Damien,

You should try and match the DDS output imedance as closely as possible.
It's not intuitive, but this will give the lowest losses, and will ensure
that the tracks do not radiate RF energy due to mismatches. If you are
taking RF signals a long way, also consider the use of solid coax, with the
outer soldered to ground every so often, as this will give the best match
and lowest radiation losses.

Good luck....Mike.

----- Original Message -----
From: "Damien Cahill" <damiencahill@AUSTARNET.COM.AU>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Friday, February 20, 2004 12:55 AM
Subject: [EE]: RF Transmission Line PCB Routing


> Hi List,
>
> I have a reasonably simple question.  I am currently routing an RF PCB
which
> uses a 1GHz DDS synthesiser.  The RF signals on the board are up to 400MHz
> in frequency and obviously I must consider the impedance of any copper
> tracks I lay.  What I am unsure of though is what impedance should I be
> aiming for with these tracks.  Should it match the DDS outputs which are
all
> 50ohm or should it be as low impedance as possible to reduce resistive
> losses.  I eagerly await the lists omnipotent response.
>
> Cheers,
> Damien Cahill
>
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