This paper describes generation of ultra wideband (UWB) waveforms with adaptive notch frequencies and hence reduced interferences on narrow band systems; by composition of derivative pair of Gaussian pulse. It is shown, through analytical formulation and/or simulation, that the notch frequencies in the composite waveforms and the number of notches can be adjusted by changing the delay time between derivative pair. In particular, MATLAB simulation results are given for combination of 4^th-4^th, 4^th-5^th, and 5^th-5^th order derivatives, which illustrate the accuracy of the technique. The composite UWB waveforms are also generated by a low-power programmable DAC-based circuit, using a 0.13µm CMOS technology.