a
resonance a bit above 3kHz. Say I use a low pass filter with a 1
second time constant, and then crank up the gain til it's just below
the oscillation point.... how 'naked' does the integrator need to be?
(would 10 seconds and more gain count?)

George H.

[Jamie]

Speaking of which, while I have it fresh on me mind, I've been wondering
how one of those cheap laser diodes would behave in PV or PR mode and
would they survive another laser of equal type pointed into them?

Just thinking out loud here. I have a few I can test that with..

Jamie

[Phil Hobbs]

If you put in a notch filter, you can get the loop BW a lot closer to
the piezo resonance, like 0.3 f_0 vs 0.03 f_0.

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 USA
+1 845 480 2058

[George Herold]

On Oct 14, 6:58 pm, Phil Hobbs

> >>>> Softwarehttp://www.wescottdesign.com-Hidequoted text -

>
> >>>> - Show quoted text -
>
> >>> OK Well I thought I was getting the type 'thing', but I'm confused
> >>> again.
>
> >>> First what's type zero?
> >>> I was thinking about a (type I?) loop with just gain control that I've
> >>> used to lock a diode laser to the side of an absorption line.  You've
> >>> got to put a (single pole) lowpass between the error signal and the
> >>> gain, or it's pretty much an oscillator.
>
> >>> George H.
>
> >> Type 0 is a loop that has no naked integrators (a low-pass isn't
> >> considered a naked integrator in this context, as it has finite DC gain).
>
> >> --
> >> 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-Hide quoted text -
>
> >> - Show quoted text -
>

> > Hmmm OK,  For the diode laser locking thing, the piezo (plant) has a
> > resonance a bit above 3kHz.  Say I use a low pass filter with a 1
> > second time constant, and then crank up the gain til it's just below
> > the oscillation point.... how 'naked' does the integrator need to be?
> > (would 10 seconds and more gain count?)
>
> > George H.
>
> If you put in a notch filter, you can get the loop BW a lot closer to
> the piezo resonance, like 0.3 f_0 vs 0.03 f_0.
>
> 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 USA
> +1 845 480 2058
>

> hobbs at electrooptical dot nethttp://electrooptical.net- Hide quoted text -

>
> - Show quoted text -

Grin, OK I'm not saying that a single pole low pass and then gain, is
in any way optimal. But it works... is it type 0 or type I?

(Does notching out the piezo resonace work? I've never tried that.)

George H.

[Phil Hobbs]

Notching works great, if the resonator Q is high. The notch filter's
phase shift goes away on the scale of its bandwidth rather than its
centre frequency, so it has almost no effect beyond a few times delta-f.

In my atomic force microscope days, I used that trick to get a factor of
10 in loop bandwidth with a piezo bimorph whose Q was right around 30.

[Tim Wescott]

If you're calling it a low pass filter and not an integrator, then you're
saying that it has finite DC gain. Therefore your loop is type 0.

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

[Phil Hobbs]

On 10/13/2012 07:25 PM, Phil Hobbs wrote:
>
>
> Jim Thompson wrote:
>>
>> On Sat, 13 Oct 2012 17:52:57 -0400, Phil Hobbs
>> <pcdhobbsSpa...@electrooptical.net> wrote:
>>
>>> John Larkin wrote:
>>>
>>>> On Fri, 12 Oct 2012 09:29:55 -0700 (PDT), George Herold
>>>> <ghe...@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

I find that I misspoke. I looked up the schematic, and I actually used
the S74 as a harmonic mixer, clocked at 10 MHz and sampling the
70+-0.454545... MHz crystal oscillators. I then locked those to the
output of a divide-by-22 counter running off the same 10 MHz.

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

[Fred Bartoli]

Tim Wescott a écrit :

With 10s time constant (15mHz corner frequency) and more gain so that
GWB is circa 3Kz, that makes for more than 100dB DC loop gain. I'd sure
call it an integrator, which I guess is George's point.


--
Thanks,
Fred.

[George Herold]

On Oct 14, 8:39 pm, Phil Hobbs

> >>>>>> Softwarehttp://www.wescottdesign.com-Hidequotedtext -

>
> >>>>>> - Show quoted text -
>
> >>>>> OK Well I thought I was getting the type 'thing', but I'm confused
> >>>>> again.
>
> >>>>> First what's type zero?
> >>>>> I was thinking about a (type I?) loop with just gain control that I've
> >>>>> used to lock a diode laser to the side of an absorption line.  You've
> >>>>> got to put a (single pole) lowpass between the error signal and the
> >>>>> gain, or it's pretty much an oscillator.
>
> >>>>> George H.
>
> >>>> Type 0 is a loop that has no naked integrators (a low-pass isn't
> >>>> considered a naked integrator in this context, as it has finite DC gain).
>
> >>>> --
> >>>> 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-Hidequoted text -
>
> >>>> - Show quoted text -
>

> >>> Hmmm OK,  For the diode laser locking thing, the piezo (plant) has a
> >>> resonance a bit above 3kHz.  Say I use a low pass filter with a 1
> >>> second time constant, and then crank up the gain til it's just below
> >>> the oscillation point.... how 'naked' does the integrator need to be?
> >>> (would 10 seconds and more gain count?)
>
> >>> George H.
>
> >> If you put in a notch filter, you can get the loop BW a lot closer to
> >> the piezo resonance, like 0.3 f_0 vs 0.03 f_0.
>
> >> 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 USA
> >> +1 845 480 2058
>

