Balance-Compensated Trans-Directional Coupled-Line Based Planar Balun with Connecting Lines of Arbitrary Impedance

This paper presents a novel method for the balance compensation of trans-directional coupled line (TRD-CL) based planar balun with connecting lines. The proposed compensation technique together with the design equations allow for achieving an arbitrary impedance of the inserted connecting line. To demonstrate the proposed theory, comparisons are made with the uncompensated TRD-CL based balun. Finally, a 0.8-GHz TRD-CL based balun with a connecting line of 10° electrical length and 75-Ω characteristic impedance is designed and fabricated. The measured results approve the effectiveness of the proposed method.