wimax turbo

does anyone know how to use poly2trellis to simulate the duobinary CTC encoder?
if it is binary:we can use poly2trellis(4,15,13)
but I don't Know when it is duobinary(or double binary)?
help me !!!!!

if you visit the following site, you should helped:
www.mathworks.com/matlabcentral/fileexchange