Fully-digital blind compensation of non-linear distortions in wideband receivers

Digital post-distortion is becoming an increasingly attractive solution to compensate for the non-linearities of RF receivers implemented in deep submicron CMOS technologies. A very promising technique which provides flexibility and robustness is the frequency spreading based digital post-distortion. This paper focuses on the analysis of this approach for wideband receivers and its main limitations, such as the anti-alias filter (AAF) impact. As a matter of fact, distortions filtered by the AAF can degrade the correction performance. To overcome this problem, a novel solution based on mimicking the AAF frequency response in the digital domain is proposed. Aspects regarding the estimation and the algorithm convergence are also studied: the noise effect and the choice of the free frequency band. Furthermore, two other techniques are developed to improve the modeling and the correction of the memory effect using, respectively, a bank of filters and two-step architecture. The proposed techniques are demonstrated by simulations and measurements on a multi-channel receiver suited for DVB-T applications. The receiver is based on a 1-GHz bandwidth RF front-end followed by a 2.7-GHz 13-bit analog-to-digital converter.