94 GHz power amplifier MMIC development in state of the art MHEMT and AlGaN/GaN technology

Solid-state power amplifiers at W-band (75 - 110 GHz) are attractive for the generation of local-oscillator (LO) power for super-heterodyne receivers operating at sub-millimetre wave frequencies, as needed for example in future space instruments for Earth observation. Apart from space applications there is a growing interest for these devices in for example millimetre wave imaging, communication and radar systems. A power amplifier with an output power of the order of 1W, followed by a chain of frequency multipliers, can provide sufficient LO power for a Schottky receiver up to terahertz frequencies. Gallium-Nitride (GaN) technology is especially interesting, and has shown power levels that exceed those achievable with other technologies, like Indium-Phosphide (InP) and Gallium-Arsenide (GaAs). Watt-level output power at W-band has been demonstrated by advanced GaN technologies of HRL, Raytheon, and Fujitsu [1-3].
This paper will present the technology, design, and demonstration of 94 GHz power amplifier Monolithic Microwave Integrated Circuits (MMICs) in two different technologies: a state-of-the-art and proven GaAs MHEMT technology and a newly developed 0.1 μm AlGaN/GaN technology on SiC substrate. Because of the lower power density of the MHEMT technology a scenario with 4 MHEMT power amplifiers in parallel will be compared to a single GaN power amplifier MMIC. All MMICs will be mounted in W-band waveguide modules. For the MHEMT-based power amplifier module a 1-to-4 power waveguide splitter and combiner has been designed