Continuous Phase Modulation Proposal for Photonics-Wireless Sub-THz Transmissions

Abstract

This paper presents a waveform proposal for photonic-wireless sub-THz transmissions. The concept of Continuous Phase Modulation (CPM) is first explained. Then, a mathematical model to simulate non-linear effects from photodiodes for the Amplitude-to-Amplitude (AM-AM) and a second model for the Amplitude-to-Phase (AM-PM) transfer functions is given. These models are then used to quantify non-linearities effects on linear waveforms (M-QAM) and non-linear waveforms (CPM). Afterwards, the communications range gained from using CPM over M-QAM from the simulated non-linear effects is calculated. To further appeal to the use of CPM, a study on energy efficiency is proposed. Finally, a proof of concept is given by experimentally comparing the CPM waveforms with a regular linear modulation, such as QPSK. An error-free data rate of 7.5 GBauds with Raised-Cosine, Gaussian Minimum Shift Keying (two CPM waveforms), and QPSK at a 107.5 GHz wireless 1-meter link is measured. To further estimate the robustness of the wireless link, a simulation of a communication with different transmit powers is done by adding white Gaussian noise to the acquired signals.

Keywords

• Continuous phase modulations
• energy efficiency
• photodiodes non-linearities
• radio-over-fiber
• sub-THz wireless communication
• THz photonics