Design of a Ku-band coplanar waveguide 90/spl deg/ branchline coupler

We apply our 3-D full wave coplanar waveguide (CPW) simulator to design a CPW 3 dB 90/spl deg/branchline coupler (BLC) for use in the Ku-band (i.e. 11.7-12.2 GHz). The substrate used for the design is alumina (/spl epsiv//sub r/=9.98). Two distinct designs of the same coupler are provided. The first is a standard sized, straight arm, BLC (SSBLC). Each arm of the SSBLC is approximately /spl lambda//4 at the design centre frequency of 11.95 GHz. The second design is a reduced sized BLC (RSBLC) which replaces the straight BLC arms with meandered arms. The area of this RSBLC is approximately 40% of the area of the SSBLC. In both designs, the T-junction compensation is carried out using optimization. Experimental and numerical results are provided for the SSBLC design. Numerical results are also given for the RSBLC design.