A nonlinear transmission-line waveform generator for generating a comb of frequencies and relatively short duration pulses, for example, in the range of picoseconds and tens of picoseconds, that are adapted to being utilized with ultra wideband radios in order to improve the bandwidth of such radios by an order of magnitude, for example, up to tens and even hundreds of GHz. In particular, the nonlinear transmission line waveform generator in accordance with the present invention consists of a microstrip or coplanar waveguide line. In accordance with an important aspect of the invention, the &Dgr;C/&Dgr;V characteristic of the nonlinear transmission line is matched to the frequency and amplitude of the input sinusoidal waveform. By matching the &Dgr;C/&Dgr;V characteristics of the nonlinear transmission line to the input sinusoidal waveform, the output of the nonlinear transmission line produces a comb of frequencies that are multiples of the input sinusoidal waveform frequency, making it suitable as a harmonic generator. The nonlinear transmission line can also be used to generate relatively short duration pulses by disposing a shorting stub at the output. The shorting stub causes the waveform to be reflected 180° out of phase so that it cancels the trailing edge of the original output from the nonlinear transmission lines to form a short duration pulse in the picosecond range. The length of the stub determines the width of the resultant output pulse.