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

Future military satellite communications systems will have higher signal capacities by employing complex modulation schemes in channels that are closely spaced in frequency (21MHz). Nonlinearities in the terminal electronics, particularly power amplifiers, cause spectral regrowth, where by extraneous power from one channel interferes with signal from adjacent channels. As a result, communication data rates are adversely affected by the adjacent channel interference.Our proposed concept is a self-contained MMIC power amplifier that incorporates a shunt cold-mode MHEMT at the input to the power amplifier. The shunt cold-mode provides the necessary predistortion to linearize the power amplifier. Both circuits will be laid out on a single chip. With the use of MHEMTs for both circuits, a single MMIC processing can be used for the final amplifier.  Based on a preliminary analysis, the ultra-linear Q-Band amplifier has an Adjacent Power ratio of < -40dB for a  typical quadrature phase shift modulation scheme (QPSK). The output power is greater than 1watt, a gain greater than 15dB, and a power added efficiency(PAE) of that exceeds 30%. BENEFIT: The successful development of the ultra-linear ampliifer has many benefits for both the military and commercial marketplace. With the communication frequencies and channels being saturated, the need exists to increase the data rate within the existing frequencies. Interference between channels prevent increasing the capacity due to nonlinearities in the system. A more linear power amplifier would allow the number of channels to be increased and thereby increasing the data rates. This would allow military systems to easily increase their data rates as well as the commercial satellite communication market.