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Resources regarding Phase Locked Loops?

Discussion in 'Electronic Design' started by Michael, Apr 11, 2007.

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  1. Michael

    Michael Guest

    Hi - I'm going to need to build a PLL circuit that can compare two
    signals in the MHz range and find the phase difference between the
    two. One will be very nice and clean while the other will be (I
    suspect) quite noisy.I have never, ever done anything with PLLs. My
    coursework at my uni (I am a senior EE, graduating in May) has not
    covered PLLs at all. I don't think the term has ever even been
    mentioned. I know about them from outside research.

    Anyways - can anybody point me towards good resources regarding
    designing such a circuit?


  2. Joerg

    Joerg Guest

    Has never been mentioned? Ouch. What university was that?

    If you've never done a PLL I suggest to get a copy of the ARRL Handbook.
    Mine are older but PLL is handled in there. If this is for a mass
    product and it's on a tight schedule get consulting help.

    I think Analog Devices has some good app notes about the topic as well.
    So did Philips but then they messed up their web site.
  3. DaveM

    DaveM Guest

    Phase-Locked Loops, 5th Edition
    Roland E. Best
    McGraw-Hill, June 2003, ISBN 0071412018

    Dave M
    MasonDG44 at comcast dot net (Just substitute the appropriate characters in the

    Life is like a roll of toilet paper; the closer to the end, the faster it goes.
  4. Michael

    Michael Guest

    It's not that PLLs aren't covered at all - they're covered in some
    classes, just none that I have taken. I took a pretty specialized
    courseload, and PLLs are far from my specialty. However, it looks as
    if I'm going to have to learn the buggers.

    It's not for a mass product (at least not on a strict timeline -
    eventually I hope to bring this device to market)

    I'll take a look at the ARRL handbook. I see it mentioned enough that
    I should check it out anyways.


  6. Joerg

    Joerg Guest

  7. I know its old, but the 7046 goes upto 20ish megs, and the basics are
    covered in the data sheet. But Micheal didn't really say how little he

    I had a quick browse on th nxp site for the app notes, it seems you
    have to email them for a copy, pathetic.

    I'll try to find a rather good (IMHO) philips PLL appnote on my
    backup drives/CD, and stuffit somewhare accesable

  8. Joerg

    Joerg Guest

    IIRC it's more like 17-ish. And probably only under the full "Princess
    on a Pea" treatment, and when Mars is in the correct constellation and
    no black cat has crossed the road from left to right.
    IMHO that whole web site has become pathetic, almost to the point of
    being useless. And then some day they'll wonder why the sales numbers
    don't come in as expected.
  9. Guest

    4046 or its superfast 74HC4046 or 77046 sisters are a good start for a
    begining PLL person, but are junk compared to whats out there now.
    However for about 3$ in parts plus a power supply and voltmeter or
    perferably a oscilloscope, it will get you started learning and may
    actually solve your problem, although a difference counter seems much
    more like a solution for you

    if you want to start with the 4046 as a learning experience, harry
    Lythall's pages are great:

    or the tutorials here:

    click on "projects" then click on "synths"

    Steve Roberts
  10. I always found the Lagrange Point pretty good for PLLs

  11. Joerg

    Joerg Guest

  12. My God. My community college engineering TECHNOLOGY students get a full
    week of PLL in the second semester of their FRESHMAN year. I'd like to
    know, just to avoid, what university are we talking about?


    I have never, ever done anything with PLLs. My
  13. Michael

    Michael Guest

    You have got to be kidding me. Why post such nonsense? Is this some
    sort of way to fluff yourself up? An attempt to put others down?
    Perhaps a way of compensating for an insecurity about a shoddy
    education, or a lack thereof? It's pitiful, sad, and a failure on all

    To answer your question - I attend the 3rd ranked university for EE in
    the USA.

    I would suggest that your CC is teaching it too early, as there is no
    way in hell that they have a strong enough background to understand
    how it works at that point. Just having quickly glanced at the math
    behind PLLs I can say that. Learning implementation should follow
    understanding, in my opinion. I suspect those running your CC feel

  14. joseph2k

    joseph2k Guest

    Not a lot of ever EE's get to design PLLs. That should certainly make an
    elective of the material. ETs often have to troubleshoot PLLs is existing
    equipment, that is the difference engineers and technologists. To clarify
    it is the difference between having to have the background to analyse it
    for design, and having to have a basic understanding of typical industrial
    applications and their various uses. Or quickly, between designing the
    chip and using the chip.
  15. Winfield

    Winfield Guest

    Not sure what you're trying to accomplish, but I'd be inclined
    to use a mixer, followed by a baseband filter, digitizing and
    appropriate signal processing. An Analog Devices AD734 linear
    multiplier would make a nice mixer.
  16. rebel

    rebel Guest

    If the two signals are locked (in a PLL ...) then mixing would be a fairly
    pointless exercise. The O/P is after phase difference.
  17. Winfield

    Winfield Guest

    In a filtered DC mixer (multiplier) output the phase difference
    shows up as a varying DC voltage which can be analyzed for phase
    jitter and slower variations with time. I don't see the role of
    a PLL, per se. PLLs are used to phase-lock an output oscillator
    to an input signal. How does a second signal fit in, two PLLs?
    Or are you only thinking of the PLL's phase detector? Remember,
    this is after all just a mixer! But often, like in a 4046, it's
    not a very good one, not as good as an accurate linear multiplier.
  18. Since the OP wants to find the phase difference of two input signals (one
    clean, one noisy) maybe two PLLs wouldn't be such a bad idea. He could then
    trivially mux the two oscillator outputs, both of which would be clean, of
    equal amplitude and 50% duty cycle.

    But as I've never done this I may be way off track here.

  19. Fred Bartoli

    Fred Bartoli Guest

    Robert Latest a écrit :
    Cleaning a signal with a PLL is just getting the signal through a narrow
    BPF (and adding some noise and phase error too).
    Mixing two PLL'ed signals the translates your BPF center frequency to
    zero, transforming it to an LPF.

    Multiplying the signal first and LPFing it after is just the reversing
    the operations (first translate your frequency, then LPF it).

    They are both mathematically equivalent, but I'd try to avoid the PLL
    If the frequency is low enough I'd go for the multiplier first and LPF
    later, and otherwise probably for a DBM and LPF.
  20. Yeah, sounds right. Like I said, I'm out of my depth here.

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