A size-reduced CPW balun using a "X"-crossing structure

A novel sized-reduced CPW balun is proposed. It has an 180° phase inverting structure, which is a "X"-crossing between signal line and ground planes of CPW transmission line. A 3λ/4 CPW transmission line can be reduced to λ/4 in physical length while the electrical length is preserved. One of previous Wilkinson baluns shown (Lim et al., 2004) has a long 3λ/4 transmission section to form the Wilkinson structure having out of phase performance between output ports. The large Wilkinson balun is quite reduced by adopting the CPW phase inverting structure. Measured results show that the size-reduced CPW Wilkinson balun has better performances than the original Wilkinson balun.