Design of three-dimensional balun based on LTCC technology

Balun, which means balanced-to-unbalanced transformer, is widely used in wireless communication systems. Balun can transform an unbalanced input signal into balanced output having equal magnitudes, 180° phase shift and vice-versa. As miniaturization is an inevitable trend of the development of today´s electronic devices, the study of the miniaturization of balun is of great significance. To realize the miniaturization of balun, a three-dimensional structure to design based on LTCC technology is used in our design. The frequency range of this balun is 1.1-2.5GHz, the amplitude unbalance is lower than 0.4dB, and the phase unbalance is smaller than 4 degree. The advantage of this design is of its small size and nice balance feature.