High-Efficiency, Ka-Band Solid-State Power Amplifier Utilizing GaN Technology

QuinStar Technology proposes to develop a high-efficiency, solid-state power amplifier (SSPA), operating at Ka-band frequencies, for high data rate, long range space communications. Specifically, we propose to develop a 20 W power amplifier with an associated PAE of 60% operating over the 31.5 to 34 GHz band. This will be accomplished by employing two major innovations. First, we plan to utilize wide bandgap Gallium Nitride (GaN) on Silicon Carbide (SiC) device technology to fabricate our high-efficiency MMICs. Operating at a higher voltage (typically 20-28 V versus 4-5 V for GaAs), GaN permits power densities which are 5-10 times higher than GaAs or InP. In addition to a higher power density, high-voltage operation results in lower matching and cell combining losses, making these MMICs more efficient. Secondly, we are proposing to utilize a switching mode of operation (Class-F) to enhance the device efficiency. While this method has demonstrated PAE levels of >80% at 2 GHz, these levels have not yet been realized at Ka-band frequencies. Computer simulations, contained in this proposal, indicate that by using this method, device PAE levels ranging up to 73% are possible at 32 GHz. Furthermore, this was verified by benchmark data from at least one GaN foundry showing a device, operating in Class-F, with a PAE of 80% at 3 GHz. Finally, simulations at Ka-band frequencies indicate that even with circuit losses, we can still maintain the efficiency (PAE) at or very close to 60%. The layout and performance of a multistage MMIC is included in this proposal, together with the overall SSPA configuration and performance.