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https://designers-guide.org/forum/YaBB.pl Design >> Mixed-Signal Design >> PCBs with 50 Ohm Zo https://designers-guide.org/forum/YaBB.pl?num=1152202969 Message started by vivkr on Jul 6th, 2006, 9:22am |
Title: PCBs with 50 Ohm Zo Post by vivkr on Jul 6th, 2006, 9:22am Various signal sources etc. are designed for 50 Ohm termination. However, if the PCB traces have a different level of characteristic impedance (Zo), then there will be some reflection, as the signal passes through the short PCB trace to a 50 Ohm termination resistance on-board, or am I mistaken? Is it possible to get PCBs where Zo is 50 Ohm? How would one do that? Regards Vivek |
Title: Re: PCBs with 50 Ohm Zo Post by ACWWong on Jul 7th, 2006, 1:56am Yes you are correct, us RFIC designers are constantly getting PCBs made with differring characteristic impedance (often 50ohm, but not always necessary) tracks to match the impedance we are teminating in (and therefore not introduce rotation on a smith chart). We do this by altering the track width depending on the other parameters of the PCB (er, dielectric thickness, conductor dimension etc.) There are quite a few tools out there for designing microstrips (single track on top layer of PCB) or stripline (embedded track). As I don't design PCBs (i only check that the PCBs made meet my criteria) i often use the lmg program included in cadence. But i'm sure if you do a google for you'll find some good stuff or try http://www.circuitsage.com/tline.html hope this helps |
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