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R-L-C structures on PCB


Autor: "Melanie Nasic" (2005-12-20 15:30:29)

Hi,

recently I was assigned with the job to design a Printed Circuit Board (PCB)
which does a kind of analog signal formatting through on-board designed
capacitances, inductances and resistances. These components must be designed
not as discrete components (SMD, etc.) but deliberately as stray
capacitances in the form of specially layouted transmission line segments
and 3D arrangements. The material of the PCB is predefined to be FR4.
Surely I can design the circuit with tools like PSpice etc. but when it
comes to design the calculated R, L, C values on the PCB Im out of luck
with my tools. So my question is: Is there a tool (Mentor?) which contains
both circuit simulation AND PCB layout where I can design my defined
capacitances, inductances and resistances in the form of specially routed
transmission lines? What would be the best way to perform that task, anyway?
In my opinion it must be an iterative process. Has anyone experience in this
particular application field? Any help, suggestions and examples (maybe)
would be appreciated.

Many thanks in advance and best regards,

Melanie

Autor: Charlie Edmondson (2005-12-20 08:35:18)

Melanie Nasic wrote:
> Hi,
>
> recently I was assigned with the job to design a Printed Circuit Board (PCB)
> which does a kind of analog signal formatting through on-board designed
> capacitances, inductances and resistances. These components must be designed
> not as discrete components (SMD, etc.) but deliberately as stray
> capacitances in the form of specially layouted transmission line segments
> and 3D arrangements. The material of the PCB is predefined to be FR4.
> Surely I can design the circuit with tools like PSpice etc. but when it
> comes to design the calculated R, L, C values on the PCB Im out of luck
> with my tools. So my question is: Is there a tool (Mentor?) which contains
> both circuit simulation AND PCB layout where I can design my defined
> capacitances, inductances and resistances in the form of specially routed
> transmission lines? What would be the best way to perform that task, anyway?
> In my opinion it must be an iterative process. Has anyone experience in this
> particular application field? Any help, suggestions and examples (maybe)
> would be appreciated.
>
> Many thanks in advance and best regards,
>
> Melanie
>
>
>
>
Melanie,
I am assuming that you are dealing with microwave frequencies, right?
If so, what you need is an RF design tool, not just a basic analog
simulator. For my money, take a look at Microwave Office
(www.mwoffice.com) and get the free demo for a month. It is a lot more
intuitive and usable than many more expensive packages, and a few
friends of mine work there!

Charlie

Autor: Charlie Edmondson (2005-12-20 08:35:18)


Autor: Charlie Edmondson (2005-12-20 08:35:18)

Melanie Nasic wrote:
> Hi,
>
> recently I was assigned with the job to design a Printed Circuit Board (PCB)
> which does a kind of analog signal formatting through on-board designed
> capacitances, inductances and resistances. These components must be designed
> not as discrete components (SMD, etc.) but deliberately as stray
> capacitances in the form of specially layouted transmission line segments
> and 3D arrangements. The material of the PCB is predefined to be FR4.
> Surely I can design the circuit with tools like PSpice etc. but when it
> comes to design the calculated R, L, C values on the PCB Im out of luck
> with my tools. So my question is: Is there a tool (Mentor?) which contains
> both circuit simulation AND PCB layout where I can design my defined
> capacitances, inductances and resistances in the form of specially routed
> transmission lines? What would be the best way to perform that task, anyway?
> In my opinion it must be an iterative process. Has anyone experience in this
> particular application field? Any help, suggestions and examples (maybe)
> would be appreciated.
>
> Many thanks in advance and best regards,
>
> Melanie
>
>
>
>
Melanie,
I am assuming that you are dealing with microwave frequencies, right?
If so, what you need is an RF design tool, not just a basic analog
simulator. For my money, take a look at Microwave Office
(www.mwoffice.com) and get the free demo for a month. It is a lot more
intuitive and usable than many more expensive packages, and a few
friends of mine work there!

Charlie

Autor: "Leo Baumann" (2005-12-20 18:33:03)

Hello Melanie,

up to 2 or 3 GHz its possible to compute by hand. It works good if i use a
thickness of PCB of 1 mm.

Computation-formulas ive found in ISBN 3-723-6545-0, but only in german
language.

regards

baumann engineering

Autor: "Marte Schwarz" (2005-12-20 18:46:57)

Hi Melanie,
> recently I was assigned with the job to design a Printed Circuit Board
> (PCB) which does a kind of analog signal formatting through on-board
> designed capacitances, inductances and resistances. These components must
> be designed not as discrete components (SMD, etc.) but deliberately as
> stray capacitances in the form of specially layouted transmission line
> segments and 3D arrangements.

