Both labs are correct.
By necessity, the labs used different HOST devices.
Problem is in the method of termination of the USB port
inside the EUT, and the termination inside the HOST. The
problem is least aggravated by those terminations.
The key evidence is the offending tones are not related to
clocks in the EUT.
- Robert -
Robert A. Macy, PE. . [email protected]
408 286 3985. . . . . . . fx 408 297 9121
AJM International Electronics Consultants
101 E San Fernando, Suite 402
San Jose, CA 95112
On Thu, 24 Mar 2005 15:13:46 -0700
[email protected] wrote:
> I was thinking about the recent US/Taiwan EMC issue
> discussed here and I
> thought I would apply "Inference to the best explanation"
> to it. There
> was much conjecture about what is going on but we still
> have no more
> than the original evidence.
>
> Inference to the Best Explanation:
>
> Evidence:
> * E1: The device passed at the US lab
> * E2: The observed signal frequencies, at the US
> lab, correspond
> to known clock frequencies
> * E3: The device failed at the Taiwanese lab
> * E4: The observed signal frequencies, at the
> Taiwanese lab, do
> not correspond to known clock frequencies (they are
> different)
> * E5: The device passes at the Taiwanese lab when a
> ferrite is
> placed on the USB cable
> * E6: The identical device was tested at both labs
>
> Hypotheses (rank ordered by me from best to worst):
> * T0: The US lab is correct and the Taiwanese lab
> is in error
> * T1: The Taiwanese lab is correct and the US lab
> is in error
> * T2: The device has changed between the US lab and
> the Taiwanese
> lab
> * T3: Both labs are in error
>
> How one ranks the hypotheses depends on how they rate the
> evidence.
>
> Dave Cuthbert
> Micron Technology
>
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