A Spread Spectrum Modulation Technique for THz Communications in the Presence of Phase Noise

Phase noise is an unconventional noise that affects the phase of a given waveform. It arises mainly from non-linear distortions in the local oscillator (LO) and is amplified in the presence of frequency-amplifying chains and non-linear amplifiers. Thus, due to current terahertz (THz)-band technologies relying heavily on these techniques to reach THz frequencies, phase noise presents itself as a challenge in the THz domain. This paper presents a unique modulation scheme that is resilient to the longtime correlation of phase noise through a code-division-based modulation scheme. The scheme utilizes the large bandwidth available in the THz domain to represent information not in the phase, but in the specific code choice itself. In addition, a time diversification factor is implemented atop this scheme to further improve resilience against phase noise. Numerical simulations demonstrate that the modulation scheme is able to provide up to 13 dB improvement over direct sequence spread spectrum (DSSS) + phase shift keying modulations.