W-band Airborne SATCOM Power Amplifier

ABSTRACT: We propose to develop a linear, solid-state power amplifier (SSPA), operating at 81 to 86 GHz, with an output power of 50 watts and a power-added efficiency (PAE) of 30%. This will be accomplished with a combination of SOA device technology and innovative circuit techniques. For the advanced device technology, we will team with a GaN MMIC foundry such a HRL, who is currently the industry leader in millimeter-wave GaN. To enhance the MMIC efficiency, we will implement two circuit innovations: 1) we will utilize a push-pull circuit configuration and 2) operate the MMIC devices in a switching mode (Class E). Neither of these techniques has been attempted before at these millimeter-wave frequencies. Simulations described in this proposal indicate that with these techniques, device drain efficiencies and PAEs of 60% and 38% respectively are possible. For the power combiner, we will implement a novel 2-tier combining system consisting of a 4-way H-tee combiner and a 16-way radial combiner. Finally, we will linearize this amplifier/combiner with an approach that employs both envelope tracking (ET) and digital pre-distortion (DPD). It is the goal of this work to develop a high-efficiency, 1-watt power MMIC operating at W-band, combine approximately 64 of these MMICs and linearize the resulting amplifier/combiner. BENEFIT: Future SATCOM terminals require linear, high-efficiency power amplifiers for transmitter up and down links at 81-86 GHz and 71-76 GHz respectively. Linearity is required in order to handle advanced spectrally efficient modulation schemes such as 32-QAM, and high-efficiency is required both for power consumption reasons and to reduce self heating. In addition to UAV uplink applications, this technology is directly applicable to the downlink at 71-76 GHz. Other applications include broadband RF cross-link communications in constellations, as well as airborne, including very high altitude long duration reconnaissance UAV, and terrestrial applications. Specific examples include the Joint Arial Layered Network (JALN) and AISR architectures. Further, this linear, high-efficiency SSPA can be readily applied to other military missions at adjacent frequencies such as V, E and upper W-band. QuinStar is currently producing the W-band transceiver for the AARGM missile program, and we have recently been awarded a contract to develop a W-band transceiver for HALS. This W-band SSPA technology is directly applicable to the transmitter for both programs, potentially reducing the cost and improving the performance.