Threshold Analysis of Loop-Delay Estimation Using Correlation Functions for Double-Carrier Signals in Digital Predistortion Subsystem

For wideband configuration double carrier (WCDC) signals, a novel phenomenon is analyzed in this paper, i.e., when the data rate is lower than a threshold, the integer loop-delay estimation (ILDE) accuracy sharply declines when traditional time-delay estimation methods are used in a digital predistortion subsystem. Assisted by the equivalent bandwidth of a single-carrier signal, a proposed cross-correlation model for WCDC signals is built to analyze the low data-rate threshold in the ILDE. The relationship between a low data-rate threshold, carrier spacing, carrier bandwidths, and the power difference is analyzed. The proposed method is qualified to estimate the low data-rate threshold for the ILDE methods, including the state of the art. Experiments and simulations are presented to validate the proposed method using three typical communication signals.