This paper describes a low power Ultra-Wideband Impulse Radio (UWB-IR) Application Specific Integrated Circuit (ASIC) transmitter implemented in UMC 0.18 μm. This transmitter has been designed for low data rate communication applications and indoor positioning systems. It is powered by 1.8 V and its current consumption is 20 mA during pulse transmission and lower than 45 μA the rest of the time. This leads to an average power for the transmitter of less than 85 μW for a 288-pulse burst at a burst repetition rate of 1 Hz. The center frequency and bandwidth of the pulse generated by this transmitter are compliant with the current international regulations (FCC/ECC).