In the first part of the paper, also in this issue of the JOURNAL, the design of the frequency synthesizer and receiver section of an FSK transceiver was described. It operates in the 434-MHz ISM (Industrial, Scientific, Medical) band and is realized in a standard digital 0.5-μm CMOS process. This companion paper focuses on the realization of the transmitter section. It includes a power amplifier, an upconverter, and the circuit generating the baseband quadrature signals with a continuous phase modulation. The overall measured efficiency of the packaged circuit is higher than 38% for a 1.2-V supply and an output power reaching 10 dBm at 433 MHz. The system is designed to still operate at 1-V supply, delivering more than 1 mW with an efficiency higher than 15%.