Iterative OFDM PAR Reduction to Limit Peak Regrowth
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Solution Overview
Problem
Conventional PAR reduction techniques for HD Radio signals, such as clipping, lead to regrowth of signal peaks in subsequent processing, and existing methods are inefficient in reducing peak-to-average ratio (PAR) for hybrid and all-digital signals.
Innovation Solution
A PAR reduction algorithm that iteratively clips and weights the signal peaks, varying the weight across iterations to mitigate regrowth, while preserving signal integrity and reducing out-of-band emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional clipping techniques are used to attenuate signal peaks, then peak levels are reduced to acceptable levels, but signal peaks reoccur in subsequent processing
Solution Approach 1:
The patent applies dynamics by making the clipping threshold variable rather than fixed. The clipping threshold adapts dynamically based on the signal's instantaneous characteristics and iteration progress, allowing the system to respond to changing signal conditions and prevent peak regrowth while maintaining signal integrity
Solution Approach 2:
The patent implements feedback through iterative processing where the output of each clipping operation is fed back into the system for further processing. The algorithm monitors the clipped signal and adjusts subsequent clipping operations based on the observed peak behavior, creating a closed-loop system that progressively reduces peaks without causing regrowth
2Object-affected harmful factors
If multiple iterations of PAR reduction are performed, then PAR is reduced more effectively, but computational complexity increases
Solution Approach 1:
The patent applies partial action by performing clipping operations on only the excessive peak portions of the signal rather than processing the entire signal uniformly. The clipping is applied selectively to exceed the threshold, avoiding unnecessary computation on signal portions that do not require processing
Solution Approach 2:
The patent segments the PAR reduction process into multiple iterative stages, where each iteration focuses on reducing remaining peaks. The segmentation of the processing into discrete iterations allows for progressive refinement while enabling early termination when targets are met, reducing overall computational burden
3Object-affected harmful factors
If aggressive clipping is applied to reduce PAR, then peak levels are suppressed, but out-of-band emissions and spectral distortions increase
Solution Approach 1:
The patent applies local quality by making the clipping operation selective in its application. Rather than uniformly clipping all signal portions above a threshold, the algorithm applies different clipping strategies to different parts of the signal based on local characteristics, preserving spectral integrity while suppressing peaks
Solution Approach 2:
The patent applies preliminary anti-action by using iterative clipping to progressively reduce peaks before they can cause significant spectral distortion. The multiple iterations allow for gentle, controlled peak reduction that prevents the generation of harmful out-of-band emissions
Data Source
AI summary
A method comprises performing iterations of a peak-to-average ratio (PAR) reduction algorithm on a modulated OFDM symbol, each of the iterations including: clipping the modulated OFDM symbol to produce a clipped modulated OFDM symbol; subtracting the clipped modulated OFDM symbol from the modulated OFDM symbol to produce a difference signal; weighting the difference signal using a weight that varies across the iterations, to produce a weighted difference signal that varies across the iterations; subtracting the weighted difference signal from the modulated OFDM symbol to produce a modified modulated OFDM symbol; and performing further PAR reduction operations on the modified modulated OFDM symbol to produce a PAR-reduced OFDM symbol for use in a next iteration.