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shyam dikshit chavali | 1 Dec 2009 09:58
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Methods to Improving eye pattern

Hi All,
Im doing signal integrity for CPRI lines, can i first know the thumb rules
to best followed methods for improving eye pattern.
Quick response is appreciated.

Cheer's
S.D

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Hirshtal Itzhak | 1 Dec 2009 13:22
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Re: AW: Multi-Giga-Hertz Rigid-Flex Feasibility

Thanks, Gert

I actually intend to use 4-mil traces on a 3-mil thick Polyamide in a Microstrip configuration. Will this
configuration get me tighter tolerances than the +/-20% I asked about? And I don't mean to include
surrounding materials or bending, just the fabrication process itself

Regards

Itzhak

-----Original Message-----
From: Havermann, Gert [mailto:Gert.Havermann@...] 
Sent: Tuesday, December 01, 2009 11:42 AM
To: Hirshtal Itzhak
Subject: AW: [SI-LIST] AW: Multi-Giga-Hertz Rigid-Flex Feasibility

Hello Itzhak,

sorry for the typo, I meant 0.08mm (3mil).
Flex base material is usually very thin (1mil) ant for impedance control, that means small traces. 3-4mil
are harder to achief on flex than on FR-4, the yield will be lower, thus cost will rise. There are thicker
laminates available, but they also cost extra.

Stripline on Flex isn't common, but in critical cases where you can not control the flex in its final
environment, you should switch to stripline to avoid problems in the field.

BR
Gert

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Scott McMorrow | 1 Dec 2009 15:05

Re: AW: Multi-Giga-Hertz Rigid-Flex Feasibility

I agree with Lee, microstrip works just fine for flex circuits with a 
cover layer.  High performance stripline is also achievable in a 
flexible assembly if you crosshatch the planes.  To do this, you need to 
do a bit of engineering homework in order to achieve controlled 
impedance and low loss.
scott

Lee Ritchey wrote:
> Itzhtal,
>
> I use both polyamide based flex material and Liquid Crystal Polymer from
> Rogers.  Both work well.  LCP has lower loss.
>
> The reason that stripline is usually not used in flex circuits is that
> makes a 3 layer assembly which is not very flexible.  There is nothing
> wrong with microstrip.  Works fine.
>
> Lee Ritchey
>
>
>
>
>   
>> [Original Message]
>> From: Hirshtal Itzhak <ihirshtal@...>
>> To: Havermann, Gert <Gert.Havermann@...>; <si-list <at> freelists.org>
>> Date: 11/29/2009 4:00:51 AM
>> Subject: [SI-LIST] Re: AW: Multi-Giga-Hertz Rigid-Flex Feasibility
>>
>> Hello Gert
(Continue reading)

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Ray Anderson | 1 Dec 2009 15:56
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Re: Methods to Improving eye pattern

Shyam-
Please do not feel that I am picking on you specifically, but there seems to be an endless number of people who
are continually asking si-list members for answers to their complex engineering problems without
apparently doing any work or study on the issue themselves. Then they want a "Quick Response".

The most effective way to ask a technical questions on the list is to demonstrate that you've done your
due-diligence in working through the problem yourself as far as you can, and then ask pointed questions
aimed at clarifying what you don't understand or are troubled by. Just asking for a complete set of rules to
solve a problem is unlikely to garner the response you were hoping for. Most, if not all, complex
engineering problems can't be solved with simple "rules of thumb". Also be aware that many of the most
prolific and knowledgable contributors to the list are not professors whose main job is to spread
knowledge to students (and who probably wouldn't answer a question like you posed anyway), but are busy
working engineers who probably aren't going to be inclined to do someone else's work for them. Those list
members who provide so much valuable information are incredibly generous in their desire to assist
others, but please don't expect them to do your job for you (an q
 uickly at that...).

