How to create multiple simultaneous signal sources from a single reference source?

Discussion in 'Analog & Mixed-Signal Design' started by John Manuel, Jul 8, 2018.

  1. John Manuel

    Thread Starter New Member

    Jun 6, 2018
    I wanted to build a circuit which would produce a set of signals of different frequencies in different channels simultaneously using a single reference source. I also want the frequencies to be changeable. I am looking to generate frequencies in kHz and MHz range. On searching on the web I came across PLL. I wanted to know if I can do it using PLL or any other methods. It should be fully analog.
  2. WBahn


    Mar 31, 2012
    The devils are in the details. How are the signals in the set supposed to be related to the reference signal?

    kHz and MHz each cover three orders of magnitude. If you are talking signals up to 5 MHz that is much different than signals up to 500 MHz. What are you actual min and max frequencies?
  3. crutschow


    Mar 14, 2008
    Why is that?
    Most PLL circuits are digital.
    Do you want all the signals to be sinewaves?
  4. John Manuel

    Thread Starter New Member

    Jun 6, 2018
    I want very quick responses without any latency. I do not know much about PLL. I thought they were analog since it came under Indirect Analog Frequency Synthesis. Will there be any Analog to Digital Conversions?
  5. danadak

    Well-Known Member

    Mar 10, 2018
    Several approaches, but some questions -

    1) Are freqs fixed at time of start ?
    2) Are signals coherent in phase ?
    3) Signals sine, square....?
    4) How many signals ?
    5) Allowed latency ?
    6) Leading edge of signals have to meet setup/hold times to digital input loads ?
    7) Source of signals ?
    8) Description of what they will be used for ?

    Regards, Dana.
  6. OBW0549

    Distinguished Member

    Mar 2, 2015
    A Direct Digital Synthesis (DDS) chip would be absolutely perfect for this job. Several chips are available, such as the AD9833, available also in an assembled module. You'll need one chip/module for each frequency you want to generate

    Phase-lock loops achieve frequency multiplication by including a divider (i.e., a counter chain) in their feedback loop; the PLL output frequency is equal to the reference frequency times the counter modulus.

    I don't think you're going to find any "fully analog" method for what you're trying to achieve, at least none that are both accurate, inexpensive and don't require Grand Master-level design skills to implement.
  7. ebeowulf17

    Distinguished Member

    Aug 12, 2014
    I could be wrong, but I'm wondering if the thread starter really means "fully analog," or maybe just means "no microcontrollers."
  8. WBahn


    Mar 31, 2012
    The phrase, "very quick responses without any latency," is pretty much devoid of any useful information. What constitutes "a very quick response"? There's no such thing as "no latency". So take some time and try to come up with a meaningful way of conveying what you are looking for. Probably the best way to do this is to sketch what you would consider to be the ideal situation and then move it away from ideal until you get to the point where you say that this has just moved into the realm of being unacceptable.

    One thing to keep in mind about using a reference signal to base other signals on, there IS going to be a latency and it IS going to take time for the generated signal to settle down every time the reference signal changes.