An intermediate-field approach of the differential time-domain single-antenna method for electrically large ultra-wide band antennas

The single-antenna method consists of a virtual transmission between the antenna under test and its image in a conducting reflector. In a previous work we proposed a differential, time-domain single-antenna approach that was found suitable for measuring the impulse response of an ultra-wide band antenna. The approach provides accurate results within the far-field distance range. However, when measuring large ultra-wide band (UWB) antennas operating in the lower UWB frequency band for military applications, i.e., from 0.1 to 1 GHz the distance between the antenna and its image usually falls close to the lower limit of the Fraunhofer region. This paper presents an intermediate-field approach of the time-domain differential single antenna method, based on defining a normalized received signal that can be averaged over a set of distances. The proposed technique is established theoretically and validated experimentally on a cylindrical UWB monopole antenna.