Multilayer MMIC directional couplers using thin dielectric layers

Low-loss and small-sized MMIC directional couplers utilizing a multilayer structure composed of coupled thin-film transmission lines on a GaAs wafer surface are newly proposed. The fundamental characteristics of the couplers are discussed through calculations by numerical analysis, and the performance of the couplers and an application to reverse-phase hybrid ring are demonstrated. The results show that a 3 dB coupler can be designed within a 0.8 mm×0.8 mm area for a center frequency of 20 GHz. Coupling losses of 3.7 dB±0.2 dB over a 4-GHz bandwidth and isolation of better than 26 dB in the frequency range of 0-30 GHz are achieved. The proposed coupler configurations can be applied to the high-density and multifunction integration of MMIC´s