> >> hobbs at electrooptical dot nethttp://electrooptical.net-Hide quoted text -

>
> >> - Show quoted text -
>
> > Grin,  OK I'm not saying that a single pole low pass and then gain, is
> > in any way optimal.  But it works... is it type 0 or type I?
>
> > (Does notching out the piezo resonace work?  I've never tried that.)
>
> > George H.
>
> Notching works great, if the resonator Q is high.  The notch filter's
> phase shift goes away on the scale of its bandwidth rather than its
> centre frequency, so it has almost no effect beyond a few times delta-f.
>
> In my atomic force microscope days, I used that trick to get a factor of
> 10 in loop bandwidth with a piezo bimorph whose Q was right around 30.
>
> 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 USA
> +1 845 480 2058
>
> hobbs at electrooptical dot nethttp://electrooptical.net- Hide quoted text -
>
> - Show quoted text -

Cool thanks, I don't know the Q, but I'd guess it's above 10.

A multi layer stack from a Japanesse company whose name is escaping me
now...
(~4 um at 100V with a SRF of ~400kHz.)
Driving an Al (7075) flexure with a grating attached.

It'd be nice to get above 3kHz since there's still mucho vibrations
up there.
(This is a bit of a 'throw away' part of the diode laser, it's mostly
a student insturment and they're happy to get it tuned
to an Rb line and see the SAS.)

George H.

[George Herold]

> >> >> Softwarehttp://www.wescottdesign.com-Hidequoted text -

>
> >> >> - Show quoted text -
>
> >> > OK Well I thought I was getting the type 'thing', but I'm confused
> >> > again.
>
> >> > First what's type zero?
> >> > I was thinking about a (type I?) loop with just gain control that
> >> > I've used to lock a diode laser to the side of an absorption line.
> >> >  You've got to put a (single pole) lowpass between the error signal
> >> > and the gain, or it's pretty much an oscillator.
>
> >> > George H.
>
> >> Type 0 is a loop that has no naked integrators (a low-pass isn't
> >> considered a naked integrator in this context, as it has finite DC
> >> gain).
>
> >> --
> >> 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-Hide quoted text -
>
> >> - Show quoted text -
>

> > Hmmm OK,  For the diode laser locking thing, the piezo (plant) has a
> > resonance a bit above 3kHz.  Say I use a low pass filter with a 1 second
> > time constant, and then crank up the gain til it's just below the
> > oscillation point.... how 'naked' does the integrator need to be?
> > (would 10 seconds and more gain count?)
>
> If you're calling it a low pass filter and not an integrator, then you're
> saying that it has finite DC gain.  Therefore your loop is type 0.

Certainly whatever I 'call' it can't make a difference.
(I may give it the wrong name.)
Sure it's got finite gain at DC.
But so does every integrator I've ever made.

There's after all some leakage in my cap, pcb, solder and flux
'cocktail'.

George H.

(DC is just a myth anway.)

>
> --
> Tim Wescott
> Control system and signal processing consultingwww.wescottdesign.com- Hide quoted text -

[josephkk]

On Fri, 12 Oct 2012 12:02:48 -0500, Tim Wescott <t...@seemywebsite.com>
wrote:

>It's not obscurity if you know what it means.

Then it becomes your job as author to clarify the use consistently and
extensively.

?-)

[Tim Wescott]

Which is exactly what I did.

[Jasen Betts]

On 2012-10-14, Jamie <jamie_ka1lpa_not_v...@charter.net> wrote:

> Speaking of which, while I have it fresh on me mind, I've been wondering
> how one of those cheap laser diodes would behave in PV or PR mode and

not sure how receptive they are.

> would they survive another laser of equal type pointed into them?

they should do, I've never seen one with a warning against pointing it at a
mirror.


--
⚂⚃ 100% natural

--- news://freenews.netfront.net/ - complaints: ne...@netfront.net ---

[glen herrmannsfeldt]

In comp.dsp Jasen Betts <ja...@xnet.co.nz> wrote:
> On 2012-10-14, Jamie <jamie_ka1lpa_not_v...@charter.net> wrote:

>> Speaking of which, while I have it fresh on me mind, I've been wondering
>> how one of those cheap laser diodes would behave in PV or PR mode and

> not sure how receptive they are.

>> would they survive another laser of equal type pointed into them?

> they should do, I've never seen one with a warning against pointing it at a
> mirror.

Most lasers don't like seeing their own reflection, though it
normally won't hurt them, but it does interfere with the LASER
action. Mostly a problem on an optical bench, though.

Now, pointing one at a phase conjugate mirror is a different
question. Actually, any shiny object near a phase conjugate
mirror can get interesting.

http://en.wikipedia.org/wiki/Nonlinear_optics#Optical_phase_conjugation

In the DSP sense, consider a device that, given a sequence of samples,
returns the sequence in the opposite order. (And, I believe, for complex
samples the complex conjugate.)

-- glen