[SI-LIST] Re: 答复: 答复: single RLC parameters at a certain frequency
- From: steve weir <weirsi@xxxxxxxxxx>
- To: xuzhengrong <Zhengrong.Xu@xxxxxxxxxx>
- Date: Tue, 20 May 2008 02:06:55 -0700
xuzhengrong, it can be used if the deviation between that extraction and
the channel behavior over the signal bandwidth is not excessive. When
IBIS was first developed, this was certainly true. At wide enough
bandwidths it breaks down.
You can check to see if the method is valid for your situation by
extracting at the high and low endpoints of your signal bandwidth. If
the deviation is large, then the single RLGC model accuracy is going to
be poor. If the deviation is not great, then a single RLGC approximation
will work adequately. You still have to get the RLGC parameters.
Extracting them at a single frequency point simply provides a well-known
and repeatable method.
Steve
xuzhengrong wrote:
> Hi Rui and Steve,
> My question isn't why we use lumped element to represent distributed =
> element
> or how many sections of RLGC in series to meet the bandwidth of the =
> model.
>
> I mean that if the single section RLGC extracted at a certain frequency =
> only
> represent the characteristic of s-param model at this frequency point, =
> it
> can't be used to approximate the bandwidth of the model which we usually =
> use
> 'the single section RLGC 'to do. The two RLGC are not the same thing.
> For example, if IBIS package model is extracted at 1GHz by default, can =
> it
> be used to approximate the low frequency band which is within 1/10
> wavelength?
>
> Best Regards,
> Zhengrong
>
>
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> =B4=FA=B1=ED Rui Yang
> =B7=A2=CB=CD=CA=B1=BC=E4: 2008=C4=EA5=D4=C220=C8=D5 13:32
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> =D6=F7=CC=E2: [SI-LIST] =B4=F0=B8=B4: single RLC parameters at a certain =
> frequency
>
> Hi, Zhengrong,
>
> Transmission line RLGC model comes from unit length transmission line
> equivalent circuit, in which each element has its own physical meaning, =
> =3D
> it
> should help you to interpret.
> The main difference between distributed element and lumped element is =
> =3D
> the
> propagation/flying time, where there is no flying time for lumped =3D
> element,
> while flying time is taken into consideration for distributed element.
>
> While for package model, under assumption the electrical length of
> interconnects inside package is less than one tenth of wavelength, we =
> =3D
> can
> treat them as lumped element. R represents interconnects conductor loss, =
> =3D
> L
> represents interconnects inductance, C represent the interconnects
> capacitance, G is negligeable here.
>
> Hope it helps!
>
> Regards,
> Rui Yang
> Hardware R&D Dept., CPD., HUAWEI TECHNOLOGIES CO.,LTD. huawei_logo
>
>
> Address: Huawei Industrial Base
> Bantian Longgang
> Shenzhen 518129, P.R.China
> Tel: +86-0755-89651191
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> =3DD6=3DF7=3DCC=3DE2: [SI-LIST] single RLC parameters at a certain =
> frequency
>
> Hi,
> To simplify the model, we often extract single RLGC parameters from the
> s-parameter model at a certain frequency.
> I wonder what on earth the meaning of the single frequency parameters =
> =3D
> is.
> First, if the parameters only represent the magnitude and phase of the
> S-parameter model at the frequency point, it may have different =3D
> combinations
> of RLGC to reach the same goal, what's the method or principle?
> Second, if the parameters are meaningful at a certain frequency, why can
> single RLGC parameters often be used to estimate characteristic of =3D
> package
> model such as IBIS? =3D20
>
> In my opinion, for example, the single RLGC model should be the =3D
> first-order
> approximation to the real model for transmission line, as Eric's book
> 'Signal Integrity: Simplified' said.
> It is equivalent to the real model within low frequency range and we can =
> =3D
> use
> it if the signal frequency component is within the range.
> However, if the RLGC model extracted at a certain frequency is only
> meaningful for the extracting frequency, it isn't the first-order
> approximation for the transmission line.
> So we can't use it as the first-order approximation and estimate its low
> frequency characteristic.=3D20
>
>
> Appreciate any idea and discussion for the problem.
>
> Best Regards,
> Zhengrong=3D20
>
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