Antenna characterisation and channel effects on digital systems

This paper investigates the characterisation of a Vivaldi antenna and the effects of various channel environments on a digital communication system (DCS). Antenna characterisation involves obtaining the reflection coefficient (S₁₁) in both amplitude and phase using a three-dimensional electromagnetic (EM) simulator and conducting experimental verification using a network analyser. Initially, the Vivaldi antenna was characterised using three techniques: (i) applying the Hilbert transform to the measurement, (ii) deriving an equivalent circuit model and (iii) processing the measurements between two identical antennas in an anechoic chamber. These techniques were then used to ascertain the transfer function (S₂₁) of the antenna. The S₂₁ values obtained through these techniques were compared to verify their validity. The S₂₁ measurements were also extended using two identical antennas in two different indoor office environments. Moreover, to evaluate the effect of these indoor channels, two different path lengths were considered. Finally, these three channels with the two identical antennas were simulated and analysed in a DCS to investigate the effects of the antenna and various channel conditions on the system.