Crest factor

Crest factor is a parameter of a waveform, such as alternating current or sound, showing the ratio of largest value to the more typical value. More specifically, crest factor is the peak amplitude of the waveform divided by the root mean square (RMS) value of the waveform. The minimum possible crest factor is 1 or 1:1. Crest factor indicates how extreme the peaks are in a waveform. Crest factor 1 indicates no peaks, such as direct current or a square wave. Higher crest factors indicate more pronounced peaks, for example sound waves tend to have high crest factors. The peak-to-average power ratio (PAPR) is the peak power (peak amplitude squared) divided by the average power (mean square or squared RMS). PAPR is the square of the crest factor. Crest factor and PAPR are both dimensionless quantities. While the crest factor is defined as a positive real number, in commercial products it is also commonly stated as the ratio of two whole numbers, e.g., 2:1. The PAPR is most used in signal processing applications. As it is a power ratio, it is normally expressed in decibels (dB). When expressed in decibels, crest factor and PAPR are numerically equal, due to the way decibels are calculated for power ratios vs amplitude ratios. The crest factor of the test signal is a fairly important issue in loudspeaker testing standards; in this context it is usually expressed in dB.

Crest factor is a parameter of a waveform, such as alternating current or sound, showing the ratio of largest value to the more typical value. More specifically, crest factor is the peak amplitude of the waveform divided by the root mean square (RMS) value of the waveform. The minimum possible crest factor is 1 or 1:1. Crest factor indicates how extreme the peaks are in a waveform. Crest factor 1 indicates no peaks, such as direct current or a square wave. Higher crest factors indicate more pronounced peaks, for example sound waves tend to have high crest factors. The peak-to-average power ratio (PAPR) is the peak power (peak amplitude squared) divided by the average power (mean square or squared RMS). PAPR is the square of the crest factor. Crest factor and PAPR are both dimensionless quantities. While the crest factor is defined as a positive real number, in commercial products it is also commonly stated as the ratio of two whole numbers, e.g., 2:1. The PAPR is most used in signal processing applications. As it is a power ratio, it is normally expressed in decibels (dB). When expressed in decibels, crest factor and PAPR are numerically equal, due to the way decibels are calculated for power ratios vs amplitude ratios. The crest factor of the test signal is a fairly important issue in loudspeaker testing standards; in this context it is usually expressed in dB.

Crest factor reduction methods

Various methods for crest factor reduction exist, such as peak windowing, noise shaping, pulse injection and peak cancellation.

General

Definition of peak-to-average ratio – ATIS (Alliance for Telecommunications Industry Solutions) Telecom Glossary 2K Definition of crest factor – ATIS (Alliance for Telecommunications Industry Solutions) Telecom Glossary 2K Peak-to-average power ratio (PAPR) of OFDM systems - tutorial

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