| Summary: | The antenna constitutes the air interface between wireless equipment and communication channel, thus, efficient operation is of great importance especially in compact user devices. An understanding of its behaviour within any communication system, and an accurate representation of its effects on received signals are vital. The nature of the multipath propagation channel and the local environment, the user's interference with its orientation and immediate vicinity are all factors that impact on antenna performance and need to be addressed. This thesis addresses issues directly arising from the nature of the interaction of impinging waves and antenna radiation patterns. Firstly, an important proportion of this research is devoted to the assessment of the application of the closed-form expression of the mean effective gain (MEG) of the antenna. Although the validity of this expression has been established in stochastic Rayleigh channels, its wider application is now questioned. Results show that the traditional MEG calculation method can result in inaccurate estimations with varying effect and significance especially in deterministic channels. Particularly, as phase is omitted from calculations on account of its random uniform distribution, it is found that phase information is in fact essential to quantify losses due to mismatches in polarisation. Here, a much more rigorous approach is taken in the form of the mean directivity formula which takes full complex information of impinging signals and radiation fields into account . Secondly, an experimental approach is taken in order to investigate the impact of scattering environments on full three dimensional, polarimetric antenna properties. A method for 3D directional channel characterisation built around standard antenna pattern measurement techniques is proposed and validated in a controlled multipath environment. The data from these measurements delivers spatial, phase and magnitude information of the channel around the antenna, within limitations imposed by the beamwidth of the measurement antenna. The results give an important insight into the phase characteristics of the incident field, namely, its continuity across clusters of incoming signal. Finally, the results obtained thus far are brought together in a performance evaluation tool, capable of predicting sensitivity to measured signal in 3D space. Indeed, future device antenna testing procedures must be truly representative of realistic usage scenarios. Tests can in no way be exhaustive in terms of the environment or usage situations they cover; they can however be made to target particularly sensitive scenarios and antenna properties that are known to have more influence on how the propagating signals are treated. The full antenna testing procedure proposed is therefore a complete tool able to predict antenna performance in the spatial and polarimetric domain
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