This paper presents a 100-120-GHz pulse transmitter chip with a 54×24 on-chip loop antenna array for indoor millimeter wave (mm-wave) imaging applications. This 4- mm×4-mm transmitter for the purpose of beam-forming is designed and fabricated in a 2.5-V 0.25-μm 4-metal-layer Si-Ge Bi-CMOS process. The 23-μm×23-μm loop antenna located on the top-metal layer operates as an inductor in an mm-wave pulse generating circuit. Each of the on-chip damping pulse generators includes an R-L-C circuit, a BJT operated as a switch and a CMOS inverter chain circuit for shaping the rising edge of the input clock. Simulation results by EMDS, ADS 2009 and HSPICE show that loop antenna's inductance and resistance at 80-120 GHz are 51 pH and 3 Ω, respectively. By using an mm-wave power meter, a 90-140-GHz standard horn antenna and a Schottky diode detector, we demonstrate the ability of an integrated mm-wave pulse generator for the purpose of beam-forming.