Coaxial Marchand Balun - Design and Fabrication

This article presents the design of an ultra-wideband coaxial Marchand balun for the pyramidal sinuous antenna. The focus of the design is related to the fabrication process and the nuances involved. Closed-form equations are used to determine the element values of the balun, which are then tuned to provide a desired equi-ripple response. The designed balun, with a 300 Ω load termination, showcases a simulated return loss better than 10 dB from 1.1 - 4.8 GHz. The initial design produced amplitude and phase balance results within ±2.5 dB and 9.8°, respectively. Updated designs achieve an amplitude balance of ± 0.2 dB and a phase balance of 1.5°.