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How can I measure jitter?

B

Boki

Jan 1, 1970
0
How can I measure jitter?

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


Best regards,
Boki.
 
P

PeteS

Jan 1, 1970
0
Boki said:
How can I measure jitter?

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


Best regards,
Boki.

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
 
P

Pooh Bear

Jan 1, 1970
0
PeteS said:
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.

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

Graham
 
P

PeteS

Jan 1, 1970
0
I'll bet he means jitter on an audio signal transported over Bluetooth but Boki
likes to evade asking a question directly.

Graham

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
 
D

Don Bowey

Jan 1, 1970
0
I'll bet he means jitter on an audio signal transported over Bluetooth but
Boki
likes to evade asking a question directly.

Graham

There is no "audio signal" transported on Bluetooth.

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

Don
 
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.
 
P

Pooh Bear

Jan 1, 1970
0
Don said:
There is no "audio signal" transported on Bluetooth.

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

Bluetooth is multi-function.

Graham
 
P

PeteS

Jan 1, 1970
0
Don said:
There is no "audio signal" transported on Bluetooth.

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

Don

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
 
P

PeteS

Jan 1, 1970
0
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.

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
 
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
 
D

Don Bowey

Jan 1, 1970
0
They use something like that for wireless headsets.

Bye.
Jasen

"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.
 
P

PeteS

Jan 1, 1970
0
Don said:
"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.

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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