Analysis of Archimedean Spiral Antenna Fed by Hecken and Exponential Microstrip Baluns

This paper presents a performance analysis of an ultra-wideband planar two-arm Archimedean spiral antenna fed by tapered printed baluns with Hecken and exponential impedance profiles. Practical baluns often exhibit amplitude and phase unbalances that cause disturbances in the antenna responses. The analysis described here addresses the dependence of antenna's performance on the balun profile, which plays an important role in the spiral design, since most of its applications require stable characteristics over the entire operating frequency band. The proposed baluns and antenna designs were simulated and optimized using ANSYS HFSS. All balun's configurations have shown a reflection coefficient better than -10 dB over the 1-18 GHz frequency band.