Hi, I am preparing a measurement on a chip, which has a differencial output. I want to use the network analyzer with a single input. I need a balun, don't I? But I don't know how to select a suitable balun. Which kind of configuration of balun should I choose if  I want to convert the differencial outpput signal to a single input signal. Could anybody introduce any experience about balun to me?

See the followings.
http://www.krytar.com/
http://www.designers-guide.org/Forum/YaBB.pl?num=1213173490/3#3
http://www.designers-guide.org/Forum/YaBB.pl?num=1233236788/1#1
http://www.designers-guide.org/Forum/YaBB.pl?num=1255331741/4#4