Re: asymmetric stripline

"John Larkin" <jjlarkin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> a écrit dans le
message de news: ie1tp3lnl4eiam1op6lkdlfcokfrobipp9@xxxxxxxxxx


Given a pc board like...

======================================= ground
^
12 mils
v
======= trace ----------

^
24 mils
v
======================================= ground

and assuming FR-4 and 1 oz copper, does anybody know what trace width
gives 50 ohms? My rough guess is 12 mils.

12mils gives 52ohm. 13mils gives a better 50.158ohm, see here under
simulation done with the (very good) GPL 2D impedance calculator software
from Kirby Goulet (cf http://sourceforge.net/projects/mdtlc/) :

Simulation pix map 400 pixels high by 1600 pixels wide.
1921024 bytes allocated for bmp.

INPUT PARAMETERS:

Layer Thick Er Specifications
Copper Plane Top 1.30 3.20 Open w=0.0 off=0.0
Laminate Layer 1 12.00 4.20 64.3% 3.2/6.0
Signal Layer 1 1.35 4.20 W=13.0 Etchback=0.00
Laminate Layer 2 24.00 4.20 64.3% 3.2/6.0
Copper Plane Bottom 1.30 3.20 Open w=0.0 off=0.0

Rdc_trace_1= 38.67 milliohms/in 20C
DC resistance by pixel count:
Rdc_trace_1= 37.291 milliohm/in.
C = 3.462 pF/in L = 8.709 nH/in.
Er = 4.200 Delay = 173.626 ps/in.
Zo = 50.158 Ohms

Friendly,
Robert Lacoste
www.alciom.com



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