Pulse Shapes That Outperform Traditional UWB Antenna/Waveform Combinations

Traditionally the Gaussian monocycle pulse and its higher derivatives have been proposed and deployed as impulse radio ultra-wideband (IR-UWB) pulses. Although relatively easy to generate in electronics, these pulses are ill-adapted to the sharp cutoffs in the US Federal Communications Commission (FCC) mask. The combination of these pulses with passband UWB antennas with steep roll-off improves power efficiency vis-a-vis the FCC mask. This approach is still quite sub-optimal and pulse shaping can provide marked improvement (to 3 dB) over the best traditional combinations. We show that optimal design of UWB waveforms, when taking into account antenna gain profiles, improves the power efficiency of the pulses. Three typical antennas are considered. A nonlinear optimization process is used to design an efficient pulse for each antenna. The proposed optimization is based on the hybrid genetic algorithm and a sequential quadratic program. We demonstrate that this method finds efficient pulses under severe antenna distortion. Simulation results confirm that the optimally designed pulses have superior performance compared to the more common Gaussian monocycle and the Gaussian fifth-derivative pulse.