To minimize reflections, match the synthesizer impedance.  Just a quick
comment about the board material.  Check the z-axis thermal characteristics
of your board shop's material.  If they're using FR-4, calculate max and min
impedances.  I ended up using a better material, but then, my application
was measuring impedance :-)

Regards,
Ed

-----Original Message-----
From: pic microcontroller discussion list
[mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Damien Cahill
Sent: Thursday, February 19, 2004 6:55 PM
To: PICLIST@MITVMA.MIT.EDU
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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