A quaternary amplitude shift keying modulator for suppressing initial amplitude distortion

This paper proposes a quaternary amplitude-shift-keying (4ASK) modulation circuit that suppresses amplitude distortion of the transmitting 4ASK signal. The performance of the proposed circuit is quantitatively verified through numerical calculation in comparison to a conventional alternative. The feasibility of the proposed circuit as integrated in a lithium niobate substrate is also demonstrated: the suppression of amplitude distortion is successfully demonstrated and minimum sensitivity of the transmitted 4ASK signal is 1.7 dB better than that offered by the conventional circuit.