Design Methodology for Automatically Designed, Integrated Marchand Baluns with Low Insertion Loss at Lowest Phase Imbalance

In this paper, a design methodology for automated Marchand balun design is shown. The goal of this methodology is a balun providing the lowest insertion loss at the smallest phase imbalance. The design process is realized by using the EM simulator Sonnet, Matlab and the Matlab-Sonnet interface. The implemented algorithm is using a simulation-based characterization of the semiconductor process and a mathematical model of the balun. For this characterization an even and odd mode analysis is carried out. Hence, the electrical and dielectric properties, such as the characteristic impedance and the effective permittivity, are determined. This enables a precise “first guess simulation” of the balun, minimizing the required number of optimization iterations. As an example, a D-band Marchand balun is presented here, that was designed with this methodology. The measurement results show a phase imbalance less than 7° over the entire D-band and an insertion loss smaller than 1.75dB. To the best of the author's knowledge, there was no software tool that enables automated development for Marchand baluns yet, although it is widely used.