Low-Complexity Digital Predistortion For Reducing Power Amplifier Spurious Emissions in Spectrally-Agile Flexible Radio

Increasing the flexibility in spectrum access is a key to enhanced efficiency in radio spectrum utilization. Noncontiguous carrier aggregation (CA) is one enabling technology towards more flexible spectrum access, but can also lead to serious implementation challenges in terms of transmitter linearity. Especially when a single power amplifier (PA) is deployed for all carriers, serious intermodulation components will rise which can easily limit the maximum transmit power. In this paper, a low-complexity digital predistortion (DPD) solution is developed to reduce the most critical spurious components at the PA output, opposed to more classical full bandwidth linearization. The developed concept and associated parameter learning and optimization are particularly tailored towards mobile devices, building on limited narrowband feedback receiver with reduced instrumentation complexity and reduced-rate DPD processing. The developed DPD solution can handle PAs with substantial memory effects, and is verified with extensive simulation examples in various non-contiguous carrier aggregation scenarios and practical PA models with memory.