This letter demonstrates a CMOS impulse radio ultrawideband (IR-UWB) on-off keying (OOK) generator with multipulses per bit generation. The proposed IR-UWB OOK generator is implemented in 0.11 lm CMOS process where 1.33 mm 2 proto-type accomplishes pulse train of 250 Mbps for one bit duration while consuming 10 mW from 1 V supply voltage. This pulse generator complies with the FCC spectral mask for indoor UWB systems. It consists of impulse generator, LC oscillator, delay cell, and pulse shaping filter with which pulses are repeated in every 4 ns irrespectively of input data rates. The output pulse centering at 3.8 GHz provides multiple pulses per bit with 210 mVpp and 40 pJ/pulse energy consumption. Bandwidth based on 210 dB attenuation from the main beam is measured to be 0.65 GHz.