Integration of ultra-wideband planar baluns into the eleven feed

Integration of decade bandwidth baluns into the Eleven feed faces many challenges. The authors present a compact, low-loss and low-cost integration solution to the ultra-wideband balun feeding network for the dual-polarised Eleven feed in this study. The design procedures are described in detail. Evaluation of the balun integration based on the BOR₁ (Body of Revolution type1) efficiency is introduced. Numerical simulations and measurements are presented for verifying the design.