Broadband Monolithic GaN Balanced Amplifier Composed of Mixed Cascade-Tandem Directional Couplers and Cascode Stages

In this paper we present a broadband monolithic balanced amplifier reaching 30 dBm output power over a range from 5.7 GHz up to 35.1 GHz. To the best of our knowledge, such broad operational bandwidth has never been reported in literature for balanced topology. The amplifier is composed of broadband tandem-cascade directional couplers and amplifying blocks designed in cascode topology. It is worth noticing that for the first time the mixed tandem-cascade couplers have been integrated in monolithic process, in which only one metallization layer is available for transmission-line structures. The broadband balanced amplifier has been fabricated in high power GH15 gallium nitride (GaN) process offered by United Monolithic Semiconductors (UMS). The measured saturation output power and 1-dB compression point are equal to 30 dBm and 27.8 dBm, respectively.