Allocation of the unlicensed frequency band around 60GHz by worldwide regulatory authorities has stimulated research for impulse based ultra wideband technology. It has the potential of offering multi-gigabit per second throughput for short range wireless systems. Ultra wide band impulse radio uses extremely short baseband pulses for transmission and reception. The role of designing ultra wideband antennas for such systems is vital, where an antenna behaves as a band pass filter. Thus distorted and dispersive effects are obtained for the received waveform. This paper investigates pulse distortion for different antennas and evaluates the amount of the dispersion caused by each antenna using the time domain parameter fidelity factor.