Abstract
A design of compact and inexpensive two-layer ultra-wideband (UWB) butler matrix beam-forming network employing trapezoidal-shaped microstrip-slot technique is presented in this paper. The proposed design uses multi-layer technology that allows having compact size and broad bandwidth. The proposed butler matrix configuration consists of four couplers and two phase shifters without using crossovers. Both couplers and phase shifters use trapezoidal-shaped broadside coupled patches and a rectangular slot created in a common ground plane of two Rogers duroid RT5880 dielectric substrates. The simulations and experimental results show a good performance in terms of transmission magnitudes and phases with good return losses and isolation characteristics across the entire UWB frequency range. To demonstrate the functionality of the designed butler matrix, four identical tapered slot antenna (TSA) elements are connected to four output ports of the butler matrix and the radiation pattern characteristics are simulated, presented and discussed.