Optimization of ultra-wideband (UWB) systems depends on the direction dependent response of the antenna. To achieve multi-directional optimization, it is necessary to have direction independent response of the UWB antenna. If the antenna has a stable radiation pattern with frequency it has direction independent response. Therefore, designing antennas with high level of pattern stability is desirable. As such a new figure of merit (PSF) we have previously presented accurately expresses the pattern stability of UWB antennas over a wideband and a wide range of directions. This parameter is calculated using directional transfer functions of a UWB antenna. In our previous studies, we used the magnitude transfer function, which is sufficient for comparing the stability of amplitude radiation patterns of small, low-cost and low-dispersion UWB antennas. In this paper we extend our investigation to calculate PSF using not only magnitude, but also complex and receive transfer functions of a given antenna. It is shown that there are differences between these PSF, with the help of planar UWB monopole example. The reasons for these differences are identified.
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