An improved planar balun design for wireless microwave and RF applications

The high frequency balun network is a vital component in the realization of certain RF and microwave system topologies, especially in wireless communication system architectures. This paper describes an improved compact coupled microstrip line design for use primarily in the exploding portable wireless market. The two main advantages of the design are that its size is a fraction of the standard λ/4 coupled line design, and that it exhibits an extremely tight coupling of ~4 dB. The design technique is illustrated by presentation of computed and measured data on a ~0.9 GHz realization developed for wireless applications