Constant Envelope Phase Modulation Inspired by Orthogonal Waveforms

Constant envelope orthogonal frequency division multiplexing (CE-OFDM) is a technique to modify the OFDM signal with high peak-to-average power ratio (PAPR) to a constant envelope zero decibel PAPR waveform. The conventional CE-OFDM uses inverse discrete Fourier transform to calculate the signal time samples before feeding them to the phase modulator. This letter describes a different approach for the implementation of a constant envelope of generating phase digitally modulated waveforms that may be easier for implementation. The new approach, which we termed 'constant envelope M-ary time orthogonal' (CE-MTO), is based on orthogonal waveforms in the time domain. A time domain-analytical study of the CE-MTO in the presence of an additive white Gaussian noise is presented. Simulations of the CE-MTO performances show the comparable results to those of the CE-OFDM technique also in a frequency selective channel.