60-GHz-band monolithic HEMT amplifiers using BCB thin film layers on GaAs substrates

A 60-GHz-band monolithic HEMT amplifier for which BCB thin film layers are adopted on GaAs substrate has been developed. The MMIC utilized a thin film microstrip line for the bias circuit and a coplanar waveguide for the RF c ircuit. The coplanar waveguide has the advantage of low loss, whereas the t hin film microstrip line has the advantage of small size. Two different typ es of transmission lines were selected to coexist in the monolithic amplifi er. As a result, the MMIC achieved high gain over a wider frequency range a t a small size. This MMIC had a gain of over 15 dB in a frequency bandwidth of 11 GHz. In particular, the high-frequency characteristics of the transm ission lines and the HEMTs were evaluated in detail for the conventional MM IC structure and the new MMIC structure. It was confirmed that this newly d eveloped MMIC using BCB thin film layers is attractive for millimeter-wave applications.