Digital-RF linearizer for improved broadband multi-carrier power amplifiers

In both communications and radar, the system performance is limited by the linearity of the high power amplifiers in the transmitters. Nonlinear power amplifiers create distortion that limits the dynamic range and causes interference. Efforts to correct this problem decrease the amplifier efficiency while increasing the hardware complexity and cost. While it is the RF waveform that gets distorted, the conventional corrective measures (such as a compensating predistortion equalizer) are applied on the baseband signals instead due to speed limitation of traditional semiconductor electronics. Such baseband schemes are fundamentally constrained to partial correction of weak nonlinearity. It would be preferable to perform the corrections on the RF waveform directly for two major reasons: (1) near-perfect correction to even strong amplifier nonlinearity and (2) substantially simpler signal processing circuitry. This improved performance has been verified in detailed simulations. Only ultra-high speed superconducting electronics are fast enough to perform digital predistortion directly on the RF waveform to improve linearity and dynamic range to unprecedented levels. This technology will pave the way for future broadband, low-distortion, multi-carrier transmitters, utilizing cheaper, more efficient high power amplifiers. This will result in enhanced system performance as well as lower cost and operating expenses of radar and communication signal transmitters.