Maker Pro
Maker Pro

R-L-C structures on PCB

M

Melanie Nasic

Jan 1, 1970
0
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 I'm 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
 
C

Charlie Edmondson

Jan 1, 1970
0
Melanie said:
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 I'm 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
 
L

Leo Baumann

Jan 1, 1970
0
Hello Melanie,

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

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

regards

baumann engineering
 
M

Marte Schwarz

Jan 1, 1970
0
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
 
J

Joerg

Jan 1, 1970
0
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 I'm 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
 
L

linnix

Jan 1, 1970
0
Melanie said:
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 I'm 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.
 
Q

qrk

Jan 1, 1970
0
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 I'm 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 don't know if this will
cover your needs.
http://www.hp.woodshot.com/
 
J

Joel Kolstad

Jan 1, 1970
0
These components must be designed
Pretty much all the "big boys" of RF design software do this: They contain a
frequency domain simulator that has some reasonably good models of
microstrips, spiral inductors, etc. and easily link up with a field solver for
when you need a more detailed answer. I.e., Agilent's ADS does this, as does
Eagleware Genesys, Sonnet, Ansoft's RF Designer, etc.

Since you're just starting out, I'd suggest you go over to Sonnet and download
a copy of Sonnet Lite for free (http://www.sonnetsoftware.com/products/lite/).
I believe they're the only one of the companies listed above that has ANY free
offerings. Agilent and Ansoft, however, will hook you up for next to nothing
if you're part of a Real University and either are or can get a professor to
contact the appropriate people. Eagleware isn't quite as generous in my
(limited) experience; I don't know about the others.

If you're buying any of these packages for "professional" usage they all come
in a dizzying number of different configurations and start with 4 digit price
tags that can rapidly creep up to 5.

One final note: Although all these RF simulators will let you do "PCB layout,"
they're really not optimized for the generic layout task. What most people do
is use the RF simulators to design just the, uh, critical RF portions and then
export the copper layers into a more conventional PCB package such as PADS,
Protel, etc. Most RF things these days hit a bunch of digital circuitry
sooner or latter, and you really don't want to use ADS to layout some 676 ball
FPGA with hundreds of digital I/O lines coming off of it. :)

---Joel Kolstad
 
J

John Larkin

Jan 1, 1970
0
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 I'm 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

Puff is an old, free (not sure if it's still free) program that lets
you simulate planar transmission-line-based filters

http://www.its.caltech.edu/~mmic/puff.html

And there's also Sonnet Lite, the free version of the Sonnet e-m
simulator.

A bit of googling should turn up the basics of planar
transmission-line-based filters.

John
 
M

Melanie Nasic

Jan 1, 1970
0
Hi Marte,

thanks for your response. Some questions still:
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.

How did you do this? I mean, if I calculated the needed capacitance, how
would I get the corresponding PCB layout for that?
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 wasn't understood well enough. later I modeled
the connector more precisely and did the Layout more exact in math.

Again, what was your approach to model the layout in maths? Sorry, if I bore
you but I never did it before and thus I have no experience on that topic.
For a seminar work at university I have to suggest a compensation network on
PCB for a certain case. I don't want any of you to do my work, I just want
to comprehend how to get there. :)

Bye Mel
 
M

Melanie Nasic

Jan 1, 1970
0
I thought about Mentor Hyperlynx since the university has some Montor
licenses but I am not quite sure if this tool is exactly what I need? Any
suggestions / experiences?

Bye Mel
 
J

John Larkin

Jan 1, 1970
0
I thought about Mentor Hyperlynx since the university has some Montor
licenses but I am not quite sure if this tool is exactly what I need? Any
suggestions / experiences?

Bye Mel

No, I can't afford Mentor products. They did buy out PADS, which we
use, and I'm wondering what they'll do with that.

John
 
J

Jim Thompson

Jan 1, 1970
0
No, I can't afford Mentor products. They did buy out PADS, which we
use, and I'm wondering what they'll do with that.

John

They'll give it the same treatment that Cadence gave PSpice ;-)

...Jim Thompson
 
J

John Larkin

Jan 1, 1970
0
They'll give it the same treatment that Cadence gave PSpice ;-)

...Jim Thompson

You mean the Autocad/GenericCad maneuver?

John
 
H

Helmut Sennewald

Jan 1, 1970
0
Melanie Nasic said:
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 I'm 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


Hello Melanie,

I am sure that nobody wants to make R with the PCB-Traces.
It may be Z(transmission line impedance) but never R.
L and C can be stubs for example or other odd shapes
along the "main" trace.

Please give a clear example(with numbers) what you have to design.
All the postings so far are pure speculations about your real task.
It's your turn to make the picture more clear.

Best regard,
Helmut
 
P

Paul Burridge

Jan 1, 1970
0
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.

Reg Edwards keeps some useful utilities for this kind of stuff on his
website. Check out this page and see if it's covered...

http://www.btinternet.com/~g4fgq.regp
 
P

Paul Burridge

Jan 1, 1970
0
I'm sure that isn't true.

It sounds totally impractical to me, at any rate, to try to make R
from copper cladding.
Anyway, I don't think the OP has thus far actually even told us the
frequency of interest!
 
H

Helmut Sennewald

Jan 1, 1970
0
Ken Smith said:
I'm sure that isn't true.

Hello Ken,

I am interested if there are other applications.
On what application do you think except current sensing?

Best regards,
Helmut
 
Top