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.