General Compensation Method for a Marchand Balun With an Arbitrary Connecting Segment Between the Balance Ports

For a Marchand balun, the output imbalance due to the inevitable physical separation between the balance ports is a problem. In this paper, a general compensation method to cope with this imbalance issue is proposed with rigorous analysis and design formulas. The compensation relies on two intentionally shortened coupling sections and a pair of short-circuited transmission lines as the terminations. The proposed method is able to deal with a long connecting segment between the balance ports as long as the coupling sections are tight enough at the desired frequencies. The theory and formulation are first treated using transient analysis with multiple reflections/couplings between the networks. Design graphs are summarized and three examples are fabricated, validated, and discussed to demonstrate the design flexibility the proposed method provides.