Delay compensation and tracking for all-digital RF-transmitter models

Abstract

All-digital radio frequency transmitters (DRFTx) offer many potential benefits for future RF applications. However, their design requires the use of nonlinear models that can describe the memory induced, nonlinear behavior of these circuits. The model needs to cover a huge bandwidth and incorporate the behavior of the digital-analog-converter within the DRFTx. Gaining highly synchronous recordings from such a mixed signal RF circuit, which is required for modeling and verification, is a demanding task. This paper demonstrates how a correlative multistage synchronization can be used to synchronize such measurements. It also demonstrates how sensitive the uncompensated normalized mean square error (NMSE) is to timing offsets when comparing signal from different recordings and how time-frequency methods can be used to gain more robust error measures through delay tracking and compensation.