Design of a planar microstrip balun at S-band

An innovation for the Marchand balun model is presented. The structure of the designed planar microstrip matching circuit is fairly simple, practical and easily fabricated without requiring complex multiple metal or dielectric layers. Moreover, the designed balun performs well. The measured phase difference between the balance ports was within 180° ±3° from 1.9 to 3.9 GHz and the magnitudes of S ₂₁ and S ₃₁ are fairly close to -3 dB from 2.4 to 3.2 GHz. The design and simulation of the planar microstrip bahm show good agreement with the measured results.