Digital Predistortion Delay Estimation Using Polynomial Curve Fitting
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Solution Overview
Problem
In wireless telecommunications systems with widely spaced narrowband signals, noise causes peak variations leading to delay misalignment and system malfunction, necessitating accurate and robust delay alignment for high performance.
Innovation Solution
A digital predistortion (DPD) system comprising a DPD circuit, delay element, delay estimator, and DPD adapter, which uses a digital signal processor to generate predistortion coefficients by determining a peak value from a polynomial curve fit of cross-correlation function values greater than a threshold, ensuring accurate delay estimation and system alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional peak detection methods are used in noise environments, then the system is simple to implement, but delay misalignment occurs and system performance deteriorates
Solution Approach 1:
The patent applies preliminary action by performing polynomial curve fitting on the cross-correlation function values before identifying the peak. This pre-processing step creates a smoothed model of the correlation data, allowing peak detection to occur at a later stage with higher accuracy. The curve fit is computed in advance, transforming raw correlation values into a predictable mathematical model that facilitates more precise delay estimation.
Solution Approach 2:
The patent introduces a polynomial curve as an intermediary between the noisy cross-correlation function values and the final peak detection. This mathematical model acts as a mediator that filters out noise while preserving the essential peak characteristics. The curve fit serves as an intermediate representation that bridges the gap between raw measurements and reliable delay estimation.
2Measurement precision
If polynomial curve fit of cross-correlation function is used, then delay estimation accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent applies partial action by selectively applying polynomial curve fitting only to cross-correlation function values that exceed a predetermined threshold. Instead of processing all correlation values, the method focuses computational resources on the most significant peaks above the threshold level. This partial processing approach reduces the number of polynomial fits required, thereby lowering computational energy consumption while maintaining delay estimation accuracy for the dominant peaks.
3Reliability
If threshold filtering is applied to cross-correlation values, then noise resistance is improved, but risk of excluding valid peaks increases
Solution Approach 1:
The patent implements feedback by using the polynomial curve fit results to inform subsequent peak detection decisions. The curve fitting process provides a mathematical model that feeds back into the peak identification stage, allowing the system to distinguish between genuine peaks and noise artifacts. This feedback mechanism ensures that threshold filtering and peak detection work together synergistically, with the curve model guiding the interpretation of threshold-exceeding values.
Data Source
AI summary
Performing digital predistortion (DPD) for widely spaced narrowband signals, such as the signal used in multi-carrier GSM, can be very difficult. Here, a system is provided the performs DPD for widely spaced narrowband signals. In particular, this system uses a polynomial curve for values of a cross-correlation function (above a predetermined threshold) to determine a delay estimate, which allows for a more robust and accurate system.