Many years ago I designed a few CAT V components with such printed
capacitors. I tested two types:

1. Two copper planes (SMD-pads from stack;-) on each side of the board (we
used only doublesided FR4 1.6 mm)
2. traces with vias in a matrix

---O O O O O
X X X X ...
---O O O O O
X X X X ...
O O O O O
.
.
.

> The material of the PCB is predefined to be FR4.

FR4 tends to include water, you know what this means in focus of tolerances?

> Is there a tool

May be you will find such a tool. I used the trial & error method. I defined
the parts in the PCB-Tool, calculated my values and measures the results.
then I used a knive and cut some parts of my cap and see what is changing.
To male the areas bigger, I used silver-colour. This worked fine, because
the connectors behaviour wasnt understood well enough. later I modeled the
connector more precisely and did the Layout more exact in math. Then I
draw my areas and inductive coupling components.

Marte

Autor: Joerg (2005-12-20 19:03:41)

Hello Melanie,

> Surely I can design the circuit with tools like PSpice etc. but when it
> comes to design the calculated R, L, C values on the PCB Im out of luck
> with my tools. So my question is: Is there a tool (Mentor?) which contains
> both circuit simulation AND PCB layout where I can design my defined
> capacitances, inductances and resistances in the form of specially routed
> transmission lines? ...


Just FWIW: R will be a problem here. For controlled resistor values you
would have to deposit carbon and laser trim. I have never done that on
FR4 but a lot on alumina (thick film hybrid).


> What would be the best way to perform that task, anyway?


I still do that by hand. Sometimes I even use the old slide rule calculator.

Regards, Joerg

http://www.analogconsultants.com

Autor: "linnix" (2005-12-20 11:13:02)

Melanie Nasic wrote:
> Hi,
>
> recently I was assigned with the job to design a Printed Circuit Board (PCB)
> which does a kind of analog signal formatting through on-board designed
> capacitances, inductances and resistances. These components must be designed
> not as discrete components (SMD, etc.) but deliberately as stray
> capacitances in the form of specially layouted transmission line segments
> and 3D arrangements. The material of the PCB is predefined to be FR4.
> Surely I can design the circuit with tools like PSpice etc. but when it
> comes to design the calculated R, L, C values on the PCB Im out of luck
> with my tools. So my question is: Is there a tool (Mentor?) which contains
> both circuit simulation AND PCB layout where I can design my defined
> capacitances, inductances and resistances in the form of specially routed
> transmission lines? What would be the best way to perform that task, anyway?
> In my opinion it must be an iterative process. Has anyone experience in this
> particular application field? Any help, suggestions and examples (maybe)
> would be appreciated.

Just wondering why? SMD R & C are so cheap and light weight. PCB area
is more expensive than the parts.

>
> Many thanks in advance and best regards,
>
> Melanie

Autor: "Leon" (2005-12-20 11:27:27)

Ansoft Designer might do what you want:

http://www.ansoft.com/ansoftdesignersv/capabilities.cfm

Leon

Autor: qrk (2005-12-21 02:15:04)

On Tue, 20 Dec 2005 15:30:29 +0100, "Melanie Nasic"
wrote:

>Hi,
>
>recently I was assigned with the job to design a Printed Circuit Board (PCB)
>which does a kind of analog signal formatting through on-board designed
>capacitances, inductances and resistances. These components must be designed
>not as discrete components (SMD, etc.) but deliberately as stray
>capacitances in the form of specially layouted transmission line segments
>and 3D arrangements. The material of the PCB is predefined to be FR4.
>Surely I can design the circuit with tools like PSpice etc. but when it
>comes to design the calculated R, L, C values on the PCB Im out of luck
>with my tools. So my question is: Is there a tool (Mentor?) which contains
>both circuit simulation AND PCB layout where I can design my defined
>capacitances, inductances and resistances in the form of specially routed
>transmission lines? What would be the best way to perform that task, anyway?
>In my opinion it must be an iterative process. Has anyone experience in this
>particular application field? Any help, suggestions and examples (maybe)
>would be appreciated.
>
>Many thanks in advance and best regards,
>
>Melanie

You might find something of interest on this site:
http://www.rfcascade.com/

HP (Agilent) has a suite for RF design. I dont know if this will
cover your needs.
http://www.hp.woodshot.com/

---
Mark

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