A GaN MMIC Stacked Doherty Power Amplifier For Space Applications

This paper presents the design and the experimental results of a Monolithic Microwave Integrated Circuit Power Amplifier in which the transistor-stacking approach is used within the Doherty architecture in order to maximize the achievable performance. In particular, the Stacked cell is realized by dividing the common source transistor into two smaller devices leading to a very compact and symmetric structure, whereas the Doherty approach is exploited to fulfill high efficiency at back-off. The chip has been manufactured on a 100 nm gate length GaN high electron mobility technology, growth on Silicon substrate, and targeting the satellite downlink Ka-band. The two-stage amplifier was designed to meet the power requirements while satisfying the thermal constraints for use in space applications. In the frequency range from 17.3 GHz to 20.3 GHz, measurement results have shown a linear gain of about 25 dB with a peak power of 38dBm and a power-added efficiency larger than 35%.