A new Marchand balun with harmonic suppression

For the first time, a new Marchand balun with harmonic suppression is proposed using a patterned ground plane structure. It is shown that the patterned ground plane structure is able to yield equal even and odd mode phase velocities and larger even/odd mode impedance ratio. Therefore the proposed structure is not only used to provide a significant harmonic band rejection, but at the same time enhances the coupling mechanism. For demonstration, a Marchand balun based on patterned ground plane structure is designed to operate at 1.4 GHz. Experimental results shows that a high third harmonic suppression level and relaxed fabrication tolerance have been achieved, while maintaining good balun performance at the fundamental frequency.