A novel programmable ultra-wideband coded signal generator based on digital integrated circuits is designed. The bipolar impulse can be generated by a transformer without any analogue circuit. A pseudorandom code is used to modulate the monocycle impulse by the time modulation (TM) scheme. The width of a monocycle pulse is variable along with the frequency of the input clock and delay time. The minimum width is as small as 0.625 ns and the amplitude is 0.64 V peak-to-peak.