Differential time delay patterns for UWB antennas

The time delay pattern for a UWB antenna is considered. Many different definitions of time delay are possible. Possibilities include (a) time delay for maximum correlation with a template function, either in terms radiated field or port-to-port transfer function, (b) time delays extracted from the linear phase part of a transfer function, and (c) time delays based on time-domain waveform features. Each of these three general definitions may be computed by multiple means. The delays can be absolute or differential, that is, taken relative to the respective delay in a reference direction. It is shown that some of definitions are equal under certain very restrictive conditions. Example data is given for a broadband (1-18 GHz) double ridged horn antenna.