Performance Optimization of an E-Band Communication Link using Open-Loop Predistortion

This paper demonstrates the performance optimization of a millimeter wave transmit frontend operating in E-band, using a digital predistortion method with an open-loop architecture. The Tx system contains a cascaded amplifier module chain, realized in different technologies, to achieve modulated signals with record output powers of 2 W. An open-loop DPD system with an indirect learning architecture and a Volterra series based nonlinear model has been selected to investigate the improvements in the frequency range from 71 to 76 GHz with bandwidths up to 800 MHz. The transmitter's linearity, signal quality, and spectral regrowth were measured with a modulated signal containing different power levels. Three channels with different sizes, located in the proposed channel arrangements by the ITU, were chosen to exemplarily test the performance of the DPD. An implemented DPD algorithm could demonstrate improvements in signal quality and adjacent channel power.