wilkinson power divider

hi,
iam doing project on wilkinson power divider and going to fabricate it in microstrip.i have found out length and width of quarter wave transmission line.but to represent transmission line in circular form i need to know radius formula.i have searched for formula but couldnt find out the right one.

C = 2 x Pi x r

thanks for reply,hagster.can u tell me still more,how will get the circumference value?

The circumference = lambda/2 + "the gap between ports 2 and 3 allotted for placing the 2Z0 resistor"