A 12-36 GHz MMIC 3dB Coplanar Waveguide Directional Coupler

For the first time, a multilayer coplanar waveguide (CPW) coupled-line 3dB directional coupler has been realised, by using two metal layers on an MMIC substrate. In the frequency range 12-36 GHz, the coupler has an equal power imbalance of less than 1 dB. The coupler design incorporates both broadside and edge coupling. The MMIC is fabricated on a total chip size of 1.75mm × 0.74mm including four sets of wafer prober bondpads. This novel circuit configuration significantly improves the coupling performance and increases the bandwidth over other previously fabricated CPW branch-line couplers.