Novel ultra-wideband Butler matrix for wireless underground mines

In this contribution, a design of a new ultra-wideband multilayer beamforming network based on a multilayer 4X4 Butler matrix is described. This matrix is based on UWB CPW directional coupler and UWB transitions. In fact, the CPW technology has been adopted due to several attractive features: mainly, absence of costly and inductive via holes, ease of making shunt and series connections, ease of controlling the characteristics of CPW lines by changing the slot and strip widths, and ability to use at mm-waves applications. It is advantageously used to offer a very wide bandwidth and to avoid using any crossing lines. Simulation results including return loss, insertion loss are presented and discussed.