Monolithic three-stage 6–18GHz high power amplifier with distributed interstage in GaN technology

This paper reports on a three-stage broadband amplifier architecture suitable for wide bandwidth applications such as electronic warfare systems. The proposed topology comprises a distributed active power splitter to function as an interstage driver amplifier, whereas the pre-driver and power amplifier stages are reactively-matched. As a result, purely resistive interstage impedances are obtained and therefore the proposed architecture allows wider bandwidth operation as compared to the conventional reactively-matched multistage topology. A 6GHz to 18GHz three-stage high gain and high power amplifier MMIC is designed and realized in order to demonstrate the capabilities of the concept. The MMIC is based on a 0.25μm gate length AlGaN/GaN HEMT microstrip transmission line technology. It shows a measured small-signal gain of (25 ± 3)over the entire frequency range. The saturated output power is higher than 25W at the center frequency in pulsed operation.