Interference minimisation of antenna-to-range interface for pattern testing of electrically small antennas

The accurate measurement of radiation patterns of electrically small antennas (ESAs) requires a reflectionless environment and minimal disturbance from the antenna support and feed cable. These influence factors constitute the “antenna-to-range interface” and hence the deviation of the antenna performance from an ideal non-invasive set-up. A study was carried out at the UK National Physical Laboratory of disturbance minimisation in the measurement of radiation patterns of ESAs. To eliminate the large distortion associated with the unwanted radiation from a coaxial cable an electro-optical (EO) transducer was employed. The shielding effect of different transducer designs is assessed with an electrically small ultra-wide band antenna (UWB). Numerical results for the radiation pattern of a dielectric resonator ESA operating at 2.45 GHz are compared with the measured results using an EO transducer or a cable.