Amazon.com, Inc.
System for reducing crest factor and peak to average power ratio

Abstract:

A constellation of many satellites and associated ground stations provide communication service to user terminals. These devices use modulation techniques such as orthogonal frequency division multiplexing (OFDM) to send large quantities of data. For transmission, a power amplifier increases the amplitude of a waveform modulated in this way. The power amplifier operates more efficiently closer to saturation. However, operation at saturation results in nonlinear distortion, producing unwanted signals and increasing bit error rate. A set of techniques are used to reduce the peak to average power ratio (PAPR) of the waveform provided to the power amplifier. A distortionless technique remaps blocks of bits to reduce the resulting PAPR of that block. Additional techniques may also be progressively applied to reduce PAPR while minimizing adverse consequences such as in-band distortion, out of band emissions, increased bit error rate, and so forth. These techniques may include filtering, peak cancellation, and circular clipping.