This paper presents a transmitter-type TMIC integrated with a rectangular microstrip patch antenna and a power amplifier. The TMIC was fabricated with GaN HEMT technology for high power density and efficient integration. The on-chip antenna was designed as a power radiator and a frequency-dependent output load tuner of the power amplifier. Load-pull technique was used to realize a good impedance match between the amplifier and the antenna. Over a bandwidth of 100~110 GHz, the power amplifier can deliver an average output of 25.2 dBm with a power-added efficiency （PAE） of 5.83%. Good radiation characteristics of the TMIC have been achieved, showing a 10-dB bandwidth of 1.5 GHz and an estimated equivalent isotropic radiated power （EIRP） of 25.5 dBm at 109 GHz.