6-GHz-to-18-GHz AlGaN/GaN Cascaded Nonuniform Distributed Power Amplifier MMIC Using Load Modulation of Increased Series Gate Capacitance

A 6-GHz-to-18-GHz monolithic nonuniform distributed power amplifier has been designed using the load modulation of increased series gate capacitance. This amplifier was implemented using a 0.25-m AlGaN/GaN HEMT process on a SiC substrate. With theproposed load modulation, we enhanced the amplifier's simulated performance by 4.8dB in output power, and by 13.1% in power-added efficiency (PAE) at the upper limit of the bandwidth, compared with an amplifier with uniform gate coupling capacitors. Under the pulse-mode condition of a 100-s pulse period and a 10% duty cycle, the fabricated power amplifier showed a saturated output power of 39.5dBm (9W) to 40.4dBm (11W) with an associated PAE of 17% to 22%, and input/output return losses of more than 10dB within 6GHz to 18GHz.