Efficient phase and frequency shift-keying modulator designs proposed with RF carbon-based transistor technologies at 2.4 GHz and 1.2 GHz, respectively, are discussed in this work. Their overall performance and power dissipation are presented. Experimentally-calibrated compact models of carbon nanotube have been used to carry out these designs. The multifunctionality features of the designs leading to the modulators proposals have been enabled by the inherent devices ambipolarity in addition to a proper design of matching and stability networks. The designs proposed in this work are suggested as potential on-chip solutions for communication systems since only one device and one circuit have been used for each modulation scheme. The requirement of biasing control CMOS-based circuits is pointed out towards heterogeneous integration of emerging transistor technologies (back-end-of-line) with silicon technologies (front-end-of-line). Brief reviews of the internal physics mechanisms leading to ambipolar transistor operation as well as their proof-of-concept applications are also presented.