Two-layer butterfly-shaped microstrip 4×4 Butler matrix for ultra-wideband beam-forming applications

This paper proposes a compact and inexpensive two-layer ultra-wideband (UWB) butterfly-shaped microstrip 4×4 Butler matrix beam-forming network. Measured and simulated results of the proposed matrix configuration confirm UWB performances for transmission magnitudes and phases with good return losses and isolation characteristics. 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.