Spurious emissions reduction using multirate RF transmitter

This paper presents a transmitter architecture able to manage its spurious emissions over a wide bandwidth. The architecture is based on a multiple-path polar transmitter with digital power amplifiers (DPA). The paths work at different sample rates, thus producing spectral images located at different frequencies. This multirate implementation generates more spurious images than conventional architectures, but with reduced image power. This leads to a significant signal-to-spurious improvement over a wide bandwidth. Using the proposed architecture in a transmitter targeting LTE standard, the spurious emissions are reduced by 20dB over a frequency band from 800MHz to 3GHz, allowing to remove any analog filter stages to respect the standard specifications.