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How can I measure jitter?

Discussion in 'Electronic Basics' started by Boki, Nov 29, 2005.

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  1. Boki

    Boki Guest

    How can I measure jitter?

    I have to measure Bluetooth jitter, could you please advice the device and
    method...


    Best regards,
    Boki.
     
  2. PeteS

    PeteS Guest

    What jitter? What chipset? Are you trying to measure jitter in the
    transported signal, or in the carrier?
    The jitter of the RF generator?
    Then we get to:
    Long term jitter (drift), cycle to cycle jitter (much more difficult
    but do-able, depending on the frequency of the signal you are
    measuring), deterministic jitter (predictable using a network analyzer
    or even a diff TDR) - the list goes on.

    Please try and be more precise as to what it is you are trying to
    measure.

    Cheers

    PeteS
     
  3. Pooh Bear

    Pooh Bear Guest

    I'll bet he means jitter on an audio signal transported over Bluetooth but Boki
    likes to evade asking a question directly.

    Graham
     
  4. PeteS

    PeteS Guest

    I'll bet he means jitter on an audio signal transported over Bluetooth but Boki
    That's what I figure. As you note, Boki has a hard time formulating a
    decent question. I consider it my teaching duty to nag him ;)

    Cheers

    PeteS
     
  5. Don Bowey

    Don Bowey Guest

    There is no "audio signal" transported on Bluetooth.

    Boki likes to make cryptic posts, which are best ignored.

    Don
     
  6. Guest

    Clock jitter. : )

    It is using a 48 MHz internal clock; this gives a jitter of ~21ns.
    Using a 4 MHz internal clock and have a higher jitter of 250 ns.

    Please advice the clock jitter measure method.

    Best regards,
    Boki.
     
  7. Guest

    Nice smell.
     
  8. Guest

    = =

    ....................


    = =

    no your business...
     
  9. Pooh Bear

    Pooh Bear Guest

    There is if you happen to use Bluetooth to do that.

    Bluetooth is multi-function.

    Graham
     
  10. Really? Are you sure about that?
     
  11. PeteS

    PeteS Guest

    I agree on the cryptic posts.

    Bluetooth does, in a way, carry audio. It is designed to pass PCM, 8k
    frame rate - standard telecom style digitised audio. Indeed, I am using
    bluetooth links with this specifically in mind (amongst other things)
    in commercial products.
    Certainly one could pass any arbitrary data on this (SCO) link with
    decent QoS, but it was designed specifically for audio. The data are
    retimed at each end, so any jitter analysis would be pretty meaningless
    from a pure signalling perspective, without knowing the limits of
    retiming.

    Boki does seem to reply further down, but has yet to specify clearly
    the question :)

    Cheers

    PeteS
     
  12. PeteS

    PeteS Guest

    If you are asking how to measure the jitter, how do you know you have
    the jitter you have stated?

    Where, in the system, are you measuring this jitter? Against what
    reference? On what signal?
    As I said above, state the problem more clearly, please

    Cheers

    PeteS
     
  13. Jasen Betts

    Jasen Betts Guest

    They use something like that for wireless headsets.

    Bye.
    Jasen
     
  14. Guest

    The bluetooth data exchange has some delay, I am confused that is
    software problem or hardware problem, I consider both

    For hardware, I think I have to check jitter, or DSP will request to
    retry the data communication.


    Best regards,
    Boki
     
  15. Don Bowey

    Don Bowey Guest

    "Something like that" gets used for lots of things. But maybe what you are
    thinking of is something like Bluetooth transporting a digital bit-stream of
    encoded audio.
     
  16. PeteS

    PeteS Guest

    Bluetooth has two data channels.

    The ACL (Asynchronous) channel is usually operated in a serial port
    style (especially when used as a cable replacement). The SCO
    (Synchronous) channel is nominally designed for audio (and meets ISDN
    data rate specs for that, as well as the normal audio rate PCM highway
    for both 8 and 16 bit samples).

    The data rates and latency are usually dependent on the software stack
    for ACL. The SCo channel is buried deep to give a guaranteed data rate.
    I have achieved up to 19k2 fairly simply on the ACL channel. I use the
    SCO channel for digitised audio with 16 bit samples, and it works just
    fine. The ACL channel is also active at that time (indeed, it needs to
    be in most applications as commands such as volume controls are passed
    over the ACL link).

    So Boki needs to tell us which channel he is using.

    Cheers

    PeteS
     
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