Design investigation of a wideband backward-wave directional coupler using neural network

This paper presents a study of wideband backward-wave directional coupler. In designing the proposed coupler, neural network technique is employed for optimization procedure. Composite Right Left Handed (CRLH) behavior of the coupler in conjunction with applied Defected Ground Structure (DGS) and also, connections between the coupled lines, leads to obtain high coupling coefficient in a wide bandwidth. The introduced coupler is numerically investigated and a prototype is made and tested. Measured results agree well with those obtained by simulation.