[SI-LIST] Re: TDR Resolution
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: "Moeller, Merrick" <mmoeller@xxxxxxxxxxxxxxx>
- Date: Tue, 18 Jan 2005 13:35:35 -0500
Merrick
Well, you are going to need to be very careful with your simulation
setup. Assuming that you have a constant coaxial section leading into
the retention structure, then you will be able to perform a good
waveport match to the coaxial mode. You'll also need to perform port
deembedding with quite a few samples across the entire broadband
spectrum to be sure that in simulation of the waveport you don't
inadvertently launch additional modes. I would highly suggest that you
model all materials as either PEC metals or lossless dielectrics,
otherwise there will be slight errors in the mode match that will cause
mode converstion at the launch. If you do all of these things, then you
may be able to reasonably resolve the retention ring.
However, this seems to be a purely academic exercise. If it takes 150
GHz bandwidth in order to resolve the structure, and the operational
bandwidth is sigificantly lower than this, for all purposes your
retention structure is invisibile. However, if you are trying to do
this in order to optimize the mechanical structure in some way, you are
probably using the wrong method. There are better ways to do this in CST.
best regards,
scott
Moeller, Merrick wrote:
> Scott,
> In this case lets assume that the retention feature is surrounded
> on either side
> by uniform impedance section. Although these sections have more length
> than the
> retention feature itself they are less than 1mm, and the retention
> feature itself
> is less than .3mm. Would it be feasible to run the simulation to a
> bandwidth that
> would allow for that kind of resolution? 150GHz? More? Also assume meshing
> is sufficient. Would Max frequency of the structure permit such a high
> frequency limit?
> Would frequency cutoff limit simulation?
>
> Merrick
> ------------------------------------------------------------------------
> From: Scott McMorrow [mailto:scott@xxxxxxxxxxxxx]
> Sent: Monday, January 17, 2005 4:50 PM
> To: Moeller, Merrick
> Cc: si-list@xxxxxxxxxxxxx
> Subject: Re: [SI-LIST] Re: TDR Resolution
>
> Merrick
>
> That's what I suspected. In that case, you need to reduce your
> problem size to that of retention structure surrounded by uniform
> impedance crosssections. Otherwise, you will obscure resolution of
> the retention structure with other reflections. If you want to TDR
> the assembly without any spurious high frequencies then you will need
> to create a custom TDR waveform that is created from a low pass
> filtered trapizoidal edge. You will also need to be sure that there
> sufficient mesh cells to correctly discretize the structure you are
> simulating. Depending upon the geometry, this might be as few as two
> cells in each direction, but quite posibly it could be more. You can
> increase the mesh density across the retention structure locally by
> selecting the component, selecting its mesh properties and changing
> them. Finally, you will need to adjust your simulation frequency for
> meshing and your minimum mesh step size to guarantee that the
> simulation will be performed at a high enough bandwidth to resolve
> your TDR rising edge.
>
> If you don't want to reduce your problem size by slicing the model,
> then you can create the necessary waveforms in CST and then pass them
> back through software the performs the reverse scattering algorihm and
> provides a true impedance profile. With a bit of data manipulation
> you should be able to pass your data back through TDA iConnect.
>
> In either case, your key to good results is to create a well filtered
> TDR waveform at the appropriate edge rates, to control the mesh
> density to gain the resolution you desire across your structure, and
> to set the frequency and smallest mesh step size so that you have
> enought simulation bandwidth.
>
> scott
>
>
> Moeller, Merrick wrote:
>
>> Scott,
>> 3D solver. CST Microwave Studio...
>> TDR impedance profile at various rise times.
>>
>> M
>>
>> ------------------------------------------------------------------------
>> From: Scott McMorrow [mailto:scott@xxxxxxxxxxxxx]
>> Sent: Monday, January 17, 2005 2:02 PM
>> To: Moeller, Merrick
>> Cc: si-list@xxxxxxxxxxxxx
>> Subject: Re: [SI-LIST] Re: TDR Resolution
>>
>> Merrick,
>>
>> It depends on the type of simulation you are performing. Is this a
>> spice simulation based on extracted cascaded model sections, or is
>> it a 3D time domain field solver/simulation environment?
>>
>> Also, it depends on what you are trying to resolve: final impedance
>> of the retention feature, electrical length of the retention feature,
>> signal distortion due to retention feature at various risetimes?
