Sub-Band Digital Predistortion for Noncontiguous Carriers: Implementation and Testing
Tarver, Chance A
Master of Science
To facilitate increasing data-rate demands and spectrum scarcity, non-contiguous transmission schemes are becoming more popular. However the non-contiguous carriers of such schemes intermodulate due to the nonlinear nature of power amplifiers (PAs). This may cause emissions which interfere with nearby channels or with one's own receiver in a frequency division duplexing transceiver. We implement a low-complexity, sub-band, block-adaptive, digital predistortion (DPD) solution that corrects the distortion in a real PA. Using WARPLab we correct up to ninth-order nonlinearities, and using a real-time FPGA design we correct up to third-order nonlinearities. This is done by targeting the most problematic spurious distortion components at the PA output and performing least mean squares training to adapt an inverse spur to inject. This sub-band method allows for reduced processing complexity over other full-band predistortion solutions. Using these techniques, we are able to suppress spurious emissions in WARP by over 20 dB.