Crest Factor Reduction Using Peak Clipping for RF Amplifier Efficiency
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Solution Overview
Problem
The peak-to-average ratio (PAR) of radio frequency input signals to amplifiers varies, causing amplifier saturation, distortion, and reduced power efficiency, as high peaks lead to spectral expansion and decreased output power.
Innovation Solution
A method involving crest factor reduction, where peak values exceeding a threshold are clipped using a clip function, reducing the peak-to-average ratio by applying a clipping function to the input signal's neighborhood, thereby reducing spectral expansion and enhancing amplifier efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the input signal is backed-off to prevent amplifier saturation, then distortion is reduced, but output power and power efficiency decrease
Solution Approach 1:
The patent applies preliminary action by detecting peak values in the input signal and pre-clipping them before amplification using a clip table and clip function. This prevents amplifier saturation in advance, allowing the amplifier to operate at higher power levels without distortion, thus resolving the contradiction between maintaining linearity and maximizing output power.
2Reliability
If the input signal is backed-off to prevent amplifier saturation, then distortion is reduced, but power efficiency decreases
Solution Approach 1:
The patent applies preliminary action by detecting peak values in the input signal and pre-clipping them before amplification using a clip table and clip function. This prevents amplifier saturation in advance, allowing the amplifier to operate at higher power levels without distortion, thus resolving the contradiction between maintaining linearity and maximizing output power.
3Reliability
If peak values are clipped using a clip function, then peak-to-average ratio is reduced, but signal fidelity may be compromised
Solution Approach 1:
The patent applies local quality by selectively clipping only the peak values that exceed the threshold while leaving the rest of the signal unchanged. The clip table stores clip coefficients for specific index values, and the clip function is applied locally at these peak positions, minimizing impact on overall signal fidelity while preventing amplifier saturation.
Solution Approach 2:
The patent uses feedback by continuously monitoring the input signal for peak values and dynamically updating the clip table with new clip coefficients when peaks are detected. The system adjusts the clipping operation based on the actual signal characteristics, ensuring optimal performance while maintaining signal fidelity.
Data Source
AI summary
A method is presented which performs crest factor reduction (CFR) on a digitized signal. The method may include determining one or more peak values in a series of data samples of a communication signal, and/or generating a peak queue comprising the one or more peak values that exceed a threshold value and a corresponding index values for each peak value. The method may further include generating, from the peak queue, an entry to a clip table, the entry including a clip coefficient at the corresponding index value, updating the clip table to include a new clip coefficient at a new corresponding index value when the clip function squared at the new index value exceeds a scaled output power for an input power at the new corresponding index value, and/or clipping the series of data samples in a neighborhood of the peak value according to the clip function.