This letter proposes an ultrawideband (UWB) transmitter for a UWB primary impulse radar that is designed for real-time pedestrian localization. The proposed transmitter applies a novel combination of a UWB pulse generator followed by a UWB amplifier to boost output pulse amplitude, which is able to be turned off automatically after one pulse transmission in order to reduce power consumption. The transmitter has been fabricated using 45-nm SOI CMOS technology and has been measured on a printed circuit board (PCB). The produced pulses possess a high measured peak-to-peak amplitude of 425 mV and a width of around 600 ps. The power spectral density (PSD) of the pulse achieves a maximum of -41 dBm/MHz at 6 GHz with a -10-dB bandwidth of 4.5 GHz from 3.3 to 7.8 GHz that assures that the proposed transmitter complies with the regulation of the U.S. Federal Communications Commission (FCC) for UWB outdoor applications. The pulse generator consumes around 10 pJ/pulse from a 1-V supply, which is very low among the similar designs, and remains almost constant with an increasing pulse repetition time (PRT).