Next Generation Ultra-linear Super High Frequency/Extremely High Frequency (SHF/EHF) Solid State Power Amplifiers

We propose to develop an ultra-linear, 1-watt solid-state power amplifier (SSPA) operating at 44 GHz with a power-added efficiency (PAE) of 40%. A cornerstone of our approach is the development of a power MMIC with an efficiency of greater than 50%. This will be achieved by employing state-of-the-art wide bandgap GaN (Gallium Nitride) devices in conjunction with two circuit innovations. First, we are using switching-mode amplifier concepts to realize these efficiency levels. This has never been done before at this frequency. Secondly, we are employing a push-pull amplifier configuration for further improvements in efficiency and harmonic content. Using this combination, computer simulations indicate that drain efficiencies of 70 percent are possible. Finally, we are utilizing Envelope Tracking (ET) or possibly Pulsed Load Modulation (PLM) to linearize this switching-mode amplifier. This also has never been attempted before at this frequency. Simulations described in this proposal indicate that with this innovative approach, we can simultaneously achieve both the linearity and efficiency goals of this program. In fact, simulations indicate that with an output power of 1 watt, we can achieve PAE levels of 40% or more, while maintaining an adjacent channel power ratio (ACPR) of better than -40 dB. BENEFIT:   Future MILSATCOM terminals require linear, high-efficiency power amplifiers for ground terminals. Linearity is required in order to prevent spectral regrowth, i.e. extraneous power from one channel interfering with signals in adjacent channels, and high efficiency is required to minimize both power consumption and self-heating, which in turn causes thermal stress. Currently available Q-band power amplifiers simply cannot simultaneously satisfy these linearity and efficiency requirements. Employing innovative switching amplifier concepts, our approach addresses this need. Applications for linear, high-efficiency amplifier technology abound for agencies other than the Air Force, ranging from SATCOM applications for the Army in the 29.5 to 31 GHz band to radar applications for all military services in the radar bands (33 to 38 GHz). For radar, high efficiency is particularly important for airborne applications such as UAVs and fire control radars where the prime power is limited.