With all that being said, might I suggest the best "rule of thumb" for solving your problem is to read, study,
experiment and then if necessary ask a few specific questions. Apologies if it seems like I was jumping on
your case, but the question just struck me as a prime example of what (to me anyway) has been transpiring too
often as of late.

Regards,

Ray Anderson
(si-list admin)

-----Original Message-----
From: si-list-bounce@... on behalf of shyam dikshit chavali
Sent: Tue 12/1/2009 12:58 AM
(Continue reading)

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Muranyi, Arpad | 1 Dec 2009 16:51
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Re: Methods to Improving eye pattern

Well said...

Arpad
============ 

-----Original Message-----
From: si-list-bounce@... [mailto:si-list-bounce@...]
On Behalf Of Ray Anderson
Sent: Tuesday, December 01, 2009 8:57 AM
To: shyam dikshit chavali; si-list@...
Subject: [SI-LIST] Re: Methods to Improving eye pattern

Shyam-
Please do not feel that I am picking on you specifically, but there
seems to be an endless number of people who are continually asking
si-list members for answers to their complex engineering problems
without apparently doing any work or study on the issue themselves. Then
they want a "Quick Response".

The most effective way to ask a technical questions on the list is to
demonstrate that you've done your due-diligence in working through the
problem yourself as far as you can, and then ask pointed questions aimed
at clarifying what you don't understand or are troubled by. Just asking
for a complete set of rules to solve a problem is unlikely to garner the
response you were hoping for. Most, if not all, complex engineering
problems can't be solved with simple "rules of thumb". Also be aware
that many of the most prolific and knowledgable contributors to the list
are not professors whose main job is to spread knowledge to students
(and who probably wouldn't answer a question like you posed anyway), but
are busy working engineers who probably aren't going to be inclined to
(Continue reading)

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Karthik Raj Guruchandran | 1 Dec 2009 20:21
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Gravatar

Re: AW: Multi-Giga-Hertz Rigid-Flex Feasibility

Itzhtal,
I have seen problems in matching 100 ohm impedance in microstrip
configuration on a 2 layer flex.The constraint that caused the problem was
flex thickness which had a direct relation to the base material thickness.
Since the di-electric had to be thin (to maintain flex thickness), the trace
width had to be smaller or the ground layer underneath had to be
compromised.

But if you don't have such strict constraints on flex thickness, then as Lee
and Scott mentioned, it should work just fine.

Cheers,
Karthik

On Tue, Dec 1, 2009 at 2:05 PM, Scott McMorrow <scott@...> wrote:

> I agree with Lee, microstrip works just fine for flex circuits with a
> cover layer.  High performance stripline is also achievable in a
> flexible assembly if you crosshatch the planes.  To do this, you need to
> do a bit of engineering homework in order to achieve controlled
> impedance and low loss.
> scott
>
>
> Lee Ritchey wrote:
> > Itzhtal,
> >
> > I use both polyamide based flex material and Liquid Crystal Polymer from
> > Rogers.  Both work well.  LCP has lower loss.
> >
(Continue reading)

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Hirshtal Itzhak | 2 Dec 2009 10:37
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Re: AW: Multi-Giga-Hertz Rigid-Flex Feasibility

Hi Scott

As I've already told a few times in my emails, my main concern is impedance continuity across the
rigid-flex-rigid combination.

If the tolerance of the 3 sections is independent of each other, and if the flex tolerance is +/-20%,
assuming a standard +/-10% tolerance on the rigid boards, this could create a substantial impedance
discontinuity, e.g: 120-Ohm on the Flex and 90-Ohm on the Rigids.

