[SI-LIST] R: high speed PCB design

HI Sunilm
I think that you could control better impedance in some ways:

1) ask to your PCB maker to give you the more parameters about =
construction
he knows, i.e. dielectric constance AFTER the PCB has been packaged and
pressed ...; than perform a more accurate simulation.
2) ask to your PCB maker to guarantee impedance (sure it'll cost a bit =
more)
3) if you choose a thicker stackup, with more fr4 between traces and
reference plane this'll reflect in making wider traces in order to =
obtain
the same impedance. In this way you'll obtain a line with more precise
characteristics, BUT it has some drowback, one is more difficulties =
during
the phase of layout!
4) use balanced vias

The question about noise is really general but I think that, in order =
to
reduce noise on boards is important  to guarantee optimum GND planes
(without moats and bridges ...) NEAR power planes, choose a good =
network of
capacitors in order to filter the components, not to use buffers at =
100% of
theirs capabilities and so on... (as the Grandmother uses to say)

I think that at 400MHZ (and 800, 1200, ...) your filtering capacitors =
act as
inductors. The intrinsic capacitance of your PCB, if you placed GND =
planes
close to power planes, will work well.

Hope this'll help you - pardon my terrible English
        Giovanni

-----Messaggio originale-----
Da: sunil Morajkar [mailto:msunil@xxxxxxxxxxxxxxxx]
Inviato: luned=EC 24 novembre 2003 10.58
A: si-list@xxxxxxxxxxxxx
Oggetto: [SI-LIST] high speed PCB design




        Hello All,


                  I am in phase of designing the 1394a high speed board =
with
max operating frequency as 400mhz.

        In my last revision of the board , there was a issue of noise &
impedance matching.

        how one can control impedance ?

        how can i reduce the noise on the overall board. Noise level @
400mhz is around 70-80 mv.

        how one can select filtering circuit. ?

        please Suggest
        regds
        Sunilm



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