[SI-LIST] Re: PLL Board Filter
- From: steve weir <weirsi@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 24 Apr 2012 06:29:34 -0700
Tying the capacitors together couples noise that rides on the the common
inductance through the capacitors. It's a good way to kill the filter
performance. Ideally you want as low a mounted inductance as possible,
particularly on the load side of the filter. You also should take care
that the filter doesn't burn you with an excited, poorly damped resonance.
Steve.
Steve.
On 4/24/2012 6:04 AM, Faraydon Pakbaz wrote:
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> Dear Signal Integrity Experts:
>
> In a scenario for Board (PCB) PLL filter generally there is a capacito=
> r
> before Ferrite Bead and capacitor after
> Ferrite Bead. Is it better to short the ground of capacitors at the boa=
> rd
> and then via it to return path/plane or is it
> better to via each capacitor ground individually to return path/plane? =
> It
> seems providing separate via for each
> ground of capacitor exposes the filter to two different source of noise=
>
> from return path/plane. Any comments and
> guidance appreciated. Thanks.
>
> Regards;
>
> Don Pakbaz
>
>
>
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> |04/23/2012 10:19 PM =
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> |[SI-LIST] Re: VNA and characterization of long cables =
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>
> Mark,
>
> You are correct, the phase-wrapping ambiguity can be pushed out if you
> have a network analyzer starting at lower frequencies. Some analyzers
> start at a few hundred kHz, some models even below 100kHz. Alternately=
>
> you can take multiple network analyzers, each covering its own frequenc=
> y
> range, and you can go down to a few Hz in frequency if you wish. The
> overlap in the frequency ranges of the different VNAs gives you the
> possibility of checking your data for consistency. Depending on how yo=
> u
> want to use your data, the cumulative data set may need to be re-sample=
> d.
>
> Regards,
>
> Istvan Novak
> Oracle
>
> On 4/23/2012 7:02 PM, Mark Filipov wrote:
>> Hi all!
>>
>> I have found an reference that says that it seems the longest cable,
>> we can measure is 10m long.
>>
>>
>> "With a wiring delay of about 5 ns/m, a 10 m cable has a time delay o=
> f
>> about 50 ns, requiring an equivalent time window of at least 100 ns.
>> The required frequency interval of 10 MHz sets 10 m as the boundary o=
> f
>> the longest-length cable that can be measured unambiguosly with a VNA=
> "
>> Source: Signal Integrity Characterization Techniques / edited by
>> M.Resso& E.Bogatin.
>>
>> Page: 489, you can read it online on Google books.
>>
>> But if we have better VNA couldn't we measure longer cables then thes=
> e
> 10m?
>> Best regards, Mark
>>
>
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--
Steve Weir
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