Discrete-Time Models Resulting From Dynamic Continuous-Time Perturbations In Phase-Amplitude Modulation-Demodulation Schemes

TL;DR

This paper characterizes discrete-time systems derived from continuous-time nonlinear transformations in phase-amplitude modulation schemes, proposing a new structure for digital compensation of analog nonlinearities with simulation validation.

Contribution

It provides a complete analytical characterization of such systems as a combination of a DT Volterra series and an LTI system, introducing a novel approach for digital nonlinear distortion compensation.

Findings

Effective nonlinear distortion compensation demonstrated in MATLAB simulations.

New analytical structure improves upon standard Volterra series methods.

Potential for enhanced digital correction in communication systems.

Abstract

We consider discrete-time (DT) systems S in which a DT input is first tranformed to a continuous-time (CT) format by phase-amplitude modulation, then modified by a non-linear CT dynamical transformation F, and finally converted back to DT output using an ideal de-modulation scheme. Assuming that F belongs to a special class of CT Volterra series models with fixed degree and memory depth, we provide a complete characterization of S as a series connection of a DT Volterra series model of fixed degree and memory depth, and an LTI system with special properties. The result suggests a new, non-obvious, analytically motivated structure of digital compensation of analog nonlinear distortions (for example, those caused by power amplifiers) in digital communication systems. Results from a MATLAB simulation are used to demonstrate effectiveness of the new compensation scheme, as compared to the standard Volterra series approach.