PLL loop design

loop.

There's a worked example in: "The Art of Electronics" by Horowitz and Hill.

There are lots of books about it e.g. Digital PLL Frequency Synthesizers: Theory and Design Ulrich L Rohde; Prentice-Hall; April 1983; ISBN 0132142392.

There are numerous resources on the web e.g.

The basic idea is to do a bode plot of the open loop response. Make sure the phase is well below 180 degrees at the frequency where the magnitude passes through unity or else your loop will oscillate!

The second most important thing after stability is loop bandwidth. Make it too wide and you'll have reference spurs on the output; too narrow and it'll be slow to lock.

You need to work out the loop filter transfer function in terms of the laplace operator 's'.

I use

for bode plots.

You'll find two worked examples on my hobby website:

Get a voltage-controlled oscillator, a crystal oscillator to lock it to, a balanced modulator, a phase-discriminator and a simple low-pass filter. It will amaze you how difficult it is to prevent it from locking.

Once you have observed operation using an oscilloscope, then, and only then, read a book or paper such as "Wolf J Gruen, Theory of AFC Synchronisation", IEEE Press, 1977.

You will need the practice first in order to understand what the author is waffling about. It's a peculiar, intriguing subject.

I found Gruen very useful too late. It was around 1962, 15 years before Gruen, that I had to teach myself, using tubes on the bench, how they really worked. I almost invented the things.

But they are fairly easy to understand once the idea suddenly clicks into place. These days I think they come on single chips.

--
Reg.

Sometimes you need to do a dual lock system, first a fast loop to acquire lock, then a slow loop so as not to distort some modulation types as FM modulation of the vco directly with slow waveforms.

Hernán Sánchez wrote:

loop.

There's a worked example in: "The Art of Electronics" by Horowitz and Hill.

There are lots of books about it e.g. Digital PLL Frequency Synthesizers: Theory and Design Ulrich L Rohde; Prentice-Hall; April 1983; ISBN 0132142392.

There are numerous resources on the web e.g.

The basic idea is to do a bode plot of the open loop response. Make sure the phase is well below 180 degrees at the frequency where the magnitude passes through unity or else your loop will oscillate!

The second most important thing after stability is loop bandwidth. Make it too wide and you'll have reference spurs on the output; too narrow and it'll be slow to lock.

You need to work out the loop filter transfer function in terms of the laplace operator 's'.

I use

for bode plots.

You'll find two worked examples on my hobby website:

The ARRL Handbook has nice explanation and some good tips for picking the filter.

Paul C

There are numerous PLL design books. The 1965 edition of Phase Locked Loops by F.M. Gardiner is a classic (but rather old).

There have been many s.e.d. threads about PLLs in the past, e.g. this one

describes the ideas behind selecting loop bandwidth to minimum output jitter.

Regards, Allan

You have to register on their site to download it. It is basically a free version of SimPLL by Applied Radio Labs.

Very nice program. WeBench at

is entirely web-hosted and does similar stuff.

-- jm

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Note: My E-mail address has been altered to avoid spam

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Do you have a direct URL for the simulator? I can't find it. Thanks!

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

I have no problem with registering... I just can't find the item in the first place. Certainly not the most intuitive site :-(

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Analog devices has a simulator that lets you try a lot of parameters. At

Rene

--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

It's one click away from the front page! Click on PLL Synthesizers/VCOs and there's a reference to ADIsimPLL right in front of you!

--
Rick

Aha! There it is hidden in the text over the device listings. I was looking down the columns on either side of the device listings.

Thanks!

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.