In low-rate UWB impulse radio the carrier pulses have very short duration that limits the energy per bit in an extremely low value. The low bit energy results in an unacceptable short radio coverage. In the paper new UWB carrier pulse generation techniques are proposed to increase the pulse duration considerably. In order to get an ultra wideband carrier a spectrum widening signal is used. Using this approach the energy per bit could be increased even by 17.6 dB when the pulse duration has been set to 70 ns. The coverage of low rate UWB impulse radio is increased considerably due to the increased energy per bit. The novel UWB carriers are all constant envelope signals, therefore, they may be amplified even by nonlinear power amplifiers.