Need of Baluns in  Radio Frequency Integrated Circuit?
Here is the introductory paragraph from the wikipedia article on baluns, which covers the basics. http://en.wikipedia.org/wiki/Balun


  A balun ( /ˈbælʌn/) is an electrical device that converts between a balanced signal (two signals working against each other where ground is irrelevant) and an unbalanced signal (a single signal working against ground or pseudo-ground). A balun can take many forms and may include devices that also transform impedances but need not do so. Transformer baluns can also be used to connect lines of differing impedance. The origin of the word balun is bal(ance) + un(balance).