Compact Butler matrix using composite right/left handed transmission line

A novel composite right/left handed transmission line (CRLH TL) is proposed, for the first time using the Wunderlich-shaped dentiform capacitor and meandered-line short-circuited stub inductor (SSI). The CRLH TL features a larger value of CL and in turn a lower resonance relative to the previous one employing an interdigital capacitor and an SSI. The unique feature of the CRLH TL is applied to engineer a compact Butler matrix. Consistent numerical and measurement results of the matrix prototype centred at 1.8 GHz are shown. The Butler matrix with comparable performance is only 45 of the area that a conventional matrix occupies and can easily facilitate a planar integrated circuit.