Spatial group delay patterns for three ultra wideband spline antennas

The IEEE ultra wideband (UWB) standard includes both a multiple frequency carrier (MB-OFDM) and an impulse spectrum (DS-UWB) method, for which application antennas should be appropriately optimized. Small printed monopoles with outline features that can be defined by a Bezier-spline [1] have good matched impedance performance across the 3.1 - 10.6 GHz band. For communications applications, an omni-directional pattern, where the gain pattern varies by less than plusmn5 dBi, and a stable frequency-gain profile in the azimuth plane, allow for an even spatial coverage in all directions. In the case of an impulse system, any non-linear phase transfer performance in the antenna adds distortion to the transieved pulses therefore reducing the data rates. Contemporary UWB antenna gain performances are often presented across the whole spectrum using contour plots. This discloses more details and compliments the conventional sampled frequency polar plots that are more suited to narrow bandwidth antennas. In this paper, the approach is extended to a group delay pattern measurement which is more comprehensive than the traditional and limited boresight-only approach.