>>
>> scott
>>
>>
>> Moeller, Merrick wrote:
>>
>>> Thanks for all the help everyone. I found
>>>Kipp's solution suitable for my needs..
>>>
>>>To continue the discussion:
>>>This scenario is taking place in a simulation. It is
>>>Possible to create increased frequency bandwidth simulations
>>>That may handle faster rise times... What are some=20
>>>Of the limiting factors when considering a MAXIMUM FREQUENCY
>>>BANDWIDTH for a simulation? For example, I wanted to=20
>>>Resolve some retention feature in a coaxial type structure.
>>>Is there a Max frequency.... Strictly speaking of TDR and
>>>Square wave reproduction. I realize that the structure will
>>>Have cutoff frequencies for particular modes.
>>>
>>>M
>>>
>>>-----Original Message-----
>>>From: Ed Sayre III [mailto:esayre3@xxxxxxxx]=20
>>>Sent: Monday, January 17, 2005 12:17 PM
>>>To: Moeller, Merrick
>>>Cc: si-list@xxxxxxxxxxxxx
>>>Subject: Re: [SI-LIST] TDR Resolution
>>>
>>>Merrick,
>>> As you can see from the responses the "Rule-of-Thumb depends on your
>>>signaling needs. The risetime of the TDR really depends on the the data
>>>rate of the signals. R. K Poon's book has an excellent section on
>>>sampling and risetime effects. I believe it is in an appendix in
>>>chapter 5.
>>> Also a word to the warning, don't use a ramp function, it tends to
>>>give you unrealistic results and lots of ringing and convergence
>>>problems.
>>>
>>>Regards
>>>-Ed
>>>
>>>
>>>At 10:21 AM 1/17/2005 -0600, Moeller, Merrick wrote:
>>>
>>>
>>>>Experts,
>>>> I am in the process of running a simulation In order to=20
>>>>resolve signal path discontinuities. Is there a Rule of thumb that=20
>>>>would give the minimum rise time signal To resolve a min length=20
>>>>discontinuity?
>>>>Regards,
>>>>Merrick
>>>>
>>>>------------------------------------------------------------------
>>>>To unsubscribe from si-list:
>>>>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>>>>
>>>>or to administer your membership from a web page, go to:
>>>>//www.freelists.org/webpage/si-list
>>>>
>>>>For help:
>>>>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>>>>
>>>>List FAQ wiki page is located at:
>>>> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>>>>
>>>>List technical documents are available at:
>>>> http://www.si-list.org
>>>>
>>>>List archives are viewable at:
>>>> //www.freelists.org/archives/si-list
>>>>or at our remote archives:
>>>> http://groups.yahoo.com/group/si-list/messages
>>>>Old (prior to June 6, 2001) list archives are viewable at:
>>>> http://www.qsl.net/wb6tpu
>>>>
>>>>
>>>>
>>>>!DSPAM:41ebe70a251711626721400!
>>>>
>>>>
>>>
>>>------------------------------------------------------------------
>>>To unsubscribe from si-list:
>>>si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>>>
>>>or to administer your membership from a web page, go to:
>>>//www.freelists.org/webpage/si-list
>>>
>>>For help:
>>>si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>>>
>>>List FAQ wiki page is located at:
>>> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>>>
>>>List technical documents are available at:
>>> http://www.si-list.org
>>>
>>>List archives are viewable at:
>>> //www.freelists.org/archives/si-list
>>>or at our remote archives:
>>> http://groups.yahoo.com/group/si-list/messages
>>>Old (prior to June 6, 2001) list archives are viewable at:
>>> http://www.qsl.net/wb6tpu
>>>
>>>
>>>
>>>
>>>
>>
>>--
>>Scott McMorrow
>>Teraspeed Consulting Group LLC
>>121 North River Drive
>>Narragansett, RI 02882
>>(401) 284-1827 Business
>>(401) 284-1840 Fax
>>
>>http://www.teraspeed.com
>>
>>Teraspeed is the registered service mark of
>>Teraspeed Consulting Group LLC
>>
>>
>
>--
>Scott McMorrow
>Teraspeed Consulting Group LLC
>121 North River Drive
>Narragansett, RI 02882
>(401) 284-1827 Business
>(401) 284-1840 Fax
>
>http://www.teraspeed.com
>
>Teraspeed is the registered service mark of
>Teraspeed Consulting Group LLC
>
>
--
Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
http://www.teraspeed.com
Teraspeed is the registered service mark of
Teraspeed Consulting Group LLC
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
