Crest Factor Reduction Clipping via Tangent Line Projection
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Solution Overview
Problem
Existing crest factor reduction methods for complex-valued signals are computationally complex, leading to processor inefficiencies due to the need for square root and division operations, which are costly in terms of computational resources.
Innovation Solution
A low-computation crest factor reduction method that involves projecting complex-valued samples onto a selected tangent line in a complex plane, using a sequence of mapping operations and reverse-mapping to determine an optimal or near-optimal clipped sample, reducing the number of actual multiplication operations required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ideal clipping operation using circle projection function is used, then clipping precision is improved, but computational complexity increases
Solution Approach 1:
The patent replaces the expensive ideal clipping operation with a series of cheaper approximation operations. Instead of directly computing the circle projection which requires square root and division, the patent uses multiple tangent line projections that can be computed with simpler arithmetic operations, sacrificing minimal precision for significant computational savings
Solution Approach 2:
The patent divides the clipping operation into multiple stages, each using a different tangent line projection. The complex clipping task is segmented into several simpler sub-tasks that can be executed sequentially with reduced computational complexity at each stage
2Measurement precision
If square root and division operations are performed multiple times, then clipping accuracy is maintained, but processor efficiency deteriorates
Solution Approach 1:
The patent substitutes expensive square root and division operations with cheaper arithmetic operations (multiplication, addition, subtraction) that can be executed efficiently by processors. Each tangent line projection uses only basic arithmetic, avoiding the computational bottleneck of square root and division while maintaining sufficient accuracy
Solution Approach 2:
The patent pre-calculates tangent line parameters and prepares approximation data in advance, so that during actual clipping operations, only simple arithmetic computations are needed rather than expensive square root and division operations
Data Source
AI summary
Disclosed are methods, systems, devices, apparatus, media, design structures, and other implementations, including a method for crest factor reduction (CFR) processing that includes receiving a first complex-valued sample of a signal for radio transmission, determining a resultant clipped complex-valued sample for the first complex-valued sample, resulting from projection of a second complex-valued sample, associated with the first complex-valued sample, into a selected one of a plurality of different tangent lines that are tangential to a circle representation with a radius h in a complex-valued plane, and processing the signal using the determined clipped complex-valued sample to produce a resultant CFR signal.