I just wanted to know if and how it's practical, and over what flex-length, to transfer a few GHz (up to
3.125GHz) signals from one rigid board to the other

Thanks

Itzhak  

________________________________

From: Scott McMorrow [mailto:scott@...] 
Sent: Tuesday, December 01, 2009 4:05 PM
To: Lee Ritchey
Cc: Hirshtal Itzhak; Gert Havermann; si-list@...
Subject: Re: [SI-LIST] Re: AW: Multi-Giga-Hertz Rigid-Flex Feasibility

I agree with Lee, microstrip works just fine for flex circuits with a cover layer.  High performance
stripline is also achievable in a flexible assembly if you crosshatch the planes.  To do this, you need to do
a bit of engineering homework in order to achieve controlled impedance and low loss.

scott
(Continue reading)

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Scott McMorrow | 2 Dec 2009 13:45

Re: AW: Multi-Giga-Hertz Rigid-Flex Feasibility

Hirshtal
Flex tolerance is not +/-20%.  It's possible to hold the tolerance to 
+/- 10%, just as it is for rigid board.

Scott

Hirshtal Itzhak wrote:
>
> Hi Scott
>
>  
>
> As I've already told a few times in my emails, my main concern is 
> impedance continuity across the rigid-flex-rigid combination.
>
>  
>
> If the tolerance of the 3 sections is independent of each other, and 
> if the flex tolerance is +/-20%, assuming a standard +/-10% tolerance 
> on the rigid boards, this could create a substantial impedance 
> discontinuity, e.g: 120-Ohm on the Flex and 90-Ohm on the Rigids.
>
>  
>
> I just wanted to know if and how it's practical, and over what 
> flex-length, to transfer a few GHz (up to 3.125GHz) signals from one 
> rigid board to the other
>
>  
>
(Continue reading)

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Tom Dagostino | 2 Dec 2009 19:23

Re: AW: Multi-Giga-Hertz Rigid-Flex Feasibility

Itzhak

Think about what determines Zo. It is the relationship between the signal
path and its return path(s).  If the signal path and return path do not
change from rigid to flex to rigid then Zo does no change.  If you add extra
metal or insulation at the boundaries that effect the fields then you will
get changes in Zo. It all depends on how you design your system.

Tom Dagostino
Teraspeed(R) Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
503-430-1285 FAX
tom@...
www.teraspeed.com

Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
401-284-1827 

-----Original Message-----
From: si-list-bounce@...
[mailto:si-list-bounce@...] On
Behalf Of Hirshtal Itzhak
Sent: Wednesday, December 02, 2009 1:37 AM
To: Scott McMorrow; Lee Ritchey
Cc: Gert Havermann; si-list@...
Subject: [SI-LIST] Re: AW: Multi-Giga-Hertz Rigid-Flex Feasibility
(Continue reading)

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Richard Jungert | 2 Dec 2009 21:00
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Favicon

Re: AW: Multi-Giga-Hertz Rigid-Flex Feasibility

Guys.

If you bend the flex cable the Zo changes too. BTW. Bend it some more while observing the eye  pattern on the
scope and watch the eye pattern open and close at higher speeds. 

One can fabricate a flex with 1/4 oz copper. We did a 100 ohm differential, 12 inches long a couple of years ago
with 1oz. copper and we could not bend it without great force. Not good and the performance was not
acceptable either.  Flex's are generally made for low speed apps like signals running inside disc drives
between motors. 

I would recommend to anyone not to do a flex but to use minature coax's or ribbonized coax's for high speed
apps and signaling between rigid boards. 

Richard Jungert

 
> From: tom@...
> To: ihirshtal@...;
scott@...; leeritchey@...
> CC: Gert.Havermann@...; si-list@...
> Subject: [SI-LIST] Re: AW: Multi-Giga-Hertz Rigid-Flex Feasibility
> Date: Wed, 2 Dec 2009 10:23:29 -0800
> 
> Itzhak
> 
> Think about what determines Zo. It is the relationship between the signal
> path and its return path(s). If the signal path and return path do not
> change from rigid to flex to rigid then Zo does no change. If you add extra
> metal or insulation at the boundaries that effect the fields then you will
> get changes in Zo. It all depends on how you design your system.
(Continue reading)

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Gmane