Far-field boundary estimation for the highpower UWB pulsed antennas

In this study, a method to estimate the far-field boundary of the high-power ultra-wideband (UWB) pulsed antennas is presented. By analysing the properties of the UWB pulsed antennas, it shows that the radiation space should be separated based on the behaviours of time or phase differences caused by the distribution of radiation elements of the antenna. In the time domain, characteristic parameters of the radiated pulse can be different due to various waveforms, which means that the farfield condition is waveform dependent. So, for all the various waveforms, it is difficult to formulate a universal far-field condition with a certain time-domain parameter. Therefore, the far-field boundary is better to be estimated in the frequency domain, which is obtained by substituting the cut-off frequencies of the UWB system into the classical far-field conditions. The cut-off frequencies are determined by the 90% energy edge frequencies of the radiating field. Finally, a reflector Impulse Radiating Antenna (IRA) system is developed to verify the proposed method. The electric fields of the IRA from the near- to far-field regions are measured, which indicates that the far-field boundary calculated by the proposed method agrees with the experimental result well.