Fractional Delay Alignment for Wideband Digital Predistortion

The patent implements a dynamic delay estimation approach where the system continuously adapts the delay parameter based on feedback signal correlation. The delay estimator dynamically adjusts the delay value to maximize the correlation between the feedback signal and the expected signal, enabling precise alignment even when carriers are widely frequency spaced. This dynamic adaptation resolves the contradiction by making the delay estimation process responsive to changing signal conditions rather than relying on fixed conventional methods.

The patent employs a feedback-based delay estimation mechanism where the delay estimator uses the correlated feedback signal to iteratively refine the delay alignment. The system compares the feedback signal with the transmitted signal and adjusts the delay parameter to maximize correlation. This feedback loop enables high precision delay alignment while maintaining manageable complexity through efficient correlation-based optimization rather than exhaustive search methods.

The patent applies preliminary action by pre-computing and storing correlation values at different delay offsets in a lookup table before operation. During real-time operation, the delay estimator simply queries this pre-computed table to find the optimal delay alignment, avoiding complex real-time correlation calculations. This approach achieves high signal alignment accuracy while maintaining system simplicity through offline preparation of correlation data.

The patent replaces complex mechanical or hardware-based delay control mechanisms with digital signal processing methods. Instead of using variable delay lines or hardware tuners in the feedback path, the system uses digital correlation-based delay estimation and fractional delay filters implemented in software/FPGA. This substitution achieves precise delay control while reducing hardware complexity and improving adaptability.