A Broadband Folded Marchand Balun Integrated with Tunable Phase-Shifting Function

A balun structure with phase-shifting function is introduced in this paper. It integrates a loaded line phase shifter on a folded Marchand balun, which maintains a very compact size, hybrid functions, and low fabrication cost. Operating mechanism of this phase-shifting balun is explained through circuit theory. As an example, a phase-shifting balun that operates in the frequency range of 0.8-2 GHz is designed, which achieves a maximum phase shift of 168°. For practical verification, a back-to-back structure is fabricated, and the measurement results are in a good agreement with the full-wave ones. To demonstrate potential applications of this structure, a phased array with two broadband dipole elements is designed. The resulting array can scan up to ±60° in the frequency range of 1-1.8 GHz.