Low-loss compact butler matrix for wireless communications in underground mines

A new compact of 4times4 Butler matrix has been proposed. The circuit is compact with 80% of size reduction compared to the conventional structure. In the proposed design, Lange coupler and Lange crossover have been used as a key component to lead with significant size reduction and loss minimization. The design has the advantage of being compact while displaying good results. These features make the proposed Butler matrix suitable for underground mine communication.