Wideband 4 × 4 Butler Matrix Based Substrate Integrated Coaxial Line for Millimeter-Wave Applications

A wideband 4×4 Butler matrix based substrate Integrated coaxial line (SICL) at 60 GHz is presented in this paper. The SICL technology is designed for low loss and integration. The defective ground structure coupler based on is improved to achieve wide band performance. The symmetrical structure Butler matrix has been designed and analyzed to achieved wide bandwidth and compact size. The −10dB bandwidth of proposed Butler matrix is 11GHz (56–67 GHz), and the insertion loss is ±1 dB. The phase difference is ±45° and ± 135°, phase error is ±7°.