This letter presents a transmitter for subterahertz radiation (up to 160 GHz), which consists of a nonlinear transmission line (NLTL) and an extremely wideband (EWB) slot antenna on a silicon substrate of low resistivity (10 Ωcm). The fabrication was realized using a commercially available 65-nm CMOS process. On-wafer characterization of the whole transmitter, of the stand-alone EWB antenna, and of the stand-alone NLTL is presented. Reflection measurements show that the stand-alone EWB antenna has a 10-dB impedance bandwidth in the frequency bands of 75-100 GHz and 220-325 GHz, which agrees very well with the simulation results. The simulated radiation patterns of the antenna are also presented, indicating that the transmitter has an ominidirectional performance. The output power of the NLTL alone and of the transmitter is measured up to 160 GHz, from which the power gain of the on-chip antenna is derived and has a maximum value of-9.5 dBi between 90 and 120 GHz.