Realization of High-Order S-Plane Bandpass Marchand Balun with No Lumped Elements

Abstract

A high-order wideband planar balun is proposed in this paper. The balun is exactly synthesized using Richards' Theorem. Applying the S-plane bandpass other than high-pass prototype can shrink the circuit size and improve the stopband performance. Using the step impedance transformation, the proposed balun can be easily implemented in planar structure without lumped elements to fit the user-defined specification. A high-order balun with bandwidth about 100% and reflection level of -20dB is designed as an example. The simulation and measurement results are matched well.