A Gaussian pulse generator for an ultrawideband impulse radio transmitter is presented. The proposed Gaussian pulse generator is based on digital intensive circuits, and the center frequency and band-width of a pulse can be controlled by a digitally tunable delay circuit and pulse width control circuit. The Gaussian pulse can be obtained by the weighted summing amplifier controlled by a digital switching sig-nal without an additional LC filter. It employs a Gaussian pulse shaper that has tunable weighting factors with bandwidth control. The energy consumption of the pulse generator is 37.4 pJ per pulse from 1.2-V supply voltage and sidelobe rejection of 20 dB is achieved without a filter. Proposed Gaussian pulse shaper is designed in a 0.11 µm CMOS technology.