Fig. 10Simulated and measured gain (dBi) of the proposed antenna
The stability of radiation pattern, gain, polarization, reflection coefficient etc, when radiated at different frequencies, the phase difference is not taken into account. At the same time all the frequency components of the UWB system are radiated. In order to reconstruct the phase on reception for different components, the stability must take into account the phase difference. The group delay is considered as the figure of merit. In the UWB communication system, UWB pulse distortion by an antenna is an important issue as the UWB system helps in pulse transmission. A constant group delay (linear phase response) is needed in the UWB system in true sense. The simulated and measured group delay of the proposed UWB notch antenna is shown in figure 11. The simulated group delay for the UWB notch antenna is around 2 ns at the notch frequency of 5.5 GHz. This disturbance of phase response as group delay occurs due to notch characteristics of the proposed UWB notch antenna at 5.5 GHz. At this frequency of 5.5 GHz, linear phase response of the UWB notch antenna is disturbed. On the other hand, the measured group delay of the proposed antenna is in accordance with the simulated one. The measured group delay of the proposed antenna is around 2.8 ns. Apart from this notch band the phase response of the proposed antenna in the UWB frequency range for simulation and measurement are consistent and are at the approximate average value of 0.2 ns from 3.097GHz to 13.326 GHz. Hence from figure 10 it is clear that the proposed antenna exhibits excellent linear response in the UWB range of 3.097GHz to 13.326 GHz except at the notch band centered at 5.5 GHz.